Cerebellar Syndrome Associated with Thyroid Disorders.

Thyroid disorders, including hypothyroidism, hyperthyroidism and Hashimoto encephalopathy, are considered the most common cause of cerebellar dysfunction due to hormonal imbalance. Typically, cerebellar impairment occurs in the course of hypothyroidism and Hashimoto encephalopathy. Information about demographic, clinical and laboratory features of cerebellar disease associated with thyroid disorders is poor. Our review of the literature (1965 to 2018) identified 28 cases associated with hypothyroidism and 37 cases associated with Hashimoto encephalitis. Both patients with hypothyroidism and Hashimoto encephalopathy presented with signs of ataxia that were similarly distributed in the two groups and were mostly predictive of vermis involvement and frequent impairment of cerebellar hemispheres. Additional neurological signs, like dystonia, psychiatric symptoms, ocular disturbances and myoclonus, could be found in the Hashimoto encephalopathy group alone. When present, atrophy of vermis and often of both cerebellar hemispheres was the main imaging abnormality in both hypothyroidism and Hashimoto encephalopathy. Anti-thyroid antibodies could be detected in three quarters of patients with hypothyroidism and in all patients with Hashimoto encephalopathy. In the patients with hypothyroidism, thyroid replacement therapy yielded complete or partial remission of ataxia. In the Hashimoto encephalopathy group, immunosuppressive treatment provided complete remission of ataxia in about 60% of patients, partial remission in the remaining cases. Owing to the treatable nature of the condition and the high prevalence of thyroid disease among general population, cerebellar syndrome associated with thyroid disorders should be considered an important clinical entity. Information from this review will hopefully stimulate and strengthen awareness of thyroid-associated ataxia among clinicians.