The Fisher Grade classifies the appearance of subarachnoid hemorrhage on CT scan:
No hemorrhage evident.
Subarachnoid hemorrhage less than 1mm thick.
Subarachnoid hemorrhage more than 1mm thick.
Subarachnoid hemorrhage of any thickness with intraventricular hemorrhage (IVH) or parenchymal extension.
Fisher C, Kistler J, Davis J (1980). “Relation of cerebral vasospasm to subarachnoid hemorrhage visualized by computerized tomographic scanning”. Neurosurgery 6 (1): 1–9.
Elderly patients, and especially the subgroup with a Fisher Scale 3 bleeding pattern, had a high risk for an unfavorable outcome, whereas the subgroup of Non perimesencephalic subarachnoid hemorrhage NPM-SAH without a Fisher Grade 3 bleeding pattern had a favorable outcome, similar to perimesencephalic subarachnoid hemorrhage (PM)-SAH.