Download Noninvasive ICP - Marchbanks Measurement Systems Limited

Transmission of
Intracranial Pressure Signals to the Human Ear
Robert J. Marchbanks1 Colin P. Please2 Tony Birch1 & David Schley1,2
1 Department
of Medical Physics and Bioengineering, Southampton General Hospital.
2 School
of Mathematics, University of Southampton.
Accurate intracranial pressure (ICP) measurements are vital for treatment and
monitoring of seriously ill patients. At present, however, the only precise
measurement devices involve inserting a probe through the skull – a highly
invasive and potentially risky procedure. The development of the ‘MMS-11
Cerebral and Cochlear Fluid Pressure (CCFP) Analyser’ by Marchbanks
Measurement Systems has provided the opportunity for non-invasive
measurements by studying the movement of the eardrum as induced by
intracranial pressure waves and in response to various stimuli. 1, 2.
The Signal Processing Challenge
We know that these intracranial pressure waves contain significant
information concerning the status of the brain, for example, in the braininjured patient. The challenge is to find the best method of analysing the
pressure signals so as to extract underlying baseline pressure shifts and
interactions between different types of pressure waves, and to take
account of distortions. The main interaction of interest is between
cerebral cardiovascular and respiratory pressure waves and how this
interaction changes with posture - finding a means of analysis and
visualisation will provide major clinical benefits.3 Methods including
spectrograms 4 and wavelet transforms 5 have been proposed but at
present none of these have been applied to our non-invasive intracranial
pressure recordings.
Clinical data will be used to develop a model to explore these
relationships and to ultimately help perfect CCFP measurements.
There is a need for signal processing expertise to support this work.
We are also directly involved in a joint US project commissioned by
the NASA Johnson Space Centre. Project E148 is to use our
technique aboard the Space Shuttles to investigate changes in crewmembers’ intracranial pressure and any relationships with spacesickness as they adapt to zero gravity conditions. There is a need for
suitable signal processing algorithms to analyse the intracranial
pressure waves and to support the planned three Shuttle missions.
Above: Spectrogram from McNames et al (2002)
Left: Wavelet analysis from Addison (2004)
From the NASA Photograph Archive
The Applications
Appeal for Collaborators
As part of an EPSRC CASE funded Mathematics PhD, due to
commence in October ’04, clinical data will be collected from patients
who are fitted with a pressure probe. This, for the first time ever, will
provide simultaneous CCFP and direct ICP wave data for comparison
purposes.
It is unclear to us what signal-processing approach is likely to work
best, and we are keen to collaborate with experts to develop this
exciting research that has major clinical benefits. Data should be
collected during the year, and there is the potential for staff time to be
made available at the hospital to carry out analysis under suitable
guidance. It is believed that close collaboration between applied
mathematicians, clinicians and signal processing experts will provide
the opportunity for publications in principal medical journals and
collaborative research on an international basis.
The proposed work includes the development of a mathematical model
of the fluid dynamics and pressure transmission through the channels
connecting the cerebral fluid to the inner ear.
In addition to providing an evidence base for current clinical practice at Southampton General Hospital, it is hoped that the work undertaken will
provide an insight into the causes of certain hearing and balance disorders,6
If you are interested in collaborating with us, or discussing the potential application of signal processing techniques to
this problem, please contact us via [email protected],
1. Samuel, M., Marchbanks, R.J. and Burge, D.M. (1998) Tympanic membrane displacement test in regular assessment in eight children with shunted hydrocephalus. J Neurosurg 88:983-995.
2. Intracranial and Intralabyrinthine Fluids: Basic Aspect and Clinical Applications’. Editors A. Ernst, R Marchbanks, M.Samii. Springer Verlag, ISBN 3-540-60979-2, 1996.
3. Klose et al (2000) Detection of a Relation Between Respiration and CSF Pulsation With an Echoplanar Technique. J of Magnetic Resonance Imaging, 11:438-444.
4. McNames et al (2003) Significance of Intracranial Pressure Pulse Morphology in Pediatric Traumatic Brain Injury. IEEE, 2491-2494.
5. Addison, P. (2004) The Little wave with the big future. Physics World, March, 35-39.
6. Intracranial and Inner ear physiology and pathophysiology. Editors A. Reid, R Marchbanks, Whurr Publishers, ISBN 1 86156 066 4, 1998.