Hashimoto encephalopathy: clinical and MRI improvement following high-dose corticosteroid therapy

Hashimoto encephalopathy (HE) is an immune-mediated encephalopathy associated with Hashimoto thyroiditis. Most patients with HE respond to corticosteroids. Diffuse or focal white matter changes suggesting primary demyelination on magnetic resonance imaging (MRI) has been reported in only a few patients with HE. Follow-up imaging studies have been sparse.

We report the case of a 48-year-old woman who presented with progressively declining cognitive function over 6 weeks without neurologic focal deficit on clinical examination. Her Mini-Mental State Examination Score was 3/30, and the MRI showed cortical and subcortical white matter demyelination. Biologic and radiologic investigations did not reveal an infective, vasculitic, or neoplastic etiology. Although her thyroid function tests were normal, thyroid antibodies were detected in high titers in her serum. A diagnosis of HE was made, and the patient was treated with high-dose corticosteroids. Over the next 8 weeks, her Mini-Mental State Examination Score improved to 24/30. The MRI changes showed resolution paralleling her clinical improvement.

This case illustrates the importance of considering rare but treatable causes of encephalopathy in a patient presenting with acute or subacute cognitive decline.