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SpecialtyLesion_header_cell_0_1_0 PathologyLesion_cell_0_1_1

A lesion is any damage or abnormal change in the tissue of an organism, usually caused by disease or trauma. Lesion_sentence_0

Lesion is derived from the Latin laesio "injury". Lesion_sentence_1

Lesions may occur in plants as well as animals. Lesion_sentence_2

Types Lesion_section_0

There is no designated classification or naming convention for lesions. Lesion_sentence_3

Because the definition of a lesion is so broad, the varieties of lesions are virtually endless. Lesion_sentence_4

Lesions can occur anywhere in the body. Lesion_sentence_5

Generally, lesions may be classified by their patterns, their sizes, their locations, or their causes. Lesion_sentence_6

Lesions are sometimes also named after the person who discovered them. Lesion_sentence_7

Some lesions have specialized names, such as Ghon lesions in the lungs of tuberculosis victims, which is named after the lesion's discoverer. Lesion_sentence_8

The characteristic skin lesions of a varicella zoster virus (VZV) infection are called chickenpox. Lesion_sentence_9

Lesions of the teeth are usually called dental caries. Lesion_sentence_10

Location Lesion_section_1

Lesions are often classified by their tissue types or locations. Lesion_sentence_11

For example, a "skin lesion" or a "brain lesion" are named for the tissue where they are found. Lesion_sentence_12

If there is an added significance to regions within the tissue—such as in neural injuries where different locations correspond to different neurological deficits—they are further classified by location. Lesion_sentence_13

For example, a lesion in the central nervous system is called a central lesion, and a lesion in the peripheral nervous system is called a peripheral lesion A myocardial lesion results from damage to the heart muscle, and a coronary lesion is a subtype that describes a lesion in the coronary arteries. Lesion_sentence_14

Coronary lesions are then further classified according to the side of the heart that is affected and the diameter of the artery in which they form. Lesion_sentence_15

Cause and behavior Lesion_section_2

If a lesion is caused by a tumor it can be classified as malignant or benign after analysis of a biopsy. Lesion_sentence_16

A benign lesion that is evolving into a malignant lesion is called "premalignant." Lesion_sentence_17

Cancerous lesions are sometimes classified by their growth kinetics, such as the Lodwick classification, which characterizes classes of bone lesions. Lesion_sentence_18

Another type of lesion is excitotoxic lesions, which can be caused by excitatory amino acids like kainic acid, which kill neurons through over-stimulation. Lesion_sentence_19

Size and shape Lesion_section_3

Lesion size may be specified as gross or histologic depending on whether they are visible to the unaided eye or require a microscope to see. Lesion_sentence_20

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. Lesion_sentence_21

Lesions may also be classified by the shape they form, as is the case with many ulcers, which can have a bullseye or 'target' appearance. Lesion_sentence_22

A coin lesion is identifiable in an X-ray as appearing like a coin sitting on the chest of the patient. Lesion_sentence_23

Research using lesions Lesion_section_4

Brain lesions may help researchers understanding brain function. Lesion_sentence_24

Research involving lesions relies on two assumptions: that brain damage can affect different aspects of cognition independently, and that a locally damaged brain functions identically to a normal brain in its "undamaged" parts. Lesion_sentence_25

Sham lesion is the name given to a control procedure during a lesion experiment. Lesion_sentence_26

In a sham lesion, an animal may be placed in a stereotaxic apparatus and electrodes inserted as in the experimental condition, but no current is passed, and therefore damage to the tissue should be minimal. Lesion_sentence_27

Research with humans Lesion_section_5

Humans with brain lesions are often the subjects of research with the goal of establishing the function of the area where their lesion occurred. Lesion_sentence_28

A drawback to the use of human subjects is the difficulty in finding subjects who have a lesion to the area the researcher wishes to study. Lesion_sentence_29

As such, transcranial magnetic stimulation is often used in cognition and neuroscience-related tests to imitate the effect. Lesion_sentence_30

Research with animals Lesion_section_6

Using animal subjects gives researchers the ability to lesion specific areas in the subjects, allowing them to quickly acquire a large group of subjects. Lesion_sentence_31

An example of such a study is the lesioning of rat hippocampi to establish the role of the hippocampus in object recognition and object recency. Lesion_sentence_32

Notable lesions Lesion_section_7

See also Lesion_section_8


Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Lesion.