Subarachnoid Hemorrhage: Classification

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).
• 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”.

Preferred classification is that of the “World Federation of Neurosurgical” (WFNS).It is based on the Glasgow Coma Scale (GCS)* :

* Scale for estimating a disorder of consciousness.