After an aneurysmal subarachnoid hemorrhage (aSAH), one of the most feared complications is cerebral vasospasm, which can lead to delayed cerebral ischemia (DCI) and stroke days after the initial bleed. The amount and pattern of blood visible on early non-contrast CT strongly correlates with this risk. To standardize this relationship, Fisher and colleagues introduced the Fisher CT grading scale in 1980.
Fischer Grade (SAH Vasospasm Risk) Calculator
A tool for healthcare professionals to assess vasospasm risk in subarachnoid hemorrhage patients
What is Fischer Grade?
The Fischer Grade is a classification system used to predict the risk of cerebral vasospasm following aneurysmal subarachnoid hemorrhage (SAH). Developed by Dr. C. Miller Fisher in 1980, this system categorizes patients based on the amount and distribution of blood visible on initial non-contrast CT scans.
Clinical Significance
Cerebral vasospasm is a serious complication of SAH that can lead to delayed cerebral ischemia and poor neurological outcomes. The Fischer Grade helps clinicians identify patients at higher risk for developing vasospasm, allowing for more intensive monitoring and prophylactic treatment.
Fischer Grade Classification
| Grade | CT Findings | Vasospasm Risk |
|---|---|---|
| 1 | No blood detected | Low |
| 2 | Diffuse deposition or thin layer of blood (<1mm thick) | Low |
| 3 | Localized clots and/or vertical layers of blood (≥1mm thick) | High |
| 4 | Diffuse or no subarachnoid blood, but with intracerebral or intraventricular clots | Low |
Limitations and Updates
While the Fischer Grade remains a valuable tool, it has been largely superseded by the Modified Fisher Scale (also known as the Claassen scale), which provides better prediction of symptomatic vasospasm. The Modified Fisher Scale incorporates the presence of intraventricular hemorrhage and uses a 0-4 grading system with improved predictive value.
Clinical Application
Patients with Fischer Grade 3 (high risk) typically require more aggressive monitoring, including frequent neurological assessments and potentially transcranial Doppler studies. They may also benefit from prophylactic therapies such as nimodipine and maintaining euvolemia.
Fischer Grade Calculator
Select the CT findings below to calculate the Fischer Grade and associated vasospasm risk.
Fischer Grade Result
Grade:
CT Findings:
