RadEssentialReading-room reference
Modified Fisher scale
Grades aneurysmal SAH on the admission CT to stratify risk of symptomatic vasospasm. Thick = clot filling any cistern or fissure completely; IVH = blood in both lateral ventricles in the original definition.
| Grade | Subarachnoid blood | Intraventricular blood |
|---|---|---|
| 0 | None | None |
| 1 | Focal or diffuse thin | Absent |
| 2 | Focal or diffuse thin | Present |
| 3 | Thick, focal or diffuse | Absent |
| 4 | Thick, focal or diffuse | Present |
Risk of symptomatic vasospasm and delayed infarction rises with grade. The original Fisher scale (1980) has 4 grades and counterintuitively places thick clot with IVH in grade 4 below grade 3 risk, which the modified scale corrects.
Original Fisher (1980), for comparison
| Grade | CT finding |
|---|---|
| 1 | No blood detected |
| 2 | Diffuse or vertical layers <1 mm thick |
| 3 | Localized clot and/or vertical layers ≥1 mm |
| 4 | Intracerebral or intraventricular clot with diffuse or no SAH |
Sources
- Frontera JA, Claassen J, Schmidt JM, et al. Prediction of symptomatic vasospasm after subarachnoid hemorrhage: the modified Fisher scale. Neurosurgery. 2006;59:21–27.PubMed ↗
- Fisher CM, Kistler JP, Davis JM. Relation of cerebral vasospasm to subarachnoid hemorrhage visualized by computerized tomographic scanning. Neurosurgery. 1980;6:1–9.PubMed ↗
Radessential summarizes published classification systems for practicing radiologists. Summaries are condensed; confirm details against the cited source before relying on them for patient care.