The Neuroscience on the Web Series:
CMSD 636, Neuropathologies of Language and Cognition

CSU, Chico, Patrick McCaffrey, Ph.D.


Chapter 2. Medical Aspects: Neurophysiological Changes


Neurophysiological Changes

Several types of neurophysiological changes occur throughout the brain as a result of infarcted tissue caused by stroke or accident. These include edema, reduced cerebral blood flow, the release of neurochemicals and diaschisis. Diaschisis is a type of post-lesional cerebral shock resulting in sudden inhibition of function in which there is a diminishment and possibly a complete loss of functioning in brain areas distal to the site of lesion. Although areas affected by diachisis may be far away from the point of original damage, they are usually connected to the infarcted area by nerve pathways (Steadman, 1997). The cause of diachisis in unknown; it may be the result of edema, reduced cerebral blood flow, the release of neurochemicals or other factors which have not yet been identified. Because these phenomena affect areas of the brain beyond the point of original damage, they explain why patients sometimes display symptoms that are unexpected in view of site of lesion information.

Swelling or edema begins two or three days after a cerebral insult. Swelling occurs only in the area that has been injured. However, as localized swelling can greatly increase pressure throughout the whole cranium, the functioning of the entire brain may be affected. Edema of the brain should begin to decrease by the beginning of the first week post-injury. As intracranial pressure returns to normal levels, any behavioral changes that were caused by the swelling rather than by the brain injury will disappear.

After an injury, arterial blood flow to all lobes in both hemispheres may decrease. This reduction usually lasts between two and four weeks but may continue for a longer period of time. As decreased blood pressure reduces the effectiveness of collateral circulation, it may cause additional infarctions when it occurs in response to an ischemic stroke.

The brain may release abnormally large amounts of neurochemicals after an injury. These substances may cause additional damage throughout the brain.


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Other courses in the Neuroscience on the Web series.
CMSD 620 Neuroanatomy | CMSD 642 Neuropathologies of Swallowing and Speech

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