What is already known about this topic?
Chiari malformation (CM) is known as the malformation of varying degrees of the descent of the brain stem and cerebellum below the foramen magnum (FM). The most common form of CM is type I, the elongation of the tonsils of the cerebellum into the upper cervical canal. Although this situation is usually presented as an incidental radiological finding, many symptoms may also guide the practitioner to such a diagnosis. The known primary radiological diagnosis of CM-I is relied on the degree of tonsillar herniation (TH) below the FM. However, recent data also shows the association of such malformation with smaller posterior cranial fossa (PCF) volume and the anatomical issues regarding the Odontoid. Recent studies suggest more radiological criteria that may aid to the diagnosis of CM.