fisher_sah_grade: Fisher Grading Scale for Subarachnoid Hemorrhage (SAH)

In cliot: Clinical Indices and Outcomes Tools

Fisher Grading Scale for Subarachnoid Hemorrhage (SAH)

Description

Calculates the Fisher Grade for patients with subarachnoid hemorrhage based on initial CT scan findings. The scale predicts the risk of cerebral vasospasm. Note that Grade 3 (Thick clot) carries the highest risk, higher than Grade 4 (ICH/IVH).

Usage

fisher_sah_grade(sah_present, ich_ivh_present, clot_thickness_ge_1mm)

Arguments

sah_present	Numeric (0 or 1). Is subarachnoid blood detected on CT? (1 = Yes).
ich_ivh_present	Numeric (0 or 1). Is there an intracerebral (ICH) or intraventricular (IVH) clot? (1 = Yes). Note: In the original Fisher scale, this finding (Grade 4) defines the category regardless of SAH thickness, though clinically Grade 3 implies higher vasospasm risk.
clot_thickness_ge_1mm	Numeric (0 or 1). Are localized clots or vertical layers >= 1mm thick present? (1 = Yes).

Value

A list containing:

Fisher_Grade	The calculated grade (1-4).
CT_Findings	The description of the grade.
Vasospasm_Risk	Estimated percentage risk of developing vasospasm.

References

Fisher CM, Kistler JP, Davis JM. Relation of cerebral vasospasm to subarachnoid hemorrhage visualized by computerized tomographic scanning. Neurosurgery. 1980;6(1):1-9. doi:10.1227/00006123-198001000-00001

Examples

# Example 1: Highest Risk (Grade 3)
# SAH present, No ICH/IVH, Thick clot
fisher_sah_grade(1, 0, 1)

# Example 2: Grade 4
# SAH present, ICH present (overrides thickness in classification logic)
fisher_sah_grade(1, 1, 0)

cliot documentation built on Dec. 1, 2025, 1:06 a.m.