The effect of elevated intracranial pressure on the vibrational response of the ovine head.

Although potentially fatal increases in intracranial pressure (ICP) can occur in a number of pathological conditions, there is no reliable and noninvasive procedure to detect ICP elevation and quantitatively monitor changes over time. In this experimental study, the relationships between ICP elevation and the vibrational response of the head were determined. An ovine animal model was employed in which incremental increases in ICP were elicited and directly measured through intraventricular cannulae. At each ICP increment, a vibration source elicited a flexural response of the animal's head that was measured at four locations on the skull using accelerometers. Spectral analysis of the responses showed changes in proportion to ICP change up to roughly 20 cm H2O (15 mm Hg) above normal; a clinically significant range. Both magnitude and phase changes at frequencies between 4 and 7 kHz correlated well (gamma > 0.92) with ICP across the study group. These findings suggest that the vibrational response of the head can be used to monitor changes in ICP noninvasively.