Objective: Tympanic membrane displacement (TMD) measurements may be useful in the management of patients with hydrocephalus if they can be directly associated with recognized measurements of ICP. We have compared such TMD measurements using the Marchbanks Measurement System against invasive ICP monitoring.
Methods: Thirteen patients who were undergoing routine invasive monitoring using a Camino fibre optic ICP measurement system as part of their clinical management were studied. Simultaneous measurements of ICP and TMD in both in sitting and supine positions were made. One patient was monitored on two separate occasions. If the test was successful in both ears the TMD results were averaged (n=8).
Results: Fourteen pairs of readings were obtained. The invasive ICP readings varied from 0 to 34mmHg (median 12mmHg) in the supine position and from -16 to +33mmHg (median -4mmHg) in the sitting position. Corresponding TMD values varied from -275 to 313 nL (median 107nL) in the supine position and -133 to 465nL (median 178nL) in the sitting position. Linear regression showed a significant negative relationship between the two measurements (r=-0.65, p< 0.001).
Conclusions: These results suggest that there is a strong negative association with TMD readings compared to those obtained from an invasive method. Intra-patient variability in these measurements may mean that making an exact estimation of ICP is difficult from the TMD readings. However serial measurements from patients may be useful in determining changes in the CSF dynamics.
Acknowledgement: We would like to thank Action Research and the Garfield Weston Foundation for their support of this work.
Shimbles S, Dodd CR, Banister K, Mendelow AD, Chambers IR. Clinical comparison of tympanic membrane displacement with invasive ICP measurements. Oral 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.
