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Subarachnoid hemorrhage (SAH) refers to a bleeding in the subarachnoid space (between the arachnoid and the pia mater) that normally is filled with CSF.


Fisher Classification

Fisher classification is useful to correlate both the entity and the distribution of a subarachnoid hemorrhage with the risk of developing a vasospasm.

Note that the the principal factor for the determination of a vasospasm is the accumulation of a sufficient amount of blood in a definite site.


CT Appearance
1 No blood clot 21%
2 Diffuse thin SAH 25%
3 Localized clot/Thick SAH 37%
4 ICH or IVH 31%


Thin SAH - Vertical layers <1mm
Thick SAH - Vertical layers >1mm
ICH - Intracerebral hemorrhage
IVH - Intraventricular hemorrhage

Modified Fisher Classification

Modified Fisher Scale is used both to classify SAH based on CT and to correlate it to vasospasm risk.

Note that this classification is more intuitive than Fisher scale because the risk is higher in grade 4 than in grade 3


CT Appearance
1 Thin SAH, no IVH 24%
Thin SAH, IVH present 33%
Thick SAH, no IVH 33%
Thick SAH, IVH present 40%


Thin SAH - Vertical layers <1mm
Thick SAH - Vertical layers >1mm
ICH - Intracerebral hemorrhage
IVH - Intraventricular hemorrhage

World Federation of Neurological Surgeon Classification (WFNS)

WFNS classification is used both for the evaluation of a patients suffering from SAH in term of severity of injury and to predict the outcome.

Note that WFNS classification is based on both GCS (to establish the level of consciousness) and the presence/absence of focal deficits.


GCS Score
Motor Deficit
1 15 Absent
14-13  Absent 
14-13  Present 
12-7  Present or Absent 
6-3  Present or Absent 


Focal Deficit - Aphasia and/or hemiparesis or hemiplegia.

Hunt & Hess Score

H&H score is used to estimate surgical risk in patients with SAH.

Note that: 

  • In grade I or II the most important mortality factor is re-bleeding;
  • Surgical risk is higher in grade II patients because vasospasm are more frequent;
  • Critical patients are amenable to conservative therapy until they reach grade I or II.


Asymptomatic or minimal headache and slight nuchal rigidity
Moderate-severe headache, nuchal rigidity, cranial nerve palsy
Drowsiness, confusion or mild focal deficits 
Stupor, moderate-severe hemiparesis, decerebrate rigidity, vegetative disturbance 
Deep coma, decerebrate rigidity, moribund appearance 


Serious systemic disease such hypertension, diabetes, severe atherosclerosis, chronic pulmonary disease and severe vasospasm seen on arteriography result in placement of the patient in the next less favorable category.

Vasograde Scale

Vasograde Scale is used to assess delayed cerebral ischemia (DCI) after SAH. It is based on WFNS scale and Modified Fisher Scale.


M-Fisher Scale
Green 1-2 1-2
Yellow 1-3 3-4
Red 4-5 Any



Relation of Cerebral Vasospasm to Subarachnoid Hemorrhage Visualized by Computerized Tomographic Scanning. C.M Fisher M.D Neurosurgery, Vol.6, N.1, 1980.

Prediction of symptomatic vasospasm after subarachnoid hemorrhage: the modified fisher scale. Jennifer A. Frontera M.D Neurosurgery, Vol.58, N.7, July 2006.

Report of World Federation of Neurological Surgeons Committee on a Universal Subarachnoid Hemorrhage Grading Scale. Journal of Neurosurgery, Vol. 68, June 1988

Surgical risk as related to time of intervention in the repair of intracranial aneurysms. William E. Hunt M.D and Robert M.Hess M.D. Journal of Neurosurgery. 1968 Jan;28(1):14-20

The VASOGRADE: A Simple Grading Scale for Prediction of Delayed Cerebral Ischemia After Subarachnoid Hemorrhage. Airton Leonardo de Oliveira Manoel M.D Stroke. 2015;46:1826-1831





Federico Nicolosi, MD

University of Milan
"Spedali Civili" Hospital Brescia (Italy)
Scientific Team - UpSurgeOn

Giorgio Saraceno, MS

Medical Student
University of Brescia (Italy) 
Scientific Team UpSurgeOn