Modified Fisher scale

The modified Fisher scale is a method for radiological grading subarachnoid hemorrhage (SAH) secondary to intracranial aneurysm rupture, assessed on the first non-contrast CT.

It was modified from the original Fisher scale to account for patients with thick cisternal blood and concomitant intraventricular hemorrhage. When using the modified Fisher scale, the risk of developing vasospasm progressively increases with each grade; in the original Fisher scale, the risk counterintuitively peaked at grade 3 and decreased for grade 4.

Classification

• grade 0

  • no subarachnoid hemorrhage (SAH)

  • no intraventricular hemorrhage (IVH)

  • incidence of symptomatic vasospasm: 0% ³

• grade 1

  • focal or diffuse, thin SAH

  • no IVH

  • the incidence of symptomatic vasospasm: 24%

• grade 2

  • focal or diffuse, thin SAH

  • IVH present

  • the incidence of symptomatic vasospasm: 33%

• grade 3

  • thick SAH

  • no IVH

  • the incidence of symptomatic vasospasm: 33%

• grade 4

  • thick  SAH

  • IVH present

  • the incidence of symptomatic vasospasm: 40%

Note: the original study did not include a specified measurement or criteria to define thick vs thin hemorrhage.

Note: Any intraventricular hemorrhage, no matter how small, is counted.

Differences with the Fisher scale

The main differences between the Fisher scale and modified Fisher scale are ^4,5:

• in Fisher scale, no SAH is grade 1

  • grade 0 in modified Fisher scale

• in Fisher scale, thin SAH with no IVH is grade 2

  • grade 1 in modified Fisher scale

• in Fisher scale, thick SAH with no IVH is grade 3

  • grade 3 in modified Fisher scale

• in Fisher scale, any IVH is grade 4, irrespective of the presence of SAH

  • in modified Fisher scale it is either grade 2 if thin or no SAH, or grade 4 if thick SAH

See also

• Hunt and Hess grading system

• WFNS grading system

• cerebral vasospasm following subarachnoid hemorrhage