Convexal subarachnoid hemorrhage (cSAH)

Non-traumatic subarachnoid bleeding localized in one or more convexity sulci without extension in the neighboring parenchyma, interhemisferic fissure, basal cisterns or ventricles.


  • Different aetiology and outcomes compared to aneurysmal or traumatic SAH
  • Possible identifiable causes (1-3 seem to be the three most common):
    1. Reversible cerebral vasoconstriction Syndrome (most common ≤60 years)
    2. Cerebral amyloid angiopathy (most common >60 years)
    3. Cerebral vein thrombosis
    4. Dural venous sinus thrombosis
    5. Posterior Reversible Encephalopathy Syndrome
    6. Arteriovenous malformations
    7. Cavernous malformation
    8. Dural arteriovenous fistula
    9. Vasculitis
    10. Mycotic aneurysms
    11. Endocarditis
    12. Abscess
    13. Drug abuse (cocaine)
    14. Moyamoya disease
    15. Ipsilateral internal carotid stenosis
    16. Arterial dissection
    17. Coagulopathy
    18. Brain neoplasms (including metastases)

Common presenting symptoms/signs

In order of decreasing frequency:


  1. Headache
    • Thunderclap-like presentation is uncommon and many patients will have mild or no headache.
  2. Transient sensorymotor deficits
    • May spread to different body parts like a migrainous march
    • May resemble TIA
  3. Lethargy / decreased alertness
  4. Seizures

Imaging recommendation

  • Brain CT
    • Sensitivity of brain CT in detecting cSAH is >90% but falls rapidly after the first 6 hours, especially if there is a small volume of blood
  • CT angiography in arterial and venous phase
    • AVM, dAVF, high-grade stenosis, RCVS, vasculitides, mycotic aneurysms, dissection, moyamoya
    • Dural sinus /cortical vein thrombosis
  • MRI including MRA and MRV
    • FLAIR very sensitive for acute subarachnoid blood
    • SWI, T2* very sensitive for microbleeds, cortical superficial siderosis, cavernoma
    • PRESS, neoplasms, abscess, CAA, CVT
  • Digital subtraction angiography
    • In cases when diagnosis is uncertain and CTA/MRA have not revealed vascular pathology
    • Some authors recommend repeat DSA if first examination is negative



References

  • Isolated Acute Nontraumatic Cortical Subarachnoid Hemorrhage 2010 Sep; 31(8): 1355–1362. AJNR Am J Neuroradiol. 2010 Sep;31(8):1355-62. doi: 10.3174/ajnr.A1986
  • Atraumatic convexal subarachnoid hemorrhage: clinical presentation, imaging patterns, and etiologies Neurology. 2010 Mar 16;74(11):893-9. doi: 10.1212/WNL.0b013e3181d55efa
  • Incidence of Convexal Subarachnoid Hemorrhage in the Elderly: The Mayo Clinic Study of Aging J Stroke Cerebrovasc Dis. 2019 Dec;28(12):104451. doi: 10.1016/j.jstrokecerebrovasdis.2019.104451