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Refining non-invasive techniques to measure intracranial pressure: Comparing evoked and spontaneous tympanic membrane displacements

Refining non-invasive techniques to measure intracranial pressure: Comparing evoked and spontaneous tympanic membrane displacements
Refining non-invasive techniques to measure intracranial pressure: Comparing evoked and spontaneous tympanic membrane displacements

Objective: Tympanic membrane displacements (TMDs) are used to non-invasively gauge inner-ear fluid pressure. Inner-ear fluid pressure equalizes with intracranial pressure (ICP) via the cochlear aqueduct and therefore TMDs can indirectly evaluate ICP. We studied the relationship between two TMD modalities, evoked and spontaneous. Evoked TMD is a reflex response to an auditory stimulus and the established stapes-footplate mechanism explains how evoked TMDs change with ICP. Spontaneous TMD refers to a pulsatile TMD waveform expressed in the form of pulse amplitudes (TMD-PAs), the origins of which are poorly understood. We investigated whether both modalities respond similarly to an ICP change, suggesting a common mechanism. Approach: ICP was manipulated in 20 healthy volunteers by a postural change from sitting (lower ICP) to supine (higher ICP). Differences between paired sitting and supine TMD results generated ΔEvoked and ΔSpontaneous values. Main results: Evoked TMDs became more inward on lying supine while spontaneous TMDs became more outward. There was no evidence of a correlation between ΔEvoked and ΔSpontaneous (Right ears: r = -0.38, p = 0.10, 95% CI -0.75 to 0.21; Left ears: r = 0.34, p = 0.16, 95% CI -0.17 to 0.75). Significance: This suggests the stapes-footplate mechanism is not the primary mechanism explaining how spontaneous TMDs respond to changing ICP.

evoked tympanic membrane displacement, intracranial pressure, non-invasive, posture, spontaneous tympanic membrane displacement, tympanic membrane displacement
0967-3334
Finch, Laurie C.
01495898-fac1-4877-a7eb-98e5590a10ea
Marchbanks, Robert J.
1ebe90b6-cb8a-4f9e-9585-4e264a951d7f
Bulters, Diederik
d6f9644a-a32f-45d8-b5ed-be54486ec21d
Birch, Anthony A.
755f2236-4c0c-49b5-9884-de4021acd42d
Finch, Laurie C.
01495898-fac1-4877-a7eb-98e5590a10ea
Marchbanks, Robert J.
1ebe90b6-cb8a-4f9e-9585-4e264a951d7f
Bulters, Diederik
d6f9644a-a32f-45d8-b5ed-be54486ec21d
Birch, Anthony A.
755f2236-4c0c-49b5-9884-de4021acd42d

Finch, Laurie C., Marchbanks, Robert J., Bulters, Diederik and Birch, Anthony A. (2018) Refining non-invasive techniques to measure intracranial pressure: Comparing evoked and spontaneous tympanic membrane displacements. Physiological Measurement, 39 (2), [025007]. (doi:10.1088/1361-6579/aaa9f8).

Record type: Article

Abstract

Objective: Tympanic membrane displacements (TMDs) are used to non-invasively gauge inner-ear fluid pressure. Inner-ear fluid pressure equalizes with intracranial pressure (ICP) via the cochlear aqueduct and therefore TMDs can indirectly evaluate ICP. We studied the relationship between two TMD modalities, evoked and spontaneous. Evoked TMD is a reflex response to an auditory stimulus and the established stapes-footplate mechanism explains how evoked TMDs change with ICP. Spontaneous TMD refers to a pulsatile TMD waveform expressed in the form of pulse amplitudes (TMD-PAs), the origins of which are poorly understood. We investigated whether both modalities respond similarly to an ICP change, suggesting a common mechanism. Approach: ICP was manipulated in 20 healthy volunteers by a postural change from sitting (lower ICP) to supine (higher ICP). Differences between paired sitting and supine TMD results generated ΔEvoked and ΔSpontaneous values. Main results: Evoked TMDs became more inward on lying supine while spontaneous TMDs became more outward. There was no evidence of a correlation between ΔEvoked and ΔSpontaneous (Right ears: r = -0.38, p = 0.10, 95% CI -0.75 to 0.21; Left ears: r = 0.34, p = 0.16, 95% CI -0.17 to 0.75). Significance: This suggests the stapes-footplate mechanism is not the primary mechanism explaining how spontaneous TMDs respond to changing ICP.

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More information

Accepted/In Press date: 23 January 2018
e-pub ahead of print date: 28 February 2018
Published date: 28 February 2018
Keywords: evoked tympanic membrane displacement, intracranial pressure, non-invasive, posture, spontaneous tympanic membrane displacement, tympanic membrane displacement

Identifiers

Local EPrints ID: 421206
URI: http://eprints.soton.ac.uk/id/eprint/421206
ISSN: 0967-3334
PURE UUID: a9b4f695-d3d8-401c-abde-af0a2fd203ed
ORCID for Anthony A. Birch: ORCID iD orcid.org/0000-0002-2328-702X

Catalogue record

Date deposited: 24 May 2018 16:31
Last modified: 07 Oct 2020 02:20

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