Intracranial pressure effects on auditory evoked responses in the rabbit: preliminary report

Acute elevated intracranial pressure (ICP) effects on the auditory evoked response (AER) were studied in the rabbit. Simultaneous CSF infusions to increase ICP and contralateral ICP pressure recordings were done through bilateral ventriculostomies. During rarefaction auditory stimulation, a minicomputer obtained a time-locked AER from ongoing electroencephalographic activity at base line ICP mean pressure and at three levels of increased ICP (250, 500, and 700 mm CSF) above base line. The results showed a statistically significant increased latency of the N3-P3 portion of the AER as well as of the P1-P3 central conduction time. The amplitude of AERs appeared unchanged. The effect is reversible and presumably is a neuropraxic type pressure effect on brain stem auditory pathways. Its clinical relevance is discussed.