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| T1 coronal post gad | PDW axial | T2 axial |
Diagnosis: Chronic subdural hematoma
Subdural hematomas may be either acute, subacute or chronic. When associated with acute trauma,they are more commonly associated with serious intracranial injury compared to epidural hematomas and are due to tearing of the bridging veins. By definition they occupy to space between the dura and the arachnoid. Subdural as opposed to epidural hematomas may cross sutures. Acute subdural hematomas are hyperdense on CT and later become isodense and finally hypodense in the chronic stage. Their MR appearance is variable depending on the age of the blood and whether or not there has been interval hemorrhage, which is the rule in chronic subdural hematomas. The major differential consideration in general for an extraaxial collection of blood is epidural hematoma. Epidural hematoma is always seen in the setting of acute trauma and is associated with skull fracture in up to 95% of cases. Furthermore, on the enhanced coronal images in this case the fluid collection occupies the space between the dura and the arachnoid. Although not always true, epidurals tend to be more lens shaped while subdurals are more crescentic. The fact that this lesion is extraaxial with mixed signal characteristics and is present between the arachnoid and the dura without a history of acute head trauma is compatible with chronic subdural hematoma.