IMPEDANCE MEASUREMENT AS A NONINVASIVE TECHNIQUE FOR THE MONITORING OF INTRACRANIAL-PRESSURE VARIATIONS

In previous reports it has been demonstrated that jugular compression causes a modification of middle ear acoustic impedance; this phenomeno n has been named the jugulotympanic reflex (JTR). The aim of the prese nt study was to contribute to the understanding of the origin of this reflex. We have analyzed the middle-ear impedance modifications induce d by unilateral and bilateral jugular compression in 12 normal subject s, in 12 patients afflicted with otosclerosis, in 3 patients with Meni ere's disease and in 6 patients demonstrating intracranial hypertensio n. In the latter group, the cerebrospinal fluid (CSF) pressure was sim ultaneously recorded. The JTR was elicited in each normal subject and in each patient affected by Meniere's disease and intracranial hyperte nsion, while it was usually absent or modified in otosclerotic patient s. The absence of the JTR in otosclerotic patients and, above all, the correspondence between CSF pressure and the middle-ear impedance modi fication induced by jugular compression suggest that it is due to the transmission of pressure changes from the CSF to the perilymph through the cochlear aqueduct.