Neuropathology of Aphasia

[Dr. Linton Hutchinson]

Aphasia is a disorder in the use of language. It is the result of
damage or injury to the language dominant region of the brain. The
most common cause of aphasia is interruption of blood supply to the
brain. Other causes of the disorder are traumatic brain injury, brain
tumors, infections, exposure to toxic chemicals, or nutritional
disturbances.

Typically following thhe first few days of an acute injury to the brain,
there is extensive disruption of cerebral processes, such that even
areas of the brain that were not actually damaged will stop functioning
properly. Following this generalized disruption of cerebral processes,
we will see a recovery of certain functions and continued dysfunction of
other functions or processes depending on the area of the brain that was
actually damaged.

The technical term for a vascular accident in the brain or brain stem is
called a cerebrovascular accident (CVA) or stroke. Stroke is among the
leading causes of death in the United States. The majority of cases of
aphasis are caused by stroke. There are two types of stroke (ischemic
of hemmorhagic). Ischemic strokes occur when an artery is blocked.
Thus, blood supply from that artery to regions of the brain served by
that artery is lost. It takes as little as 3 to 5 minutes of loss of
blood supply to the brain to cause death of nerve tissue also known as
necrosis. Ischemic strokes can be either thrombolic or embolic. In a
thrombolic ischemic stroke, an artery is gradually occludeded by some
material that accumulates until it completely interrupts the blood
supply. An embolic ischemic stroke occurs when an artery is suddenly
occluded by some material moving within the blood stream. This type of
ischemic stroke results in the sudden interruption of blood flow to the
brain.

Hemorrhages occur when a blood vessel in the brain is ruptured. The
etiology of a ruptured wall may be due to weakness of a vessel,
traumatic injury to a vessel, or by fluctuations in blood pressure.
Hemorrhages can be subcategorized depending on where in the brain they
occur. For example, if the hemorrhage occurs within the brain or brain
stem, it is called intracerebral and it it occurs on the surface of the
brain it is called extracerebral.