[Venous and meningeal prolapse during enlarged trans-labyrinth approach]

One hundred consecutive operations using the enlarged trans-labyrinthic (ETL) approach for acoustic neurinoma performed by the same surgeon were analyzed to determine incidence of venous and/or meningeal prolapses. Findings showed that ETL approaches were normal in 51 cases : normal superficial sinusodural space--external auditory canal and on deep dissection a superior petrous sinus and jugular space separated from the internal auditory canal. Prolapse was observed in 49 approaches : 30 very narrow sinusodural spaces due usually to temporal meninges prolapse (76%) associated in 25% of cases with a prolapse of lateral sinus; 29 prolapses of jugular space and 10 of superior petrous sinus, detected mainly in the narrow sinusodural spaces. In these cases, superficial displacement of the temporal meninges and lateral sinus appears indispensable in order to recover normal operating conditions towards the labyrinth and pontocerebellar angle.