The tympanic membrane displacement analyser for monitoring intracranial pressure in children

Abstract

Purpose: Raised intracranial pressure (ICP) is a potentially treatable cause of morbidity and mortality but tools for monitoring are invasive. We sought to investigate the utility of the tympanic membrane displacement (TMD) analyser for non-invasive measurement of ICP in children.

Methods: We made TMD observations on normal and acutely comatose children presenting to Kilifi District Hospital (KDH) at the rural coast of Kenya and on children on follow-up for idiopathic intracranial hypertension at Evelina Children's Hospital (ECH), in London, UK.

Results: We recruited 63 patients (median age 3.3 (inter-quartile range (IQR) 2.0-4.3) years) at KDH and 14 children (median age 10 (IQR 5-11) years) at ECH. We observed significantly higher (more negative) TMD measurements in KDH children presenting with coma compared to normal children seen at the hospital's outpatient department, in both semi-recumbent [mean -61.3 (95 % confidence interval (95 % CI) -93.5 to 29.1) nl versus mean -7.1 (95 % CI -54.0 to 68.3) nl, respectively; P = 0.03] and recumbent postures [mean -61.4 (95 % CI -93.4 to -29.3) nl, n = 59) versus mean -25.9 (95 % CI -71.4 to 123.2) nl, respectively; P = 0.03]. We also observed higher TMD measurements in ECH children with raised ICP measurements, as indicated by lumbar puncture manometry, compared to those with normal ICP, in both semi-recumbent [mean -259.3 (95 % CI -363.8 to -154.8) nl versus mean 26.7 (95 % CI -52.3 to 105.7) nl, respectively; P < 0.01] and recumbent postures [mean -137.5 (95 % CI -260.6 to -14.4) nl versus mean 96.6 (95 % CI 6.5 to 186.6) nl, respectively; P < 0.01].

Conclusion: The TMD analyser has a potential utility in monitoring ICP in a variety of clinical circumstances.

Fig. 1

A schematic representation of the communication between the subarachnoid space and the inner ear through the cochlear aqueduct

Fig. 2

TMD baseline pressure measurement patterns. a shows a positive deflection of the TMD curve representing a low ICP pressure pattern while b shows a negative deflection indicating a raised ICP pattern. c A bilateral deflection indicating normal ICP. The area shaded in blue is the area under the curve over the duration of the stapedius reflex response. Calculation of this area is done by the machine software with the user indicating the most negative deflection of the curve and the end of reflex response

Fig. 3

Study flow chart of patients admitted in coma and recruited at the Kilifi High Dependency Unit. Six patients were eligible for recruitment but the study clinician was not aware at the time of their admission

Fig. 4

TMD baseline pressure measurements at Kilifi District Hospital. Semi-recumbent (A) TMD baseline pressure measurements were greater (more negative) for HDU children (inpatient coma) (mean −61.3 (95 % CI −93.5 to −29.1) nl, n = 63) than for OPD normal children (mean −7.1 (95 % CI −54.0 to 68.3) nl; n = 24, P = 0.03). Recumbent (B) measurements were similarly greater for HDU children (mean −61.4 (95 % CI −93.4 to −29.3) nl, n = 59) than for OPD children (mean −25.9 (95 % CI −71.4 to 123.2) nl; n = 17, P = 0.03). HDU children showed much less variation with a mean clustered around −60 nl

Fig. 5

TMD baseline pressure measurements at Evelina Children’s Hospital. Semi-recumbent (A) TMD baseline pressure measurements were greater (more negative) for ECH children with raised ICP (mean −259.3 (95 % CI −363.8 to −154.8) nl, n = 6) compared to those with normal ICP (mean 26.7 (95 % CI −52.3 to 105.7) nl; n = 10, P < 0.01). Recumbent measurements were also similarly greater for children with raised ICP (mean −137.5 (95 % CI −260.6 to −14.4), n = 4) than for those with normal ICP (mean 96.6 (95 % CI 6.5 to 186.6) nl; n = 7, P < 0.01)

Fig. 6

Comparison between TMD and LP manometry measurements in a 5-year-old child. Corresponding TMD and LP manometry measurements in a 5-year-old child with IIH taken at three separate occasions