Abstract
Acquired cerebellar ataxia has been described with hypothyroidism, and is typically reversible by thyroid hormone replacement therapy. The cerebellar dysfunction has been attributed to metabolic and physiological effects of the endocrine disorder. In a few patients, however, ataxia has persisted despite thyroid replacement therapy. Other mechanisms may be involved in ataxia associated with thyroid disorders. OBJECTIVE: To document progressive non-familial adult onset cerebellar degeneration (PNACD) occurring in six patients with raised antithyroid antibodies (Hashimoto's/autoimmune thyroiditis), and other autoimmune manifestations, in the absence of hypothyroidism; and to document the independence of the cerebellar disorder from the endocrine dysfunction. METHODS: A case study of six patients with PNACD reviewing the clinical course and relation to endocrine and autoimmune status. RESULTS: All six patients were euthyroid when they developed their symptoms; had raised antithyroid antibodies consistent with Hashimoto's autoimmune thyroiditis; and had strong personal or family histories of organ specific autoimmune diatheses. Brain MRI disclosed atrophy of the cerebellar vermis in four patients and olivopontocerebellar atrophy in two. Other possible causes of cerebellar degeneration were excluded. De novo treatment (two patients) or continued treatment (three patients) with L-thyroxine did not modify the progression of the ataxia. CONCLUSIONS: Cerebellar degeneration in these patients with raised antithyroid antibodies may be immune mediated. The presence of antithyroid antibodies may signal or cause the autoimmune process producing cerebellar degeneration. "Hashimoto's associated ataxia" seems to represent a recognisable and not uncommon condition; a trial of immunomodulating therapy should be considered in these patients.