Cranial mononeuropathy III - compression type is a mononeuropathy, which means that only one nerve is affected. In this case, the third cranial (oculomotor) nerve, one of the cranial nerves that controls eye movement, is damaged by compression of the nerve caused by localized lesions or by swelling in the area of the nerve. Specific causes may include tumors or other lesions (especially tumors located at the base of the brain and pituitary gland), trauma, infections, infarction (tissue damage from loss of blood flow), some cerebral aneurysms, other vascular malformations, sinus thrombosis, and disorders such as mononeuritis multiplex. On rare occasions, people with migraine headaches may demonstrate a temporary type of oculomotor nerve involvement, probably because of a spasm of the blood vessels. In some cases, no cause can be found.
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