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Convexal Subarachnoid Hemorrhage (cSAH)


KEY FACTS

Terminology

  • Unique type of subarachnoid hemorrhage (SAH)

    • Localized to sulci over top (“convexity”) of brain

Imaging

  • NECT: Hyperdensity in 1 or several adjacent dorsolateral convexity sulci

    • Spares basal, perimesencephalic cisterns

  • MR

    • Sulcal cerebrospinal fluid (CSF) replaced by isointense fluid in convexity sulcus (“dirty CSF”)

    • Hyperintense sulcus on FLAIR

    • GRE, SWI show “blooming” in affected sulci

Top Differential Diagnoses

  • Aneurysmal SAH

  • Perimesencephalic nonaneurysmal SAH

  • Traumatic SAH

Pathology

  • Most common etiology varies with age

    • Elderly patients: Amyloid angiopathy, venous thrombosis, vasculitis

    • Middle aged: Reversible cerebral vasoconstriction syndrome (RCVS), vasculitis, vein thrombosis

    • Young adults, children: Drugs, vasculitis, vein/dural sinus thrombosis

Clinical Issues

  • 7% of all spontaneous (nontraumatic) SAH

  • Most common: Middle-aged women

  • Presentation varies with age

    • < 60 years of age: Sudden “thunderclap” headache (e.g., RCVS)

    • > 60 years of age: Transient sensory, motor symptoms, less intense headache (cerebral amyloid angiopathy)

Graphic of brain seen from above shows convexal subarachnoid hemorrhage in purple affecting adjacent sulci but sparing the basal cisterns.

Axial NECT in a 28-year-old woman with severe headache following delivery shows focal subarachnoid hemorrhage
over the right cerebral convexity.

Axial T1WI MR in the same patient shows “dirty” fluid filling, effacing the normal sulcal cerebrospinal fluid (CSF) in the right convexity sulci
(compare to normal hypointense signal intensity in the contralateral sulci
).

Axial FLAIR MR in the same patient shows hyperintense right convexity sulci
(contrast with the normal suppressed hypointense CSF over the left convexity). Postpartum vasculopathy was diagnosed at DSA (not shown).

TERMINOLOGY

Abbreviations

  • Subarachnoid hemorrhage (SAH)

  • Convexal subarachnoid hemorrhage (cSAH)

Definitions

  • Unique type of SAH

    • SAH localized to sulci over top (“convexity”) of brain

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