SUBARACHNOID HEMORRHAGE

Nontraumatic convexial subarachnoid hemorrhage (cSAH)

Created 06/04/2021, last revision 19/05/2022

Definition

  • non-traumatic spontaneous subarachnoid hemorrhage at the convexity (non-traumatic convexial SAH – cSAH) is defined as a collection of blood in 1 or more adjacent sulci in the absence of SAH in another localization
  • it is relatively rare, but the etiological DDx is quite broad
    • in patients ≤ 60 years of age, the most common cause is RCVS  [Kumar, 2010]
    • in patients > 60 years of age,  the most common cause is CAA 

Clinical features

  • severe headache typical for classic SAH is usually not present [Beitzke, 2011]
    • headaches are generally present in cerebral venous thrombosis, RCVS, and PRES
  • transient focal symptoms (paresthesias, paresis) are frequent, which leads to suspicion of stroke/TIA (cSAH belongs to stroke mimics)
    • etiopathogenesis of transient symptoms is unclear; cortical spreading depression triggered by blood in the SA space is considered [Beitzke, 2011]

Diagnostic evaluation

Computed tomography

  • the primary diagnostic method
  • a finding of sulcal hyperdensity leads to the indication of CTA (both arterial and venous phase)
    • CT sensitivity is approx. 90% in the acute phase but decreases quickly with time (the lesion becomes isodense)
  • because of the wide DDx, it is advisable to add MRI

Magnetic resonance imaging

  • perform the following sequences:
    • FLAIR
    • GRE or SWI
    • DWI+ADC
    • 3D TOF MRA + MR venography
    • T1 and T1 C+
  • FLAIR is highly sensitive to lesions in the subarachnoid space; cSAH appears as a hyperintense band
  • in DDx of cSAH exclude:
    • meningitis
    • leptomeningeal metastases (LMM) and leptomeningeal melanosis
    • post status epilepticus lesions
    • previous contrast examination with gadolinium
    • artifact
  • FLAIR further reveals other typical structural changes in the parenchyma (e.g., PRES, etc.)
  • GRE/SWI – confirms the hemorrhagic nature of sulcal hyperintensities and may also help in the detection of older hemorrhages or venous thrombosis
Non-traumatic convexial SAH

Etiology

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Differencial diagnosis

  • traumatic SAH
    • history of trauma
    • usually, a more significant extent of SAH on the imaging methods
    • concurrent contusions (sometimes only seen on a follow-up CT scan)
    • a skull bone trauma visible in the bone window
  • cortical laminar necrosis
    • associated hyperintense lesions on MR DWI
  • leptomeningeal metastases
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