Noninvasive methods for ICP assessment and monitoring

Enclosed in a rigid cranium, the brain is unyielding and unforgiving, if the pressure inside the cranium rises beyond the physiologic limits of the human body to contain it. More damage may be caused by the effects of raised intracranial pressure, than by the pathology causing it. Modern protocols for management of intracranial pathologies thus revolve around maintenance of intracranial pressure within physiologic limits. This is only possible if we are able to monitor intracranial pressure, and the effects of treatment on it. It was our understanding that to reliably measure fluid pressure in close confines, the measure should be exposed to the inside in some way. For the cranium this meant an invasive device such as an external ventricular drain that remained the gold standard. More recently, several less invasive methods have largely replaced the external ventricular drain in common practice. However, an equally reliable non-invasive method of monitoring intracranial pressure would most certainly be preferable by both physicians and patients. Several non-invasive or indirect means of measurement have been studied with some showing reasonable promise in the past. As technology improves, newer methods, as well as modifications to older methods are helping to bring the promise of the ideal non-invasive method of intracranial pressure measurement closer to patient care. In this chapter, we summarize the history of non-invasive intracranial pressure measurement, the currently available modalities and the most promising recent advancements.