The effect of raised intracranial pressure on intracochlear fluid pressure: three case studies.

The effects of changes in intracranial fluid pressure (ICP) on cochlear fluid pressure have been studied in 3 patients who underwent ventriculo/lumbar-peritoneal shunt operations. The operations were performed in order to alleviate problems caused by an abnormally raised ICP. Indirect measurements of perilymphatic pressure were made before and after surgery using a non-invasive technique which measures tympanic membrane displacement. This technique proved extremely sensitive and revealed changes in cochlear fluid pressure brought about by changes in the ICP. The results emphasise the need to consider audiological measurements in the context of ICP abnormalities. These findings have important implications in that an audiological technique may be used for the simple and non-invasive serial monitoring of changes in ICP and may even assist differential diagnosis in a number of neurological patients.