Encephalopathy occasionally occurs in association with thyroid disorders, but most of these are treatable. These
encephalopathies include a neuropsychiatric disorder associated with
hypothyroidism, called
myxedema encephalopathy. Moreover,
Hashimoto's encephalopathy (HE) has been recognized as a new clinical disease based on an autoimmune mechanism associated with Hashimoto's
thyroiditis.
Steroid treatment was successfully administered to these patients. Recently, we discovered that the serum
autoantibodies against the NH2-terminal of α-
enolase (NAE) are highly specific diagnostic
biomarkers for HE. Further, we analyzed serum anti-NAE
autoantibodies and the clinical features in many cases of HE from institutions throughout Japan and other countries. Approximately half of assessed HE patients carry anti-NAE
antibodies. The age was widely distributed with 2 peaks (20-30 years and 50-70 years). Most HE patients were in euthyroid states, and all patients had anti-thyroid (TG)
antibodies and anti-
thyroid peroxidase (TPO)
antibodies. Anti-
TSH receptor (TSH-R)
antibodies were observed in some cases. The common neuropsychiatry features are consciousness disturbance and
psychosis, followed by
cognitive dysfunction,
involuntary movements,
seizures, and
ataxia. Abnormalities on electroencephalography (EEG) and decreased cerebral blood flow on brain SPECT were common findings, whereas abnormal findings on brain magnetic resonance imaging (MRI) were rare. HE patients have various clinical phenotypes such as the acute
encephalopathy form, the chronic psychiatric form, and other particular clinical forms, including
limbic encephalitis, progressive
cerebellar ataxia, and
Creutzfeldt-Jakob disease (CJD)-like form. The cerebellar ataxic form of HE clinically mimics
spinocerebellar degeneration (SCD) and is characterized by the absence of nystagmus, absent or mild cerebellar
atrophy, and lazy background activities on EEG. Taken together, these data suggest that the possibility of
encephalopathy associated with thyroid disorders must be considered.