A case of alpha coma in acute brainstem dysfunction--consecutive electroencephalograms and evoked potentials

A 31-year-old woman was admitted because of severe headache and dysarthria in December 1985. Neurological examination on admission revealed severe impairment of consciousness, anisocoria, absent light reflex on the right side, and evidence of left hemiparesis, but other brainstem reflexes were intact. A CT scan taken shortly after arrival demonstrated a large hematoma in the right temporal lobe and the right cerebellum. Breathing became irregular and intubation was needed. An emergency operation was performed. After the operation the patient remained comatose without any spontaneous respiration or brainstem reflexes. The next day she was still comatose without any spontaneous movement and other neurological finding remained unchanged. An initial EEG obtained at this time showed an 8- to 9-Hz alpha rhythm of about 15-40 microV with preponderance over the posterior and central regions. Some spontaneous variability was noted. The same day, investigations of brainstem auditory evoked potential (BAEP), visual evoked potential (VEP), and somatosensory evoked potential (SEP) were performed. BAEP showed only the first, second and third waves (I-III) bilaterally. VEP was able to elicit the primary response (II-III) without the secondary response. SEP could not be obtained from the early cortical response to left median nerve stimulation, but showed N14 bilaterally and small N20 upon right median nerve stimulation. On the second day of hospitalization, a repeated EEG showed generalized slowing with loss of alpha frequency rhythms and it proved impossible for SEP to elicit N20 bilaterally. At this time, BAEP showed bilateral I-IIIth waves and VEP still showed primary response.(ABSTRACT TRUNCATED AT 250 WORDS)