We report a case of a patient with neuromyelitis optica spectrum disorder (NMOSD) who was originally treated for multiple sclerosis (MS) due to a negative anti-aquaporin-4 (AQP4) antibody test, but later the antibody titer became positive. A 58-year-old woman without prior medical history developed acute left facial pain, vomiting, and hiccups. MRI showed an intraparenchymal lesion extending from the medulla oblongata to cervical cord with high T₂-weighted signal intensity. The patient responded to steroid pulse therapy. However, she developed diplopia and gait disturbance after six months, and follow-up MRI revealed a new lesion in the left middle cerebellar peduncle. The patient was diagnosed with MS due to the dissemination in the time and space of her lesions and negative anti-AQP4 antibody status. There was no relapse for three and a half years on fingolimod therapy. However, a severe relapse occurred four years later that involved optic neuritis and multiple new brain lesions. During this episode, the anti-AQP4 antibody test was positive, and the patient was diagnosed with NMOSD. This case highlights the possibility that seroconversion of anti-AQP4 antibody may occur at any time in NMOSD patients. Therefore, this diagnostically paramount antibody should be measured several times during the treatment of relapsing-remitting MS in patients with repeat frequent recurrences and uncommon symptoms of MS.

A 64-year-old Japanese woman presented with 1 week of recurrent convulsive seizures. At the time of admission, she was in a coma and did not present with convulsions. Intravenous diazepam administration improved her consciousness, although severe psychomotor excitement developed. Brain MRI demonstrated diffusion restriction in the cerebral cortex of the right hemisphere. Electroencephalography (EEG) showed periodic discharges centered around the parietal regions with right-sided dominance. Nonconvulsive status epilepticus (NCSE) was suspected, and the patient was actively treated with anti-epileptic drugs. She developed akinetic mutism and generalized myoclonus 1 month after admission. Follow-up EEG studies disclosed periodic synchronous discharges. Abnormal prion protein in the cerebral fluid was detected using a real-time quaking-induced conversion assay. The clinical diagnosis in the present case was sporadic Creutzfeldt–Jakob disease (CJD). Seizures as an initial symptom in patients with CJD are relatively rare. Our case suggests that CJD should be considered as a differential diagnosis when a patient presents with refractory NCSE.

We have reported a case of a 44-year-old woman with anti-signal recognition particle (SRP) antibody-positive immune-mediated necrotizing myopathy triggered by human parvovirus B19 (PVB19) infection. She was admitted to the hospital because of lower leg edema and muscle weakness after erythema infectiosum. Magnetic resonance imaging of the lower extremities revealed high signals in the proximal muscles and subcutaneous edema on STIR. Muscle biopsy showed myofiber regenerative changes and variation in fiber size. A myositis-specific autoantibody profile indicated a positive result for anti-SRP antibodies. We diagnosed the patient with immune-mediated necrotizing myopathy (IMNM). Muscle strength and subcutaneous edema improved gradually in 3 months following immunotherapy. This is the first case report of an IMNM associated with PVB19 infection.

A 63-year-old woman with no medical history of note developed acute-onset abnormal behavior persisting for one week. Mild disturbance of consciousness was noted on physical examination. Her blood and spinal fluid test results were normal. On brain MRI, diffusion-weighted image showed a high-intensity signal in U-fiber areas of the bilateral frontal lobes, and fluid-attenuated inversion recovery showed white matter lesions. We suspected neuronal intranuclear inclusion disease (NIID) based on brain MRI findings; therefore, we performed a skin biopsy and genetic test. Pathological findings of the skin biopsy revealed the presence of anti-p62-positive intranuclear inclusion bodies in fibroblasts and adipocytes. The genetic test showed GGC repeat expansion of NOTCH2NLC, but no mutation of FMR1. Thus, we diagnosed her with NIID. The acute-onset abnormal behavior was improved by levetiracetam. The present case indicates that patients with a high-intensity area in the corticomedullary junction should undergo a skin biopsy, even though they may present with non-specific symptoms such as acute-onset abnormal behavior.

We report the case of a 65-year-old man who gradually developed numbness in both hands, lower limb muscle weakness and atrophy, and orthostatic hypotension over two and a half years. These symptoms indicated hereditary ATTR amyloidosis (ATTRv amyloidosis), and the final diagnosis was established through proof of TTR gene mutation (V30M). We initiated patisiran therapy, and a continuous 6-minute walking test performed 3 weeks from the start of therapy demonstrated improvement in the walking distance. This is a single case report showing the improvement in the motor and sensory function on administration of patisiran monotherapy from an early stage.

A 73-year-old man developed delayed-onset multiple cranial neuropathies of cranial nerves V, VII and VIII, and segmental paresis in the ipsilateral upper extremity related to the C4 to Th1 segment, after all skin lesions with varicella zoster (VZV) on the left neck of the C3–4 dermatome had dried and crusted over. On admission, cerebrospinal fluid (CSF) revealed pleocytosis (all mononuclear cells, 12/μl). Treatment was started with intravenous acyclovir (10 mg/kg, every 8 h for 14 days) and methylprednisolone (1,000 mg/day for 3 days). Four days after starting treatment, left segmental paresis was improved, but the multiple cranial neuropathies persisted. Oral prednisolone (0.5 mg/kg/day) was administered for 5 days, then tapered off. All neurological symptoms had disappeared by hospital day 23. Of particular interest was the discrepancy between skin regions affected by VZV (C3–4) and the regions of cranial neuropathy (cranial nerves V, VII, and VIII) and muscle weakness innervated by C4–Th1. Although CSF was negative for VZV DNA according to PCR testing, the antibody index for VZV was elevated. This suggests intrathecal synthesis of VZV antibodies and supports the diagnosis of VZV meningitis. Also, all cranial nerves involved in this case were reported to have the cranial nerve ganglia where VZV could have established latency and been reactivated. This suggests concurrent reactivation on each cranial nerve ganglia without cutaneous lesions, as zoster sine herpete. In addition, anastomoses among the upper cervical nerves, which are found in some patients, may have contributed to this condition. These mechanisms underlie various neurological symptoms associated with VZV infection.

A 61-year-old man who had suffered two episodes of generalized convulsion in a two-year period was admitted to our hospital because of progressive gait disturbance during the previous five months. Neurological examination revealed cognitive impairment, spasticity of the lower limbs, truncal ataxia, and dysautonomia including orthostatic hypotension, dysuria and hypohydrosis. Brain fluid-attenuated inversion recovery (FLAIR) MRI detected high-signal-intensity lesions in the periventricular white matter and centrum semiovale, with punctate gadolinium (Gd) enhancement. Spinal MRI detected swollen cervical long cord lesions extending from C2 to C6. Although methylprednisolone pulse treatment initially ameliorated the symptoms and MRI abnormal findings, clinical symptoms and MRI abnormalities including new cervical lateral column lesions reminiscent of those in autoimmune glial fibrillary acidic protein (GFAP) astrocytopathy (GFAP-A) relapsed two months later. At this point, anti-GFAPα antibody was detected in the cerebrospinal fluid. Although the clinical course of GFAP-A has been well reported, the present case showed a chronic refractory course.

We report a rare case with unilateral dysgeusia due to cerebrovascular disease. A 45-year-old man was admitted to the hospital with a sudden onset of dysesthesia in the right face and upper and lower limbs. A CT scan revealed a left pontine hemorrhage. A day after onset, the patient became aware of unilateral dysgeusia. Electrogustometry showed significantly higher thresholds in the left chorda tympani nerve and glossopharyngeal nerve compared to the right nerves. We diagnosed the hemorrhage caused unilateral dysgeusia. Although dysesthesia in the right face and upper and lower limbs disappeared, the dysgeusia in the left tongue persisted six months after symptom onset. Based on the neurological and radiological findings in this case, we discuss the central gustatory pathway with literatures.

A 72-year-old man, who had received pembrolizumab of immune checkpoint inhibitor (ICI) over 6 months for ureter cancer, developed progressive skeletal muscle weakness, dysarthria, dyspnea, and consciousness disturbance over the past two weeks. The systemic work-up tests documented an encephalitis, myopathy, and myocarditis. Multiple autoimmune antibodies of anti-Tr, anti-titin, anti-kv1.4, anti-GM1 and anti-GD1a were positive in the serum. Although myopathy and myocarditis responded to high-dose steroid pulse therapy, encephalopathy deteriorated. Electroencephalogram showed a fluctuated pattern of rhythmic delta activity with fast waves, and a rapid response to intravenous diazepam revealed a condition of nonconvulsive status epileptics (NCSE). The patient had an uneventful course after anti-epileptic medication. The ICIs therapy may trigger a broader activation of multiple autoimmune mechanisms. When an encephalitis by immune-related adverse events does not respond to standard immunotherapy, NCSE may be a main pathophysiological mechanism, thereby anti-epileptics being an alternative treatment option.