Pulsed phase lock loop technique to measure intracranial pressure non-invasively

Elevated intracranial pressure (ICP) is a major factor associated with morbidity and mortality in patients with neurological disorders such as head trauma, cerebral stroke, hydrocephalus, and brain tumor. Conventional methods for ICP monitoring are currently limited to patients with severe neurological conditions because of their invasive nature. We have developed an ultrasonic device to monitor intracranial pressure waveforms non-invasively using pulsed phased lock loop (PPLL) technique. The PPLL device records slight movement (several microns) of the skull associated with ICP pulsations. The purpose of this study was: 1) confirm the PPLL outputs represent known distance oscillations; and 2) correlate PPLL waveforms with invasively measured ICP waveforms in patients at UCSD Medical Center (n=12). The PPLL outputs linearly correlated with known distance oscillations in an experimental setting (r²=0.997). Also, a high correlation existed between PPLL and invasively measured ICP waveforms in time and frequency domains. In conclusion, PPLL technology enables in vivo evaluation of ICP dynamics non-invasively in clinical settings.