The Chiari 3 Malformation and a Systemic Review of the Literature

Chiari type 3 is a rare hindbrain malformation that has been reported in the literature primarily as case reports and case series. Radiological, pathophysiological and surgical definitions of the malformation are inconsistent in the literature and subsequently can be confusing, and outcomes have also been uniformly poor. The definition of this rare malformation will be clarified through a case presentation.

A retrospective review of prior publications in the PubMed and MEDLINE databases was performed looking for reports of 'Chiari 3 +/- malformation' and 'occipital encephalocele'. Relevant papers were reviewed and compiled into table format with associated descriptions of a Chiari type 3 malformation. A case illustration is presented with radiological and intraoperative imaging to reinforce and clarify the definition.

Upon review of the prior publications in the detail of the descriptions and imaging associated with each article, there is a wide range of variability in the description of what is considered a Chiari 3 malformation. Occipital, occipitocervical and high cervical defects have all been described as Chiari 3 malformation. Our case illustration presents a patient with an occipitocervical encephalocele with neural elements, which is the classic and accepted definition of the Chiari 3 malformation.

Chiari type 3 is a rare congenital malformation, and prior publications describing this developmental disorder have not demonstrated a consensus in its definition. In addition, outcomes have traditionally been reported as poor. This case illustration of a Chiari type 3 enforces the definition of an occipitocervical encephalocele with hindbrain herniation, and with proper management not all Chiari 3 malformation patients have bad outcomes.