Fundamentals of Spinal Cord
Stimulation (SCS)
Patient Selection: SCS
SCS may prove beneficial after failure of conservativ...
NONORGANIC PHYSICAL SIGNS IN LOW BACK PAIN (Waddell Signs)
I.A Set of Five Types of Physical Signs
II.Can Be Used to Scree...
The effect of the psychological and behavioral involvement
with pain perception cannot be overemphasized and care
should b...
Tarsal tunnel syndrome (tibial)
Etc
Nerve injury
Partial v. complete
Neuroma, neuroma-in-continuity
Plexopathy/plexus inju...
Some WDRs may degenerate
Excitotoxicity?
Spinal Cord Stimulation
Indications
Failed back surgery syndrome (leg>back pain)
...
Contraindications to SCS:
1. Cannot implant an IPG SCS in patients with demand
pacemakers
2. Since patients with SCS as of...
sequentially or simultaneously. CONCLUSION: Some clinical or experimental
support can be found in the literature for 10 sp...
RECHARGEABLE IPG SYSTEMS
While there are advantages and disadvantages to each company’s system, it
is in general a good id...
Lead Types
Fundamentally there are
two types of lead:
percutaneous (round)
leads and neurosurgical
(flat) leads. The
percu...
Electrodes Contact Size
(mm)
Electrode
Spacing (mm)
Vertebral
bodies covered
Pices Quad
(Medtronics)
4 3 6 1
Pices Quad
Co...
skin and discarded. This method saves a step of lead replacement. Many
experienced implanters are now using this method.
3...
need for cross stimulation between leads. For lower extremity pain and low back pain
coverage, the entry point into the li...
veer off the midline during lead placement, removal of the stylette from the lead followed
by introduction of a 20 degree ...
60% pain relief or 60% increase in function is possible, no painful stimulation, the
stimulation pattern covers the painfu...
reference for insurance and referral purposes, and will also permit ready access to
information which is needed in case of...
Perhaps the most important feature in permanent system implantation is the
patient response to the trial lead. Other facto...
Potential complications should be discussed in detail with the patient prior
to permanent implantation, and should be incl...
Permanent lead plus generator implantation uses scrupulous surgical skin
prep, IV antibiotics, and appropriate
anesthesia ...
developed by a
separate incision in
the subcutaneous
tissues above the
gluteus musculature.
Some implanters
prefer to use ...
the head or sleeping prone for at least 3 weeks, no immersion bathing or
showering until the post operative checkup at 7-1...
Neurology 2002 Oct 22;59(8):1203-9
Economic evaluation of spinal cord stimulation for chronic reflex sympathetic
dystrophy...
RESULTS: The insulated array performed significantly (P = 0.0005-0.0047) better
than the temporary percutaneous electrode ...
level), the success or failure of 3 months of SCS was correctly predicted in 88%
of the study population. Our results sugg...
to chronic pain of spinal origin. SUMMARY OF BACKGROUND DATA: The first
spinal
cord stimulation was implanted by Shealy in...
Anesth Analg 2002 Mar;94(3):694-700; table of contents
Spinal cord stimulation in postherpetic neuralgia and in acute herp...
cell velocity, capillary density, and capillary permeability was demonstrated.
At follow-up 18 months after surgery the pa...
the system in place and who could be contacted, for an interview. The aim of
this study was to evaluate the efficacy of an...
OBJECTIVE: To compare the outcome of spinal cord stimulation (SCS) in patients
with nonspecific limb pain versus patients ...
therapy had a mean reduction of 2.4 cm in the intensity of pain at six months,
as compared with an increase of 0.2 cm in t...
quad lead works best transforaminally or retrocaudally.
Peripheral nerve stimulation may also be used.
Occipital nerve sti...
often works extremely well for occipital neuralgia which responds to occip.
N. blocks.
Other peripheral nerves can be stim...
increasing in the US. There are also uses reported for facial pain via specific
trigeminal terminal branch stimulation. Ob...
Fax (763) 559-4161
http://www.neuromodulation.org/
American Pain Foundation
11 South Calvert St.
Suite 2700
Baltimore, MD ...
Ottawa, ON K2P 1E2
Canada
Phone (613) 234-0812
Fax (613) 234-9894
http://www.medicine.dal.ca/gorgs/cps/
International Asso...
www.nih.gov
Pain and Neurological Disorders Information
National Institute of Neurological Disorders
Government web site t...
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Spinal Cord Stimulation Primer

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Spinal Cord Stimulation Primer

  1. 1. Fundamentals of Spinal Cord Stimulation (SCS) Patient Selection: SCS SCS may prove beneficial after failure of conservative therapy in selected patients. At least 3-6 months of conservative therapy should be attempted before SCS. Substance abuse issues must be under control and further definitive surgery for treatment or cure should have been exhausted before SCS is implanted. It is strongly suggested that all patients who are to undergo a SCS trial implantation or permanent implant have pre-operative psychological screening. A face to face interview is always more valuable than psychometric testing, however an MMPI or Behavioral Health Index (BHI) may be obtained as a prelude to the psychological interview. Such face to face encounters may reveal personality disorders, homicidal tendency elucidation, etc. that may not be apparent on psychometric testing. In addition, it is suggested that a functional evaluation such as an Oswestry test be incorporated along with physical capacity examination prior to implantation or trial. Good Candidates: 1. Peripheral Neuropathic Pain 2. CRPS Marginal Candidates: Spinal Cord Etiology Pain Poor Candidates: Mechanical Pain or Pain that is Not Constant, eg. Can Find a Position In Which Pain Is Completely Eradicated. Those with cerebral or cranial etiology pain do not respond to SCS. Other poor candidates are Those with untreated psychological disorders esp. depression and anxiety disorders. Do not implant SCS in schizophrenics or those with major personality disorders or homocidal tendencies. Patients who have 3/5 positive Waddells signs are not candidates.
  2. 2. NONORGANIC PHYSICAL SIGNS IN LOW BACK PAIN (Waddell Signs) I.A Set of Five Types of Physical Signs II.Can Be Used to Screen Individuals Who Require Detailed Psychological Assessment III.Scoring A.Any individual sign counts as positive for that type B.Three or more types positive = clinically significant IV.The Signs A.Tenderness 1.superficial - skin is tender to light pinch over a wide area of lumbar skin 2.nonanatomic - deep tenderness over a wide area, not localized to one structure, often extends to thoracic spine, sacrum, or pelvis B.Simulation Tests - give the impression that an examination is being done, when in fact it is not 1.axial loading - vertical loading over the standing patient’s skull by the examiner’s hands - may cause neck pain, but shouldn’t cause low back pain 2.rotation - turn standing patient to one side by rotating lower extremities (not spine) C.Distraction Tests - reevaluating a positive finding while the patient’s attention is not focused on the test - distraction must be nonpainful, nonemotional, and nonsurprising 1.indirect observation - can patient move the body part without pain when not being directly examined? 2.straight leg raise - if positive when examined supine, do "flip test" (sitting SLR) - can be done while testing for Babinski sign while sitting - if no pain in sitting then distraction sign is positive D.Regional Disturbances - widespread divergence from accepted neuroanatomy 1.weakness - "cogwheeling" or many muscle groups that cannot be explained neuroanatomically 2.sensory - "stocking" distribution of sensory changes E.Overreaction 1.disproportionate verbalization, facial expression, muscle tension and tremor, collapsing, sweating 2.most difficult type of sign to assess because: a.cultural variation b.examiner bias Waddell G, McCulloch JA, Kummel E, Venner RM: Nonorganic physical signs in low-back pain. Spine, 5(2) 117-125, March/April 1980. Special Situation Candidates: Peripheral vascular disease without diabetes may respond to the vasodilatory effect of SCS. Intractable angina patients who are at maximum medical management and are not surgical or angioplasty candidates may benefit from SCS. Interstitial cystitis and pelvic pain may be treated with sacral nerve stimulation via the caudal canal approach, retrocaudal approach, or transforaminal approach.
  3. 3. The effect of the psychological and behavioral involvement with pain perception cannot be overemphasized and care should be taken to sufficiently screen patients. Patients who have significant deficits in the above require intensive treatment followed by re-testing before any further discussion of SCS transpires. Remember, once you implant a stimulator in these patients, you are marrying them. Dance with them for awhile before you jump into marriage. Neuropathic Pain Diagnoses Neuropathic pain diagnoses: peripheral Sensory neuropathies Diabetes Proximal motor (mononeuritis multiplex) Distal sensory (polyneuropathy) Toxic Vitamin deficiency (beri beri) Collagen vascular diseases (PN) Lead poisoning Guillian-Barre Leprosy Ischemic Hereditary Etc Peripheral nerve tumor Neurofibroma Cancer Entrapment neuropathies Carpal tunnel syndrome (median) Cubital tunnel syndrome (ulnar)
  4. 4. Tarsal tunnel syndrome (tibial) Etc Nerve injury Partial v. complete Neuroma, neuroma-in-continuity Plexopathy/plexus injury Intercostal neuralgia Post-rhizotomy, post-ganglionectomy pain Post-herpetic neuralgia Failed back surgery syndrome (radicular pain) Neuropathic pain diagnoses: spinal cord Spinal cord injury pain (SCIP) syndrome Syringomyelia Brachial plexus avulsion pain Phantom pain (post amputation) Multiple sclerosis Post-herpetic neuralgia (?) Post-cordotomy pain Neuropathic pain diagnoses: cranial neuralgias and brainstem Cranial neuralgias Trigeminal neuralgia Glossopharyngeal neuralgia Geniculate neuralgia Sphenopalatine neuralgia (cluster HA?) etc CVA (i.e., Wallenberg) MS (trigeminal neuralgia) Syringobulbia Neuropathic pain diagnoses: cerebral Post-stroke (Dejerine-Roussy syndrome or “thalamic pain”) Neuropathic pain diagnoses: controversies Reflex Sympathetic Dystrophy Complex Regional Pain Syndrome (CRPS) I “Sympathetically-Maintained Pain” Or “Sympathetically Independent Pain” Causalgia CRPS II Neuropathic pain diagnoses: controversies What is known Injured axons develop alpha-adrenergic receptor-like activity This may permit a chemical “coupling” between sympathetic efferents and A/C fibers A-beta fibers mediate most hyperalgesia This may explain “sympathetically” dependant pain Injured axons are mechanosensitive This explains “Tinel’s” sign at neuroma Injured axons become hyperactive with hypoxia Entrapment? Poorly vascularized scar? Dorsal root ganglia also become spontaneously active after nerve injury. Ventral root afferents Role in phantom pain? WDR RFs increase in size WDR thresholds change WDRs become “sensitized” and respond to non-noxious stimulation (A-beta) with high frequency discharge ? Signals pain
  5. 5. Some WDRs may degenerate Excitotoxicity? Spinal Cord Stimulation Indications Failed back surgery syndrome (leg>back pain) Painful peripheral nerve injury Reflex sympathetic dystrophy (RSD) Amputation stump pains Painful distal sensory neuropathies Postherpetic neuralgia “End-zone” pains of paraplegia Intercostal neuralgia Post-thoracotomy pain syndrome Spinal Cord Stimulation Technique Golden rule of SCS “ Stimulation-induced paresthesias must cover the painful area for effective pain relief. ”
  6. 6. Contraindications to SCS: 1. Cannot implant an IPG SCS in patients with demand pacemakers 2. Since patients with SCS as of 2006 can never have another MRI, those who will need MRIs in the future are not candidates 3. Significant bony canal abnormalities which will divert the leads during placement (eg. Severe spinal stenosis) 4. Cervical spinal stenosis (causes potential lead indentation of the cord) 5. Uncorrected coagulopathy 6. Concurrent infection during time of implantation 7. Patient inability to understand or use controller devices 8. Failure to attain at least 60% relief or 60% increase in function during the trial of SCS 9. Post operative diathermy, ultrasound, or microwave therapies Theory of Spinal Cord Stimulation SCS is thought to be effective secondary to stimulation of the dorsal horns which subsequently interrupts neuronal signal flow through the spinothalamic tracts. However, there may be multiple mechanisms of action as is illustrated in the review below: Spine 2002 Nov 15;27(22):2574-83 Spinal cord stimulation: mechanisms of action. Oakley JC, Prager JP. Northern Rockies Pain and Palliative Treatment Center, Billings, Montana 59101, USA. joshir@aol.com STUDY DESIGN: A literature review and synthesis were performed. OBJECTIVE: To present the current understanding of the mechanisms of spinal cord stimulation in relation to the physiology of pain. SUMMARY OF BACKGROUND DATA: Spinal cord stimulation has been used for more than 30 years in the armamentarium of the interventional pain specialist to treat a variety of pain syndromes. Traditionally used for persisting leg pain after lumbar spinal surgery, it has been applied successfully in the treatment of angina pectoris, ischemic pain in the extremity, complex regional pain syndrome Types 1 and 2, and a variety of other pain states. This review presents the current status of what is known concerning how electrical stimulation of the spinal cord may achieve pain relief. METHODS: A literature review was conducted. RESULTS: The literature supports the theory that the mechanism of spinal cord stimulation cannot be completely explained by one model. It is likely that multiple mechanisms operate
  7. 7. sequentially or simultaneously. CONCLUSION: Some clinical or experimental support can be found in the literature for 10 specific mechanisms or proposed mechanisms of spinal cord stimulation. Implant System Types Currently there are three manufacturers of SCS implantable devices: ANS, Advanced Bionics and Medtronic. ANS has implantable programmable generator (IPG) systems, rechargeable generator, and radiofrequency (RF) systems. AB sells only rechargeable systems while Medtronic currently sells rechargeable and IPG systems. IPG systems incorporate a battery and stimulator generator in a sealed single unit which must be replaced when the battery life has expired. Typically current IPG systems last 3-7 years, but high current usage will cause a shorter life span, sometimes less than one year. High amperage and high frequency stimulation are the strongest determinants of early battery failure. The rechargeable IPG units are smaller than the corresponding IPG units and have solved some of the issues of limited battery life. Rechargeable units are believed to last 5-10 years, although one must be wary of claims of overzealous salesmen that state battery life may be up to 50 years. Most of the units implanted today are rechargeable units. Genesis (ANS) IPG
  8. 8. RECHARGEABLE IPG SYSTEMS While there are advantages and disadvantages to each company’s system, it is in general a good idea to implant devices only from companies that have a long track record of spinal cord stimulation devices that thereby shows the long term commitment to patients and physicians necessary for these potentially lifetime devices. The long term service required is a non- negotiable item and upstart companies may not have the finances or commitment to assure they will be available 10 years later when system revision is needed. The lead systems and generators are not necessarily interchangeable between different companies. The RF stimulation unit manufactured by ANS uses an external battery pack/controller which transmits RF energy transcutaneously to a subcutaneous radio receiver which is connected to the stimulator leads. Advantages of such a unit include lack of expensive IPG surgical replacement (rechargeable batteries are used in the control pack), expanded programmability characteristics which is useful in complex or positionally related pain, and the capability of a very high stimulation frequency which is far higher than available in IPGs (this characteristic is useful in sacral nerve stimulation). RF units are better suited to patients with normal to high current demands during the SCS trial. Disadvantages of RF systems include convenience since there is an external antenna ring which must be applied directly over the receiver, minimum of one amp current (less is often needed for nerve root stimulation such as sacral nerve), inability to use the system in water, and the need to change the rechargeable batteries every day in the external battery pack. This lack of convenience may be a great deterrent in the use of RF units. Since both rechargeable and non rechargeable IPG units are totally implanted, there are no external components visible. ANS, AB, and Medtronic provide an external control unit for their IPGs. Both IPG and RF units may be connected to the leads with or without extension wires, however Medtronic always uses extensions while with ANS this is optional.
  9. 9. Lead Types Fundamentally there are two types of lead: percutaneous (round) leads and neurosurgical (flat) leads. The percutaneous leads are almost always used during spinal cord stimulator trials and by pain medicine surgeons during permanent implants. The round leads may be placed through a 14ga Tuohy needle into the epidural space while the neurosurgical lead arrays require a partial laminectomy performed by a neurosurgeon (NS) or orthopedic spine surgeon (OSS). Round leads have a tendency to migrate more often than neurosurgical leads, have less favorable spinal stimulation characteristics (inadvertent and sometimes painful stimulation of the fibers of the ligamentum flavum), and may have slightly less transverse stimulation profiles when dual leads are used. Flat lead placement requires a NS or OSS, laminectomy, overnight hospital stay, and may be difficult to guide to the proper level. Whereas round leads are usually guideable in the spinal canal from levels far distal to the final placement, flat leads must be placed immediately under the final resting position of the lead. In some practice situations, the pain medicine interventionalist will place the trial leads while the NS or OSS will perform the permanent implant with the neurosurgical leads. In other practice situations, the pain medicine interventionalist will perform both the trial and the implantation of the permanent lead systems, but using a round lead for permanent placement. While this is a political issue and reimbursement issue (NS and OSS collect an additional fee for the laminectomy), the issue of patient safety is a real consideration. Those without surgical skills or any surgical training may wish to utilize the NS or OSS for permanent lead implantation. Because the Medtronic and ANS lead systems are currently incompatible with AB systems. In general, the generator and company must be chosen to match the leads, however ANS has implantable conversion kits available to permit use of their generator with the Medtronic leads. The chart below compares the differences in the percutaneous leads: Laminectomy
  10. 10. Electrodes Contact Size (mm) Electrode Spacing (mm) Vertebral bodies covered Pices Quad (Medtronics) 4 3 6 1 Pices Quad Compact (Medtronics) 4 3 4 1 Pices Quad Plus (Medtronics) 4 6 12 2 Octrode (ANS) 8 3 4 2 Quatrode (ANS) 4 3 4 1 Advantages of the octrode lead include less chance of having to replace the lead since it spans a larger segment of spine. Reprogramming is possible. Disadvantages are the need for having the lead completely parallel to the spine if migration concerns are a consideration. Generally these are theoretical concerns with the trial leads since the trial period is so short, but can be of significance with permanent lead implant. The Medtronic Quad plus spans two vertebral spaces just as the octrode (ANS), but the spacing between the electrodes is very large. Cross stimulation and adjacent electrode coverage may be incomplete. The pices quad compact uses a compact lead design for maximum programming flexibility, but spans only one vertebral body. Since I have used both systems, it is my opinion that familiarity with the representative and the system is the most important feature. Trial Lead Placement Typically, the spinal cord stimulator trials are 3-14 days, although the Belgian trials were conducted for a period of 3 months with no evidence of an increased infection rate. Types of SCS trials are: 1. Percutaneous temporary lead trials…use disposable leads which are less expensive than the permanent leads. Later, the patient is brought back into the office and the leads are simply pulled out at the end of the trial. If the trial is successful and the patient meets all other criteria, a permanent lead system plus stimulator generator is implanted approximately 1-4 weeks later. There should be at least one week of time between the removal of the temporary leads and the permanent system implant in order to permit the epidural tract to close. It is suggested this method of performance of SCS trials be used when initially beginning to implant SCS or when there is a question in the physician’s mind regarding appropriate patient selection. 2. Permanent lead placement with anchoring to the interspinous ligament with concomitant extension wire use to connect the permanent lead to the trial box. During generator (or RF receiver) implantation, the extension is removed through the
  11. 11. skin and discarded. This method saves a step of lead replacement. Many experienced implanters are now using this method. 3. Neurosurgical lead initial placement with extension wire to the external trial box. As above, with a successful trial, the extension wire is discarded and the generator stimulator unit is implanted during the second step.he most important technical factor in determining lead placement is knowing the corresponding anatomical level of anticipated spinal stimulation with respect to the target pathology. The diagram below demonstrates this. Percutaneous Lead Placement for SCS Trial One or two leads are used for a SCS trial, depending on the location of pathology and the Dual Octrode Leads
  12. 12. need for cross stimulation between leads. For lower extremity pain and low back pain coverage, the entry point into the ligamentum flavum is chosen to be L1-2 or L2-3 (it is suggested for those inexperienced with epidural needle placement that L3-4 be the point of entry in order to avoid the spinal cord). Needle placement is slightly paramedian, usually on the side to be covered, at a rather acute angle to the skin when possible. Often the entry point in the skin is at 1 to 1 ½ vertebral levels lower than that of the ligamentum flavum penetration point. The glass syringe-saline loss of resistance technique is used with occasional use of iodinated contrast injection when necessary. Obviously, fluoroscopy must be used for placement. Use of cones and filters is suggested to reduce radiation exposure. Advancement is made under AP fluoroscopy true to the spine, ie. spinous processes aligned in the middle of the spine. Typically, during lead advancement is made on the same side as needle entry unless midline final placement is desired. Occasionally, final lead placement on the contralateral side is used when advancement unilaterally is not feasible due to anatomical considerations. During lead advancement, care must be taken to avoid the lead’s tendency to “dive” anterior-laterally into the lateral gutter, which often occurs when the lead tip moves lateral to a point halfway between the spinous process and the medial pedicular line.. Use of the guidance angle on the lead tip can help prevent this. As a first approximation, the lead tip is placed in the T9-11 region dependent on the pathology. Obstructions encountered during advancement of leads include ligamentum flavum or zygapophyseal hypertrophy, peridural fibrosis, dorsal fat pad, Batson’s epidural venous plexus, and dura. Care should be taken not to be too vigorous in attempts to pass a lead when excessive force is required lest spinal cord damage or dural penetration ensue. If the lead continues to Tuohy Needle Placed with Temporary Lead Dual Quad Leads
  13. 13. veer off the midline during lead placement, removal of the stylette from the lead followed by introduction of a 20 degree bend on the stylette then replacement of the stylette in the lead is helpful. Never externally intentionally bend the leads themselves as this may cause lead fracture. Reserve any bending manipulations to the stylette. If placement is not possible due to scar tissue, hypertrophied ligamentum flavum, or a small canal, care must be taken on any further lead advancement due to potential injury. However, the use of an Introde over the lead to stent the part of the lead in the epidural space between the tip and the entry point into the epidural space may permit further lead advancement and manipulation. Finally, use of a lead blank or a stiffer stylette may be necessary to create lead passage. After the patient is awake from anesthesia (we prefer to avoid midazolam be used since this drug slows the patient response: propofol is the preferred sedative if any sedation is used during lead placement), then stimulation is performed using a moderate frequency 100-150 hz, and various cathodes are activated during advancement of the amperage. Optimal placement is when the middle electrodes are active. If a low stimulation current (<1 mA) is possible with good stimulation (feeling of a tingly sensation covering the painful area), then the electrodes are closest to the ideal location. When two leads are used, a staggered array is preferable as demonstrated above for final placement. Increasing the frequency is sometimes needed for spreading the coverage area, or alternatively, one may change the cathode/anode array. Cross stimulation from one lead to that on the contra-lateral side is possible and is useful for primary low back pain syndromes. High frequency stimulation (>300 hz) is sometimes necessary to provide pain relief. (Bennet, Alo, Oakley, Feler 1999 "Higher frequencies of stimulation were found to be essential in re-establishing pain control in 15.5% of the patients using dual-octapolar systems. Of the 71 patients in this group, 11 lost pain control in the presence of paresthesia coverage over the area of described pain. With use of frequencies greater than 250 Hz (with no change or an increase in pulse width), all had return of pain control” Repositioning of the leads with the epidural needle still in place is sometimes necessary when coverage dictates a placement alternative to the initial placement. Some physicians utilize an Epimed RK needle which does not have the sheering quality as a Tuohy if they are frequently advancing and retracting leads. Once final placement is assured, the lead is either secured to the skin using benzoin or mastosol which is then covered with a clear plastic dressing. Alternatively, the lead can be stitched into place. The programmer is attached in the recovery area and the patient is sent home for a 3-14 day trial. During the trial period, oral antibiotic coverage may be desirable. A positive trial is one in which Crossover Lead Array for Bilateral Coverage with One Lead
  14. 14. 60% pain relief or 60% increase in function is possible, no painful stimulation, the stimulation pattern covers the painful area, the patient is able to tolerate the sensation of continuous stimulation of the back or extremities, etc. For many implanters, a higher standard of 75% reduction in the constant burning pain is used (independent of mechanical pain). After the completion of the trial period, the leads placed percutaneously are removed in the office, and if successful, permanent implantation may be scheduled anytime after one week has elapsed since lead removal. The permanent implant system used is partially dependent on the amperage used during the trial, patient convenience, and on whether the patient would ever be a candidate for a replacement generator in the future (Medicaid does not pay facilities sufficiently to implant spinal cord stimulation systems). Those utilizing high currents or voltage during the trial may benefit from a RF system or rechargeable IPG since the battery life will be depleted with that high of a current drain. Also, one may consider implantation of neurosurgical leads in such an instance in order to reduce the current used (reduces power consumption by 25-50%). Cervical spinal cord trial lead placement should always be performed with a interlaminar entry site at C7T1 or below. In up to 25% of patients, there is anatomically no posterior epidural space above the level of C6, therefore just as with interlaminar epidural steroid placement, advancement of a catheter or lead from below this level is desirable. It is strongly suggested at least 10 lumbar epidural SCS be placed before advancing to cervical levels. Complications of Trial SCS Lead Placement 1. Superficial infection 2. Subdural puncture with resultant post-dural puncture headache (depends on the experience of the physician) 3. Deep epidural infection (rare) 4. Meningitis (rare) 5. Local irritation without infection (common) 6. Lead migration (common) 7. Lead fracture (rare) 8. Spinal cord or nerve root injury 9. Patient intolerance of stimulation pattern 10. Shock due to patient inability to properly use programmer 11. Bleeding from around lead entry site It is suggested that a log book be maintained with check off areas to assure proper follow through and billing is achieved. The patients names are logged into the book followed by spaces to write in clinical diagnosis, and checkoff spaces for conservative therapy failed, not a candidate for definitive surgery, psych eval completed, physical therapy eval completed, patient history and physical complete, trial date, success of trial, implant date, follow up date for post operative visit. In addition, the type and number of leads should be noted along with the specific system chosen. This log book will serve as a ready
  15. 15. reference for insurance and referral purposes, and will also permit ready access to information which is needed in case of a problem or complication. Comparison of Various Non Rechargeable SCS Generators Genesis XP (ANS) Synergy (Medtronics) Renew (ANS) Type IPG IPG RF Amplitude 0-25 mA (12.5V) 0-10.5V 0-12V Pulse Width 52-507 microsecs 60-450 microsecs 10-500 microsecs Current Regulated Yes No No Size mm 70x58x14 76x61x15 50x35x15 Vol cm3 46 51 26 Weight g 81 83 30 Battery Capac Amp-hrs 8.2 6.4 Rechargeable External No. electrodes 8 8 16 Lead extensions Optional Mandatory Optional # programs 24 1 24 # stimulation sets 2 2 8 Permanent System Implantation
  16. 16. Perhaps the most important feature in permanent system implantation is the patient response to the trial lead. Other factors which are of paramount importance are patient understanding of complications of permanent system implantation. These include: Lead complications: lead migration (25% of round leads), lead fracture, lead disconnection from the generator or extension, cord compression, epidural hematoma, epidural abscess, dural leak, spinal cord injury during or after placement Generator complications: migration with weight gain or too large of a pocket, generator flip resulting in inability to program or access generator, pain from generator over iliac crest or ribs, seroma, infection resulting in removal of generator and leads, patient weight gain resulting in erosion of stimulator or leads through the skin, shock, generator battery failure or early depletion, potential for spinal cord injury due to diathermy or MRI, potential for SCS failure due to airport magnetic screening. System complications: gradual loss of pain relief (20%) The ANS product warning is listed as follows: Warnings/Precautions/Adverse Events Safety has not been established for pregnancy or pediatric use. Patients should not drive or use dangerous equipment during stimulation. Systems may be affected by or adversely affect cardioverter/defibrillators, external defibrillators, MRIs, diathermy, ultrasonic equipment, electrosurgical equipment, radiation therapy, theft detectors, security systems, and aircraft communications systems. Adverse events may include: undesirable changes in stimulation described by some patients as uncomfortable, jolting, or shocking; epidural hemorrhage, hematoma, infection, spinal cord compression, paralysis, chest wall stimulation, CSF leakage, pain at implant site, seroma, allergic response, hardware malfunction or migration, loss of pain relief, and surgical risks. Patient selection criteria includes psychological origin for the pain, appropriate surgical candidate, detoxification from narcotics, and availability of long-term, post-surgical management. Diathermy Therapy — Do not use short-wave diathermy, microwave diathermy, or therapeutic ultrasound diathermy (all now referred to as diathermy) on patients implanted with a neurostimulation system. Energy from diathermy can be transferred through the implanted system and cause tissue damage at the location of the implanted electrodes, resulting in severe injury or death. Diathermy is further prohibited because it may also damage the neurostimulation system components resulting in loss of therapy, requiring additional surgery for system implantation and replacement. Injury or damage can occur during diathermy treatment whether the neurostimulation system is turned "on" or "off." All patients are advised to inform their health care professional that they should not be exposed to diathermy treatment.
  17. 17. Potential complications should be discussed in detail with the patient prior to permanent implantation, and should be included on the consent form. Generally, neurosurgical lead placement requires an overnight hospital stay whereas the flat lead placement, without a laminectomy, may be performed as an outpatient implant. General anesthesia, MAC, or local anesthesia can be used for permanent implantation. However, if during the permanent implantation of the generator lead implantation is also performed, it is suggested that MAC anesthesia be used. Local anesthesia is reserved for patients in which the permanent leads have already been placed, and the extension has also been placed. It is very painful to the patient to have the tunneling of the lead from the spine to the pocket under strict local anesthesia, therefore if the leads plus generator need implantation, MAC is useful. General is not the preferred anesthetic during lead plus generator placement surgeries since the patient does need to respond to questions during lead placement. General anesthesia may be used if the permanent leads were placed, anchored, and tunneled subcutaneously for the trial. There is a report of spinal anesthesia being used during lead placement, but this is fraught with potential problems both technically and medico-legally.
  18. 18. Permanent lead plus generator implantation uses scrupulous surgical skin prep, IV antibiotics, and appropriate anesthesia to provide a quiet field. One such technique involves placement of the leads percutaneously followed by advancement of the leads through the needles. A piggyback paramedian approach may be used or a bilateral paramedian approach for dual lead placement. Once the leads have been tested to cover the appropriate area with the patient awake and responsive, an incision is made around the lead and carried down to the intraspinous ligament. A lead anchor is placed over the lead which is subsequently secured to the interspinous ligaments with non-absorbable suture. This is the most critical part of permanent implantation, and Medtronics has adopted the tact of using 4 separate anchoring sutures into the interspinous ligaments. Deep retractors may be needed for such procedure and hemostasis is attained through electrocautery. Once the lead is anchored securely, the generator pocket is developed by a separate incision in the subcutaneous tissues above the gluteus musculature. Some implanters prefer to use a lateral or anterolateral abdominal pocket, but this is technically more difficult. The pocket is developed rather superficially since the generator must communicate through the skin with the RF powered programmer. A tunneling device is used to pass the leads from the spinous incision to the generator pocket. In the case of Medtronics products, a lead extension is used due to the short length of the leads, whereas with the ANS products, the extension is optional. Silastic boots are used over the lead connection points and are secured with silk ties. The generator itself does
  19. 19. developed by a separate incision in the subcutaneous tissues above the gluteus musculature. Some implanters prefer to use a lateral or anterolateral abdominal pocket, but this is technically more difficult. The pocket is developed rather superficially since the generator must communicate through the skin with the RF powered programmer. A tunneling device is used to pass the leads from the spinous incision to the generator pocket. In the case of Medtronics products, a lead extension is used due to the short length of the leads, whereas with the ANS products, the extension is optional. Silastic boots are used over the lead connection points and are secured with silk ties. The generator itself does not require suturing to underlying tissues. This necessitates the development of a pocket that is just very slightly larger than the generator itself in order to maintain generator orientation with the receiver side of the generator directed towards the skin. SCS leads are secured to the generator with set screws. ANS uses a torque screwdriver which prevents overtightening. Final skin closure is in layers with a subcutaneous absorbable suture, and skin staples or subcuticular stitch for superficial closure. In the case of the Renew RF system, it is not activated for about 10 days after implantation to allow skin healing. The IPG systems may be activated immediately. Post operative instructions include avoidance of trunk flexion, no lifting or elevation of hands above
  20. 20. the head or sleeping prone for at least 3 weeks, no immersion bathing or showering until the post operative checkup at 7-10 days, no massages for at least 2 months, no vigorous exercise for at least 2-3 months. SCS Success Rates for Various Conditions (Kim Burchiel, MD) Overall 50% of patients who received a SCS trial lead had a successful permanent implant, but 78% of those with a successful trial had a successful permanent implant. The relatively low overall success rate above demonstrates poor patient selection. This underscores the need for SCS trials to effectively screen patients before a permanent spinal cord stimulator implantation system. Obviously, patient selection plays a great part in determining success. Patients without significant psychological aberrations and who are competent without histrionic behavior and have peridural fibrosis with radicular pain are far more likely to have a successful trial and implant than those patients with multiple psychiatric diseases and generalized pain disorders. The better we become at patient selection before trial SCS lead placement, the better will be our rate of successful trials and ultimately successful permanent implants. Selected Additional SCS Outcome Studies:
  21. 21. Neurology 2002 Oct 22;59(8):1203-9 Economic evaluation of spinal cord stimulation for chronic reflex sympathetic dystrophy. Kemler MA, Furnee CA. Department of Surgery, Maastricht University Hospital, Maastricht, The Netherlands. kemlerm@mzh.nl OBJECTIVE: To evaluate the economic aspects of treatment of chronic reflex sympathetic dystrophy (RSD) with spinal cord stimulation (SCS), using outcomes and costs of care before and after the start of treatment. METHODS: Fifty-four patients with chronic RSD were randomized to receive either SCS together with physical therapy (SCS+PT; n = 36) or physical therapy alone (PT; n = 18). Twenty-four SCS+PT patients responded positively to trial stimulation and underwent SCS implantation. During 12 months of follow-up, costs (routine RSD costs, SCS costs, out-of-pocket costs) and effects (pain relief by visual analogue scale, health-related quality of life [HRQL] improvement by EQ-5D) were assessed in both groups. Analyses were carried out up to 1 year and up to the expected time of death. RESULTS: SCS was both more effective and less costly than the standard treatment protocol. As a result of high initial costs of SCS, in the first year, the treatment per patient is $4,000 more than control therapy. However, in the lifetime analysis, SCS per patient is $60,000 cheaper than control therapy. In addition, at 12 months, SCS resulted in pain relief (SCS+PT [-2.7] vs PT [0.4] [p < 0.001]) and improved HRQL (SCS+PT [0.22] vs PT [0.03] [p = 0.004]). CONCLUSIONS: The authors found SCS to be both more effective and less expensive as compared with the standard treatment protocol for chronic RSD. Neurosurgery 2002 Aug;51(2):381-9; discussion 389-90 Spinal cord stimulation electrode design: prospective, randomized, controlled trial comparing percutaneous and laminectomy electrodes-part I: technical outcomes. North RB, Kidd DH, Olin JC, Sieracki JM. Department of Neurosurgery, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21287-7713, USA. rnorth@jhmi.edu OBJECTIVE: The clinical use of spinal cord stimulation for treatment of chronic intractable pain has been increasingly successful because of recent technical improvements, particularly the development of multiple-contact electrodes supported by programmable implanted pulse generators. Contemporary electrodes can be placed percutaneously in some cases and require a limited laminectomy in other cases. METHODS: We performed a prospective, randomized, controlled trial comparing two prototypical electrode designs, using a computerized system that allows direct patient interaction and quantitative measurements. A series of 24 patients with chronic lumbosacral pain syndromes first underwent testing with percutaneous four-contact electrodes and then underwent implantation, at the same spinal level, of one of two different electrode configurations; 12 patients received a new percutaneous four-contact electrode of the same design and 12 received an insulated four-contact array, which was implanted via laminectomy.
  22. 22. RESULTS: The insulated array performed significantly (P = 0.0005-0.0047) better than the temporary percutaneous electrode for the same patients, according to all three measures tested (ratings of paresthesia coverage of pain, coverage calculated from patient drawings, and amplitudes), at the "usage" amplitude for the three standard bipoles examined. The insulated array also performed significantly (P = 0.0000-0.026) better than the permanent percutaneous electrode in terms of coverage ratings and amplitude requirements. Low back coverage ratings were significantly better for the insulated array than for the temporary percutaneous electrode, and scaled amplitudes necessary for low back coverage were significantly better for the permanent percutaneous electrode than for the temporary electrode. In comparison with the percutaneous temporary electrode, at subjectively identical stimulation intensities, the permanent insulated array required significantly lower amplitude. CONCLUSION: We can immediately infer from these technical data that the use of an insulated array, in comparison with a percutaneous electrode, would double battery life. Extended follow-up monitoring will be required to assess the extent to which the technical advantages we observed for the insulated array might be associated with improved clinical outcomes. Neurosurgery 1995 Jun;36(6):1101-10; discussion 1110-1 Prognostic factors of spinal cord stimulation for chronic back and leg pain. Burchiel KJ, Anderson VC, Wilson BJ, Denison DB, Olson KA, Shatin D. Division of Neurosurgery, Oregon Health Sciences University, Portland, USA. Spinal cord stimulation (SCS) has been used for more than 20 years in the treatment of diverse pain conditions. Although recent studies have identified more clearly those conditions for which SCSoffers a favorable prognosis, the identification of a patient population in whom reasonably long-term success can be expected has been difficult. In an effort to improve patient selection and increase the overall success rate of treatment, we have examined various physical, demographic, and psychosocial variables as predictors of SCS outcome. The study population consisted of 40 patients with chronic low back and/or leg pain, 85% of whom were diagnosed with failed back surgery syndrome. Medical history and demographic data were collected as part of an initial assessment along with patient responses to the Minnesota Multiphasic Personality Inventory, the visual analogue pain rating scale (VAS), the McGill Pain Questionnaire, the Oswestry Disability Questionnaire, the Beck Depression Inventory, and the Sickness Impact Profile. Treatment outcomes were examined and found to improve significantly after 3 months of stimulation. Subsequent regression analysis revealed that patient age, the Minnesota Multiphasic Personality Inventory depression subscale D, and the evaluative subscale of the McGill Pain Questionnaire (MPQe) were important predictors of posttreatment pain status. Increased patient age and D subscale scores correlated negatively with pain status, as measured by the percentage of changes in pretreatment and posttreatment VAS scores, % delta VAS. In contrast, higher MPQe correlated with improved pain status. By the use of the following equation and the definition commonly associated with SCS success (at least 50% decrease in the VAS pain
  23. 23. level), the success or failure of 3 months of SCS was correctly predicted in 88% of the study population. Our results suggest that patient age, Minnesota Multiphasic Personality Inventory depression, and MPQe may be clinically useful in the prediction of pain status after 3 months of SCS in patients with chronic low back and/or leg pain. % delta VAS = 112.57 - 1.98 (D)-1.68 (Age) + 35.54 (MPQe). Z Orthop Ihre Grenzgeb 2002 Nov-Dec;140(6):626-31 [Spinal Cord Stimulation (SCS) using an 8-pole Electrode and Double-Electrode System as Minimally Invasive Therapy of the Post-Discotomy and Post-Fusion Syndrome - Prospective Study Results in 34 Patients] [Article in German] Rutten S, Komp M, Godolias G. Klinik fur Orthopadie am Lehrstuhl fur Radiologie und Mikrotherapie, Universitat Witten/Herdecke, Ressort Wirbelsaulenchirurgie und Schmerztherapie, St.-Anna-Hospital Herne, Deutschland (Direktor: Prof. Dr. med. Georgios Godolias). AIM: Therapy of a pronounced post-discotomy (PDS) and post-fusion syndrome (PFS) is often unsatisfactory because of the complexity and multifactorial pain genesis. If surgical interventions cannot promise relief and if the entire interdisciplinary spectrum of conservative treatment measures is inadequate, the area of neuromodulative procedures offers spinal cord stimulation (SCS). The objective of this study was to examine the therapeutic possibilities of SCS using an 8-pole electrode and double electrode system in PDS and PFS with extensive back-leg pain areas. METHOD: An appropriate SCS system was implanted in 34 patients with PDS and PFS. Follow-up examinations were made prospectively over a period of 24 months using general criteria and psychometric test measuring instruments validated for German-language use. RESULTS: An 8-pole double electrode system was implanted 23 times, a single electrode sufficed in 11 cases. The area of pain was covered in all patients. This required special technical capabilities of the SCS system. The results remained constant over 24 months. The morphine dose could be reduced by at least 50 %. All measuring instruments confirmed a clear reduction in pain and improvement in quality of life as a result of SCS implantation. CONCLUSION: The SCS is an minimally invasive surgical procedure which can enlarge the therapeutical possibilities of pronounced PDS and PFS resistant to other modes of treatment. Special technical possibilities of parameter setting are required to cover the pain areas. Spine 2002 Nov 15;27(22):2584-91; discussion 2592 Spinal cord stimulation for chronic pain of spinal origin: a valuable long-term solution. North RB, Wetzel FT. Department of Neurosurgery, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA. rnorth@jhmi.edu STUDY DESIGN: A literature review was conducted. OBJECTIVE: To review the indications and efficacy of spinal cord stimulation, particularly in reference
  24. 24. to chronic pain of spinal origin. SUMMARY OF BACKGROUND DATA: The first spinal cord stimulation was implanted by Shealy in 1967 via a subarachnoid route. Early systems were plagued with a high rate of complications and technical problems. With the evolving technology, especially the advent of multichannel programmable systems and more precise epidural placement, the ability of spinal cord stimulation to treat various pain syndromes improved. This article reviews the literature on spinal cord stimulation from 1967 to the present. METHODS: The literature is reviewed, with a particular focus on recent studies investigating the efficacy of spinal cord stimulation for low back pain. RESULTS: Most studies are limited by the same flaws, namely, retrospective study design. At this writing, the few published randomized prospective studies have suggested that spinal cord stimulation may be superior to repeat surgery. Complication rates have declined to approximately 8%, and reoperation is necessary in approximately 4% of patients. When current percutaneous techniques are used, a lead migration rate lower than 3% may be achieved. For certain topographies, laminotomy leads may be superior, particularly with regard to low back pain. CONCLUSIONS: The ultimate efficacy of spinal cord stimulation remains to be determined, primarily because of limitations associated with the published literature. However, on the basis of the current evidence, it may represent a valuable treatment option, particularly for patients with chronic pain of predominantly neuropathic origin and topographical distribution involving the extremities. The potential treatment of other pain topographies and etiologies by spinal cord stimulation continues to be studied. Cardiology 2003;99(1):20-4 Cost-Effectiveness of Spinal Cord Stimulation versus Coronary Artery Bypass Grafting in Patients with Severe Angina Pectoris - Long-Term Results from the ESBY Study. Andrell P, Ekre O, Eliasson T, Blomstrand C, Borjesson M, Nilsson M, Mannheimer C. Multidisciplinary Pain Centre, Sahlgrenska University Hospital/Ostra, Goteborg, Sweden. The present study is a 2-year follow-up of the 104 patients participating in the ESBY study (Electrical Stimulation versus Coronary Artery Bypass Surgery in Severe Angina Pectoris), a randomised prospective study including patients with increased surgical risk and no prognostic benefit from revascularisation. Hospital care costs, morbidity and causes of death after spinal cord stimulation (SCS) and coronary artery bypass grafting (CABG) were assessed, as well as the complication rate of SCS treatment. SCS proved to be a less expensive symptomatic treatment modality of angina pectoris than CABG (p < 0.01). The SCS group had fewer hospitalisation days related to the primary intervention (p < 0.0001) and fewer hospitalisation days due to cardiac events (p < 0.05). The groups did not differ with regard to causes of death. There were no serious complications related to the SCS treatment. Copyright 2003 S. Karger AG, Basel
  25. 25. Anesth Analg 2002 Mar;94(3):694-700; table of contents Spinal cord stimulation in postherpetic neuralgia and in acute herpes zoster pain. Harke H, Gretenkort P, Ladleif HU, Koester P, Rahman S. Department of Anesthesia and Pain Therapy, Klinikum Krefeld, Krefeld, Germany. We studied the effects of spinal cord stimulation (SCS) on postherpetic neuralgia (PHN). Data of 28 patients were prospectively investigated over a median period of 29 (quartiles 9--39) mo. In addition, four patients with acute herpes zoster (HZ) pain were studied simultaneously. After intractable pain for more than 2 yr, long-term pain relief was achieved in 23 (82%) PHN patients (median, 70 yr) during SCS treatment confirmed by a median decrease from 9 to 1 on the visual analog scale (P < 0.001). In five cases with serious comorbidity, the initial pain alleviation could not be stabilized. Spontaneous improvement was always confirmed or excluded by SCS inactivation tests at quarterly intervals. Eight patients discontinued SCS permanently because of complete pain relief after stimulation periods of 3--66 mo, whereas 2 reestablished SCS because of recrudescence after 2 and 6 mo. Considerable impairments in everyday life, objectified by the pain disability index, were also significantly improved (P < 0.001). In 4 patients with acute HZ pain, SCS was promptly effective and after periods of 2.5 (quartiles 2--3) months the pain had subsided. SCS seems to offer a therapeutic option for pharmacological nonresponders. IMPLICATIONS: In many patients with postherpetic neuralgia and acute herpes zoster pain is not satisfactorily alleviated with pharmacological approaches. We report on 23 of 28 patients with postherpetic neuralgia and 4 of 4 with acute herpes zoster whose chronic pain was improved by electrical spinal cord stimulation. Am Surg 2001 Nov;67(11):1096-7 Clinical and objective data on spinal cord stimulation for the treatment of severe Raynaud's phenomenon. Neuhauser B, Perkmann R, Klingler PJ, Giacomuzzi S, Kofler A, Fraedrich G. Department of Vascular Surgery, University Hospital Innsbruck, Austria. Ischemic vascular disease of the upper extremity represents a difficult therapeutic problem wherein medical treatment often fails. Epidural spinal cord stimulation has been shown to be an effective alternative in severe peripheral arterial disease. Although this method has been used for nearly two decades only limited experience exists in Raynaud's phenomenon of the upper limbs. In addition objective parameters to prove therapeutic success are not well defined. Herein we describe a patient with severe primary Raynaud's phenomenon over several years who had significant pain relief and complete healing of ischemic digital ulcerations after spinal cord stimulation. Pain level was evaluated using a visual rating scale before and after surgery. Microcirculatory parameters were assessed before and after spinal cord stimulation by capillary microscopy and laser Doppler anemometry. Significant improvement of red blood
  26. 26. cell velocity, capillary density, and capillary permeability was demonstrated. At follow-up 18 months after surgery the patient had no complaints and all ulcerations of her fingertips had healed. Spinal cord stimulation appears to be an effective treatment in severe cases of Raynaud's phenomenon and we recommend its use in the case of failed medical therapy. Pain rating and capillary microscopy enable one to assess and visualize the effects of spinal cord stimulation. Br J Neurosurg 2001 Aug;15(4):335-41 Spinal cord stimulation--a long-term evaluation in patients with chronic pain. Kay AD, McIntyre MD, Macrae WA, Varma TR. Ninewells Hospital Medical School, Dundee, UK. adk4z@clinmed.gla.ac.uk Spinal cord stimulation (SCS) is an established treatment modality for chronic pain, angina pectoris, and peripheral vascular disease. This study evaluates experience with SCS over a 13-year period with emphasis on surgical complications, revisions and pain relief. It took the form of a retrospective study of medical/surgical records coupled with a postal/telephone questionnaire. The subjects consisted of seventy patients, aged from 21 to 76 years (mean 47; median 46), with severe, chronic pain refractory to conventional treatment, who underwent SCS implantation between 1984 and 1997. It investigated surgical revisions, complications and pain relief. There were 72 surgical revisions comprising electrode replacement/repositioning (32), generator replacement (22), cable failure (6) and implant removal (12). Half the devices were revised within 3 years (95% confidence interval: 2-5 years) of implantation. Six (8.6%) implants became infected. Sixty per cent of patients reported substantial relief of pain. This study shows that the majority of patients undergoing SCS derive significant benefit in terms of pain relief, but commonly require surgical revisions due to both technical and biological factors. These devices require systematic evaluation to determine optimal usage, clinical effectiveness and cost-benefit analysis. Eur J Pain 2001;5(3):299-307 Efficacy of spinal cord stimulation: 10 years of experience in a pain centre in Belgium. Van Buyten JP, Van Zundert J, Vueghs P, Vanduffel L. Department of Anaesthesia, AZ Maria Middelares, Hospitalstraat 17, B-9100 St. Niklaas, Belgium. vanbuyten@skynet.be Spinal cord stimulation is a minimally invasive mode of treatment in the management of certain forms of chronic pain that do not respond to conventional pain therapy. Several authors have reported encouraging findings with this technique. Over a 10-year period in a single centre, 254 patients were subjected to a trial period of spinal cord stimulation with an externalized pulse generator. Two hundred and seventeen of the patients showed satisfactory results justifying permanent implantation of a spinal cord stimulation system. In 1998, an independent physician invited 153 patients (155 pain cases), who still had
  27. 27. the system in place and who could be contacted, for an interview. The aim of this study was to evaluate the efficacy of an implanted spinal cord stimulation system in terms of pain relief and quality of life and to assess the accuracy of the patient selection criteria. The results of this study demonstrate a high success rate as evaluated by the patients' own assessments--68% of the patients rated the result of the treatment as excellent to good after an average follow-up of almost 4 years. The resumption of work by 31% of patients who had been working before the onset of pain supports these positive findings. Copyright 2001 European Federation of Chapters of the International Association for the study of Pain. N Z Med J 2001 Apr 27;114(1130):179-81 Comment in: N Z Med J. 2001 Aug 10;114(1137):365-6. N Z Med J. 2001 Aug 10;114(1137):366. Cost-effectiveness of spinal cord stimulation in patients with intractable angina. Merry AF, Smith WM, Anderson DJ, Emmens DJ, Choong CK. Department of Anaesthesia, Green Lane Hospital, Auckland. glanaest@ahsl.co.nz AIM: To review the cost of healthcare utilisation by patients suffering from intractable angina, unsuitable for coronary revascularisation, before and after treatment with spinal cord stimulation. METHODS: Data were collected for eight patients treated for intractable angina with spinal cord stimulation at Green Lane Hospital before April 1999. Information on consumption of specified medica resources for the twelve months preceding implantation, the implantation period, and the twelve months following implantation was collected. Where available, data were also collected for the eighteen months preceding and following treatment. RESULTS: In six patients successful permanent stimulation was established; in two it proved technically impossible to implant a stimulator. The six patients with successful stimulation spent fewer days in hospital (p=0.028) and consumed fewer resources (p=0.046) following implantation than in the period before implantation. The two patients for whom spinal cord stimulation was unsuccessful spent more days in hospital and consumed more resources in the twelve months following, than in the twelve months preceding attempted implantation. Extrapolation of data for all eight patients suggests that, on average, the cost of implanting a spinal cord stimulator will be recovered in approximately fifteen months. CONCLUSION: Spinal cord stimulation is a cost-effective treatment for intractable angina pectoris. Neurosurgery 2001 May;48(5):1056-64; discussion 1064-5 Spinal cord stimulation for nonspecific limb pain versus neuropathic pain and spontaneous versus evoked pain. Kim SH, Tasker RR, Oh MY. Department of Neurosurgery, Yeungnam University, Taegu, Korea.
  28. 28. OBJECTIVE: To compare the outcome of spinal cord stimulation (SCS) in patients with nonspecific limb pain versus patients with neuropathic pain syndromes and in patients with spontaneous versus evoked pain. METHODS: A retrospective review of 122 patients accepted for treatment with SCS between January 1990 and December 1998 was conducted. All patients first underwent a trial of SCS with a monopolar epidural electrode. Seventy-four patients had a successful trial and underwent permanent implantation of the monopolar electrode used for the trial (19 patients), or a quadripolar electrode (53 patients), or a Resume quadripolar electrode via laminotomy (2 patients). RESULTS: Of the 74 patients, 60.7% underwent implantation of a permanent device and were followed for an average of 3.9 years (range, 0.3-9 yr). Early failure (within 1 yr) occurred in 20.3% of patients, and late failure (after 1 yr) occurred in 33.8% of patients. Overall, 45.9% of patients were still receiving SCS at latest follow-up. Successful SCS (>50% reduction in pain for 1 yr) occurred in 83.3% of patients with nonspecific leg pain, 89.5% of patients with limb pain associated with root injury, and 73.9% of patients with nerve neuropathic pain. SCS was less effective for the control of allodynia or hyperpathia than for spontaneous pain associated with neuropathic pain syndromes. Third-party involvement did not influence outcome. There was a lesser incidence of surgical revisions when quadripolar leads were used than with monopolar electrodes. CONCLUSION: SCS is as effective for treating nonspecific limb pain as it is for treating neuropathic pain, including limb pain associated with root damage. N Engl J Med 2000 Aug 31;343(9):618-24 Spinal cord stimulation in patients with chronic reflex sympathetic dystrophy. Kemler MA, Barendse GA, van Kleef M, de Vet HC, Rijks CP, Furnee CA, van den Wildenberg FA. Department of Surgery, Maastricht University Hospital, The Netherlands. mkeml@shee.azm.nl BACKGROUND: Chronic reflex sympathetic dystrophy (also called the complex regional pain syndrome) is a painful, disabling disorder for which there is no proven treatment. In observational studies, spinal cord stimulation has reduced the pain associated with the disorder. METHODS: We performed a randomized trial involving patients who had had reflex sympathetic dystrophy for at least six months. Thirty-six patients were assigned to receive treatment with spinal cord stimulation plus physical therapy, and 18 were assigned to receive physical therapy alone. The spinal cord stimulator was implanted only if a test stimulation was successful. We assessed the intensity of pain (on a visual-analogue scale from 0 cm [no pain] to 10 cm [very severe pain]), the global perceived effect (on a scale from 1 [worst ever] to 7 [best ever]), functional status, and the health-related quality of life. RESULTS: The test stimulation of the spinal cord was successful in 24 patients; the other 12 patients did not receive implanted stimulators. In an intention-to-treat analysis, the group assigned to receive spinal cord stimulation plus physical
  29. 29. therapy had a mean reduction of 2.4 cm in the intensity of pain at six months, as compared with an increase of 0.2 cm in the group assigned to receive physical therapy alone (P<0.001 for the comparison between the two groups). In addition, the proportion of patients with a score of 6 ("much improved") for the global perceived effect was much higher in the spinal cord stimulation group than in the control group (39 percent vs. 6 percent, P=0.01). There was no clinically important improvement in functional status. The health-related quality of life improved only in the 24 patients who actually underwent implantation of a spinal cord stimulator. Six of the 24 patients had complications that required additional procedures, including removal of the device in 1 patient. CONCLUSIONS: In carefully selected patients with chronic reflex sympathetic dystrophy, electrical stimulation of the spinal cord can reduce pain and improve the health-related quality of life. Advanced Techniques SCS may be used to treat interstitial cystitis through a retrocaudal approach to the caudal canal, through a trans- sacrococcygeal ligament approach, or trans-sacral foraminally. With the trans- sacrococcygeal ligament approach (the easier of the three), the leads are advanced to the level of S1 and with the tips more lateral than the base. This places the electrodes across the sacral nerves which can be stimulated by activating specific electrodes. Obviously, this works best with the ANS octrode since it possesses sufficient length and narrow enough electrode spacing to permit highly selective programming over a long distance. The Pices compact Retrocaudal Approach Sacrococcygeal Ligament Approach
  30. 30. quad lead works best transforaminally or retrocaudally. Peripheral nerve stimulation may also be used. Occipital nerve stimulation is possible with a lateral approach placing the lead directly over the x-ray projection of C1 and across the greater occipital nerve subcutaneously. The permanent generator is implanted in the anterior chest wall. This technique
  31. 31. often works extremely well for occipital neuralgia which responds to occip. N. blocks. Other peripheral nerves can be stimulated via the use of special flat leads with suture wings placed directly on peripheral nerves. Below is a picture of a dorsal scapular nerve stimulator placement. Dorsal root ganglion stimulation is possible by utilizing a trans-sacrococcygeal ligament placement, then curving the lead out the lateral foramen to the DRG. Stimulation at this location requires very low current and may be used for radicular pain which will not be amenable to definitive surgical intervention. Alternatively, placement of the lead in the lateral gutter of the spinal canal affords an opportunity to utilize low current stimulation of specific target nerves. Finally, utilization of spinal cord stimulation for non-traditional uses continues to grow. In Europe, the greatest use of SCS is not for low back or lumbar neurogenic pain, but for peripheral vascular disease. Use of SCS in PVD affords vasodilation of constricted vessels and improves circulation, except in advanced diabetes patients. Use of SCS as an alternative treatment for intractable angina is
  32. 32. increasing in the US. There are also uses reported for facial pain via specific trigeminal terminal branch stimulation. Obviously all these advanced techniques require training with experts and should not be attempted without appropriate training. Useful Links Advanced Neuromodulation Systems www.ans-medical.com Medtronics www.medtronics.com American Academy of Pain Medicine 4700 W. Lake Glenview, IL 60025 Phone (847) 375-4731 Fax (847) 375-6331 http://www.painmed.org./ American Academy of Physical Medicine and Rehabilitation One IBM Plaza, Suite 2500 Chicago, IL 60611-3604 Phone (312) 464-9700 Fax (312) 464-0227 http://www.aapmr.org/ American Chronic Pain Association P.O. Box 850 Rocklin, CA 95677-0850 (916) 632-0922 www.theacpa.org American Neuromodulation Society 6287 Cheshire Lane North, Minneapolis, MN 55311-4245 Phone (763) 559-4108
  33. 33. Fax (763) 559-4161 http://www.neuromodulation.org/ American Pain Foundation 11 South Calvert St. Suite 2700 Baltimore, MD 21202 Phone (914) 351-1010 http://www.painfoundation.org/ American Psychological Association 750 First Street NE Washington, DC 20002-4242. Phone (202) 336-5500 www.apa.org The American Society of Interventional Pain Physicians 2831 Lone Oak Road Paducah, KY 42003270 Phone (270) 554-9412 www.asipp.org American Society of Regional Anesthesia and Pain Medicine P.O. Box 11086 Richmond, VA 23230-1086 Phone (804) 282-0010 Fax (804) 282-0090 http://www.asra.com Arthritis Foundation 1330 Peachtree Street NW Atlanta, GA 30309 Phone (800) 283-7800 www.arthritis.org Canadian Pain Society 50 Driveway
  34. 34. Ottawa, ON K2P 1E2 Canada Phone (613) 234-0812 Fax (613) 234-9894 http://www.medicine.dal.ca/gorgs/cps/ International Association for the Study of Pain® 909 NE 43rd St., Suite 306 Seattle, WA 98105-6020 USA Phone (206) 547-6409 Fax (206) 547-1703 www.halcyon.com/iasp International Neuromodulation Society Thomas Jefferson University 1015 Chestnut Street, Suite 1400 Philadelphia, PA 19107 Phone (215) 955-4049 Fax (215) 923-4939 International Spinal Injection Society 10 Edgehill Way San Francisco, CA 94127 Phone (415) 661-6177 or (888) 255-0005 Fax (415) 661-6179 www.spinalinjection.com/ISIS1/ National Pain Foundation 3070 South Williams Denver, CO 80210 Phone (303) 756-0889 Fax (303) 692-8414 www.painconnection.org World Institute of Pain (WIP) http://www.wipain.org/ Government Resources National Institutes of Health (NIH)
  35. 35. www.nih.gov Pain and Neurological Disorders Information National Institute of Neurological Disorders Government web site that collects and disseminates research information related to neurological disorders. Phone (800) 352-9424 www.ninds.nih.gov/health_and_medical/disorder_index.htm U.S. House of Representatives www.house.gov/writerep/ U.S. Senate www.senate.gov Insurance and Reimbursement Information Centers for Medicare and Medicaid Services National healthcare insurance information and disease coverage, eligibility, enrollment, publications, and state contacts for questions; interactive database compares health plan options. Phone (800) 638-6833 www.hcfa.gov The American and International Neuromodulation Societies are the premier sources of information and advances in techniques via journal publication and annual meetings. SCS, intrathecal therapies, functional motor stimulation, and other advanced techniques are discussed. If you plan to perform either trials or permanent implants of SCS, it is strongly suggested you join the American Neuromodulation Society.

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