Evaluation of the brain-stem function by the auditory brain-stem response and the caloric vestibular reaction in comatose patient.

The auditory brain-stem response (ABR) and the caloric vestibular reaction (CVR) were investigated in 100 patients in deep coma to evaluate the brain-stem function of these patients precisely and to predict their prognosis accurately. In the first ABR examination, 54 patients showed normal and 46 abnormal ABRs. Among the latter, five showed partial wave disappearance and 21 exhibited no ABRs. Twenty-six of the 30 patients who recovered (87%) showed normal ABRs and 21 of the 57 who died (37%) also exhibited normal latency at that time. On the other hand, all the patients who showed wave disappearance (the absence of or only wave I response) died. Forty of 86 patients who underwent the CVR test showed some reaction. However, 46 patients showed no CVRs even in the first examination. Twenty-two of 26 patients who recovered exhibited some eye movements, while the remaining four showed no reaction at that time. From these results the following statements can be made. If total or partial (wave I) disappearance of the ABR in comatose patients is observed, one can predict a poor prognosis or death. If no reaction is observed in the CVR, however, one cannot always expect a poor prognosis.