Monitoring Intracranial Pressure Using Non-Invasive Brain Stethoscope

Monitoring intracranial pressure (ICP) is vital for patients with elevated, or potentially elevated ICP. This pressure can be monitored using invasive procedures such as lumbar puncture manometry or various methods of direct measurement in or upon the brain, each with attendant complication risks. Measurement of naturally occurring tympanic membrane pulse (TMp) may provide an alternative non-invasive method of monitoring ICP, which would help the risks of invasive methodologies. This paper discusses a piezo based sensor (which we term the “brain stethoscope”) designed and tested to acquire TMp signals. In addition, the TMp signals were acquired from five human subjects where ICP was expected to vary. ICP was increased in this experimental model using head down positioning on a tilt table. Results showed that tympanic membrane waveform changed in morphology and amplitude with increased ICP. The lead time between the TMp signal and a reference signal (Ear lobe blood flow pulse) was found to increase as ICP increased using this model. We conclude that measurement of TMp changes may provide a new non-invasive, low cost and easy to perform technique for monitoring patients at risk of elevated ICP.