Detection and localization of occult lesions with brainstem auditory responses.

Seven vertex-positive potentials--the brainstem auditory response--can be recorded from the human scalp within 10 milliseconds of an appropriate acoustic stimulus. The first of these potentials is generated in the acoustic nerve, the third in the pons, and the fifth in the midbrain. Measurement of the relative latencies and amplitudes of these potentials allowed detection of subclinical lesions in 37 (53 percent) of 70 patients with suspected multiple sclerosis who had no signs or symptoms of brainstem involvement by the disease. Abnormalities in the brainstem auditory response provided the first evidence of the pressence of multiple lesions in 14 (35 percent) of 40 patients with suspected multiple sclerosis who had clinical evidence of only a single spinal or cerebral lesion. Response abnormalities also suggested the presence of tumors of the posterior fossa in three patients with nonspecific symptoms and normal neurologic examinations, the test indicated the need for contrast studies, which then led to the correct diagnosis of infratentorial neoplasm.