Arnold-Chiari malformation

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noun

Ar·​nold-Chi·​ari malformation ˈär-nᵊld-kē-ˈär-ē- 

: a congenital abnormality in which the lower surface of the cerebellum and the lower brain stem protrude into the spinal canal through the foramen magnum

She was born with Arnold-Chiari malformation, a rare and random birth defect that occurs, according to one study, in about 8 of 100,000 people. A deformity of the base of the skull and spine, it can cause chronic pain and loss of balance.

—Arthur Allen, The Washington Post

Note: Arnold-Chiari malformation often occurs with spina bifida and hydrocephalus. It is classified as a type of Chiari malformation.

Chiari-Frommel syndrome

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noun

Chi·​ari-From·​mel syndrome kē-ˈär-ē-ˈfrȯm-əl-, -ˈfräm- 

: a condition usually occurring postpartum and characterized by amenorrhea, galactorrhea, obesity, and atrophy of the uterus and ovaries

Chiari malformation

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noun

Chi·​ari malformation kē-ˈär-ē- 

: a congenital abnormality of the hindbrain in which the cerebellum and often parts of the brain stem protrude into the spinal canal through the foramen magnum

Blocked spinal fluid can cause hydrocephalus or, as is more common in Chiari malformation, a fluid-filled cyst known as a syrinx.

—Rebecca Voelker, The Journal of the American Medical Association

Note: Chiari malformation is usually classified into four types. Type 1 involves protrusion only of the lower part of the cerebellum into the spinal canal and is often asymptomatic. Type 2 is the Arnold-Chiari malformation. In type 3, the cerebellum is completely displaced into the spinal canal. In type 4, the cerebellum fails to develop completely.