Abstract
Auditory evoked brain-stem responses (ABRs) reflect activities of the auditory pathway in the brain-stem and by inference activities of the structures surrounding the auditory pathway. It is said that ABR is a reliable diagnostic tool for predicting the outcome of patients with primary or secondary brain-stem injuries as a result of head trauma, cerebrovascular disorders, and others. However, the evaluation of ABRs has depended mostly on the delay of the fifth wave, and such parameters as intracranial pressure (ICP), mean arterial pressure (MAP), cerebral perfusion pressure (CPP), were not considered.
The authors have made a new automatic and serial monitoring system of ABRs, which is composed of an audio-stimulator, a stimulus-controller, an amplifier, a signal processor, and a X-Y recorder. The stimulus-controller enables to monitor ABRs automatically and serially. The clinical study consisted of 17 patients with severe brain damage, including 10 head injuries, five cerebrovascular disorders and others. Following findings were observed. 1) The fifth wave delayed synchronously with a decrease in CPP in critical brain failure. 2) In some cases, decreases in the amplitude of the waves except the fifth wave were exaggerated during trans-tentorial herniation. For better use of the new monitoring system, the ABR-ICP-MAP correlative arrays are being made up, in which ICP, MAP, and other vital signs are evaluated at a glance, which makes it easy to recognize the status of the brain failure and to decide on the appropriate therapy.
