SUBARACHNOID HEMORRHAGE
Diagnosis of subarachnoid hemorrhage
Created 30/03/2021, last revision 10/01/2023
- 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
- SAH is found in typical localisations (see below) but may be limited to convexity (hyperdense strips in sulci) → convexial nontraumatic SAH
- SAH is found in typical localisations (see below) but may be limited to convexity (hyperdense strips in sulci) → convexial nontraumatic SAH
- 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
- CT scan sensitivity decreases over time – by day 3, it is 70%, and < 50% one week later
| SAH localization |
Aneurysm localization |
| Sylvian fossa | MCA |
| interhemispheric fissure |
ACoA |
| suprasellar cistern |
distal ICA |
| perimesencephalic cistern | top basilar artery |
| 4th ventricle | PICA |
Combination of SAH and intraparenchymal bleeding
- SAH may combine with intraparenchymal hematoma (mainly with MCA aneurysms) or intraventricular bleeding
- an opposite situation can also occur – primary ICH from AVM or ICH in basal ganglia can secondary expand into a subarachnoid space (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)
- other signs of trauma are present (SDH, EDH, ICH, contusion, subcutaneous hematoma, a skull bone fissure ( inspect in a bone window)
- 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
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
- 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
Spectrophotometry
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Cytology
- 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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