Spinal cord infarction: varying degrees of upper and lower motoneuron dysfunction

Five patients with spinal cord infarction underwent electrophysiologic evaluation. Two subjects with complete paralysis had absent compound muscle action potentials (M-responses), suggesting complete loss of lower motoneurons (LMN). Three subjects with incomplete cord infarction had preserved M-responses, reduced voluntary recruitment and abnormally slow motor-unit firing rates during maximal effort, suggesting upper motoneuron (UMN) weakness. These five patients demonstrate a range of neuronal damage after cord ischemia. With severe cord infarction, there is LMN degeneration and paralysis. With partial cord infarction, there is selective interneuron loss, resulting in UMN weakness. Electrodiagnostic evaluation can help determine prognosis for motor recovery after spinal cord infarction.