Chiari malformation

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Chiari malformation is a developmental abnormality of the brain.



  • Headaches, occipital.
  • Dizziness.
  • Nocturnal respiratory abnormalities.


Numbered from least severe to most severe:

  • Chiari type I - tonsils herniated[2] (radiologic definition: 4-6 mm below the plane of the foramen magnum).
    • Associated with: sudden death,[3] sleep apnea, cerebellar ataxia.
  • Chiari type II - often assoc. with hydrocephaly at birth. Often associated with myelomeningocele.
  • Chiari type III - cerebellum + brain stem herniate through foramen magnum +/- encephalocele.[4]
  • Chiari type IV - cerebellar hypoplasia or no cerebellum.


Surgery depends on clinical symptoms due to CSF obstructions. Specimens may include: [5]

  • Vertebral bone (decompression)
  • Hermiated cerebellar tonsils.
  • Reactive / dysplastic choroid plexus.
  • Glial nodules.
  • Arachnoidal cysts.
  • Subependymomas.

In cases with myelomeningocele at autopsy, the posterior fossa should be examined.


See also


  1. Ferré Masó, A.; Poca, MA.; de la Calzada, MD.; Solana, E.; Romero Tomás, O.; Sahuquillo, J. (Mar 2011). "Sleep disturbance: a forgotten syndrome in patients with Chiari I malformation.". Neurologia. doi:10.1016/j.nrl.2011.01.008. PMID 21420201.
  2. URL: Accessed on: 6 May 2011.
  3. Zhang, J.; Shao, Y.; Qin, Z.; Liu, N.; Zou, D.; Huang, P.; Chen, Y. (Dec 2012). "Sudden Unexpected Death due to Chiari Type I Malformation in a Road Accident Case.". J Forensic Sci. doi:10.1111/1556-4029.12051. PMID 23278920.
  4. URL: Accessed on: 6 May 2011.
  5. Piatt, JH.; D'Agostino, A. (Feb 1999). "The Chiari II malformation: lesions discovered within the fourth ventricle.". Pediatr Neurosurg 30 (2): 79-85. doi:28767. PMID 10325563.