Image from "Consciousness Studies"
The thalamus is a major relay centre in the brain, and is responsible for regulating sleeping and waking states. Located between the cerebral cortex and midbrain, it relays motor signals to the cerebral cortex. Located on the midline, there is a thalamus on each side of the brain. Thalamic strokes are caused by the blood flow to the brain stopping suddenly. Within a few minutes of the stroke, brain cells begin to die, thus effecting the thalamus's normal function. Severe damage to the thalamus can lead to a coma.
Types of Strokes
There are two types of strokes: ischemic strokes, which are most common, and hemorrahagic strokes. Ischemic strokes are caused when a blood clot that blocks a blood vessel in the brain. When the blood vessel breaks and bleeds into the brain, that is called a hemorrhagic stroke. Smaller strokes can also occur, called transient ischemic attacks (TIA), where the blood supply is only briefly interrupted. The thalamus is highly susceptible to intracerebral hemorrhaging. Risk factors for thalamic hemorrhaging include hypertension, diabetes mellitus and previous medication use to prevent blood clots.
When the stroke occurs on the right side of the brain, paralysis can happen on the left side of the body. This occurs because the right half of the brain controls the left half of the body and vice versa. In addition to paralysis, right hemisphere damage can also result in difficulty in reasoning or thinking after the stroke.
When the stroke occurs on the left side of the brain, paralysis is also possible on the right side of the body. After the stroke, left-hemisphere-damaged patients may also have problems speaking, as the language region of the brain is located on the left half of the brain.
In a study done by the American Heart Association, patients who had thalamic strokes experienced hemisensory symptoms, which are strange sensations that occur on only one side of the body. Parts of the body that are effected include the face, arms and legs, and these are due to the thalamus's connection to the cerebral cortex.
Timing is crucial in preventing further damage to the thalamus after a stroke. The more time that lapses after the stroke occurs, the detrimental effect to the thalamus increases and the symptoms become worse. Due to serious effects of a stroke, such as a coma, patients can require constant help for daily activities.
- Image from "Consciousness Studies"