Modified Fisher scale

The modified Fisher scale is a method for radiological grading subarachnoid haemorrhage (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 (IVH) 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 haemorrhage (SAH)
  • no intraventricular haemorrhage (IVH)
  • incidence of symptomatic vasospasm: 0% ³
• grade 1
  • focal or diffuse, thin SAH
  • no IVH
  • the incidence of symptomatic vasospasm: 24%
• grade 2
  • thin focal or diffuse SAH
  • IVH present
  • the incidence of symptomatic vasospasm: 33%
• grade 3
  • thick focal or diffuse SAH
  • no IVH
  • the incidence of symptomatic vasospasm: 33%
• grade 4
  • thick focal or diffuse SAH SAH
  • IVH present
  • the incidence of symptomatic vasospasm: 40%

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

Note: Any IVHintraventricualr haemorrhage, 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 haemorrhage