An 8-month-old male German shepherd dog presented with a 3-month history of episodes of circling, pacing, loss of balance, and head tilt. The episodes are triggered by excitement or stress such as being in an unusual environment, like the consultation room. In between and since a very early age, this dog has been showing a very mild head tilt and clumsy gait. The episodes occur daily. The neurological status including the frequency and intensity of the episodes is considered static.

On the video, this dog shows bilateral vestibular ataxia, circling to either side, so-called ‘positioning head tilt’ with the head being tilted to the opposite side of the direction of the circling and the head in a level position when static. The neurolocalisation was vestibular-cerebellum. MRI revealed an absence of the cerebellar nodulus and ventral uvula as well as partial hypoplasia of the ventro-caudal cerebellar hemispheres on both sides. Similar cases have been reported in the literature and are often referred as Dandy-Walker variant in human patients.

The nodulus and uvula as well as fastigial nuclei are mainly responsible for maintenance of equilibrium and coordination of head and eye movement. They play an important part in vestibular control of head position and movement by inhibiting stimulation of brainstem vestibular nuclei to maintain a level head position in response to head movement. This inhibition was absent in this case as a consequence of this malformation. As a result, the head was tilted to the opposite side from the turning direction.

Courtesy of Dr. Lorena Martinez