Arnold Chiari malformation type II

Case contributed by Dr Ghada Sheta

Presentation

32 weeks pregnant , meningocele detected by prenatal ultrasound

Patient Data

Age: 30 years
Gender: Female

Fetal

mri
  • dilatation of the supratentorial ventricular system (reaching 2.2 cm at the level of atrium) associated with colpocephaly. There is a descend of the cerebellar tonsils in the cervical spinal canal through foramen magnum. Normal size and configuration of the 4th ventricle
  • corpus callosum is thin with an indistinct menu and rostrum 
  • lower lumbar and sacral spinal defect associated with meningomyelocele measuring 3.2 x 7.6 x 7.5 cm in the AP, transverse, and CC dimensions respectively
  • the subarachnoid space is compatible with the gestational age
  • the degree of gyration and sulcation is as expected for the stated gestational age
  • no structural abnormalities are noted in the cerebral hemispheres
  •  the cavum septum pellucidum is normally formed

Annotated images

mri

Annotated image of the key features seen in Chiari type II.

Case Discussion

Findings are suggestive of Arnold Chiari malformation type II associated with corpus callosum dysgenesis and severe ventriculomegaly.

MRI is the modality of choice for detecting and characterizing the full constellation of findings associated with Chiari II malformation. The key features are myelomeningocele (lumbosacral spina bifida aperta) and a small posterior fossa with descended brainstem and cerebellar tonsils. Numerous associated abnormalities are also frequently encountered.  

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