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| ==Pathophysiology== | | ==Pathophysiology== |
| Unlike in [[epidural hematomas]], which are usually caused by tears in [[artery|arteries]], subdural bleeding usually results from tears in veins that cross the [[subdural space]]. This bleeding often separates the dura and the arachnoid layers.
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| 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. The collected blood may even develop its own membrane.<ref>McCaffrey P. 2001. [http://www.csuchico.edu/~pmccaff/syllabi/SPPA336/336unit11.html "The neuroscience on the web series: CMSD 336 neuropathologies of language and cognition."] California State University, Chico. Retrieved on [[August 7]], [[2007]]. </ref>
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| 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.
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| 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. 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 (biology)|cell]] death.
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| The body gradually reabsorbs the clot and replaces it with [[wound healing phases|granulation tissue]]. A [[subdural hygroma]] can then develop in which there is no blood but CSF is present.
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| ==References== | | ==References== |