We report the case of a 45-year-old man who visited our hospital for treatment of myasthenia gravis. He had an invasive thymoma, for which he had undergone an operation 7 years earlier. He suffered from muscular twitching, hyperhidrosis, lower limb pain, urinary retention and orthostatic hypotension serially just after influenza A infection. Electrophysiological study revealed myokymic discharges and stimulus-induced repetitive discharges (SIRD), and a serological examination showed the patient was anti-VGKC antibody-positive. Although our diagnosis was Isaac’s syndrome, the patient had various symptoms such as insomnia, panic attacks, increased urinary excretion of catecholamine and latent enteric intussusception during the course of treatment. Many other autoimmune antibodies, including anti-GAD antibody, N-type anti-VGCC antibody, anti- striated muscle antibody, anti-AchR blocking antibody and anti-AchR modulating antibody were also positive. Therefore, we thought that the patient had contracted a rare disease related to the invasive thymoma.

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A 64-year-old man was admitted to our hospital because of acute onset of fever and impaired awareness. He showed altered levels of consciousness and neck stiffness. Cerebrospinal fluid (CSF) examination showed a marked increase in the cell count (646/mm3). He required ventilator management because of rapidly progressing disturbance of consciousness, respiratory failure and hypotension. The paired sera showed a more than a 4-fold elevation in the complement fixation titer for Japanese encephalitis virus (JEV). T2-weighted magnetic resonance imaging (MRI) images, which were obtained about 2 months after the onset of symptoms, revealed areas of abnormal intensity in the thalamus and substantia nigra. The patient was diagnosed with Japanese encephalitis (JE) on the basis of the findings of the serological tests and MRI. Two months after the onset of symptoms, the patient experienced tremors and rigidity in his left side. JE should always be considered as a differential diagnosis since the incidence of JE is expected to increase in the future because of the decrease in the vaccination rate among children in Japan and global warming.

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Stiff-person syndrome (SPS) is characterized by generalized stiffness of the muscles. Although the substratum responsible for producing stiffness is mainly concentrated in the spinal cord, a recent study using electromagnetic stimulation has revealed hyperexcitability of the cerebral motor cortex is related to SPS. In this report, we present a SPS patient with increased excitability of the cerebral motor cortex suggested by sensory evoked potentials (SEPs). The patient was a 70-year-old woman who first noticed stiffness of the legs 10 years ago. A local physician diagnosed the condition as “dystonia” and prescribed diazepam, which ameliorated the symptoms. She was admitted to our hospital at the age of 70 because of right hemiparesis and dysarthria. Cranial MRI showed infarct in the left pre-Rolandic area. We diagnosed cerebral embolism and therapy with tissue plasminogen activator (tPA) dramatically ameliorated the patient’s neurological deficit. However, on the fourth day of admission, both the patient’s legs and trunk became markedly stiff, like a board, probably due to the cessation of diazepam. Neurological examination showed marked stiffness of the lower limbs and trunk, and intermittent muscle spasms in the femoral muscles. Stiffness was exacerbated by passive movement, but was not induced by touch stimuli or tapping the tendon. Deep tendon reflexes were normal and the sensory system was intact. Laboratory tests showed a high titer of anti-glutamate decarboxylase (GAD) antibody (69,000 U/ml) and a diagnosis of SPS was made. Surface electromyograms showed continuous and spontaneous discharges lacking reciprocity between agonist and antagonist muscles. Giant SEPs were evoked by electrical stimulation of both tibial nerves (right 12.5, left 17.8 μV). However, stimulation of the median nerves of both arms, where stiffness was absent, did not elicit giant SEPs (right 5.3, left 6.0 μV). The waveforms of giant SEPs of this case were similar to those previously reported for cortical reflex myoclonus, suggesting hyperexcitability of the cerebral cortexes. Re-administration of diazepam ameliorated the stiffness and the amplitudes of the SEPs were reduced significantly to right 6.0 μV, left 6.8 μV. Our case results suggest that hyperexcitability in the primary motor cortex contributes to the pathophysiological mechanism underlying the “stiffness” in SPS.

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We report the case of a 34-year-old male with mild aseptic meningitis, of which the initial symptoms were dysarthria, recovered naturally within a day, and headache. His brain MRI at onset showed an oval-shaped lesion in the splenium of the corpus callosum, which had high signal area in the diffusion and T2 weighted images. The lesion disappeared in follow-up MRI images at 19 days after the onset, when neither increasing cell number in his spinal fluid nor increasing intracranial pressure returned to the normal range. We diagnosed the lesion a reversible splenial lesion based on the clinical and the radiological characteristics. These characteristics suggest that the etiological candidate of this lesion was related to immunological reactions with certain materials or wastes which were essential to the developmental construction of the corpus callosum.

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