The following forms of subarachnoid hemorrhage (SAB) are classified according to cause:
- Nontraumatic (spontaneous) subarachnoid hemorrhage.
- Aneurysmal SAB (85% of cases).
- Rupture (rupture) of a cerebral aneurysm
- Bleeding is most severe in the basal cisterns (cisterns = cavities around the brain)
- Non-aneurysmal SAB (15% of cases).
- Perimesencephalic SAB
- Blood pools around the mesencephalon (midbrain) and pons (“bridge”; a section of the brain that, along with the cerebellum, is part of the hindbrain)
- Cause is probably a venous hemorrhage
- Prognostically more favorable type, usually without recurrent bleeding (new bleeding).
- Complications as in aneurysmal SAB.
- Non-perimencephalic basal SAB.
- Without evidence of a bleeding source
- Cortical SAB
- Small cortical (“originating in the cerebral cortex”) subarachnoid hemorrhages
- Focal seizures or deficits occur in adjacent brain regions (focal = focal, affecting only one part)
- Most common cause in affected individuals,
- Who are younger than 70 years of age is reversible cerebral vasoconstriction syndrome (RCVS; synonym: Call-Fleming syndrome: constriction (contraction of muscles) of cerebral vessels leading to severe headache (annihilation headache) with or without other neurological abnormalities).
- Who are older than 70 years, cerebral amyloid angiopathy (ZAA; degenerative vasculopathy (vascular damage) caused by deposits of beta-amyloid (peptides/determined protein molecules) in the wall layers; beta-amyloid plaques are also considered the main trigger of dementia and Alzheimer’s disease)
- Other causes:
- Arteriitis (inflammation of one or more arteries).
- Vascular anomalies such as arteriovenous malformation (AVM; congenital malformation of blood vessels), durafistula (pathological short-circuit connection between arteries and veins at the level of the meninges)
- Intracranial (occurring in the skull) arterial dissection (splitting of the wall layers of an artery).
- Cocaine abuse
- Reversible cerebral vasoconstriction syndrome (RCVS; see above).
- Tumors
- Venous thrombosis (vascular disease in which a blood clot (thrombus) forms in a vein).
- Cerebral amyloid angiopathy (ZAA; see above).
- Perimesencephalic SAB
- Aneurysmal SAB (85% of cases).
- Traumatic subarachnoid hemorrhage
- In the context of severe traumatic brain injury (TBI; accidents, etc.) – in about 40% of traumas.
The classification of stages or severity of subarachnoid hemorrhage, as well as a corresponding assessment of the prognosis can be made according to the “Hunt and Hess scale”.
Hunt and Hess grade | Symptoms | Perioperative mortality |
0 |
|
– – |
I |
|
0-5 % |
II |
|
1-10 % |
III |
|
10-15 % |
IV |
|
60-70 % |
V |
|
70-100 % |
Preferred classification is that of the “World Federation of Neurosurgical” (WFNS).It is based on the Glasgow Coma Scale (GCS)* :
Class | Criterion | GCS score |
1 | – – | 15 |
2 | Without focal CNS signs | 13-14 |
3 | with focal CNS signs | 13-14 |
4 | With or without focal CNS signs. | 7-12 |
5 | With or without focal CNS signs. | < 7 |
* Scale for estimating a disorder of consciousness.