Objectives: To compare tympanic membrane displacement (TMD) measurements in patients who had interventions to alter ICP.
Methods: Twelve hydrocephalus patients requiring surgical intervention to alter ICP were studied. Tympanic membrane displacement was measured using the Marchbanks Measurement System pre and post intervention with the patient supine. In 3 patients, TMD was measured bilaterally and the results averaged; in 9 patients TMD was measured in only one ear. All patients had normal middle ear pressure and compliance and a positive postural change.
Results: In one case intervention was to increase ICP (insertion of antisiphon device) and the TMD measurement decreased by 279nL. The eleven other cases involved a reduction of ICP (lumbar puncture, shunt insertion or revision). Changes in TMD response varied from -288nL to +167nL. In two cases there was an unexpected reduction in TMD (-147nL and -288nL). In three cases the TMD measurements were within ±20nL. In the remaining six cases the TMD increased (range 85nL to 167nL).
Discussion: These preliminary results suggest that TMD measurement may be useful to detect ICP changes when a baseline asymptomatic measurement has been performed. Given an inverse relationship between TMD and ICP, correct detection of ICP changes were made in 7/12 cases. No change was observed in 3 cases.
The range of readings observed in this small sample of patients suggests significant differences in intra-patient values but there was no absolute determination of the change in ICP or its magnitude. However regular serial measurements of TMD may be useful in the determination of intracranial dynamics.
References: ¹. Samuel M, Burge DM, and Marchbanks RJ. Tympanic membrane displacement testing in regular assessment of intracranial pressure in eight children with shunted hydrocephalus. Journal of Neurosurgery, 1998; 88: 983-995.
Acknowledgement: We would like to thank Action Research and the Garfield Weston Foundation for their support of this work.
Chambers IR, Dodd CR, Banister KR and Mendelow AD. Changes in tympanic membrane displacement measurements in relation to ICP. Poster presentation at the 12th International symposium on Intracranial Pressure and Brain Monitoring. Hong Kong 16-26th August 2004.
Dr. Iain R. Chambers, Cleveland Unit, Middlesbrough. Tel: +44 (0)1642-854-778.
Regional Medical Physics Department, Newcastle General Hospital, Newcastle upon Tyne, NE4 6BE, UK.
Tel: +44 (0)191-233-6161 Fax: +44 (0)191-226-0970 E-mail: webmaster@rmpd.org.uk Web: http://www.rmpd.org.uk
By using this site you agree to our Terms and Conditions of Use. Please read our legal page.
Regional Medical Physics Department, a Clinical Directorate of the Newcastle upon Tyne Hospitals NHS Foundation Trust.
Copyright ©1999-2008 All Rights Reserved. Revised 28 April, 2008.
