Fisher Grade
The Fisher grade, developed in 1980, is commonly used to predict the risk of cerebral vasospasm after subarachnoid hemorrhage (SAH) based on the amount of blood shown on initial CT scans within 5 days of SAH (for more information, see Imaging in Subarachnoid Hemorrhage). [1, 2] They concluded that a localized clot or diffuse blood greater than 1 mm was highly predictive of vasospasm. [3]
However, the scale has been criticized and modifications suggested since grades 1-2 do not have clear clinical differences from grades 3-4 and since the presence of intraventricular blood does not change the classification of patients with thick clots in the cisterns. [4, 5, 6, 7, 8]
More recent scales use quantitative approaches to determine the amount of SAH and intraventricular hemorrhage (IVH) to predict the risk of vasospasm and poor clinical outcomes. [7, 8, 9]
The Fisher grading system is as follows:
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Grade 1: No blood
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Grade 2: Diffuse or thin layer of blood less than 1 mm thick (interhemispheric, insular, or ambient cisterns)
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Grade 3: Localized clots and/or layers of blood greater than 1 mm thick in the vertical plane
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Grade 4: Intracerebral or intraventricular clots with diffuse or absent blood in basal cisterns
