Transcranial electrical stimulation in patients with apallic syndrome.

Muscle responses (MEPs) to transcranial electrical stimulation were studied in 7 patients with apallic syndrome. All the patients showed clinical signs of upper motor neurone impairment in the upper and lower limbs. MEPs were absent or markedly delayed in 4 of the 7 patients. Since patients with apallic syndrome show only minimal voluntary movement, transcranial stimulation is the only way to demonstrate abnormalities of fast corticospinal axons in these patients. Even though these patients often look similar clinically, with tetraplegia and decorticate or decerebrate posture, only some cases showed dysfunction of fast corticospinal neurons.