Introduction of a Novel, Continuous, Noninvasive Estimation of Intracranial Pressure and Cerebral Perfusion Pressure Based on Tympanic Membrane Temperature

Abstract

Objective: Hydrocephalus is a common but potentially life-threatening condition. However, valve malfunction makes further diagnosis difficult. Thus, we tried to develop a noninvasive method to detect the hydrocephalus intracranial pressure (ICP) during routine follow-up.

Methods: In group I, the patient was recruited because a spinal tap test was necessary for either disease diagnosis or treatment. In group II, patients were diagnosed with high ICP hydrocephalus and received shunt surgery. The tympanic membrane temperatures (TMTs) were recorded and plotted against the spinal tap pressure (STP) and shunt valve pressures.

Results: All patients in group I showed an above-normal STP (from 180 to 400 mm H₂O). The STP presents with an inverted U-shaped curve when it is plotted against TMT (R² = 0.9). When the STP was 286.1 mm H₂O, the TMT approached its peak value, which was 38.61°C (101.5°F). However, when ICP was in the normal range (50-200 mm H₂O), the TMT correlated with ICP in a linear regression model (R² = 0.69; P < 0.001). In addition, the cerebral perfusion pressure (CPP) was calculated and plotted against TMT. The TMT-CPP was also shown as a parabola (R² = 0.74). Based on the TMT-ICP algorithm, we invented a noninvasive ICP monitor system, which performs in a manner comparable to the Codman ICP Transducer (R² = 0.9; P < 0.01).

Conclusions: Both Y-Jiang TMT-ICP and TMT-CPP algorithms are useful to monitor the shunt outcomes and identify potential shunt failure. More importantly, these algorithms open the possibility for the rational acquisition of ICP and CPP noninvasively.

Keywords: Cerebral perfusion pressure; Hydrocephalus; Intracranial pressure; Noninvasive; Shunt; Tympanic membrane temperature.