The external capsule is a collection of white matter fibers found in the brain. White matter is an important part of the central nervous system, working to pass information between various areas of grey matter within the brain. This external capsule connects to the structure known as the internal capsule which is located near the lenticular nucleus. The white fibers making up the capsule are found between the claustrum and the lentiform nucleus.
The white matter of the external capsule contains fibers known as corticocortical association fibers. These fibers are responsible for connecting one cortex, or the outermost layer, of the brain to another. The capsule itself appears as a thin white sheet of white matter.
The central nervous system is comprised of two major components, white matter and grey matter. The white matter making up the external capsule consists primarily of lipid, or fatty, tissue. White matter is actually a pinkish color in its natural state. When preserved in formaldehyde for research purposes, the color appears white. The white matter portion of the brain continues to develop throughout a person's life, not reaching its peak until around middle age.
The fibers which form the external capsule move between the claustrum and the lentiform nucleus. The claustrum is a sheet of grey matter located between the tracts of white matter in the capsule. The lentiform nucleus is situated near the internal capsule and is a large, cone-shaped structure made of grey matter.
Heat stroke is a common cause of brain injury causing damage to the external capsule. Heat stroke occurs when the body becomes overheated and includes symptoms such as difficulty breathing, rapid pulse, and confusion. Extreme behavior changes frequently occur with a heat stroke, often due to hallucinations. This is a medical emergency that can quickly lead to coma and death if not treated immediately.
Treatment for a heat stroke begins by cooling the body as quickly as possible. Once the body has been cooled, the extent of the damage to the brain and other organs of the body are assessed and treated as necessary. Depending on the extent of the injury, the damage to the brain may be either temporary or permanent. If the brain does not fully recover, the damage to the external capsule can result in personality changes, and coordination issues may remain.