title: Nonsynostotic Posterior Brachycephaly with Hindbrain Herniation.
abstract: BACKGROUND
  Positional plagiocephaly is the most common cause of cranial asymmetry. The underlying cause of Chiari-1 malformation has many possible theories, and anecdotally some pediatric neurosurgeons have had experience of severe cases of positional brachycephaly with Chiari-1. However, to date, there have been no published cases linking nonsynostotic plagiocephaly with Chiari-1 malformation.
  
  
  METHODS
  An 18-month-old boy presented with a head injury. On examination he had a Glasgow Coma Score of 15 with no focal neurologic deficits, but he was noted to have marked posterior brachycephaly. A computed tomography scan showed a slim left-sided hemispheric acute subdural hematoma with no mass effect, which was treated conservatively. Of note, all of his cranial vault sutures were open, and a diagnosis of incidental positional plagiocephaly was made. Subsequent magnetic resonance imaging as part of a work-up to exclude nonaccidental injury showed a small posterior fossa with a steep tentorium and herniation of the cerebellar tonsils to the level of the body of the second cervical vertebra.
  
  
  CONCLUSIONS
  Chronic hindbrain herniation is well reported in cases of craniosynostosis, but to our knowledge this is the first published case associated with nonsynostotic deformational plagiocephaly. We hypothesize that severe posterior plagiocephaly can cause disproportion of the posterior fossa: hindbrain volume ratio and acquired chronic cerebellar herniation. Nevertheless, positional plagiocephaly and Chiari-1 are common entities, and it is possible that the dual diagnoses were coincidental in this case. This report serves to raise awareness of a putative causal relationship between positional plagiocephaly, reduced posterior fossa volume, and hindbrain herniation.
authors.affiliation: Department of Paediatric Neurosurgery, Royal Manchester Children's Hospital, Manchester, United Kingdom.
authors.forename: Omar N
authors.initials: ON
authors.lastname: Pathmanaban
authors.affiliation: Department of Paediatric Neurosurgery, Royal Manchester Children's Hospital, Manchester, United Kingdom. Electronic address: kerry.burke@nhs.net.
authors.forename: Kerry A
authors.initials: KA
authors.lastname: Burke
authors.affiliation: Department of Paediatric Neurosurgery, Royal Manchester Children's Hospital, Manchester, United Kingdom.
authors.forename: Paul
authors.initials: P
authors.lastname: Leach
authors.affiliation: Department of Paediatric Neurosurgery, Royal Manchester Children's Hospital, Manchester, United Kingdom.
authors.forename: John
authors.initials: J
authors.lastname: Thorne
authors.affiliation: Department of Paediatric Neurosurgery, Royal Manchester Children's Hospital, Manchester, United Kingdom.
authors.forename: Ian D
authors.initials: ID
authors.lastname: Kamaly-Asl
mesh_terms: D002675:Child, Preschool; D003398:Craniosynostoses / Q000150:complications / Q000000981:diagnostic imaging* / Q000601:surgery; D004677:Encephalocele / Q000150:complications / Q000000981:diagnostic imaging* / Q000601:surgery; D006801:Humans; D007223:Infant; D008297:Male; D049068:Plagiocephaly, Nonsynostotic / Q000150:complications / Q000000981:diagnostic imaging* / Q000601:surgery; D012249:Rhombencephalon / Q000000981:diagnostic imaging* / Q000601:surgery
keywords: Chiari malformation; Deformational brachycephaly; Hindbrain herniation; Positional plagiocephaly; Posterior fossa; Tentorium