Subarachnoid hemorrhage CT
Subarachnoid Hemorrhage Microchapters
AHA/ASA Guidelines for the Management of Aneurysmal Subarachnoid Hemorrhage (2012)
Subarachnoid hemorrhage CT On the Web
American Roentgen Ray Society Images of Subarachnoid hemorrhage CT
The modality of choice for diagnosis of subarachnoid hemorrhage is noncontrast head computed tomography (CT), with or without lumbar puncture The sensitivity of CT to the presence of subarachnoid blood is strongly influenced by both the amount of blood and the time since the hemorrhage
The modality of choice for diagnosis of subarachnoid hemorrhage is noncontrast head computed tomography (CT), with or without lumbar puncture. The diagnosis of subarachnoid hemorrhage cannot be made on clinical grounds alone. Medical imaging is usually required to confirm or exclude bleeding.
- The sensitivity of CT to the presence of subarachnoid blood is strongly influenced by both the amount of blood and the time since the hemorrhage
The diagnosis is suspected when hyperattenuating material is seen filling the subarachnoid space. Most commonly this is apparent around
- Circle of Willis (account of the majority of berry aneurysms)
- Sylvian fissure
Small amounts of blood can sometimes be appreciated pooling in the interpeduncular fossa, appearing as a small hyperdense triangle, or within the occipital horns of the lateral ventricles.
Sensitivity of CT may be reduced in the following conditions:
- Patients with atypical symptoms (isolated neck pain)
- Minor bleeds
Subarachnoid haemorrhages are grouped into four categories according to the amount of blood by the Fisher Grade.
|Grading||Amount of blood shown on initial CT scans|
- The sensitivity of CT in the first 3 days after aSAH is very high (close to 100%)
- Acute Subarachnoid hemorrhage is typically 50-60 HU
Several days to weeks
- When CT scanning is performed several days to weeks after the initial bleed, the findings are more subtle
- The initial high-attenuation of blood and clot tend to decrease, and these appear as intermediate gray
- These findings can be isointense relative to normal brain parenchyma
The following are the CT scans associated with diffuse subarachnoid hemorrhage.
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- Perry JJ, Stiell IG, Sivilotti ML, Bullard MJ, Emond M, Symington C; et al. (2011). "Sensitivity of computed tomography performed within six hours of onset of headache for diagnosis of subarachnoid haemorrhage: prospective cohort study". BMJ. 343: d4277. doi:10.1136/bmj.d4277. PMC 3138338. PMID 21768192. Review in: Evid Based Med. 2012 Feb;17(1):27-8
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