Subdural hematoma pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Pathophysiology
Unlike in epidural hematomas, which are usually caused by tears in arteries, subdural bleeding usually results from tears in veins that cross the subdural space. This bleeding often separates the dura and the arachnoid layers.
Collected blood from the subdural bleed may draw in water due to osmosis, causing it to expand, which may compress brain tissue and cause new bleeds by tearing other blood vessels.[1] The collected blood may even develop its own membrane.[2]
In some subdural bleeds, the arachnoid layer of the meninges is torn, and cerebrospinal fluid (CSF) and blood both expand in the intracranial space, increasing pressure.[3]
Substances that cause vasoconstriction may be released from the collected material in a subdural hematoma, causing further ischemia under the site by restricting blood flow to the brain.[4] When the brain is denied adequate blood flow, a biochemical cascade known as the ischemic cascade is unleashed, and may ultimately lead to brain cell death.
The body gradually reabsorbs the clot and replaces it with granulation tissue. A subdural hygroma can then develop in which there is no blood but CSF is present.