Effects of a Parietal Lobe Stroke

Visual, Sensory, and Perception Dysfunctions

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A stroke occurs when a blood vessel that carries oxygen and nutrients to the brain is either blocked by a clot or ruptures). When that happens, part of the brain cannot get the blood and oxygen that it needs, so the affected brain cells become damaged or die.

A parietal lobe stroke is one that occurs in the back part of the brain known as the parietal lobe. The parietal lobe is one of the most important areas in the brain, providing connections and integration between several other regions of the brain. The parietal lobe serves two primary functions:

  • Processing sensory information regarding the location of parts of the body
  • Interpreting visual information and processing language and mathematics

This is why a parietal lobe stroke can have such a profound impact even if the stroke is relatively mild.

Visual Symptoms

There are a number of different visual effects of a stroke, many of which involve the parietal lobe either directly or indirectly.

One of the more common symptoms is the inability to visually scan one’s surroundings despite having a full range of eye movements. This prevents the person from seeing objects on the outer periphery of vision.

A parietal stroke can often cause spatial dysperception in which a person has difficulty processing visual information such as length, depth, and the size of objects. Hand-eye coordination can suffer severely as a result.

There are also nerve fibers that carry information from the lower parts of our visual field and travel through the parietal lobes on their way to the occipital lobe (where vision is processed). These nerve fibers can be damaged by parietal strokes, causing vision referred to as homonymous quadrantanopia.

Sensory Symptoms

The parietal lobe is where the sensory cortex is located. The sensory cortex integrates the nerve signals by which we perceive sensations such as touch, temprature, vibration, pain, and pressure. A stroke in the sensory cortex can cause numbness or the inability to detect the location or type of sensation being experienced.

By impairing the sensory cortex, a parietal stroke can lead to a condition known as astereognosis in which you are unable to identify an object by touch and require other sensory clues, such as vision or smell, to make the identification.

Perception Symptoms

Perception symptoms are those that involve a person's understanding of space or the interpretation of visual or other sensory clues.

One such example is finger agnosis in which a person is unable to name a finger, such as thumb, when looking at it. There may also be an inability to tell right from left or to translate written words into language, speech into written words, or numbers into math.

People with a parietal stroke on the one side of the brain will often be entirely unaware of anything of the opposite side of their body. The condition, known as hemineglect, is one in which you are unable to recognize your own body parts or anything occurring on that half of your body or space.

Other common symptoms include iideomotor apraxia (inability to mimic a performed gesture), constructional apraxia (inability to copy a drawing), or eye-opening apraxia (inability to open one's eyes on command).

Inattentiveness, apathy, and emotional blunting are also characteristic of a parietal stroke.

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