Fig. 11.

Tympanic membrane pressure (TMP) as a surrogate marker of intracranial pressure. (a) Schematic illustration of the anatomical structures involved in measurements of TMP waveforms. The non-invasive TMP waveforms were measured in the outer ear and used as input for the estimation of non-invasive ICP. ICP ICP input signal, CA cochlear aqueduct, OW oval window, RW round window, T tympanic membrane, and S sensor. (b) An example showing 6 seconds of the input signals and the corresponding transfer function estimate based on a total 10 minutes are shown in b1 and b2, respectively. The resulting output from the combination of b1 and the inverse of b2 is presented in b3. (c) The non-invasive ICP waveform estimate (nICP, interrupted red line) is shown together with the invasive ICP waveform (continuous red line) for four different 6-second time windows after the beginning of the measurement. The time delay between the nICP and ICP signals, as seen in b1, has been removed for visual comparison.

Adapted from Evensen et al. [177]