Neurologic manifestations of thyroid disease.

Animals with polyneuropathy associated with primary hypothyroidism have clinical neurologic signs that range from peripheral vestibular signs, lower motor neuronal deficits, laryngeal paralysis, to megaesophagus; however, a few affected animals also show evidence of a more generalized polyneuropathy with cranial (facial more than vestibular nerve) and spinal nerves being affected most commonly. Confirmation of the diagnosis will depend on neurologic signs, clinicopathologic results including an abnormally low T4 response to TSH and electrodiagnostic findings. Successful treatment is based on thyroxine supplementation therapy. In severe cases with laryngeal paralysis, additional surgical treatment is indicated. Some animals with megaesophagus may develop permanent neurologic disabilities.