Diagnosing Vasospasm After Subarachnoid

Aneurysmal subarachnoid hemorrhage (A-SAH) has potentially devastating consequences acutely, sub-acutely and long term. The incidence of A-SAH varies widely among populations with up to a tenfold difference. Incidence ranges from 2.0 per 100,000 per year in China to 22.5 per 100,000 per year in Finland.1 One of the most feared complications in patients who survive the acute A-SAH is cerebral vasospasm (CV). The peak incidence of CV is between 5 and 14 days after A-SAH. Cerebral vasospasm may occur angiographically in up to two-thirds of A-SAH patients, however this is only symptomatic in about one-third of them. Delayed neurologic defects or delayed cerebral ischemia (DCI) occurs in approximately half of patients with angiographic CV.2,3 Early diagnosis and treatment of CV can reduce morbidity and mortality.4 Therefore, it is important to diagnose and thereafter treat CV as early as possible in order to avoid permanent neurologic deficit. The pathogenesis of CV is a poorly understood, although it can be thought of as an abnormal and prolonged contraction of vascular smooth muscle due to the presence of subarachnoid blood. Breakdown products of blood in the subarachnoid space appear to be involved in the development of CV after SAH. In a canine model, a relationship between the volume of blood in the subarachnoid space and the severity of CV was demonstrated.5 In humans, the amount of blood on computed tomogram (CT) in ABSTRACT: Cerebral vasospasm is a potentially devastating complication in patients with aneurysmal subarachnoid hemorrhage. The purpose of this article is to review the use of computed tomogram (CT) angiography and CT perfusion in the diagnosis of cerebral vasospasm after aneurysmal subarachnoid hemorrhage and also assess their use in guiding treatment decisions. Both techniques are widely used for other indications but their use in cerebral vasospasm has not been well defined. Computed tomogram angiography can directly visualize arterial narrowing and CT perfusion is able to evaluate differences in perfusion parameters after aneurysmal subarachnoid hemorrhage with high sensitivity and specificity. CT perfusion is better at predicting which patients require endovascular treatment.