Hashimoto’s encephalopathy

Abstract

Hashimoto’s encephalopathy (HE) has been recognized as a new clinical disease based on an autoimmune mechanism associated with Hashimoto’s thyroiditis (HT), and steroid treatment has been successfully administered. Recently, we discovered that the serum autoantibodies (Abs) against the NH2-terminal of a-enolase (NAE) can serve as a highly specific diagnostic biomarker for HE. We reviewed the clinicoimmunological features of 80 cases of HE with serum anti- NAE Abs from institutions throughout Japan. The mean age of the patients was 62 years, but the ages were widely distributed, with two peaks (20-30 and 60-70 years). Most patients with HE were in euthyroid states. All patients had anti-thyroid Abs, and, in rare cases, anti-TSH receptor Abs. The common neuropsychiatric symptoms were consciousness disturbances and psychosis, followed by cognitive dysfunction, involuntary movements, seizures, and ataxia. EEG abnormalities and decreased blood flow on the brain SPECT were common, whereas abnormalities on the brain MRI were rare. Patients with HE show various clinical phenotypes such as acute encephalopathy and chronic psychiatric forms including limbic encephalitis, followed by progressive cerebellar ataxia and Creutzfeldt- Jakob disease-like forms. The cerebellar ataxic form of HE clinically mimics spinocerebellar degeneration and is characterized by an absence of nystagmus, absent or mild cerebellar atrophy, and lazy background activities on the EEG. Although steroids have been the first-choice and favored medication for the treatment of patients with HE, some patients show resistance to them. In such a case, plasmapheresis or intravenous administration of immunoglobulin is recommended. We should pay attention to the possibility of HE as a treatable disease.