ToolsCalculators
Modified Fisher Grading Scale for Subarachnoid Hemorrhage (SAH)
Refines the Fisher scale to better stratify vasospasm risk using intraventricular hemorrhage.
Modified Fisher Grading Scale for Subarachnoid Hemorrhage (SAH)
CT appearance
ResultModified Fisher grade 0
No subarachnoid or intraventricular blood – lowest risk of symptomatic vasospasm.
When to use
- Estimating symptomatic vasospasm risk after aneurysmal subarachnoid hemorrhage, preferred over the original Fisher scale because it accounts for intraventricular hemorrhage.
Formula
Grade assigned from non-contrast CT based on thickness of cisternal/fissural SAH (thin vs thick) crossed with presence or absence of intraventricular hemorrhage (grades 0-4 as above); grade is not additive.
Pearls and pitfalls
- Unlike the original Fisher scale, risk increases monotonically with grade, which makes the modified scale easier to apply clinically.