Gravida two female with previous history of abortion came for fetal MRI to ruleout congenital malformation showing lumbosacral myelomeningocele (arrow in first and third image), tonsillar herniation and corpus callosum dysgenesis (arrow in second image). features suggestive of Chiary 2 malformation.
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.
Type I - Is generally asymptomatic during childhood, but often manifests with headaches and cerebellar symptoms. Herniation of cerebellar tonsils
Type II - Usually associated with myelomeningocele leading to partial or complete paralysis below the spinal defect. Abnormal development of the cerebellar vermis andmedulla oblongata occur, and they both descend into the foramen magnum. Hydrocephalus is frequently present.
Type III - Type II associated with with an encephalocele.
Type IV - Lack of cerebellar development.
The Chiari II malformation is a complex congenital malformation of the brain, nearly always associated withmyelomeningocele. This condition includes downward displacement of the medulla, fourth ventricle, and cerebellum into the cervical spinal canal, as well as elongation of the pons and fourth ventricle, probably due to a relatively small posterior fossa.