chiari malformation

Classification and external resources A T2-weighted sagittal MRI scan, from a patient with Chiari-like symptomatology, demonstrating tonsillar herniation less than 3 mm ICD-10 Q07.0 ICD-9 741.0 OMIM 207950 DiseasesDB 899 MeSH D001139

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] Contents [hide] 1 Terminology 2 Diagnosis 3 Incidence 4 History and classification 5 Symptoms 6 Treatment 7 History 8 References 9 See Also 10 External links //

Terminology

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.

Diagnosis

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]

Incidence

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]

History and classification

The Austrian pathologist Hans Chiari in the late 1800s described seemingly related anomalies of the hindbrain, the so called Chiari malformations I, II and III. Later, other investigators added a fourth (Chiari IV) malformation. The scale of severity is rated I - IV, with IV being the most severe. Types III and IV are very rare.[7] The most common form of Arnold-Chiari Malformation is Type I, which is generally asymptomatic during childhood, but often manifests with headaches and cerebellar symptoms. Type II is usually accompanied by a myelomeningocele[8] leading to partial or complete paralysis below the spinal defect. Abnormal development of the cerebellar vermis and medulla occur, and they both descend into the foramen magnum. Hydrocephalus is also nearly always present. Type III causes severe neurological defects. It is associated with an encephalocele.[9] Type IV involves a failure of brain development.[10]

Other conditions sometimes associated with Chiari Malformation include hydrocephalus,[11] syringomyelia, spinal curvature, and connective tissue disorders[12] such as Ehlers-Danlos syndrome and Marfan Syndrome.

Symptoms

The brainstem, cranial nerves, and the lower portion of the cerebellum may be stretched or compressed. Therefore, any of the functions controlled by these areas may be affected. The blockage of Cerebro-Spinal Fluid (CSF) flow may also cause