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Hashimoto encephalopathy (HE) is believed to be an immune-mediated disorder associated with Hashimoto’s thyroiditis. It was suggested that neuropsychiatric symptoms, the presence of antithyroid antibody, and good response to steroids were important for the diagnosis of HE. It has been reported that homovanillic acid (HVA) and 3-methoxy-4-hydroxyphenylglycol (MHPG), which are monoamine metabolites of dopamine and noradrenaline, respectively, are the possible biomarkers of neuropsychiatric diseases. We report a case of Hashimoto encephalopathy, in which we longitudinally measured the plasma levels of monoamine metabolites. A 52-year-old woman developed acute psychosis, and was admitted to the psychiatric ward of our hospital due to psychotic state, 6 days after a traffic accident. An extensive evaluation showed no remarkable findings, except an increase in antithyroglobulin antibodies. Plasma levels of HVA and MHPG were extremely high at 66.5 and 41.8 ng/mL, respectively. On day 16, 50 mg/day oral prednisolone was administered, which improved her psychotic symptoms. Plasma levels of HVA and MHPG decreased to 7.2 and 9.9 ng/mL, respectively, on day 19. After the temporary worsening of psychosis and increase in plasma levels of HVA and MHPG, the dosage of prednisolone was tapered and low-dose risperidone was started. Her psychiatric symptoms gradually improved and plasma monoamine metabolite levels decreased again (HVA: 17.9 ng/mL; MHPG: 7.7 ng/mL). Although autoimmune mechanism has been suggested to be involved in HE, neural mechanism and pathogenesis of HE remain unknown. Our findings suggest that monoaminergic neural activity might be associated with psychotic symptoms in patients with HE and plasma levels of monoamine metabolites might be useful as state markers.

Deviant sounds occurring in a sequence of standard sounds, in the absence of attention, elicit an event-related potential known as mismatch negativity (MMN). Standard sounds are encoded in auditory sensory memory trace and processed as a single unit within 160-170 ms, where each unitary event stored is closely related to the temporal window of integration. The temporal window of integration of pure tone sound has already been reported. However, there are no reported correlations between segmented-speech sounds and a temporal unit. It is well known that pure tone sounds are predominantly recognized in the right hemisphere, whereas speech sounds are recognized in the left hemisphere. The aim of this study was to examine whether segmented-speech sounds were processed as a temporal unit like pure tone sounds and whether there were differences between right and left ear stimuli. Twenty-five right-handed healthy Japanese men participated in this study. Stimuli consisted of the vowel /a/ spoken by a Japanese female and the stimuli sequences were randomized from short standard sounds and three types of long deviant sounds. The stimuli were presented to both ears separately. All bilateral stimuli induced definite MMN with similar peak latencies. The MMN amplitude gradually enhanced from the short to the long duration deviant. There were no differences in MMN between the right and the left ear stimuli. These findings perhaps show that bilateral deviant segmented-speech sounds were processed equally as a temporal unit.