Extinction (neurology)

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Neurological phenomenon related to sensory perception

Extinction is a neurological phenomenon observed in patients with certain types of brain damage, particularly those affecting the parietal lobe. It is characterized by the inability to perceive a stimulus on one side of the body when a similar stimulus is presented simultaneously on the opposite side. This condition is often associated with unilateral neglect and can provide insights into the functioning of attention and perception in the human brain.

Pathophysiology

Extinction occurs when there is a lesion in the parietal lobe, most commonly in the right hemisphere, which is responsible for processing sensory information from the left side of the body. The phenomenon is thought to arise from a disruption in the attentional networks of the brain, particularly those involved in the integration of sensory information from both sides of the body.

The right parietal lobe is crucial for spatial awareness and attention, and damage to this area can lead to a dominance of the left hemisphere's attentional processes. As a result, when stimuli are presented to both sides of the body simultaneously, the brain may only register the stimulus on the side contralateral to the undamaged hemisphere, leading to the extinction of the stimulus on the affected side.

Clinical Presentation

Patients with extinction may not report any deficits when stimuli are presented unilaterally. However, during clinical examination, when identical stimuli are presented simultaneously to both sides of the body, the patient may fail to perceive the stimulus on the side opposite the brain lesion. This is often tested using visual, tactile, or auditory stimuli.

For example, in a visual extinction test, a patient may be able to see a finger wiggling in their left visual field when it is the only stimulus. However, if a finger is wiggled in both the left and right visual fields simultaneously, the patient may only report seeing the finger in the right visual field.

Diagnosis

The diagnosis of extinction is primarily clinical and involves specific testing to reveal the phenomenon. Neurologists may use a variety of sensory tests to assess the presence and extent of extinction. These tests often involve presenting stimuli to both sides of the body and observing the patient's responses.

Neuroimaging techniques, such as MRI or CT scan, can be used to identify the location and extent of brain lesions that may be responsible for the extinction phenomenon.

Treatment and Management

There is no specific treatment for extinction itself, as it is a symptom of underlying brain damage. Management focuses on addressing the primary cause of the brain lesion, such as stroke or traumatic brain injury, and on rehabilitation strategies to improve the patient's overall function.

Rehabilitation may involve occupational therapy, physical therapy, and cognitive therapy to help patients compensate for their deficits and improve their quality of life.

Prognosis

The prognosis for patients with extinction depends on the underlying cause and the extent of the brain damage. Some patients may experience improvement over time, particularly with rehabilitation, while others may have persistent deficits.

Also see

• Unilateral neglect
• Parietal lobe
• Attention
• Sensory processing disorder

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External links

• Comprehensive information from the National Institute of health.
  

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