HISTORY: 64 year-old male with alcohol abuse and frequent falls.
DIAGNOSIS: Bilateral acute on chronic subdural hematomas with midline shift.
FINDINGS: Subdural hematomas are able to cross suture lines and conform to the contour of the brain, forming a concave or "crescent" shape. In comparison, an epidural hemorrhage does not cross suture lines and forms a convex or "lens" shape.
Acute clotted blood products are hyperdense on CT. Over time, the clot is absorbed and becomes progressively hypodense, eventually matching the density of CSF. These density differences allow us to tell the age of a hemorrhage. The hematomas in this case are mixed in density, suggestive of acute and chronic components. It is important to note that "hyperacute" blood (which has just leaked from a vessel and hasn't clotted yet) will be hypodense and mimic chronic hemorrhage!
In any case of intracranial hemorrhage, it is important to evaluate "mass effect", or how much the hematoma pushes on the adjacent brain. Since the skull is a fixed structure, a subdural hematoma will push the brain to the opposite side. In this case, the hematomas compress the brain from both sides. Since the left hematoma is bigger than the right, there is an overall shift of the brain to the right side. This can be measured at the midline as "midline shift." Severe mass effect can result in herniation, hydrocephalus, compression of arteries/nerves, and ultimately brain ischemia. This is an indication for surgical hematoma evacuation.
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