Levetiracetam suppresses long-loop reflexes at the cortical level

Posthypoxic coma is often associated with cortical and brainstem hyperexcitability. Five months following cardiopulmonary resuscitation after myocardial infarction and ventricular arrhythmia, a 47-year-old man presented with posthypoxic cerebral dysfunction, minimal responsiveness, severe spastic-dystonic tetraparesis, and stimulus-sensitive muscle spasms upon acoustic and sensory stimulation. Neurophysiological examination revealed increased long-loop reflexes in abductor pollicis brevis muscle following median nerve stimulation at the wrist, consistent with cortical hyperexcitability. Exaggerated startle responses provided evidence of concomitant brainstem disinhibition. Levetiracetam up to 3,000 mg per day suppressed transcortical long-loop reflexes in a dose-dependent manner without concomitant suppression of the H-reflex and only mild attenuation of the startle response. The present findings suggest a suppressive effect of levetiracetam on cortical neurons in the absence of a spinal effect on monosynaptic reflexes, and thus support the drug's efficacy in posthypoxic cortical hyperexcitability.