Abnormalities of visual, brainstem auditory, and somatosensory evoked responses were demonstrated in two of seven individuals with vitamin B12 deficiency. The evoked response delays correlated directly with the degree of neurological dysfunction. Abnormalities were present in sensory systems without clinical evidence of involvement and were similar to those found in individuals with multiple sclerosis.

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The value of standard electrophysiological studies using electroencephalography and evoked responses was evaluated in patients with Tourette's syndrome. Sixteen-channel electroencephalograms were obtained in 40 patients (36 males, 4 females) awake and asleep, and evoked responses were obtained in a subgroup of 17 patients. Evoked response variables evaluated included latencies and amplitudes of visual evoked responses, brainstem auditory evoked responses, and somatosensory evoked responses to median and peroneal nerve stimulation. Only 5 of the 40 patients (12.5%) demonstrated electroencephalographic abnormalities, which included central spikes, generalized and paroxysmal slow activity, and slowing of the normal basic frequency. Evoked response studies demonstrated no consistent differences between the patients with Tourette's syndrome and age- and sex-matched controls. The data demonstrate no notable diagnostic or therapeutic value for routine electroencephalographic or evoked response studies in Tourette's syndrome.

SUMMARY Brainstem stroke syndromes are primarily determined by clinical criteria. There are few diagnostic procedures which are of benefit for the evaluation of brainstem ischemic events. Brainstem auditory evoked responses (BAERs) are a new electrophysiologic technique for assessing brainstem func tion. To evaluate the use of BAERs in patients with brainstem ischemic events, 35 individuals with recent brainstem strokes, selected by strict clinical criteria, were evaluated with BAERs. The initial BAER was abnormal in 22 of 35 patients (63%). When the clinical course and site of the lesion are correlated with the BAER results, several trends emerge. An unstable course, characterized by progression or remission and relapse, was present in 19/35 (54%) of patients, and 15/19 (79%) of these individuals had an initially abnormal BAER. The other 16 brainstem stroke patients with a stable clinical course had an initially abnormal BAER in 7 instances (44%). This difference is statistically significant at the p = 0.04 level. The principal sites of ischemia were mesencephalic in 11/35, pontine in 13/35, and medullary in 11/35. The association of an abnormal BAER with an unstable clinical course seemed independent of the site of the lesion. However, of the 9 deaths that occurred, all were in patients with mesencephalic or pontine lesions, and 8 of these individuals had an initially abnormal BAER.Abnormal BAERs in patients with brainstem ischemic lesions correlate with an unstable clinical course. Furthermore, individuals with pontomesencephalic infarction and abnormal BAERs have an especially r. poor prognosis. The BAER may be of prognostic value in the early evaluation of patients with brainstem ischemic strokes.