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

Aneurysmal subarachnoid hemorrhage (bleeding on the brain due to a ruptured aneurysm) is a serious condition with a high morbidity (incidence of having ill health) and mortality (death). There are approximately 11 cases per 100,000 in the 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 aneurysmal 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 aneurysmal subarachnoid hemorrhage. For these reasons, it is essential to diagnose cerebral vasospasm early, before permanent deficits develop. There may be another option to solve this dilemma. The field of neuro-monitoring (neurological monitoring) has the technology available to continuously monitor brain activity of these sedated ICU subjects. This may allow for early diagnosis and possibly identify changes in neurologic function before they become symptomatic. In the past, neuro-monitoring was primarily used in the operating room to monitor neurologic function during surgery in and around the spinal cord. Surgery to the spine or spinal cord also carries its own form of risk, either from mechanical trauma to the spinal cord or its nerve roots, or from interruption of the blood supply to these structures. Should damage to nerve fibers occur, the end result could be paralysis, loss of sensation, and onset of severe burning (i.e. neuropathic) pain. The field of intraoperative neuro-monitoring (IOM) was developed to address these risks during spine surgery, whereby nerves rostral (toward the head) or caudal (toward the feet) to the site of surgery are stimulated (usua