Thursday, 21 June 2012


2 months baby with a large meningocele

Sagittal T2 images revealed small posterior fossa with herniation of elongated cerebellar tonsil.
Large meningomyelocele in the lumbar region with a neural placode within it.
Axial T2 image of brain showed dilated atrium and occipital horn of left ventricle- s/o colpocephaly.

•Chiari I malformation
  • most common
  • peg-like cerebellar tonsils displaced into the upper cervical canal through the foramen magnum
•Chiari II malformation
  • displacement of the medulla, fourth ventricle and cerebellum through the foramen magnum
  • usually with associated with a lumbosacral spinal myelomeningocoele
•Chiari III malformation
  • features similar to Chiari II  but with an occipital and / or high cervical encephalocoele
•Chiari IV malformation
  • severe cerebellar hypolasia without displacement of the cerebellum through the foramen magnum
  • probably a variation of cerebellar hypoplasia
Arnold chiari type II malformation:
  • Usually accompanied by a lumbar myelomeningocele leading to partial or complete paralysis below the spinal defect.  
  • As opposed to the less pronounced tonsillar herniation seen with Chiari I, there is a larger cerebellar vermian displacement.
  • Low lying torcular herophili, tectal beaking, and hydrocephalus with consequent clival hypoplasia are classic anatomic associations.
  • The position of the torcular herophili is important for distinction from Dandy-Walker syndrome in which it is classically upturned.
  •  This is important because the hypoplastic cerebellum of Dandy-Walker may be difficult to distinguish from a Chiari malformation that has herniated or is ectopic on imaging.
  • Colpocephaly may be seen due to the associated neural tube defect.
Reference : Pediatric brain and spine, an atlas of MRI and spectroscopy. Springer Verlag. (2005) ISBN:3540213406

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