Long-Latency Motor Evoked Potentials in Spinal Cord Injury

Long-Latency Motor Evoked Potentials in Spinal Cord Injury

David S. Barnkow, Au.D., D.ABNM, CNIM, CCC-ADirectory of Quality AssuranceMedsurant, LLCDenver, Colorado, USA

Peter A. Raudzens, M.D., F.R.C.P, (C)Chief Medical Officer, Medsurant Holdings, LLCChairman, Sensory Testing SystemsPhoenix, Arizona, USA

Intraoperative Neurophysiology in Neurosurgery – Part III Spine and Spinal Cord Surgery Lazise, Italy October 19, 2012

Long-Latency Motor Evoked Potentials in Spinal Cord InjuryD. Barnkow & P. Raudzens, October 19, 2012

Case 1, The Beginning:• Patient: 56 year old male, 13 year post-injury

• Dx: cervicothoracic syrinx, post-operative ataxia, myelopathy, post-traumatic tethered spinal cord

• Chief Complaint: progressive lower extremity dysfunction, sensory/motor loss and bladder dysfunction

• Previous Surgeries: • ACDF C5-7, 1995• PSF C3-7 1995• syringosubarachnoid shunt T1-2, 3/2000• shunt revision, 9/2000• revision syringosubarachnoid shunt T1-3, 2004• spinal cord untethering, 2005• thoracic shunt removal and lumbar drain placement, 12/2005• CSF leak repair, 1/2006• wound debridement and mesh removal, 7/2006• shunt revision, 7/2006• ventriculopleural shunt, 8/2006• new syringosubarachnoid shunt, 2/2007

• Procedure: cervical laminectomy, spinal cord untethering, expansion duraplasty


Case 1, The Beginning:• Primary AbH response 50.29 ms, LLMEP approx. 90 ms

• C4’ anodal transcranial electrical mMEPs• Intensity: 160-220V, Train: 6, ISI: 2, Pulse Width 200 usec


• Literature search for Long-Latency MEPs revealed a paucity of publication related to spinal cord injury.

• References• Dimitrijević et al. Early and late lower limb motor evoked potentials elicited by

transcranial magnetic motor cortex stimulation. 1995• Vandermeeren et al. Long-latency motor evoked potentials in congenital

hemiplegia. 2003• Bastings et al. Mechanisms of hand motor recovery after a stroke: an

electrophysiological study of central motor pathways. 1997• Calancie et al. Motor-unit responses in human wrist flexor and extensor

muscles to transcranial cortical stimuli. 1987• Heald et al. Longitudinal study of central motor conduction time following

stroke. 1. Natural history of central motor conduction. 1993• Rapisarda et al. Can motor recovery in stroke patients be predicted by early

transcranial magnetic stimulation? 1996• Turton et al. Contralateral and ipsilateral EMG responses to transcranial

magnetic stimulation during recovery of arm and hand function after stroke. 1996


Introduction: • Previous studies in children with congenital

hemiplegia and adults with stroke of have demonstrated muscle motor evoked potentials (mMEPs) to transcranial magnetic stimulation with repeatable response latencies significantly longer than anticipated for typical corticospinal tract mediated mMEPs.

• Intraoperative assessment of individuals with pre-existing spinal cord injury (SCI) using transcranial electric mMEPs recorded with epochs greater than 100 milliseconds has also revealed a frequent, but not universal, appearance of long-latency motor evoked potentials (LLMEPs).

• Research Question: “Are LLMEPs clinically significant to spinal cord injury?”


Material and Methods:

• A retrospective review of intraoperative mMEP data obtained over a five year period from individuals with pre-existing SCI undergoing spine surgery identified LLMEPs in 150 of 356 cases (42%).

• Stimulus and recording parameters followed established clinical techniques. Recording epochs ranged from 100 ms to 300 ms.

• These six case studies were chosen to illustrate the LLMEPs observed in individuals with SCI over a broad range of etiologies, spinal levels, injury severity, and post-injury duration, as well as the variety of LLMEP characteristics.


• Case 2, 44 y/o female, C12DB-067

• Hx: C6 Incomplete quadriplegia, ASIA D, Brown-Sequard Type cord injury due to Motor Vehicle Accident.

• CC: Loss of function in arms and legs requiring a cane to ambulate.

• Dx: Post-traumatic tethered spinal cord with myelocystocele.

• Procedure: Spinal cord untethering and subarachnoid peritoneal shunt.


• Case 2, 12DB-067, C6, ASIA D, Dx: Brown-Sequard.

• Note: Contralateral LLMEP threshold below ipsilateral mMEP.


• Case 3, 50 y/o male C12DB-067

• Hx: Thoracic spinal cord cavernous hemangioma with bleeding and right cerebellar cavernous hemangioma with bleeding 16 years previously. Required a cane to ambulate.

• CC: Increasing weakness in both legs, right worse than left. Decreased sensation left worse than right.

• Dx: T8 post-traumatic tethered cord, ASIA D, L2-4 spinal stenosis, acquired scoliosis.

• Procedure: Spinal cord decompression and PSF w/ instrumentation T10-L5.


• Case 3, 50 y/o male C12DB-067

• Hx: Thoracic spinal cord cavernous hemangioma with bleed, right cerebellar cavernous hemangioma with bleed 16 years previously. Required a cane to ambulate.

• CC: Increasing weakness in both legs, right worse than left. Decreased sensation left worse than right.

• Dx: Post-traumatic tethered spinal cord, ASIA D, L2-4 spinal stenosis, acquired scoliosis.

• Procedure: Spinal cord decompression and PSF w/ instrumentation T10-L5.


• Case 3, C12DB-067, 50 y/o male Hx: Thoracic spinal cord and right cerebellar cavernous hemangioma with bleed,

• Note: Robust LLMEP in left Gracilis/VL and contralateral abductor hallucis.


• Case 4: 44 y/o male C011DSB-077

• Hx: C4 incomplete quadriplegia due to diving injury 20 years previously. ACDF C2-5 at time of injury. Subsequent ACDF C6-7.

• CC: increasing spasticity, neck pain upon flexion and neuropathic pain.

• Dx: C5-6 3mm retrolisthesis, post-traumatic tethered cord, C4 ASIA C

• Procedure: Anterior discectomy and spine fusion C5-6


• Case 4: 44 y/o male C011DSB-077, C4 incomplete quadriplegia• Note: LLMEPs in bilateral brachioradialis and contralateral pronator teres and

APB


• Case 5, 16 y/o female, NB-081216

• CC: 2 day history of low back pain upon flexion following a fall from a handstand. No sensory, motor or bowel/bladder complaints.

• Dx: L1 burst fracture.

• Procedure: T12-L2 posterior spine fusion with bone morphogenic protein for fusion.


• Case 5, 16 y/o female, L1 burst fracture, NB-081216

• 14:48: pre-positioning

• 14:54: post-positioning

• 15:11: incision

• 15:28: exposure complete

• 15:31: L1 decompression and reduction

• 15:51: decompression complete, begin pedicle screws

• 16:31: placing rods


• Case 6: 62 y/o male, CO11DSB-123, 30 years post-injury, C6 tetraplegia due to wrestling accident, ASIA Impairment Scale A

• CC: Recent onset neuropathic pain, decreased sensation, increased spasm

• Dx: C5-C6 intramedullary cyst with cystic changes ascending to C1-2.

• Procedure: cervical laminectomy, spinal cord untethering, expansion duraplasty, subarachnoid-peritoneal shunt placement.


• Case 6: 62 y/o male, CO11DSB-123, C6 tetraplegia.• Note: Contralateral threshold 80V below target muscle


Results: • LLMEPs were observed alone and in the presence

of typical mMEPs.

• LLMEPs were observed in the target muscles alone, in the non-target muscles alone or simultaneously in bilateral muscle pairs.

• LLMEPs were observed in muscles innervated from above, at, and below the level of SCI.

• LLMEPs demonstrated wide variations in morphology, latency, amplitude, and stimulation threshold relative to typical mMEPs.


• Y. Vandermeeren et al. (2003)

• “Long-latency MEPs have been described in normal subjects, and anecdotally reported in CH patients, but their origin is still controversial and their prognostic value has never been explicitly investigated.”

• The same statement appears true for LLMEPs in Spinal Cord Injury in 2012.


Conclusions: • LLMEPs can be easily collected with simple

recording epoch (time sweep) adjustment.

• LLMEPs present a variable constellation of characteristics over the broad continuum of SCIs.

• Additional data and meta-analysis are needed to determine if LLMEPs are an important prognostic indicator of spinal cord status.

• A theoretical model for the generation of LLMEPs in SCI is needed.


• References

• Dimitrijević MR, Koflera M, McKay WB, Sherwood AM, Van der Lindenb C, Lissensc MA. Early and late lower limb motor evoked potentials elicited by transcranial magnetic motor cortex stimulation. Electroencephalography and Clinical Neurophysiology/Evoked Potentials Section. 85, 6, (1992), 365–373

• Vandermeeren Y, Bastings E, Fadiga L, Olivier E. Long-latency motor evoked potentials in congenital hemiplegia. Clin Neurophys. 114, (2003) 1808-1818

• Bastings E, Rapisarda G, Pennisi A, Maertens de Noordhout A, Delwaide PJ. Mechanisms of hand motor recovery after a stroke: an electrophysiological study of central motor pathways. J Neurol Rehab 1997; 11:97–108

• Calancie B, Nordin M, Wallin U, Hagbarth KE. Motor-unit responses in human wrist flexor and extensor muscles to transcranial cortical stimuli. J Neurophysiol 1987;58:1168–85

• Heald A, Bates D, Cartlidge NEF, French JM, Miller S. Longitudinal study of central motor conduction time following stroke. 1. Natural history of central motor conduction. Brain 1993a;116:1355–70

• Heald A, Bates D, Cartlidge NEF, French JM, Miller S. Longitudinal study of central motor conduction time following stroke. 2. Central motor conduction measured within 72 h after stroke as a predictor of functional outcome at 12 months. Brain 1993b;116:1371–85

• Rapisarda G, Bastings E, Maertens de Noordhout A, Pennisi G, Delwaide PJ. Can motor recovery in stroke patients be predicted by early transcranial magnetic stimulation? Stroke 1996;27:2191–6

• Turton A, Wroe S, Trepte N, Fraser C, Lemon RN. Contralateral and ipsilateral EMG responses to transcranial magnetic stimulation during recovery of arm and hand function after stroke. Electroenceph clin Neurophysiol 1996;101:316–28.


Long-Latency Motor Evoked Potentials in Spinal Cord Injury

Health & Medicine

spinal cord untethering

spinal cord injurydavid

motorunit responses

spinal cord surgery

shunt revision

ventriculopleural shunt

latency meps

transcranial electric