ToolsCalculators
Modified Fisher Grading Scale for Subarachnoid Hemorrhage (SAH)
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.