Calcifying aponeurotic fibroma in a dog.

A calcifying aponeurotic fibroma involving the soft tissue and bone of the occipital area compressed and attenuated the cerebellum and brainstem of a 9-year-old female dog of mixed breeding. Clinical signs included a head tilt to the left; gait ataxia; anisocoria, with a midly dilated left pupil; horizontal nystagmus, with the fast phase to the right; and a mild depression of the level of consciousness. The signs were sequential and progressive.