Youmans Neurological Surgery

1. Dorsal root entry zone lesions
Youmans Chapter 171
Diaa Bahgat, Diyendu K. Ray, Kim J. Burchiel
Schmidek Chapter 130
Kevin Cahill,Allan J.Belzberg,William S. Anderson

2. Termination
• Analgesia (pain or pin sensation)
• Anesthesia (touch)
• Hypesthesia (touch)
• Hypalgesia
• Hyperesthesia (touch)
• Dysesthesia
• Paresthesia
• Hyperpathia
,

3. Pain mechanism
• Pain perception
– Pain receptor
• pain stimuli : chemical(heat, cold,histamine, serotonin etc.),
physical(touch)
• free nerve ending  electrical potential  pain impulse
– Pain pathway
• Epicritic pain, pricking pain, fast pain
– Small myelinated or A delta
• Protopathic pain, slow pain ,ache
– Unmyelinated or C fiber
• 1st
order neuron : dorsal root ganglion
• 2nd
order neuron : cell bodies in dorsal horn  contralateral
spinothalamic tract
• 3rd
order neuron : thalamus  post central gyrus

4. Ablation of
Dorsal root entry zone(DREZ)
• Thermocoagulation at entry zone of the dorsal spinal root
• Destructive of 2nd
order neuron of nociceptive pain
• 1972 France,Lyon by Sindou
pain due to pancoast tumour
• Cancer-related pain
• Refractory pain
– brachial plexus avulsion(BPA)
– spinal cord injury(SCI)
– postamputaion pain
– radiation-induced plexopathy(numbness, paresthesia, and
dysesthesia, along with swelling and weakness of the arm)

5. Anatomy
• DREZ : region of the spinal cord that contains the
• dorsolateral fasciculus of Lissauer and Rexed laminae I
to V
• Small rootlet 1 cm before to dorsolateral spinal cord
• Small fiber : laterally, nociceptive pain, enter Lissauer’s
tract  laminae I and II(substantia gelatinosa) of the
dorsal horn  superficial for surgery
• larger fibers : medial somatic receptors

6. Anatomy

7. Anatomy

8. Indication
• Pain from neoplasm, trauma, and infection
– Pancoast tumour
• BPA has been the most widely described application and
is associated with the best results
– Scar form at dorsal horn and stantia gelatinosa  loss of
inhibitory of large caliber sensory fiber and to spontaneous
activity in nociceptive specific
– constant crushing-type sensation
– Episodic
– pain in the hand or bursts of pain traveling down the arm
– resistant to most medical therapies

9. Indication
• spinal cord or cauda equina injury
– Nociceptive
• activation of peripheral nociceptors due to ongoing tissue
damage
• responsive to NSAID
• physical therapy.
– Neuropathic
• 10 – 25 %, immediate or several years
• result of an abnormally functioning nervous system :
burning character
• At level(> 40 yrs)and below level( < 40 Yrs)

10. Indication
• postherpetic neuralgia
– More common in thoracic level
• occipital neuralgia
• phantom limb pain
– Not first line,option for fail medical or surgical method
– sensation of shortening or lengthening of the limb
– Numbness,Itchiness,temperature differences,cramping
• radiation-induced plexopathy
• decreased muscle tone and abolished stretch reflex

11. Surgical technique
• Preoperative consideration
– Pt with fail medication
• selectively destruct
– excitatory pain fibers,
– unmyelinated and small myelinated pain fibers in the
ventrolateral DREZ and the medial portions of Lissauer’s tract
• Pre-op : intravenous corticosteroid for acute SCI
• Prone position : expose to C3- T1 lamina, pin fixation
• Cervical hemilaminectomy : unilateral procedures
• Complete laminectomy : bilateral procedures

12. Surgical technique
• Open dura then nerve root expose
• Root identification : bipolar stimulation, with a 2.5-Hz
frequency and an increasing voltage from 1 to 6 V.
• Incision depth 2 mm at the junction of the rootlets and
the dorsolateral funiculus, open both for comparison
• Stimulation dorsal column with recording of a
somatosensory evoked potential to identify midline :
dorsal column fiber

13. Surgical technique
• Microcoagulation : Radiofr35-degree angle,depth of 3
mm ,Staccato fashion
• High frequency-generated heat
– cordotomy needle placed in the posterolateral sulcus
– slight contraction of the tissue is evident (10-20 seconds) or heat
the electrode to 75°C for 15 seconds
– Multiple lesions are placed at 1- to 2-mm intervals covering the
area of avulsion
– Continue lesion fron avulsion to partial injured lesion : maximal
result
• Carbon dioxide laser, Ultrasound-mediated DREZ
ablation , Nd:YAG(neodymium:yttrium-aluminium-garnet)

14. Surgical technique
• Bipolar
– Power 20-25
– DREZotomy
• Landmark
– Line last intact dorsal root to visible root intact distal
– Pit left by avulsion root
– Small vein run laterally to DREZ
• Avoid injury to dorsal column medially and corticospinal
tract laterally

15. Surgical technique

16. Surgical technique

17. Surgical technique

18. Outcome
• BPA,SCI,postherpetic neuralgia, arachnoiditis, pain
secondary to spinal cysts, and cauda equina lesions
• No RCT comprare to other therapy
• Relieve pain at least 50%
• SCI : 54%, BPA : 84%
• Sindou and coauthor, 42
– 66% good excellent outcome
– 71% improve in daily activity
– Mean F/U 6 Yrs
• Better result in Pt who underwent surgery more than 1 Yr

19. Outcome
• Long term follow up
– John Hopkin Hospital 28 mo,relieve 85%
– 87% of patients, with an average follow-up of 47.5 months
– 94.6% (55) excellent pain relief on hospital discharge, with
65.9% showing persistent relief on long-term follow-up.
• Pain relief greater in paroxysmal pain alone compared
to that in patients with continuous pain
• SCI
– Incomplete cord
– 3% : 3 months, 68% : 1 year

20. Outcome
• postamputation phantom pain
– good long-term relief in 36%
– Some report, not respond
• postherpetic neuralgia
– 17 / 10
– Superficail burning pain
– Only 20 % persistent pain
• radiation-induced plexopathy
– 8/10,respond

21. Complication
• general complications following spinal surgery
– CSF leak 1/55
– Meningitis 2/55
– Post-amputaiotn pain : epidural hematoma 1/28
• neurologic complications
– Decreased sensation(hypoesthesia) sensation ipsilateral to the
DREZ ablation
– Dysesthesias(unusual and frightening physical disorder)
ipsilateral to the DREZ ablation
– Ataxia, motor weakness
– sphincter dysfunction