Dorsal root entry zone lesions

Youmans Chapter 171Diaa Bahgat, Diyendu K. Ray, Kim J. Burchiel

Schmidek Chapter 130Kevin Cahill,Allan J.Belzberg,William S. Anderson

Termination• Analgesia ไมม่คีวามรูส้กึเจบ็ปวด(pain or pin

sensation)• Anesthesia ไมม่คีวามรูส้กึ(touch)• Hypesthesia ความรูส้กึสมัผัส(touch)ลดลง• Hypalgesia ความรูส้กึเจบ็ปวดลดลง• Hyperesthesia ความรูส้กึเพิม่(touch)• Dysesthesia ความรูส้กึแปลกๆ บอกไมถ่กูเกิดจากการกระตุ้น• Paresthesia ความรูส้กึท่ีผิดปกติคล้ายเขม็แทงซึ่งเกิดขึ้นเองโดยไมม่กีารกระตุ้น

• Hyperpathia ความรูส้กึเจบ็ปวดมากกวา่ปกติหลังการกระตุ้น

ประสาทศาสตรพ์ื้นฐาน, กัมมนัต์พนัธุมจนิดา

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

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)

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

Anatomy

Anatomy

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

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)

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

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

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

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)

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

Surgical technique

Surgical technique

Surgical technique

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

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

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

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