• the diagnosis of SAH should be considered in any patient with a severe and sudden onset or rapidly escalating headache
  • deciding which patients require a workup for SAH is often a challenging part of the emergency care
  • imaging methods can confirm the diagnosis of subarachnoid hemorrhage (SAH)
    • the standard imaging method is computed tomography (CT) – NCCT followed by CTA to detect or exclude a source of bleeding
    • negative CT scan is followed by a lumbar puncture (LP) with proper CSF analysis

Computed tomography

  • SAH is manifested by increased density of subarachnoid (SA) space  → Fisher scale
  • CT scan sensitivity for SAH: 90-95% within the first 24 h, but it depends on the amount of blood
    • CT scan sensitivity decreases over time – by day 3, it is 70%, and < 50% one week later
    • if there is a significant amount of blood on CT after one week, rebleeding is very likely
Aneurysmal SAH

SAH caused by rupture of top basilar artery aneurysm

SAH localization
Aneurysm localization
Sylvian fossa MCA
interhemispheric fissure
suprasellar cistern
distal ICA
perimesencephalic cistern top basilar artery
4th ventricle PICA
SAH caused by rupture of PComm aneurysm
SAH caused by rupture of basilar apex aneurysm
SAH caused by ACA aneurysm rupture
SAH caused by MCA aneurysm rupture
Saccular A1 aneurysm

Combination of SAH and intraparenchymal bleeding

  • SAH may combine with intraparenchymal hematoma (mainly with MCA aneurysms) or intraventricular bleeding  Intracerebral hemorrhage from MCA aneurysm  Intraventricular bleeding from an ICA aneurysm
  • an opposite situation can also occur – primary ICH from AVM or ICH in basal ganglia can secondary expand into a subarachnoid space (secondary SAH)  Hypertonic hemorrhage in basal ganglia with secondary SAH

Convexial SAH

  • traumatic
    • other signs of trauma are present (SDH, EDH, ICH, contusion, subcutaneous hematoma,  a skull bone fissure ( inspect in a bone window) Subcutaneous hematoma Traumatic SAH and epidrual hematoma on NCCT  Traumaic SAH with skull fissure
  • bleeding from a dural fistula
  • rarely, intracranial venous thrombosis may initially manifest as convexial SAH  [Sharma, 2010] [Oppenheim, 2005]
    • rupture of a dilated feeding vein due to retrograde intravenous hypertension
    • secondary rupture of a hemorrhagic infarction into the SA space

→ nontraumatic convexial SAH

Perimesencephalic SAH (PMSAH)

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Magnetic resonance imaging (MRI)

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Cerebrospinal fluid analysis

  • there is a recommended interval of >12 hours between the onset of presenting symptoms and lumbar puncture (LP) [Beetham, 2003]
    • if performed earlier, the CSF can be “artificially normal”
  • rapid analysis of collected CSF is required
  • bedside multiple-tubes test   Multiple tubes test - no clearing of blood points toward SAH diagnosis
    • in case of bleeding caused by the puncture, a clearing of the CSF should happen when sampling in multiple tubes
  • xanthochromia is proof of older bleeding
  • risk of early recurrence of SAH as a complication of lumbar puncture is negligible


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  • cytology is helpful only when the activation of the monocyte elements and the phagocytosis of erythrocytes have begun
  • aseptic meningitis is usually present at later stages of SAH
  • cytology helps to distinguish repeated bleeding
    • there is a disruption in the sequence of erythrocytes phagocytosis and the gradual appearance of hematogenous pigments in macrophages
    • a simultaneous presence of phagocytosis of intact erythrocytes together with hemosiderin granules or simultaneous appearance of hematoid crystals together with erythrocyte digestion can be observed
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Diagnosis of subarachnoid hemorrhage
link: https://www.stroke-manual.com/diagnosis-of-subarachnoid-hemorrhage/