SUBARACHNOID HEMORRHAGE
Definition and etiology of subarachnoid hemorrhage
Created 29/03/2021, last revision 21/04/2023
Definition, epidemiology
- subarachnoid hemorrhage (SAH) is a clinical syndrome resulting from bleeding into the subarachnoid space (the area between the arachnoid membrane and the pia mater surrounding the brain)
- the most common cause of SAH is head trauma (traumatic SAH)
- non-traumatic SAH is often caused by rupture of a cerebral aneurysm (~80%) or, less frequently, due to arteriovenous malformation (AVM)
- aneurysms are acquired lesions related to hemodynamic stress on the arterial walls at bifurcations and bends
- aneurysmal SAH is a cause of 3-8% of all strokes; aneurysms 5-15 mm in size are the most common aneurysm to rupture
- unruptured aneurysms are found in 0.3-5% of the population, multiple in 15-20% of cases
- the annual incidence of aneurysmal SAH is race-, sex-, and age-related
- reported rates vary between 10 and 26 cases per 100,000 population
- the incidence of SAH in women is higher than in men (ratio of 3 to 2)
- incidence increases with age
- the peak at the age of 40-65 years (80% of SAH)
- only 15% occur in people aged 20-40 years and 5% in people < 20 years of age
- SAH is rare in children
- SAH may have an unfavorable prognosis (reported percentages vary in the literature):
- 5-15% of patients die before arriving at the hospital
- 30% have initially severe deficits (Hunt-Hess 4-5)
- about 2/3 have a mild deficit initially; 50% deteriorate soon (spasms, rebleeding, surgery, and other complications)
- 10-20% of those admitted to hospital die within 24 hrs due to rebleeding
- risk factors
- smoking, hormonal oral contraception, alcohol, hypertension, stimulants
- genetic predisposition – family history of a ruptured aneurysm increases risk 3-7 times
Etiology
- there are three distinct SAH patterns; for each pattern, specific etiologies, treatment, and prognostic implications were described
- suprasellar cisterns with peripheral extension
- perimesencephalic SAH (pmSAH)
- convexial SAH (cSAH)
Traumatic SAH
- history of trauma
- localization at the convexity between gyri is common
- compared to cSAH, more significant bleeding is usual
- exclude concomitant traumatic changes (e.g., hemorrhagic contusion, subdural hematoma, skull bone fissure, subcutaneous hematoma)
- ! contusions may become apparent after a few hours ⇒ perform a control CT scan with sufficient delay
- ! contusions may become apparent after a few hours ⇒ perform a control CT scan with sufficient delay
Spontaneous (non-traumatic) SAH
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Prognosis
- prognosis depends on the severity of the initial insult and our ability to prevent complications, specifically rebleeding (by early detecting and treating the source)
- overall mortality up to 50%
- 10-15% of patients die before arriving at the hospital
- another 10-12% die within 24 h
- rebleeding or brainstem dysfunction due to a massive intraventricular hemorrhage or decompensated intracranial hypertension are the usual causes of death
- 1/3-1/2 of the survivors have significant functional deficits (motor and/or cognitive)
- cognitive deficits are present in numerous patients considered to have a good outcome
- SAH patients commonly experience deficits in memory, executive function, and language; these symptoms are accompanied by depression, anxiety, fatigue, and sleep disturbances
Factors affecting morbidity and mortality in SAH |
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