Traumatic Subarachnoid Hemorrhage (tSAH)
- Hemorrhagic collection within the subarachnoid space, located between pia and arachnoid membranes.
- Hunt and Hess scale: describes 5 grades of the severity of subarachnoid hemorrhage based on clinical correlates and is used to predict survival
- Fisher scale: a CT-based classification of subarachnoid hemorrhage into four groups based on the amount of blood, and is useful in predicting cerebral vasospasm
- World Federation of Neurosurgical Societies (WFNS) is a grading system for the severity of subarachnoid hemorrhage, based on Glasgow Coma Scale and presence of focal neurological deficits. Conscious state is used as a predictor of mortality and neurological deficits like hemiparesis or aphasia as a predictor of morbidity. (Radiopaedia)
- Location
- Focal
- Isolated to convexity sulci adjacent to contusion, subdural/epidural hematoma, fracture/laceration
- Diffuse
- Spread diffusely within the subarachnoid spaces and the basal cisterns
- May show layering on tentorium
- Focal
Neuroimaging
- CT Findings
- CT without contrast
- Best imaging tool
- Hyperattenuation in the subarachnoid spaces and cisterns (See Figure 1)
- Hyperattenuation within the interpeduncular cistern may be the only sign of a subtle tSAH (For additional images reference the Epidural Hematoma chapter)
- CT with contrast
- Should not be used to identify tSAH as contrast enhancement of cortical veins will obscure subarachnoid blood
- CT without contrast
- MRI Findings
- T1WI: sometimes hyperintense to ventricular CSF
- T2WI: Isointense to CSF, not usually detectable
- FLAIR:
- Very sensitive for detecting subtle tSAH
- SAH detected as hyperintense signal relative to CSF (See Figure 1)
- T2*/GRE/SWI: Occasionally hypointense (See Figure 2)
- DWI: May see restricted diffusion in acute SAH (but not chronic) due to areas of ischemia from SAH induced vasospasm
- Angiographic Findings
- Can evaluate tSAH-induced vasospasm, which presents as beaded vessels noted during a window of 2 days to 2 weeks
- Digital subtraction angiography is the gold standard to exclude aneurysm, arterio-venous malformation, dural arterio-venous fistula
- However, unless planning a surgical intervention, this has been largely superseded by CT angiography due to the risk profile of angiography
- Differential Diagnosis for traumatic subarachnoid hematoma
- Non-traumatic SAH
- Meningitis with cellular and proteinaceous debris
- Carcinomatosis Meningitis
- Pseudosubarachnoid Hemorrhage secondary to diffuse cerebral edema
- Gadolinium Administration may cause FLAIR hyperintensity near pathology
- High-Inspired Oxygen as in during general anesthesia, may present as hyperintensity on FLAIR
For more information, please see the corresponding chapter in Radiopaedia.
Contributor: Priya Rajagopalan, MD
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