Delayed cerebral ischemia is a major cause of morbidity and death following aneurysmal subarachnoid hemorrhage and requires timely intervention for a successful outcome to be achieved. In this study the investigators compared the commonly used Fisher scale with 2 newer radiographic scales for the prediction of vasospasm, delayed infarction, and poor outcome.
This was a single-center, retrospective cohort study involving 271 consecutive patients with a ruptured cerebral aneurysm. Without knowledge of subsequent events, admission CT scans were each assigned scores by using 3 different grading schemes: the Fisher, modified Fisher, and Claassen scales. For each of the scales, the relationship between an increasing score and the risk of later complications was assessed in univariate and multiple logistic regression analyses.
With the Fisher scale, the risk of complications was relatively high when the score was 3, but not for other scores. In contrast, using the other scales, there was a more linear relationship between a rising score and the frequency of complications. This was particularly true for the modified Fisher scale, in which each stepwise increase was associated with an escalating risk of vasospasm, delayed infarction, and poor prognosis. Kappa scores measuring interobserver variability among 4 CT readers were also slightly better with the newer scales.
Although the modified Fisher and Claassen scales have yet to be prospectively validated, the authors' findings suggest that the clinical performance of these systems is superior to that of the Fisher scale.