A case report: resolution of Chiari I malformation after helmet therapy for deformational brachycephaly.

Positional plagiocephaly is the most common cause of cranial asymmetry. Deformational brachycephaly denotes a head shape characterized by occipital flattening and increased bilateral width, which can also be caused by external deformation of the moldable infant cranium in positional bilateral posterior plagiocephaly. There are reports of craniosynostosis associated with Chiari I malformation (CIM), possibly caused by decreased posterior fossa volume and related to increased intracranial pressure. To the best of our knowledge, this is only the second case report demonstrating acquired CIM in a child with positional brachycephaly. Of note, the fact that the CIM resolved after helmet therapy could support the hypothesis that CIM is associated with decreased volume of the posterior fossa. However, these two conditions may be independent of one another. More research is needed to identify an association between the two conditions.