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Subdural Hematoma

Nina J Abramson, MD
Liangge Hsu, MD

November 29, 1994

Presentation

A 36-year-old man with a history of alcohol abuse presented with left-sided weakness and memory loss.

Imaging Findings

Computed Tomography

Axial CT images of the brain show a large isodense right-sided subdural hematoma (short arrows) extending from the high convexities to the low frontal lobe. It is producing extensive right to left midline shift with subfalcine (arrow) and right uncal (arrow) herniation. There is trapping of the ventricles and left temporal horn with acute ependymal cerebrospinal fluid seepage, predominantly in the left periatrial and occipital regions (long arrow).

Cerebral and cerebellar atrophy is also present. Note the difference in the sulci of the two hemispheres.

Differential Diagnosis

The main differential considerations include subdural and epidural hematoma. Epidural hematomas (EDH) form in the space between the dura and the inner table of the skull. Unlike subdural hematomas, EDH can cross the midline, but will not cross the cranial sutures where the dura is firmly attached. The subdural hematoma (SDH), however, may freely cross the midline insertion of the falx or the tentorial attachment. Also in comparison to SDH, EDH is often associated with skull fractures (85 - 95% of adult cases) which disrupts the middle meningeal artery, resulting in a lenticular or biconvex extra-axial collection.

Subarachnoid hemorrhages can be distinguished radiographically from SDH by their extension into cerebrospinal fluid space, and appearance on CT as linear areas of high attenuation within the cisterns and sulci.

Diagnosis

Subacute subdural hematoma.

Discussion

Subdural hematoma (SDH) is the most common extra-axial collection and is seen in 5% of head trauma patients. SDH occurs between the dura and the arachnoid membrane, most often due to venous bleeding from the "bridging" subdural veins which connect the cerebral cortex to the dural sinuses. However, SDH may also result from disruption of the penetrating branches of superficial cerebral arteries. These ollections tend to conform to the shape of the brain and the cranial vault, exhibiting concave inner margins and convex outer margins. Occasionally, SDH may be straight or even concave in appearance.

Patients with SDH commonly present after acute deceleration injury from a fall or motor vehicle accident, but are rarely associated with skull fracture. More rarely, coagulopathies, tumors, or aneurysms may be responsible for SDH.

SDH may be classified as hyperacute (low density) if less than 12 hours from the acute event, acute (high density) if less than few days, subacute (isodense) from a few days to 2-3 weeks, and chronic (low density) if more than 3 weeks after the time of injury.

References

1. Rosen P, et al. Diagnostic Radiology in Emergency Medicine. Mosby Year Book, 1992;Chapter 3 (Head and Neck Trauma).

2. Woodruff WW. Fundamentals of Neuroimaging. Philadelphia: WB Saunders, 1993;Chapter 4 (Intracranial Hemorrhage).

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