Objective assessment of cervical spinal cord injury levels by transcranial magnetic motor-evoked potentials.
BACKGROUND
The neurologic examination serves as the optimal method to record the level of spinal cord injury (SCI). However, this test is subject to interexaminer variability. To address this shortcoming, we describe a technique that uses transcranial magnetic motor-evoked potentials (tcMMEPs) and dermatomal somatosensory-evoked potentials (d-SSEPs) to more accurately measure the precise level of SCI.


METHODS
Two groups of subjects were studied: (1) complete cervical SCI (n = 10) and (2) neurologically intact volunteers (n = 10). Two additional patients were evaluated: one with a cervical central spinal cord syndrome and another with a head injury with a suspected cervical SCI. Each subject underwent upper extremity tcMMEPs and d-SSEPs.


RESULTS
Transcranial magnetic motor-evoked potentials were elicited from all upper limb myotomes (C4-T1, bilaterally) in neurologically intact volunteers (20 sides). The level of injury was determined using tcMMEPs by observing the lowest level of measurable response. The level of injury obtained using tcMMEPs was the same as that determined by neurologic examination in 13 (65%) of the 20 sides. In 7 sides, tcMMEP responses were obtained 1 level lower than that assessed by physical examination. Dermatomal somatosensory-evoked potentials were obtained from all dermatomes of volunteers tested in the laboratory compared with only 5 of the 9 patients with SCI who underwent d-SSEP testing.


CONCLUSIONS
Testing using tcMMEPs provides an objective supplement to the neurologic examination after acute cervical SCI. Dermatomal somatosensory-evoked potentials were of limited value in determining the level of cervical SCI.
Shields
Christopher B
CB
Kentucky Spinal Cord Injury Research Center, University of Louisville School of Medicine, Louisville, KY 40202, USA. cbshields1@aol.com
Ping Zhang
Yi
Y
Shields
Lisa B E
LB
Burke
Darlene A
DA
Glassman
Steven D
SD
D000293:Adolescent; D000328:Adult; D001132:Arm / Q000294:innervation / Q000503:physiopathology; D002574:Cervical Vertebrae / Q000293:injuries; D004525:Efferent Pathways / Q000293:injuries / Q000503:physiopathology; D004566:Electrodes / Q000592:standards; D019054:Evoked Potentials, Motor / Q000502:physiology; D005073:Evoked Potentials, Somatosensory / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009431:Neural Conduction / Q000502:physiology; D011237:Predictive Value of Tests; D012016:Reference Values; D013116:Spinal Cord / Q000473:pathology / Q000503:physiopathology*; D013119:Spinal Cord Injuries / Q000175:diagnosis* / Q000503:physiopathology*; D050781:Transcranial Magnetic Stimulation / Q000295:instrumentation / Q000379:methods* / Q000592:standards