Dandy is a 1 year old F/S Cavalier King Charles Spaniel dog with a history of progressive head tilt to the left and scratching at the left ear. Initial evaluations suggested possible otitis media. An MRI was ordered to further evaulate the bulla. The cervical spine was also imaged due to the high incidence of Chiari malformation in this breed1. The Chiari Malformation (also called the Arnold Chiari Malformation) is a developmental anomaly at the base of the brain which results in the downward displacement of some of the brains structures into the spinal canal. These malformations have been subdivided to reflect the degree of displacement as well as the varying etiology of the malformations. Type I malformations consist of a downward displacement of the cerebellar tonsils (two pegs of tissue which hang off the inferior surface of the cerebellum at the base of the brain) out the inferior opening of the skull into the spinal canal. No other structures of the brain are displaced. Patients with Chiari Malformations often have an associated accumulation of fluid within the interior of the spinal cord. This condition is termed syringomyelia or hydromyelia. The condition ultimately results in progressive neurological deficits. The treatment of Chiari Malformation and associated anomalies is controversial, largely owing to a lack of complete understanding of the entity.
1Syringohydromyelia in Cavalier King Charles Spaniels. J Am Anim Hosp Assoc 36:34-41 Jan-Feb00.