Case Report: Positioning head tilt observed in six dogs with meningoencephalitis of unknown origin

Positioning head tilt (PHT) is a dynamic clinical neurological sign that is characterized by a head tilt to the opposite side of a voluntary lateral turn of the head. Based on recent publications, various etiologies are proposed for the occurrence of PHT in dogs and cats. One suggested cause is a lack of inhibitory input to the vestibular nuclei due to dysfunction of the cerebellar nodulus and uvula (NU). In that category, it has been reported in dogs with hypoplasia of the NU, dogs with lysosomal storage diseases, and in a dog with a cerebellar tumor. Other proposed causes of PHT include reduced input of either proprioceptive information from the spindles of cervical muscles or information about head movement in space from peripheral vestibular apparatus. As examples of the former, it has been observed in feline cases of hypokalemic myopathy and myasthenia gravis. As an example of the latter, it has been observed in a dog and four cats with bilateral peripheral vestibular dysfunction. In this study, we describe and discuss our observations of PHT in six dogs with meningoencephalitis of unknown origin (MUO). Although it was not possible to identify the causative lesion site in these dogs, the possibility of MUO causing the clinical sign of PHT in dogs is deemed to be clinically relevant.