Continuous Neurophysiological Monitoring Detection of Cerebral Vasospasm in Aneurysmal Subarachnoid Hemorrhage Subjects

Aneurysmal subarachnoid hemorrhage is a serious condition with a high morbidity and mortality. There are approximately 11 cases per 100,000 population per year, and approximately 40% of these cases are fatal. (Ingall) Among the fortunate subjects who survive the initial bleed, vasospasm and subsequent stroke are a major cause of morbidity. Vasospasm is defined as a prolonged severe, although reversible cause of arterial narrowing that occurs after bleeding into the subarachnoid space, most commonly after aneurismal rupture. (Youman) The reduced arterial diameter inhibits blood flow and deprives the brain of oxygen, which often results in a stroke. Vasospasm is a major problem when treating subjects with aneurismal subarachnoid hemorrhage. Up to 75% of subjects with aneurismal subarachnoid hemorrhage will develop vasospasm, and 30% of subarachnoid hemorrhage subjects will become clinically symptomatic, with muscle weakness as the primary symptom. (Dorsch) Even with intervention, 12% of patents with symptomatic vasospasm will develop permanent clinical deficits (after a ruptured aneurysm) including hemiplegia, aphasias, and visual loss. Less severe strokes may lead to modest loss of strength and sensation on one side of the body, and/or deterioration in higher brain functions, such as memory, speech comprehension, and planning. Continuous Neuro-monitoring has previously been used in the trauma ICU setting as a means to detect deterioration in brain function after closed head injury (Amantini, Daubin), ischemic encephalopathy (Hakimi) and in subjects with MCA stroke to determine function (Tzvetanov). It was also observed that monitoring changes occur prior to ICP elevations in critically ill subjects (Amantini). These studies have demonstrated the feasibility as well as the safety of monitoring in an ICU. No studies to date have attempted monitoring for vasospasm in subjects who suffered an aneurysmal subarachnoid hemorrhage. Motor evoked potential have also not been trialed in the ICU, although MEP may be more useful to determine both cerebral ischemia, as well as functional outcome.