Chiari 1.5 malformation is characterized by an inferior herniation of the cerebellar tonsils below the foramen magnum greater than 5 mm in adults (Chiari I) ^1,2, in combination with inferior descent of some portion of the brain stem, often the obex of the medulla oblongata (Chiari 1.5) ^2,3. In children, the tonsils usually are located below the foramen magnum, and measurements of 7 mm may be usual ¹.

Chiari I and 1.5 malformations may be associated with craniocervical osseous anomalies including platybasia, basilar invagination, retroflexion of the odontoid, and short hypoplastic clivus ^2,4, all of which may be predictive factors for the formation of syringohydromyelia ⁴.

This case illustrates the appearance of a Chiari 1.5 malformation, associated with craniocervical osseous anomalies, but without syrinx formation.

Case courtesy

• Sterfferson Morais, MD - PGY-3, Radiology Resident, Department of Radiology
• Antonio Rodrigues de Aguiar Neto, MD - Radiologist, Department of Radiology
•  Hospital da Restauração – Recife, PE – Brazil