Paroxysmal dyskinesia associated with hyperthyroidism in 7 cats: a novel manifestation of a metabolic encephalopathy

BACKGROUND: Paroxysmal dyskinesia associated with hyperthyroidism (HT) is a well-described disorder in humans and has not been previously reported in cats. HYPOTHESIS/OBJECTIVES: Paroxysmal dyskinesia might develop as a consequence of HT in cats, with improvement or cessation of the episodes once normal thyroid function is restored. ANIMALS: Seven client-owned cats. METHODS: Multicenter retrospective observational study comprising cats with clinical signs consistent with the clinical phenotype of paroxysmal dyskinesia based on video recordings, and a concurrent diagnosis of HT. Follow-up information was obtained by contacting referring veterinarians and owners. RESULTS: Seven cats were included. No signs of neurological disease were observed between the episodes except for plantigradism in one cat. Brain MRI studies were performed in 2 cats, revealing no intracranial abnormalities. In 1 cat, a 2-h video-assisted wireless electroencephalography confirmed the absence of epileptic activity. Clinical signs associated with HT were noted in all but 1 cat. After treatment for HT, complete remission of paroxysmal dyskinesia episodes was achieved in all cases, with euthyroid state confirmed in 6 cats. CONCLUSIONS AND CLINICAL IMPORTANCE: HT should be considered a differential diagnosis in cats with paroxysmal dyskinesia, even in the absence of other suggestive signs. Similar to the analogous disorder in humans, the prognosis appears excellent once appropriate treatment for HT is initiated.