Somatosensory evoked potentials: abnormalities with focal brain lesions remote from the primary sensorimotor area.

Somatosensory evoked potentials (SEPs) were recorded in 41 patients with focal brain lesions recognized by computerized tomography. 21 patients presented damage of the primary sensorimotor area (PSMA), and their SEPs were reduced in amplitude and increased in latency for the two early components (N-22 and N-39), in accordance with previous evidence. The other 20 patients pesented lesions remote from the PSMA, 15 (71%) showing abnormal SEPs mainly characterized by increment in amplitude and duration of N-22 and N-39. Abnormalities of the N-70 and later waves were not specific for any type of lesion. SEPs appeared more sensitive than the EEG for detecting brain dysfunction. The physiopathological and clinical importance of these findings are discussed.