Reversible electroencephalographic and single photon emission computed tomography abnormalities in Hashimoto's encephalopathy.

Hashimoto's encephalopathy (HE) is a well-established disease that occurs most commonly in patients with euthyroidism. We report 3 patients diagnosed with HE. Cases 1 and 2 were young females who had experienced intractable seizures and presented with cognitive impairment. Reversible slow waves on the electroencephalogram (EEG), and nearly complete recovery of cognition, were noted after steroid treatment. Case 3 was an elderly male who presented with a sudden onset of vertigo, diplopia, and recurrent gait ataxia. Reversible hypoperfusion in the upper portion of the left cerebellum, on (99m)Tc hexamethylpropyleneamine oxime (HMPAO) single photon emission computed tomography (SPECT), was noted after steroid treatment. We also review 25 cases from the literature of patients diagnosed with HE. All patients had antithyroid antibodies. A reversible inflammatory process is supported by brain magnetic resonance imaging, SPECT, EEG and cerebrospinal fluid studies. Vasculitis is the most probable pathogenesis according to laboratory findings. Steroids are the treatment of choice, and result in a favorable outcome when administered early in the disease course.