Dictionary

meningeal metastases See meningitis, neoplastic.

meninges The three membranes that cover the brain and spinal cord (singular: meninx). The outside meninx is called the dura mater, and is the most resilient of the three meninges. The center layer is the pia mater, and the thin innermost layer is the arachnoid. Inflammation of the meninges (meningitis) can occur due to infection….

meningioma A common type of slow-growing, usually benign brain tumor that arises from the dura, one of the meninges, the membranes covering the brain and spinal cord. A meningioma may occur wherever there is dura (the outermost of the three meninges), but the most common sites are over the cerebral hemispheres of the brain. Meningiomas…

meningitis Inflammation of the meninges, the three membranes that envelop the brain and the spinal cord. Meningitis can be caused by infection by bacteria, viruses, and protozoa. Other causes include cancer (metastasis to the meninges), inflammatory diseases, and drugs. In some cases the cause of meningitis cannot be determined. The treatment depends on the cause…

meningitis, aseptic See meningitis, viral.

meningitis, bacterial Inflammation of the meninges due to a bacterial infection. Haemophilus influenzae type B (HIB) was formerly the leading cause of bacterial meningitis before the 1990s, but childhood vaccinationshave reduced the occurrence of meningitis due to H. influenzae. Streptococcus pneumoniae and Neisseria meningitidis are the leading causes of bacterial meningitis. High fever, headache, and…

meningitis, benign recurrent aseptic See meningitis, Mollaret.

meningitis, cryptococcal Inflammation of the meninges due to infection with the fungal organism Cryptococcus neoformans, which is found mainly in dirt and bird droppings. Most people have been exposed to this organism at some time, but normally it causes no problems. Often associated with AIDS, cryptococcal meningitis is considered an opportunistic infection: a disease that…

meningitis, infectious Inflammation of the meninges due to bacterial, viral, or protozoan infection. Most of the agents known to cause meningitis are infectious, but very few people exposed to them develop meningitis. Those at greatest risk for infectious meningitis include people with AIDS, infants, transplant patients, and others whose immune systems may be compromised. For…

melanoma The most dangerous form of skin cancer, a malignancy of melanocytes, the cells that produce pigment in the skin. Melanoma is most common in people with fair skin, but it can occur in people with all skin colors. Most melanomas present as dark, mole-like spots that spread and, unlike moles, have irregular borders. The…

melanoma, acral-lentiginous A type of malignant melanoma that is uncommon in white people but the most common type in nonwhite people. Acral-lentiginous melanoma starts as an irregular enlarging black flat spot (macule), most often on the palm of the hand and the sole of the foot, less often on a mucosal surface, such as the…

melanoma, amelanotic A colorless melanoma that is detectable only on close examination of the skin.