Mean intracranial pressure monitoring by a non-invasive audiological technique: a pilot study.

Intracranial pressure is normally transmitted to the perilymph of the cochlea via the cochlear aqueduct. The relationship between perilymphatic pressure, indirectly measured by tympanic membrane displacement, and mean intracranial pressure defined either clinically or by direct measurement has been examined in 58 patients (aged 5-77 years), with hydrocephalus, benign intracranial hypertension, intracranial tumours, subarachnoid haemorrhage and head injuries. The most consistent results were obtained in young patients with hydrocephalus and benign intracranial hypertension. However, the technique was not suitable when the stapedial reflex was absent as a result of middle ear/brainstem dysfunction and did not reflect intracranial pressure when the cochlear aqueduct was not patent. This pilot study suggests that the tympanic membrane displacement technique may provide a useful non-invasive method for serial monitoring of intracranial pressure in young patients with hydrocephalus or benign intracranial hypertension.