Modified Fisher scale
The modified Fisher scale is a method for grading subarachnoid hemorrhage (SAH) seen on CT. It was developed from the original Fisher scale which was modified to account for patients with thick cisternal blood and concomitant intraventricular (IVH) or intraparenchymal hemorrhage.
Moreover, the risk of developing vasospasm progressively increases with each level of the modified Fisher grade. Whereas the risk was highest for Grade 3 and then decreased for Grade 4 while using the original Fisher scale.
- grade 0: no SAH or IVH
- grade 1: focal or diffuse, thin SAH, no IVH
- grade 2: focal or diffuse, thin SAH, with IVH
- grade 3: focal or diffuse, thick SAH, no IVH
- grade 4: focal or diffuse, thick SAH, with IVH
Note: thin SAH is < 1mm thick and thick SAH is >1 mm in depth.