| Lesion | |
|---|---|
| Specialty | Pathology |
Alesion is any damage or abnormal change in thetissue of anorganism, usually caused byinjury ordiseases. The termLesion is derived from the Latinlaesio meaning "injury".[1] Lesions may occur in both plants and animals.
There is no designated classification or naming convention for lesions. Because lesions can occur anywhere in the body and their definition is so broad, the varieties of lesions are virtually endless. Generally, lesions may be classified by their patterns, sizes, locations, or causes. They can also be named after the person who discovered them. For example,Ghon lesions, which are found in the lungs of those withtuberculosis, are named after the lesion's discoverer, Anton Ghon.[1] The characteristicskin lesions of avaricella zoster virus infection are calledchickenpox. Lesions of the teeth are usually calleddental caries, or "cavities".
Lesions are often classified by their tissue types or locations. For example, "skin lesions" or "brain lesion" are named for the tissue where they are found. 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. For example, a lesion in thecentral nervous system is called a central lesion, and a lesion in theperipheral nervous system is called aperipheral lesion.[1] Amyocardial lesion results from damage to the heart muscle, and a coronary lesion is a subtype that describes a lesion in thecoronary arteries. Coronary lesions are then further classified according to which side of the heart is affected and the diameter of the artery in which they form.[2]
If a lesion is caused by atumor, it can be classified asmalignant orbenign after analysis of abiopsy. A benign lesion that is evolving into a malignant lesion is called "premalignant".[1] Cancerous lesions are sometimes classified by their growth kinetics, such as the Lodwick classification, which characterizes classes of bone lesions.[3] Another type is anexcitotoxic lesion, which can be caused by excitatoryamino acids likekainic acid that kill neurons through overstimulation.
Lesion size may be specified asgross, meaning it is visible to the unaided eye, orhistologic, meaning a microscope is needed to see it.[4][5] Aspace-occupying lesion, as the name suggests, has a recognizable volume and may impinge on nearby structures, whereas anon space-occupying lesion is simply a hole in the tissue, such as a small area of the brain that has turned to fluid following astroke.[1]
Lesions may also be classified by the shape they form, as is the case with manyulcers, which can have abullseye or 'target' appearance. Acoin lesion seen in an X-ray has the appearance of a coin sitting on the patient's chest.[1]
Brain lesions may help researchers understand brain function. 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.[6]
Sham lesion is the name given to a control procedure during a lesion experiment. 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, so damage to the tissue should be minimal.
Humans with brain lesions are often subjects of research with the goal of establishing the function of the area where their lesion occurred.[7]
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. As such,transcranial magnetic stimulation is often used in cognition and neuroscience-related tests to imitate the effect.[8]
Using animal subjects gives researchers the ability to study lesions in specific body parts, allowing them to quickly acquire a large group of subjects. An example of such a study is the lesioning of rat hippocampi to establish the role of thehippocampus in object recognition and object recency.[9]
Diabetes-associated lesions
Bone lesions
Brain lesions
Skin lesions
Gastrointestinal lesions
Endodermal lesions
Misc. disease-associated lesions
