Somatosensory evoked potentials in aphasic patients.

The purpose of this study was to employ evoked potentials to evaluate the function of the somatosensory system in a group of right hemiplegic aphasic patients in whom conventional physical examination was inapplicable. Bilateral somatosensory evoked potentials (SEPs) in response to stimulation of the median nerve were recorded in 20 patients, and unilateral recordings were performed with 20 healthy, aged, matched controls. The major abnormality, present in 13 patients, was absence or reduction of the amplitude of the cortical components N19 and P22 in the lesioned side of the brain. Consequently, the only significant difference between the lesioned versus nonlesioned brain side in patients, and between patients and control subjects was in the amplitude of the cortical components. Since a strong correlation exists between the detected abnormality and impaired somatosensory function, it is concluded that it is highly probable that many aphasic patients suffer somatosensory deficits which, being difficult to assess, are overlooked by the medical personnel.