The speed of completion of the decremental responses on repetitive nerve stimulation.

Objective: It is generally believed that the decremental response in repetitive nerve stimulation (RNS) stabilizes at the fourth or fifth response. We have a preliminary impression that the decremental response approaches a plateau earlier in proximal muscles than in distal muscles. We investigated the speed of the completion of the decremental response in different muscles. Methods: The "decrement completion ratio (DCR)" in the second or third response (DCR2 or DCR3) was defined as the ratio of the decremental percentage of the second or third response to that of the fourth response. Patients showing more than 10% decremental response both in the abductor pollicis (APB) and deltoid muscles were retrospectively extracted from our EMG database. The DCR2 and DCR3 were compared between two muscles in patients with myasthenia gravis (MG) and amyotrophic lateral sclerosis (ALS). Results: Identified subjects consisted of 11patients with MG and 11 patients with ALS. Multiple regression analysis revealed that only the difference of muscle influenced on DCR2 and DCR3, with no contribution from the different disorder (MG or ALS) or the initial amplitude of the compound muscle action potential (CMAP). Both DCR2 and DCR3 were significantly higher in deltoid than in APB. In ALS, the normalized CMAP amplitude was not different between APB and deltoid whereas the decremental percentage was significantly higher in deltoid, suggesting a lower safety factor of the neuromuscular transmission in proximal muscles. Conclusions: The decremental response completed more rapidly in deltoid than in APB which may be related to the lower safety factor also documented by this study. Significance: Unexpected early completion of the decrement such as at the second response in RNS is not a technical error but may be an extreme of the rapid completion in deltoid, a proximal muscle.

Utility of the Repetitive Nerve Stimulation Test and Needle EMG in the Trapezius Muscle for the Early Diagnosis of ALS.

OBJECTIVES: To document the utility of decremental responses in the repetitive nerve stimulation test (RNS) and spontaneous activities in needle electromyography (EMG) in the trapezius muscle for the diagnosis of amyotrophic lateral sclerosis. METHODS: Subjects were retrospectively identified from our EMG database. Cervical spondylosis was represented as a disease control group. We investigated the sensitivity and specificity of RNS and EMG in the trapezius muscle and those of diagnostic criteria including the Gold Coast criteria (GCC). RESULTS: We reviewed 120 patients with amyotrophic lateral sclerosis and 17 patients with cervical spondylosis. "RNS or EMG" achieved the highest sensitivity (85%). The specificity was the highest for RNS (94%). Addition of RNS of the deltoid muscle achieved 98% sensitivity in the upper-limb onset amyotrophic lateral sclerosis. The sensitivity of the GCC was very high (88%). CONCLUSIONS: Neurophysiological parameters investigated in this study having close to 100% specificities or sensitivities are useful as complements to the GCC.

Utility of the Clustering Index method for diagnosing neuromuscular disorders as compared with needle electromyography.

INTRODUCTION/AIMS: Concentric needle electromyography (CNEMG) is an essential examination for evaluating neuromuscular disorders, although pain is a drawback. Clustering Index (CI) method is a non-invasive quantitative analysis for surface electromyography (SEMG) that evaluates whether the signal area is clustered into the few large motor unit potentials (MUPs) or is evenly distributed. However, the diagnostic yield of the CI method in comparison with CNEMG is not known. In this study, we aimed to compare the sensitivity of the CI method with MUP parameters in CNEMG for diagnosing neurogenic or myogenic disorders. METHODS: We retrospectively identified patients for whom both SEMG and CNEMG were performed on the same tibialis anterior (TA) muscle. In CNEMG, seven MUP parameters were evaluated, including size index (SI) and revised size indices for neurogenic (rSIn) and myogenic (rSIm) disorders. RESULTS: Identified were 21 patients with neurogenic and 21 patients with myogenic disorders. Control data were constructed from 30 control subjects. The sensitivities of the CI method for the neurogenic and myogenic groups were 76% and 62%, respectively, which were not significantly different from MUP parameters, except for being significantly higher than those of amplitude and duration for myopathy (24%). Among MUP parameters, the sensitivities of rSIn (62%) and rSIm (57%) for myopathy were significantly higher than those of amplitude and duration. The CI method significantly correlated with the strength of the TA muscle in myopathy. DISCUSSION: The CI method, having comparable diagnostic yields to MUP parameters, is promising as a non-invasive diagnostic measure.

Acute Leriche Syndrome Mimicking Spinal Cord Infarction: A Case Report.

Introduction: Acute Leriche syndrome is a rare but potentially life-threatening condition. Pain, pallor, and coldness of the lower extremities serve as clues for suspecting Leriche syndrome. However, the absence of these findings may pose a diagnostic challenge. Case Presentation: An 83-year-old man presented at our emergency department with a complaint of sudden-onset paraparesis. Initially, spinal cord infarction was suspected due to clinical course and neurological findings, but thoracolumbar MRI showed normal findings. On admission, symptoms associated with aortoiliac occlusion were not present, except for muscle atrophy in the thigh. CT angiography revealed aortoiliac occlusion, leading to a diagnosis of Leriche syndrome. Conclusion: Leriche syndrome should be considered as a potential differential diagnosis in patients with acute paraparesis. Muscle atrophy of the lower limbs disproportionate to the clinical course may be the clue for suspecting acute Leriche syndrome with symptoms related to atherosclerotic occlusion which are inconspicuous.

HLA and KIR genetic association and NK cells in anti-NMDAR encephalitis.

Introduction: Genetic predisposition to autoimmune encephalitis with antibodies against N-methyl-D-aspartate receptor (NMDAR) is poorly understood. Given the diversity of associated environmental factors (tumors, infections), we hypothesized that human leukocyte antigen (HLA) and killer-cell immunoglobulin-like receptors (KIR), two extremely polymorphic gene complexes key to the immune system, might be relevant for the genetic predisposition to anti-NMDAR encephalitis. Notably, KIR are chiefly expressed by Natural Killer (NK) cells, recognize distinct HLA class I allotypes and play a major role in anti-tumor and anti-infection responses. Methods: We conducted a Genome Wide Association Study (GWAS) with subsequent control-matching using Principal Component Analysis (PCA) and HLA imputation, in a multi-ethnic cohort of anti-NMDAR encephalitis (n=479); KIR and HLA were further sequenced in a large subsample (n=323). PCA-controlled logistic regression was then conducted for carrier frequencies (HLA and KIR) and copy number variation (KIR). HLA-KIR interaction associations were also modeled. Additionally, single cell sequencing was conducted in peripheral blood mononuclear cells from 16 cases and 16 controls, NK cells were sorted and phenotyped. Results: Anti-NMDAR encephalitis showed a weak HLA association with DRB1*01:01~DQA1*01:01~DQB1*05:01 (OR=1.57, 1.51, 1.45; respectively), and DRB1*11:01 (OR=1.60); these effects were stronger in European descendants and in patients without an underlying ovarian teratoma. More interestingly, we found increased copy number variation of KIR2DL5B (OR=1.72), principally due to an overrepresentation of KIR2DL5B*00201. Further, we identified two allele associations in framework genes, KIR2DL4*00103 (25.4% vs. 12.5% in controls, OR=1.98) and KIR3DL3*00302 (5.3% vs. 1.3%, OR=4.44). Notably, the ligands of these KIR2DL4 and KIR3DL3, respectively, HLA-G and HHLA2, are known to act as immune checkpoint with immunosuppressive functions. However, we did not find differences in specific KIR-HLA ligand interactions or HLA-G polymorphisms between cases and controls. Similarly, gene expression of CD56dim or CD56bright NK cells did not differ between cases and controls. Discussion: Our observations for the first time suggest that the HLA-KIR axis might be involved in anti-NMDAR encephalitis. While the genetic risk conferred by the identified polymorphisms appears small, a role of this axis in the pathophysiology of this disease appears highly plausible and should be analyzed in future studies.

Evaluation of diagnostic yield of the 2021 European Academy of Neurology/Peripheral Nerve Society diagnostic criteria for CIDP.

INTRODUCTION/AIMS: It is unclear whether the revised European Academy of Neurology/Peripheral Nerve Society diagnostic criteria (EAN/PNS 2021 criteria) improved the diagnostic yield for chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) compared with the previous version. Therefore, this study aimed to compare the sensitivity and specificity of the EAN/PNS 2021 criteria and the European Federation of Neurological Societies/Peripheral Nerve Society 2010 diagnostic criteria (EFNS/PNS 2010 criteria), with a specific focus on the electrodiagnostic criteria. METHODS: Data of patients with clinically suspected CIDP who exhibited objective treatment response, and of those with chronic axonal neuropathies, obtained between 2009 and 2021, were extracted retrospectively from our database. Patients who underwent nerve conduction studies in at least unilateral upper and lower extremities were enrolled. We compared the sensitivity and specificity of the EAN/PNS 2021 and EFNS/PNS 2010 criteria. RESULTS: In total, 55 patients with clinically suspected CIDP and 36 patients with chronic axonal neuropathies were enrolled. When considering the "possible CIDP" category, the EAN/PNS 2021 criteria showed lower sensitivity than the EFNS/PNS 2010 criteria (78% vs. 93%, p < .05), whereas its specificity was higher (78% vs. 61%, p < .05). The lower sensitivity was caused mainly by the failure to fulfill the sensory nerve conduction criteria. The revised definition of abnormal temporal dispersion of the tibial nerve contributed markedly to the improved specificity. DISCUSSION: To improve the sensitivity of the EAN/PNS 2021 criteria, increasing the number of tested sensory nerves may be necessary.

Weak gluteus maximus and weak iliopsoas with normal gluteus maximus: Two complementary new signs to diagnose lower limb functional weakness.

BACKGROUND AND PURPOSE: The diagnosis of functional neurological disorder should be actively made based on the neurological signs. We described two new complementary signs to diagnose functional weakness of the lower limb, "weak gluteus maximus (weak GM)" and "weak Iliopsoas with normal gluteus maximus (weak iliopsoas with normal GM)," and tested their validity. METHODS: The tests comprised Medical Research Council (MRC) examinations of the iliopsoas and GM in the supine position. We retrospectively enrolled patients with functional weakness (FW) or structural weakness (SW) who presented with weakness of either iliopsoas or GM, or both. Weak GM means that the MRC score of GM is 4 or less. Its complementary sign, weak ilopsoas with normal GM, means that the MRC score of ilopsoas is 4 or less, whereas that of GM is 5. RESULTS: Thirty-one patients with FW and 72 patients with SW were enrolled. The weak GM sign was positive in all 31 patients with FW and in 11 patients with SW, that is, 100% sensitivity and 85% specificity. Therefore, the complementary sign, weak iliopsoas with normal GM, was 100% specific for SW. DISCUSSION: Although 100% should be discounted considering limitations of this study, these signs will likely be helpful in differentiating between FW and SW in the general neurology setting. Downward pressing of the lower limb to the bed in the supine position is interpreted by the patient as an active movement exerted with an effort and might be preferentially impaired in FW.

Tibial nerve SEPs in diagnosing lumbar spinal stenosis: The utility of segmental evaluation using P15 and N21.

Objective: To establish the utility of the additional evaluation of the P15 potential generated at the greater sciatic foramen in the tibial nerve somatosensory evoked potentials (SEPs) in diagnosing lumbar spinal stenosis (LSS). Methods: We retrospectively reviewed tibial nerve SEP findings in patients having MRI-confirmed LSS at the cauda equina or conus/epiconus region. P15 and N21 potentials were recorded and the following findings were defined as localizing abnormalities: 1) normal P15 latency either with prolonged P15-N21 interval or with absent N21; 2) decreased ratio of the N21 amplitude to P15 amplitude. As non-localizing abnormalities, N21 and P38 latencies were also evaluated. Tibial nerve F-wave findings were also investigated. Results: According to the entry criteria, 18 patients were included, 15 with cauda equina lesions and 3 with conus/epiconus lesions. Localizing abnormalities in SEPs were found in 67% of patients, achieving significantly higher sensitivity than delayed P38 latency (28%), and higher sensitivity than N21 abnormalities (39%), though this was not significant. Localizing abnormalities were observed even in 6 out of 11 patients lacking both sensory symptoms and signs. Tibial nerve F-wave was abnormal in 36% of 14 patients with F-wave examinations, whereas the localizing abnormalities in SEPs were found in 64% of the same patient population. P15 amplitude was depressed in 4 patients (22%), which may indicate the involvement of the dorsal root ganglion in LSS, although its latency was normal even for these patients. Conclusions: Tibial nerve SEPs with the recording of P15 and N21 potentials achieved sufficiently high sensitivity in diagnosing LSS. They have the advantage over F-wave in that they can localize the lesion at the cauda equina or conus/epiconus level. Significance: Tibial nerve SEPs are promising in evaluating LSS, especially in documenting sensory tract involvement in cases lacking sensory symptoms/signs.

Idiopathic Inflammatory Myopathy with Delayed Finger Opening Resembling Grip Myotonia.

Grip myotonia can be a clue for the diagnosis of myotonic disorders. However, several clinical conditions cause delayed finger opening mimicking grip myotonia. We herein report a 44-year-old man with idiopathic inflammatory myopathy who presented with delayed finger opening resembling grip myotonia. The delayed finger opening differed from grip myotonia given the absence of the warm-up phenomenon and percussion myotonia, relative sparing of the thumb extension, and pronounced weakness of the extensor digitorum. Focusing on the extension of the thumb and other fingers may aid in the differentiation between delayed finger opening and true grip myotonia.

Utility of the tibial nerve somatosensory evoked potentials in differentiating between neuromyelitis optica spectrum disorders and multiple sclerosis.

BACKGROUND: Somatosensory evoked potentials (SEPs) are widely used for the diagnosis and evaluation of neuromyelitis optica spectrum disorder (NMOSD) and multiple sclerosis (MS). However, whether the parameters of tibial nerve SEPs can help to distinguish NMOSD from MS remains unclear. Thus, the aim of this study was to investigate the utility of tibial nerve SEP parameters in differentiating patients with NMOSD and MS. METHODS: The clinical data of patients with NMOSD or MS treated in our institution between 2005 and 2021 were retrospectively extracted from our electronic database. Additional inclusion criteria were presentation with sensory symptoms in the lower extremities with corresponding lesions in the magnetic resonance images as well as available data on anti-aquaporin-4 antibodies and tibial nerve SEPs. The Z-scores of the N21-P38 interval (central sensory conduction time), P38 latency, and P38 amplitude were compared between the patients with NMOSD and MS. The relationship of disease severity with the parameters of the tibial nerve SEPs was also evaluated. RESULTS: Twenty patients with NMOSD and 13 patients with MS were enrolled. The Z-scores of the N21-P38 interval and P38 latency were significantly higher in the MS group than in the NMOSD group (p < 0.05 and p < 0.01, respectively), whereas there was no difference in the Z-scores of the P38 amplitude between the two groups. In the MS group, only the N21-P38 interval and P38 latency were significantly correlated with disease severity (p < 0.05 and p < 0.01, respectively). In contrast, none of the tibial nerve SEP parameters were significantly correlated with disease severity in the NMOSD group. CONCLUSION: Evaluation of the N21-P38 interval and P38 latency in tibial nerve SEPs potentially helps in differentiating between NMOSD and MS.

[Finger drop variant of Guillain-Barré syndrome: a case report].

We report the case of a 31-year-old man with a finger drop variant of Guillain-Barré syndrome (GBS). The patient visited a neurological clinic with complaints of difficulty in extending the fingers, which occurred seven days after he had fever and diarrhea. The physician who first saw the patient suspected posterior interosseous nerve palsy and referred him to our hospital. Neurological examination 35 days after the onset revealed distal weakness of the upper extremities, particularly in the bilateral extensor digitorum (Medical Research Council [MRC] scale 1/1 [right/left]). The left triceps surae muscle was also weak (MRC scale 5/4). Bilateral Achilles tendon reflexes were absent, but other neurological findings were normal. Cerebrospinal fluid examination showed albuminocytologic dissociation. Serum immunoglobulin G antibodies against GM1 were positive. Nerve conduction studies revealed reduced amplitude of compound muscle action potentials (CMAPs) without evidence of demyelination in the median, ulnar, radial, and tibial nerves. CMAP amplitude was most severely reduced in the radial nerve among the upper extremity nerves. We diagnosed the patient with acute motor axonal neuropathy. His symptoms gradually improved after treatment with intravenous immunoglobulin. When encountering acute finger drop, neurologists should consider the finger drop variant of GBS as a differential diagnosis.

Estimation of the true infection rate and infection fatality rate of coronavirus disease 2019 in each country.

The True Infection Rate (TIR) in the whole population of each country and the Infection Fatality Rate (IFR) for coronavirus disease 2019 (COVID-19) are unknown although they are important parameters. We devised a simple method to infer TIR and IFR based on the open data. The prevalence rate of the Polymerase Chain Reaction (PCR) tests among the population (Examination Rate; ER) and the positive rate of PCR tests (Infection Rate; IR) for 66 countries were picked up at a website 5 times from April 10th to June 13th, 2020, and the trajectory of each country was drawn over the IR vs. ER plot. IR and ER showed a strong negative correlation for some countries, and TIR was estimated by extrapolating the regression line when the correlation coefficient was between -0.99 and -1. True/Identified Case Ratio (TICR) and IFR were also calculated using the estimated TIR. The estimated TIR well coincided with local antibody surveys. Estimated IFR took on a wide range of values up to 10%: generally high in the Western countries. The estimated IFR of Singapore was very low (0.018%), which may be related to the reported gene mutation causing the attenuation of the viral virulence.

Weak shoulder and arm sparing signs in amyotrophic lateral sclerosis.

INTRODUCTION/AIMS: Various signs of selective involvement have been reported in amyotrophic lateral sclerosis (ALS). In this study, we describe two new signs, "weak shoulder" and "arm sparing" signs. METHODS: Subjects were retrospectively identified from our electrodiagnosis database. Medical Research Council scores of relevant muscles were evaluated. Weak shoulder was defined as the deltoid (Del) muscle being weaker than the biceps brachii (BB)/triceps brachii (TB) muscles; that is, Del was weaker than either or both of the muscles and no stronger than either. Arm sparing was defined as both Del and the first dorsal interosseous (FDI) being weaker than BB/TB. Sensitivities of these signs were compared with other signs of selective involvement. The specificities of these signs were investigated in patients with cervical spondylotic amyotrophy (CSA) and multifocal motor neuropathy (MMN). RESULTS: We reviewed 130 patients with ALS, 64 patients with CSA, and 16 patients with MMN. The weak shoulder and the arm sparing signs were observed in 73% and 55% of patients with ALS, 44% and 2% of patients with CSA (93% and 0% of patients with proximal CSA), respectively, and no patients with MMN. The sensitivity of the weak shoulder was higher than with conventional signs, whereas that of the arm sparing sign showed no difference. DISCUSSION: The weak shoulder sign was highly sensitive in ALS, and was specific when compared with MMN. The arm sparing sign was highly specific for ALS. These two new signs are promising as clinical clues in the diagnosis of ALS.

[Subacute cognitive impairment and urinary retention due to primary central nervous system post-transplant lymphoproliferative disorder: a case report].

We report a 66-year-old man with primary central nervous system post-transplant lymphoproliferative disorder (PCNS-PTLD). He had received a living-donor kidney transplantation at the age of 64 years. Although he had a good postoperative course by continuing to take oral immunosuppressive agents, he was admitted to our hospital for subacute cognitive impairment and urinary retention two years after the transplantation. Brain MRI revealed high-intensity lesions on FLAIR and T2-weighted images in the left parietal operculum, deep white matter around the anterior horn of the lateral ventricle, and the genu and splenium of the corpus callosum. A part of these lesions showed ring enhancement. The cerebrospinal fluid examination revealed lymphocytic pleocytosis, elevation of protein level, and mild hypoglycorrhachia. Blood tests showed no abnormalities except for positive serum VCA-IgG antibody of Epstein-Barr virus. A brain biopsy was performed and diagnosis of PCNS-PTLD was made. There was no evidence of systemic PTLD. We reduced the dose of immunosuppressive agents and started the initial treatment with methylprednisolone pulse therapy. The patient showed a partial response to the treatment and transferred to another hospital for subsequent chemotherapy. PTLD is an important post-transplant complication that can affect the patient's prognosis. The incidence of PTLD is increasing with the growing numbers of transplantations and older age of donors and recipients. Although CNS involvement is known to be rare, PCNS-PTLD is an important differential diagnosis when symptoms of CNS origin develop in post-transplant patients.

The course of facial corticobulbar tract fibers in the dorsolateral medulla oblongata.

BACKGROUND: The course of the corticobulbar tract (CBT) to the facial nucleus has been investigated by some previous studies. However, there are some unclear points of the course of the CBT to the facial nucleus. This study aimed to elucidate the detailed course of the CBT to the facial nucleus through the analysis of lateral medullary infarction (LMI) cases. METHODS: The neurological characteristics and magnetic resonance imaging findings of 33 consecutive patients with LMI were evaluated. The location of the lesions was classified rostro-caudally (upper, middle, or lower) and horizontally. Further, we compared the neurological characteristics between the groups with and without central facial paresis (FP). RESULTS: Eight (24%) patients with central FP ipsilateral to the lesion were identified. Dysphagia and hiccups were more frequently observed in the group with central FP than in the group without central FP. In patients with central FP, middle medullary lesions and those including the ventral part of the dorsolateral medulla were more frequently observed. Contrastingly, patients with lesions restricted to the lateral and dorsal regions of the dorsolateral medulla did not present with central FP. CONCLUSION: The results of this study indicate that the CBT to the facial nucleus descends with the corticospinal tract at least to the middle portion of the medulla, and then ascends to the facial nucleus through the medial and ventral areas of the dorsolateral medulla after decussation.

Myasthenia gravis with inflammatory myopathy without elevation of creatine kinase.

Cases of myasthenia gravis with inflammatory myopathy usually show elevated creatine kinase (CK) levels. There are few case reports of myasthenia gravis with inflammatory myopathy without elevated CK levels, and clinical features and useful diagnostic methods for these patients are little known. We describe the case of a 79-year-old man with myasthenia gravis that was complicated with inflammatory myopathy without elevated CK levels and successfully treated with immunological treatment. Initially, he was diagnosed with ocular myasthenia gravis and treated with pyridostigmine, but dysphagia and weakness in the neck and bilateral upper limb without fatigability gradually developed. Needle electromyography revealed myopathic changes, and the results of muscle biopsy were consistent with inflammatory myopathy. Blood tests showed normal CK levels throughout the clinical course and elevated myoglobin levels alone. The possibility of developing inflammatory myopathy in patients with myasthenia gravis cannot be excluded, even if CK levels are normal.

Nasogastric Tube Syndrome: The Size and Type of the Nasogastric Tube May Contribute to the Development of Nasogastric Tube Syndrome.

Nasogastric tube syndrome (NGTS) is a rare but life-threatening complication associated with nasogastric tube (NGT) placement. The effect of the NGT size and type on the development of NGTS has not yet been fully elucidated. We herein report the case of a 77-year-old man with cerebral infarction who was complicated with NGTS. The immediate removal of the NGT improved the symptoms of NGTS. Although the NGT was passed through the same route during reinsertion, the use of a softer and smaller-sized NGT did not cause any NGTS recurrence. To prevent the development of NGTS, using a NGT that is appropriate for the patient's condition is important.

Appropriate window width for the "clustering index method" in the tibialis anterior muscle.

We previously reported a new quantitative analysis of single-channel surface electromyography (EMG), the "clustering index method" (CI method), in the tibialis anterior muscle, which achieved sufficiently good sensitivity to detect neurogenic or myogenic abnormalities. The window width is a fundamental parameter of the CI method, and was arbitrarily set at 15 ms in that study. In this study, we searched for the most appropriate window width using expanded patient data. The data from our previous study were reanalyzed, and new patients were enrolled. Window width in the CI method was changed from 5 to 27.5 ms with a step of 2.5 ms. For each window width, Z-score values of individual subjects were calculated and the diagnostic yield was investigated. We enrolled 67 controls, 29 subjects with neurogenic disorders, and 39 with myogenic disorders. When the window width was set at 22.5 ms, the highest sensitivity was achieved both for neurogenic (97%) and myogenic (72%) disorders, with a specificity of 97%. Seven of 10 patients with inclusion body myositis were also abnormal. Reliable results were obtained by collecting 15 epochs per subject. There are two conflicting effects that appear to be best balanced at a window width of 22.5 ms: a wider width decreases the chance that a motor unit potential (MUP) is divided into two adjacent windows, and a narrower width reduces the possibility that an MUP firing at a low-frequency is counted twice by the differential sequences. CI is promising as a non-invasive method to diagnose neuromuscular disorders.

Aquaporin-4-antibody-positive Neuromyelitis Optica Spectrum Disorder in a Patient with Charcot-Marie-Tooth Disease Type 1A.

Charcot-Marie-Tooth disease type 1A (CMT1A) is a hereditary peripheral neuropathy, and its involvement in the central nervous system (CNS) is very rare. We herein report a 51-year-old woman with CMT1A who suffered from recurrent optic neuritis and myelopathy. Under the diagnosis of anti-aquaporin-4 (anti-AQP4) antibody positive neuromyelitis optica spectrum disorder (NMOSD), we treated her successfully with corticosteroids. This is the first report of CMT1A complicated with anti-AQP4-positive NMOSD. Although the coexistence of the two disorders may simply be a coincidence, we speculated that immune cross-reaction between overexpressed peripheral myelin protein 22 and CNS myelin may have caused concomitant CMT1A and NMOSD.

[COVID-19 in Japan: Insights from the Epidemiological Data].

The coronavirus disease 2019 (COVID-19) pandemic is a worldwide peril. The PCR tests are widely used to detect infections. However, multiple regression analysis revealed no correlation between the examination rate among population (ER) and the success of containment, which is achieved by social distancing. ER and fatality rate were even positively correlated. Japan has been criticized for its very low ER, but it achieved better containment than other major countries with much higher ER on 29 May. The estimation of the true infection rate (TIR) among population revealed that the low fatality rate in Japan and other Asian countries is partly due to low TIR. Fatality of COVID-19 is highly accentuated in aged persons. Despite having the highest aging rate in the world, the fatality rate in Japan is relatively low. The corrected fatality rate of Japan is the second-lowest among the G20 countries. Mimicking the attenuation of viral virulence due to natural selection would be a promising strategy to overcome pandemic. The prevention of in-hospital transmission, especially from severe cases, would be the key to achieve this. Attenuation of the viral virulence in the second wave is evident in many European countries, and also in Tokyo.