Effect of craniotomy and cerebrospinal fluid loss on the inner ear. An experimental study.

Craniotomy with cerebrospinal fluid (CSF) suction was performed on 18 guinea pigs to determine the effects on the inner ear morphology. Six control animals received anaesthesia only and 12 were operated on with a postoperative survival time of 1 or 24 h. The histologic examinations showed no signs of endolymphatic hydrops or injury to other structures in any of the animals. In 11 of the operated animals, red blood corpuscles were demonstrated in the perilymphatic space of the cochlea, the subarachnoid space, and the cochlear aqueduct (CA). After 1 h survival time blood had entered primarily the basal part of the scala tympani, but in the animals of 24 h survival time the blood was more abundant in both the scala tympani and the scala vestibuli indicating flow within the inner ear. The CA thus provides a pathway between the CSF and the whole of the perilymph through which noxious effects could take place.