Noninvasive testing of intracranial pressure changes due to body position in infants

INTRODUCTION: The hydrostatic fluctuations of intracranial pressure are transmitted to the inner ear and then the tension of the anular ligament of the stapes changes. This causes a change of the impedance of the transmission apparatus in the oval window. This in turn can be shown by the measurement of otoacoustic emissions (OAE), since both the stimulus and the emissions travel through the oval window. It has been shown that in adults the phase of otoacoustic emissions changes due to changes in intracranial pressure (eg. during positioning from sitting to head-down (Trendelenburg) position). AIMS: The aim of their study was to examine if these phase changes can be elicited in infants and children. RESULTS: In young infants (between 2 and 4 months old) there was no reproducible phase shift during positioning into Trendelenburg position, in children (between 3 and 4 years old) there was a significantly smaller phase shift than in adults. According to their theory that difference is due to the smaller hydrostatic pressure change and the fact that the skull distents easily thereby compensating for the volume change.