Vol. 3, Issue 4: Radiculopathies

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Vol. 3, Issue 4: Radiculopathies

  1. 1. Physicians South Anthony Dacunha, MD ELECTRODIAGNOSIS NEWSLETTER Volume 03, Issue 04, July 2001 RADICULOPATHIES PART 1 -THE LUMBAR SPINE 1- DEFINITION: Radiculopathies are conditions which affect the exiting spinal nerves. Pain with specific characteristics is the main symptom. A dysesthesic pain radiating from the spine to certain areas of the limbs and chest help localize the root/roots involved. Cauda Equina Syndrome is the name of a condition in which multiple roots are affected. Spinal canal stenosis, large central herniated discs and intrathecal tumors cause the Cauda Equina Syndrome. 2- ANATOMY: There are 8 cervical roots, 12 thoracic roots, 5 lumbar roots, 5 sacral roots and 1 coccigeal root in each side. In the lumbar area the L5 and SI roots are the most important in everyday clinical practice. In the neck it is important to know that only 7 vertebrae are present for the 8 roots. In the cervical spine the root is named by the vertebral body below. At the junction with the thoracic spine, above the 7th cervical vertebra the root is C7 and below is C8. From Tl the roots are named for the vertebral body above. The sensory ganglia are located distally to the roots. This is very important for the clinician and the neurodiagnostic consultant, considering that radiculopathies show normal findings in the sensory NCS as opposed to the plexopathies which are conditions involving the nerves distal to the sensory ganglia. The spinal cord ends at the Ll level but a few patients may have the spinal cord tethered at lower levels by lipomas from spina bifida.
  2. 2. 3- CLINICAL CONSIDERATIONS: The working diagnosis of a radiculopathy is given by the history. Do not expect findings in the neurological examination in the majority of patients. The explanation for this is in the complex neuronetwork found at the lumbosacral and brachial plexus. A detailed history is decisive and can give the location of the root affected. For instance, the SI root pain stops at the calf- ankle and the little toe feels numb and tingly. The L5 root pain settles at the popliteal fossa and the big toe feels numb and tingly. The lack of sensation in the perineal region is typical of the Cauda Equina Syndrome. The absence of the ankle reflex is common in the SI radiculopathies. Difficulties in tapping the foot on the floor and doing a deep knee bend are seen also in SI radiculopathies. The straight leg raising test is valuable, but only if done correctly. Pain alone is not enough to call the SLR test positive. It has to happen at around 45 degrees and reproduce the radicular pain as described in the history. The presence of tripping and crossing of symptoms to the other leg is clinically significant. 4- NEUROIMAGING: The development of the MRI in the late 1980's was a decisive step in the diagnosis and understanding of the radiculopathies. The plain X-Rays, the myelogram with pantopaque and the CT-myelogram were used but they are not nearly as valuable as the MRI. For the past five years the constantly evolving technology of the MRI reached the point in which a good MRI is more than enough for the imaging part of the evaluation of a radiculopathy. The CT- myelogram has a small niche, and this is in the evaluation of root avulsion from the cervical spinal cord. The MRI with contrast is valuable for the evaluation of patients with a history of previous surgery for herniated discs and helps distinguish scar tissue from a recurrent herniated disc. Discograms are useless and dangerous. 5- ELECTRODIAGNOSIS: Another major development in the evaluation of the radiculopathies is the use of Nerve Conduction Studies, Needle Electromyography, Somatosensory Evoked Potentials and the Motor Evoked Potentials (Magnetic Stimulation). In the 1980's the computer made the electrodiagnosis instruments more easy to use and reliable. Today the evaluation of a radiculopathy without electrodiagnosis is incomplete. The EDX can be invaluable for the surgeon prior to a decision to operate. A patient with a radiculopathy and a peripheral neuropathy ("Double crush syndrome") will have very poor results from the surgery. A patient with a herniated disc at L5-SI but with electrodiagnostic evidence for a L5 root lesion may not benefit from the surgery considering the small chance of the L5 root to be affected solely by a L5-SI herniated disc. The EDX may also give information about reinnervation and chronicity. A SI root which is permanently damaged shows large MUAP's with no sign of reinnervation or muscle membrane instability; and this indicates an almost certain poor result if the surgery is done.
  3. 3. NCS: The nerve conduction studies for the lumbar radiculopathies are invaluable mainly if a SI root lesion is suspected. The H-reflex is the most important test and should be done in every case of lumbar radiculopathy. The H-reflex is the EDX equivalent of the ankle reflex. The test is done by stimulation of the tibial nerve at the popliteal fossa and recording in the soleus muscle. The reflex may be absent in patients over 60 years of age. The most important information is from a unilateral prolongation of the latency indicating a SI root lesion. In the advanced radiculopathies the amplitude of the CMAP's may be reduced. The F-waves are not helpful in radiculopathies. Needle EMG: This is the best test and should be done with a plan. First the distal muscles are tested. If the Tibialis anterior shows evidence for "denervation" a L5 root lesion is suspected; then the Tensor Fascia Lata should be tested which is a proximal muscle by a different nerve. Last the paraspinals are tested. The paraspinal muscles are invaluable to the EDX consultant but the yield is low. If the gastrocnemius muscle shows evidence of "denervation" then a Sl root lesion is suspected and the Gluteus Maximus muscle should be tested, plus the paraspinals. SSEP's (Somatosensory Evoked Potentials): Are indicated when a Cauda Equina Syndrome is suspected (spinal stenosis, large central herniated discs and intrathecal tumors). The localization of the root involved is invaluable for the pain management physician to guide the selective nerve root blocking procedure. The identification of a peripheral neuropathy is important for the decision to start any type of treatment for an isolated radiculopathy. 6- TREATMENT: Most radiculopathies resolve with or without treatment. A few chronic cases, if a single root is identified by the EDX, may benefit from selective root blocking procedures. Acute or subacute large herniated discs compressing the root in the lateral recess, with no evidence of chronicity in the EDX, give the best results from surgical intervention (laminectomy in the lumbar area). Cauda Equina Syndrome from large central herniated discs should be corrected surgically. Rare cases of radiculopathy are caused by multiple myeloma, synovial cysts arising from the facets, compression by osteophytes, neurinomas and other neoplasias. Spinal Canal Stenosis is with an ill reputation as far as surgical procedures are concerned and is responsible for the vast majority of the so-called " failed back syndromes" (See Addendum). Anthony Dacunha, MD, Editor Board Certified in Neurology
  4. 4. NEWSLETTER - ADDENDUM THE "FORGOTTEN RADICULOPATHIES" The upper lumbar root/nerve lesions are frequently overlooked by clinicians and the lumbar canal spinal stenosis has a poor previous record. Both are considered the "forgoffen radiculopathies". 1- THE UPPER LUMBAR ROOTS: The LI, L2 and L3 roots are frequently forgotten by most non-neurologists but it is important to know a few facts related to these nerves. The genitofemoral nerve, the ilioinguinal nerve and the lateral femoral cutaneous nerve are all originated at the LI -L2-L3 group of roots and are exclusively sensorial nerves. As opposed to the lower roots, in the majority of the cases, one of the nerves above is involved and not the root itself. The genitofemoral nerve supplies sensory innervation to the groin and inner aspect of the thigh. The ilioinguinal nerve supplies sensory innervation to the pubic area and genital area (not to the perineum, which is innervated by the pudendal nerve). The two nerves above are frequently injured during surgical procedures in the lower abdomen, mainly gynecological laparoscopies. The genitofemoral nerve and the ilioinguinal nerve are superficial in the anterior wall of the lower abdomen and they cross each other at about the place where appendectomies are made. The lateral femoral cutaneous nerve entrapment at the inguinal ligament is the cause of Meralgia Paresthetica, which was the subject of an EDX Newslefter in August of 2000. Rarely a herniated disc; at LI-L2 or L2-L3 may cause the symptoms in the area of the three nerves. The iliohypogastric nerve is not important from a clinical point of view and runs in the retroperitoneal region and may be affected by neoplastic processes. Only the lateral femoral cutaneous nerve has EDX available for its evaluation. 2- SPINAL CANAL STENOSIS: The diagnosis of spinal canal stenosis is today a source of embarrassment for many in the medical profession, much like Reflex Sympathetic Dystrophy (RSD). After neuroimaging became available, mainly in the 1980's, a legion of patients was submitted to multilevel laminectomies with the placement of metal plates and many pedicle screws for the treatment of lumbar spinal canal stenosis. Many patients had up to five operations in their lower back and ended up labeled
  5. 5. "failed back syndrome". Many patients were involved in car accidents after the operations and the plates and screws broken and scattered all over the lumbar region. As a result, today, few doctors talk about spinal stenosis, and the radiologists avoid even mentioning the "dirty" word. As a matter of fact Lumbar Spinal Canal Stenosis is a common condition. The typical patient starts with recurrent lower back pain at an early age. They start to complain of lower back pain in the their 20's or 30's, and frequently there is a family history of lower back pain or even a " failed back syndrome". Later on sciatic pain starts and evolves to become bilateral with the typical forward bending posture and severe pain with extension of the lumbar spine. The reports from MRI's are usually not helpful since the radiologists frequently avoid the dreadful diagnosis. The patients with lumbar spinal canal stenosis are not candidates for surgical procedures and do not benefit, in general, from selective nerve blocking . The patients with spinal canal stenosis are usually the ones which are drug seeking and rejected by most doctors, even the pain management specialists. The use of a static bike and water aerobics is recommended for this population of sufferers.

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