Danilo Cadim is a PhD research student working with Professor Marek Czosnyka in the Department of Clinical Neurosciences at Cambridge. He has recently begun a project examining the utility of non-invasive measurement of intracranial pressure in patients with acute encephalopathy.


 

The standard methods currently used for clinical monitoring of ICP are all invasive, requiring a hole to be drilled in the skull to insert a pressure probe or catheter into the brain parenchyma, or through the brain tissue into the ventricular space. All these approaches thus require neurosurgical expertise and carry the risk of infection and tissue damage.

The invasive nature of ICP monitoring methods in current clinical practice has prevented more extensive availability of this neurological parameter. A method for ICP monitoring that requires no surgery and poses no risks of infection or haemorrhage would certainly be welcomed by medical professionals, and at the very least could become a reliable tool in neuro-intensive care units provided it is sufficiently accurate and easy to use.

A variety of modalities has been explored for nICP estimation through measurement of related physiological variables, for instance, using ultrasound signals to measure CBF velocity (CBFV) indices. Some nICP estimation methods are based on simultaneous measurements of peripheral arterial blood pressure (ABP) along with TCD measurements of CBFV to generate the ICP estimate. The recording of ABP and CBFV waveforms in the clinical setting is quite routine; ABP measurement is already necessitated in a wide spectrum of critical care patients, and CBFV is the standard of care in patients with certain neurovascular pathologies. In relation to these methods, the associated error in estimating ICP in TBI patients for two of them was reported as less than 12 mmHg (Czosnyka, Matta, Smielewski, Kirkpatrick, & Pickard, 1998; Schmidt & Klingelhöfer, 2002) in comparison to the standard intraparenchymal method. These techniques are currently available at Addenbrooke’s Hospital as part of a PhD research about non-invasive ICP monitoring in the Department of Clinical Neurosciences, at Brain Physics Laboratory.

The non-invasive ICP trolley consists of TCD machine, computer, and non-invasive arterial blood pressure monitor (Finapress). The steps for nICP monitoring consist of TCD probe placement on the patients’ temporal window with the aid of a head band and connecting the computer to the bed-site monitor for ABP acquisition or application of Finapress cuff. Once cerebral blood flow (MCA) is found, monitoring starts and lasts 30 minutes. nICP is displayed instantly on the computer screen (ICM+ software), requiring a minimum of 10 minutes for reliable time averaging.

To evaluate accuracy, these methods will be applied to harvest clinical data from patients at NCCU during the course of the research. To study clinical feasibility daily service to assess ICP non-invasively in patients with intracranial pathologies but without ICP monitoring will be provided.


nICP Monitoring Figure

Left: Plateau wave in TBI patient evaluated with nICP methods on ICM+. Right: nICP trolley. Click for full size image.


Czosnyka, M., Matta, B. F., Smielewski, P., Kirkpatrick, P. J., & Pickard, J. D. (1998). Cerebral perfusion pressure in head-injured patients: a noninvasive assessment using transcranial Doppler ultrasonography. Journal of Neurosurgery, 88, 802–808. doi:10.3171/jns.1998.88.5.0802

Schmidt, B., & Klingelhöfer, J. (2002). Clinical applications of a non-invasive ICP monitoring method. European Journal of Ultrasound, 16(1-2), 37–45. doi:10.1016/S0929-8266(02)00044-7mu

Links

Non-invasive ICP