[Peroperative auditory evoked potentials in surgery of the posterior fossa]. / Potentiels Evoqués Auditifs peropératoires dans la chirurgie de la fosse postérieure.

Intraoperative brainstem audiometry electric responses were measured in 22 operations of the posterior fossa, including 11 acoustic neurinomas. The first observation shows the recordings obtained during the exeresis of a voluminous tumor of the cerebellopontine angle and wave V disappearance for 90 minutes. At the end of the operation we noted a better plotting synchronization and the wave V form reappeared. The wave preservation was confirmed by an electrocochleography carried out few days after intervention. The second observation enables the visualization of modifications on ipsi- and contralateral plottings of the cerebellum retraction and brainstem mobilization during a cerebellum medulloblastoma operation. The third observation shows the immediate and considerable extension of wave V latency during mobilization of the antero-inferior cerebellar artery during an acoustic neurinoma operation. The authors discuss the various operative times leading to significant variations in the latency of waves I, V and I-V delays and the advantages of such a monitoring for the brainstem vital functions and hearing preservation.