Chiari II malformation

Case contributed by Dr Fadi Aidi


Abnormal obstetric ultrasound with evidence of cystic lesion seen in the lumbar region. Uncomplicated delivery , otherwise normal newborn.

Patient Data

Age: Two days
Gender: Female

The posterior fossa is small with evidence of tonsillar herniation through the crowded foramen magnum. Mild cervico-medullary kinking. Downward displacement of cerebellar vermis is also noted. Pulled down brainstem.
A small/collapsed fourth ventricle is noted. Dilated both occipital horns (colpocephaly). No evidence of hydrocephalus. 

No obvious tectal beaking. Hypoplastic/ underdeveloped tentorium with abnormally low insertion at the occipital bone and low torcula.
The cerebellar hemispheres are wrapped around the brainstem.
Abnormal course straight sinus is noted.
Mild flattening of the pons with effacement of the prepontine cistern.
Severe thinning of the corpus callosum with possible absence/dysgenesis of its distal body and splenium. Septum pellucidum is present.

No evidence of encephalocele.

Thoracolumbar meningocele is noted through bony defect without evidence of neural or fatty elements.
Normal level of conus medullaris, no evidence of tethered cord.


Photos of our patient before and after the surgical repair.

The dorsal sac is clear representing the meningocele.

Case Discussion

Chiari II malformation representing an abnormality of the spine and posterior fossa characterized by a small posterior fossa with the descent of its structures (hindbrain herniation). Multiple associated abnormalities are frequently seen.

About 95% of a newborn with myelomeningocele have an associated Chiari II.

It can be associated with multiple spinal, cerebral, and cranial vault abnormalities.

Brain and spine MRI are essential modalities for the assessment of Chiari II malformation.

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