Lesion

Wikipedia:

A lesion is any abnormality in the tissue of an organism (in layman's terms, "damage"), usually caused by disease or trauma. Lesion is derived from the Latin word laesio which means injury.

History

DuVerney was the first to use experimental ablation method on animals in 1679. Flourens first publish the method in 1824, describing the method and behavioral effect of brain damage.

Lesions done by knife cuts and suction techniques were called mechanical lesions were tried by Veyssiere and Nothnagel in 1874. The process was using a fine wire blade through head. Rotate the curved or angled wire, and cut neural projection. Baginski and Lehmann in 1886 used this method with thin glass tube lowered through a small hole in the skull.

In 1895, Golsinger first to make electrolytic lesions in animals. In 1898 by Sellier and Verger destroyed discrete areas in the caudate and anterior segment of internal capsule passing current through double needle electrodes insulated. This process kills surrounding of the electrode.

1908, Horsley and Clark develop stereotaxic method and combine with electrolytic lesions to improve localization, precision, and reliability of brain damage in subcortical structures.

Types

Because the definition of a lesion is so broad, the varieties of lesions are virtually endless. Lesions can occur anywhere in the body that consists of soft tissue or osseous matter, though most frequently found in the mouth, skin, and the brain, or anywhere where a tumour may occur. They are subsequently classified by their features. If a lesion is caused by a tumor it will be classified as malignant or benign. Lesions may be classified by the shape they form, as is the case with many ulcers, which can have a bullseye or 'target' appearance. Their size may be specified as gross or histologic depending on whether they are visible to the unaided eye or require a microscope to see.

An additional classification that is sometimes used is based on whether or not a lesion occupies space. A space-occupying lesion, as the name suggests, has a recognizable volume and may impinge on nearby structures, whereas a non space-occupying lesion is simply a hole in the tissue, e.g. a small area of the brain that has turned to fluid following a stroke.

Some lesions have specialized names, such as Ghon lesions in the lungs of tuberculosis victims. The characteristic skin lesions of a varicella-zoster virus (VZV) infection are called chickenpox. Lesions of the teeth are usually called dental caries.

Another type of lesion is excitotoxic lesions that can be caused by excitatory amino acid like kainic acid that kills neuron by stimulating to death.

Sham lesions are the process of putting stereotaxic apparatus and insert it inside the skull to produce a lesion to see if behavior correlates with the brain lesion.

Finally, lesions are often classified by their location. For example, a 'skin lesion' or a 'brain lesion'.

Causes

Lesions are caused by any process that damages tissues. Lesions can also be caused by metabolic processes, like an ulcer or autoimmune activity, as in the case with many forms of arthritis.

Lesions are sometimes intentionally inflicted during neurosurgery, such as the carefully placed brain lesion used to treat epilepsy and other brain disorders. (See Ablative brain surgery.)

Note that lesions are not limited to animals or humans; damaged plants are said to have lesions.

Effects

Studies show there is a correlation with lesion with language, speech, and category-specific disorders. However, lesion to Broca's and Wernicke's areas not found to alter language comprehension.

Lesion in amygdala would eliminate the enhanced activation seen in occipital and fusiform visual areas in response to fear with the area intact. Amygdala lesions change the functional pattern of activation to emotional stimuli in regions that are distant form the amygdala.

Lesion size has a correlation with with severity, recovery, and comprehension.

In the Wisconsin Card Sorting Test with unilateral frontal or nonfrontal lesions patients. Left frontal lesions did more poorly but had high perseverative error score. In right frontal and nonfrontal lesions are impaired but due to differences in patients. As a result, medial frontal lesions are associated with poor performance.