BACKGROUND Hashimoto's encephalopathy (HE) is an autoimmune encephalopathy that can involve various symptoms including psychosis. Syndrome of inappropriate secretion of antidiuretic hormone (SIADH) may be a complication in some neurological diseases. However, the simultaneous occurrence of subacute psychosis and SIADH as the manifestation of HE, observed in the present case, has rarely been reported. CASE REPORT A 72-year-old man was hospitalized with a 4-month history of abnormal behaviors, including talkativeness, stopping consumption of coffee and cigarettes, hoarding garbage, and sleep disorders. On physical examination, increased and incoherent speech with flight of idea and delusion were observed. The Mini-Mental State Examination score was 28/30. Laboratory findings included hyponatremia due to SIADH and a positive result for anti-thyroid and anti-NH2 terminal of alpha-enolase antibodies. Cerebrospinal fluid examination revealed only elevation of IL-6. Brain magnetic resonance imaging was unremarkable; however, (I-123)-iodoamphetamine single-photon emission computed tomography showed extensive hyperperfusion involving the brainstem and bilateral frontal and medial temporal lobes. Electroencephalography showed generalized slow waves, but there were no epileptiform discharges. After 2 courses of high-dose intravenous methylprednisolone followed by oral prednisolone, his symptoms improved. Based on the findings of clinical features and steroid responsiveness, he was diagnosed with HE. Oral prednisolone and antipsychotic drugs were decreased without a relapse and he was discharged to his home. CONCLUSIONS Although psychosis complicating SIADH is rare, HE should be considered in the differential diagnosis because of its treatment efficacy.

The present study characterized the degeneration of nigrostriatal dopaminergic neurons in the early stages of parkinsonian disorders using integrative neuroimaging analysis with neuromelanin-sensitive MRI and ¹²³I-FP-CIT dopamine transporter (DAT) SPECT. Thirty-one, 30, and 29 patients with progressive supranuclear palsy (PSP), corticobasal syndrome (CBS) with abnormal specific binding ratio (SBR) in either hemisphere (mean ± 2SD), and parkinsonism-predominant multiple system atrophy (MSA-P), respectively, were enrolled. Neuromelanin-related contrast (NRC) in the substantia nigra (NRC_SN) and locus coeruleus (NRC_LC) and the SBR of DAT SPECT were measured. All the patients underwent both examinations simultaneously within five years after symptom onset. After adjusting for interhemispheric asymmetry on neuromelanin-related MRI contrast using the Z-score, linear regression analysis of the NRC_SN and SBR was performed for the most- and least-affected hemispheres, as defined by the interhemispheric differences per variable (SBR, NRC_SN, standardized [SBR + NRC_SN]) in each patient. Although the variables did not differ significantly between PSP and CBS, a significant correlation was found for CBS in the most-affected hemisphere for all the definitions, including the clinically defined, most-affected hemisphere. No significant correlation was found between the NRC_SN and SBR for any of the definitions in either PSP or MSA-P. Together with the findings of our previous study of dementia with Lewy bodies (DLB) and Parkinson's disease (PD), the present findings indicated that neural degeneration in the disorders examined may be categorized by the significance of the NRC_SN-SBR correlation in PD and CBS and its non-significance in DLB, PSP, and MSA-P.

Among the symptoms of Parkinson’s disease (PD), apathy comprises a set of behavioral, affective, and cognitive features that can be classified into several subtypes. However, the pathophysiology and brain regions that are involved in these different apathy subtypes are still poorly characterized. We examined which subtype of apathy is elicited in a mouse model of PD with 6-hydroxydopamine (6-OHDA) lesions and the behavioral symptoms that are exhibited. Male C57/BL6J mice were allocated to sham (n = 8) and 6-OHDA (n = 13) groups and locally injected with saline or 4 µg 6-OHDA bilaterally in the dorsal striatum. We then conducted motor performance tests and apathy-related behavioral experiments. We then pathologically evaluated tyrosine hydroxylase (TH) immunostaining. The 6-OHDA group exhibited significant impairments in motor function. In the behavioral tests of apathy, significant differences were observed between the sham and 6-OHDA groups in the hole-board test and novelty-suppressed feeding test. The 6-OHDA group exhibited impairments in inanimate novel object preference, whereas social preference was maintained in the three-chamber test. The number of TH+ pixels in the caudate putamen and substantia nigra compacta was significantly reduced in the 6-OHDA group. The present mouse model of PD predominantly showed dorsal striatum dopaminergic neuronal loss and a decrease in novelty seeking as a symptom that is related to the cognitive apathy component.

Tumor necrosis factor (TNF)-α inhibitors rarely cause optic neuritis as a side effect although the disease associated with ozoralizumab, a novel anti-TNF-α NANOBODY® compound, has not been reported. A 76-year-old female with rheumatoid arthritis, medicated with ozoralizumab, was hospitalized with a two-day history of extending partial visual field loss in the left eye. Campimetry revealed top horizontal hemianopia in the left eye. Swelling and abnormally high intensity of the left optic nerve were observed in magnetic resonance imaging. Visual evoked potential tests revealed delayed latency and reduced amplitude on the left side. She was diagnosed with ozoralizumab-associated isolated optic neuritis and cured with two courses of high-dose intravenous methylprednisolone, followed by oral prednisolone. Ozoralizumab may be associated with optic neuritis although early diagnosis and immunotherapy possibly achieve a good outcome.

Autoimmune cerebellar ataxia (ACA) is an immune‐mediated cerebellar disorder arising from various underlying conditions. Because ACA is potentially treatable, identifying associated neuronal antibodies is important for diagnosis. We report the case of a 55‐year‐old woman with subacute progressive ataxia who presented with dysarthria and impaired handwriting and gait. Her scale for the assessment and rating of ataxia (SARA) score was 20.5, with particularly high subscores for gait and stance. She had a history of Hashimoto’s thyroiditis. Laboratory testing showed markedly elevated antithyroid antibody levels with normal thyroid function, initially suggesting the cerebellar ataxic subtype of Hashimoto’s encephalopathy (HE). Cerebral blood flow single‐photon emission computed tomography revealed cerebellar hypoperfusion, which was most prominent in the superior cerebellar vermis. Intravenous methylprednisolone (1000 mg/day for 3 days) was administered; however, her response was poor. Further evaluation revealed positivity for anti‐Ma2 antibodies, leading to a diagnosis of anti‐Ma2‐associated ACA. Subsequent intravenous immunoglobulin therapy improved the clinical symptoms and imaging findings, and the follow‐up SARA score decreased to 10. Comprehensive imaging revealed no underlying malignancy. This case is unique not only because both rare diseases were key considerations in the differential diagnosis, but also because it is instructive in two respects: the construct of HE remains insufficiently specific and should not preclude consideration of alternative immune‐mediated etiologies, and patients positive for anti‐Ma2 antibody require sustained oncological surveillance, even in the absence of malignancy at presentation.