Magnetic cortical stimulation in acute spinal cord injury

We studied 25 patients within 6 hours of acute spinal cord injury using magnetically evoked cortical motor evoked potentials (MEPs). The subjects included 16 quadriplegics with cervical spine injuries and eight paraplegics. MEPs were recorded from abductor digiti minimi (ADM), biceps, flexor hallucis brevis, and tibialis anterior muscles on each side using appropriate directions of coil current. MEPs were not obtained, either at rest or during attempted voluntary contraction, in patients without preceding clinical evidence of voluntary activation. This was the case even for muscles that later had motor recovery after an initial paralysis. In comparison with normal controls, MEP thresholds at rest in ADM and biceps were elevated even for muscles innervated above the level of injury (p < 0.001). On repeat testing, 6 weeks postinjury, there was a return toward normal, but a significant threshold elevation remained for ADM (p < 0.05). We conclude that in acutely injured spinal cord patients, magnetically evoked MEPs do not provide useful information regarding the likelihood of motor recovery.