In a study done by Fisher et al in 1980, the relationship between cerebral vasospasm and the amount of subarachnoid bleed (SAH) detected in CT was assessed. It identified that when subarachnoid bleed is not detected or when present diffusely, vasospasm hardly ever occurred. They identified an important relation between location of blood clot and cerebral vasospasm.
However over the years, lots of criticism has been directed to this classification system.
