Chiari Malformation Type I

Alternative Names

  • CM1
  • Chiari Malformation Type I with Syringomyelia
  • CM1 with Syringomyelia
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WHO-ICD-10 version:2010

Diseases of the nervous system

Other disorders of the nervous system

OMIM Number

118420

Mode of Inheritance

Autosomal dominant

Description

Chiari malformations (types I-IV) are a group of congenital brain abnormalities affecting the structural relationships between the cerebellum, brainstem, the upper cervical cord, and the bony cranial base.  Chiari type I malformation is the most common and the least severe of the spectrum and is often diagnosed in adulthood.  The prevalence of Chiari I is 0.1-0.5% with a slight female predominance.  Most patients with CMs have no symptoms and their malformations are discovered while conducting diagnostic procedures for other disorders.  Symptoms include headaches, neck pain, dizziness and balance problems, muscle weakness, numbness or tingling in the arms or legs, blurred vision, double vision, sensitivity to light, insomnia and depression. 

The hallmark of Chiari I malformation is a cerebellar tonsillar herniation below foramen magnum.  Some CM1 patients are asymptomatic and the condition does not interfere with a person’s activities of daily living.  In other cases, medications may ease certain symptoms, such as pain.

Chiari malformations type I follows an autosomal dominant inheritance pattern. The molecular basis of the disease is unknown.

Epidemiology in the Arab World

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Other Reports

Saudi Arabia

Alorainy (2006) reviewed and analysed the MRI studies on pediatric patients (aged 3-days to 15-years) over a 3-year period.  Out of 581 patients with MR examinations of the brain, 86 were diagnosed with congenital cerebral malformations. Chiari I malformation was seen in only one patient in association with Apert’s syndrome.

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