Intracranial Pressure Monitoring Using Non-invasive Technique

On 15th December 2015, British astronaut Tim Peake started a six month space mission as part of the crew on board the International Space Station (ISS). Amongst the myriad of technical equipment that he took with him was a Cerebral and Cochlear Fluid Pressure (CCFP) analyser, which measures Intracranial Pressure (ICP) using a method known as Tympanic Membrane Displacement (TMD). The CCFP, brainchild of Dr. Robert Marchbanks consultant clinical scientist at Southampton General Hospital in the UK, is the first piece of non-invasive equipment capable of monitoring ICP.

Having realised that astronauts commonly suffer fluctuations in intracranial pressure (high pressure can be a particular concern, leading to what has become known as Visual Impairment Intracranial Pressure (VIIP) syndrome) NASA and the European Space Agency worked alongside Dr. Marchbanks to include the CCFP as part of the equipment on the ISS so that an astronaut could use it in space to monitor their own intracranial pressure. On 6th May 2016, Tim Peake used the CCFP on board the ISS.

This same piece of equipment has the potential to be used in hospitals worldwide to measure ICP without using the usual, invasive methods of using either a bolt screwed into the skull under general anaesthetic or by performing a lumbar puncture.

I was fortunate enough to get the opportunity to ask Dr. Marchbanks some questions about the CCFP on behalf on the CSF Leaks Association and am very pleased to be able to share his answers here.

(SM) How does the efficacy of the MMS-11 compare with the standard form of intracranial pressure (ICP) monitoring using a bolt screwed into the skull and resting on the meninges?

(RM) At the current time we are unable to provide an absolute measure of intracranial pressure, that is we cannot give an actual value for the pressure. We are able perform a screening test to ascertain whether the pressure is likely to be low, high or normal pressure. Perhaps more important in the case of CSF leaks, we are able to track pressure changes in an individual person and say if the pressure is likely to be the same, higher or lower.

Although we have seen patients with low pressure and have detected this, we have not specifically researched a group of patients who suffer from CSF leaks. We would need to do this to establish the efficacy of the Southampton CCFP (Cerebral and Cochlear Fluid Pressure) Analyser in this specific group of patients. Without a trial we would not know the likelihood of false-positive or false negative results, i.e. people we diagnose with a leak but are normal or people we diagnose as being normal but have a leak.

The technique is referred to as the ‘Cerebral and Cochlear Fluid Pressure (CCFP) Analyser’ and also the ‘Tympanic membrane Displacement (TMD) Analyser’, since measurements are made by detecting small movement of the tympa

nic membrane, i.e. ear drum.

(SM) I have read your paper on 'The tympanic membrane displacement analyser for monitoring intracranial pressure in children', has the MMS-11 been tested on adult patients that have known problems with low/high intracranial pressure?

(RM) We have researched children and adults who have a cerebrospinal shunt to control hydrocephalus. These can become blocked with the risk of high pressure or they can be too effective and the intracranial pressure become too low. The symptoms of both are similar and include headaches, so it good to have a means of differentiating one condition from the other. We have published a number of papers on this including:-

• Moss SM, Marchbanks RJ, Burge DM. Long term assessment of intracranial pressure using the Tympanic Membrane Displacement Measurement Technique. European Journal Paediatric Surgery Supp I 1991: 25-26.

• Samuel M, Marchbanks RJ, Burge DM. Quantitative assessment of intracranial pressure by the Tympanic Membrane Displacement Audiometric Technique in children with shunted hydrocephalus. European Journal Pediatric Surgery 1998; 8: 1-9.

• Samuel M, Marchbanks RJ and Burge DM. Tympanic membrane displacement test in regular assessment in eight children with shunted hydrocephalus. Journal Neurosurg1998; 88: 983-995.

(SM)The TMD technique is being used in a KEMRI (Kenya Medical Research Institute), has it been used by the NHS yet and if not do you know of
any plans to do so?

(RM) The CCFP Analyser is CE-Marked for clinical use in Europe and elsewhere. It is used clinically in the NHS mostly at Southampton and for children in a London Hospital. It is not used extensively, and before this happens then we need to establish what is normal and the efficacy of the device. This work is underway in Southampton were we are collecting data from 360 normal adult volunteers. This work is being funded by Innovate UK. It is also being used on the International Space Station by NASA in collaboration with other Space Agencies. They need to establish how the intracranial pressure changes in space.

(SM) What training is involved for medical professionals using the equipment and those interpreting the results?

(RM) A medical professional can be trained to use the CCFP Analyser in a day, however, it takes a while before they have the confidence to interpret the test results. One of the main objectives of the Southampton work is to make testing easier both in terms of operation and interpreting findings.

(SM) Are there plans to share the results from the testing with UK doctors?

(RM) We wish to encourage UK and doctors worldwide to use the CCFP Technique. We are pleased to give advice to help set up clinical trials, and to support in any way we can. The Southampton reference data from the 360 normal adults will be available to medical professionals who need this for clinical use or medical research.

Autumn 2016

NB. If there are any further questions you would like us to put to Dr. Marchbanks on your behalf, please send them to: sarah@csfleak.info