Read more about this disease, some with Classification – Types – Signs and symptoms – Genetics – Pathophysiology – Diagnosis – Screening – Prevention – Treatment and management – Cures and much more, some including pictures and video when available.
Arnold-Chiari malformation is a malformation of the brain. It consists of a downward displacement of the cerebellar tonsils and the medulla[1] through the foramen magnum, sometimes causing hydrocephalus as a result of obstruction of CSF outflow.[2]
Some sources use “Chiari malformation” to describe four specific grades of the condition, reserving the term “Arnold-Chiari” for type II only.[3] Other sources use “Arnold-Chiari” for all four types.[4] This article uses the latter convention.
One advantage of using “Arnold-Chiari” is that the term “Chiari’s syndrome” can refer to Budd-Chiari syndrome,[5] a hepatic condition also named for Hans Chiari.
The average age at diagnosis is about 27 and it is more common in women, but is also found in men.
Some characteristics are visible prenatally.[6]
The incidence of Arnold-Chiari Malformation (Chiari I malformation) defined as tonsilar herniations of 3 to 5 mm or greater is approximately 1 in 1,200.[citation needed] The incidence of symptomatic Chiari is less but unknown.
A prevalence of approximately 1 in 1000 has been described.[7]
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