Ultrasonographic evaluation reveals thinning of cervical nerve roots and peripheral nerves in spinal and bulbar muscular atrophy.

BACKGROUND: Ultrasonography (US) is a noninvasive and patient-friendly tool for the evaluation of peripheral nerves. In motor neuron diseases, amyotrophic lateral sclerosis (ALS) has been reported to show the atrophy of peripheral nerves on US. However, the US findings are still unclear in spinal and bulbar muscular atrophy (SBMA), an adult-onset lower motor neuron disease caused by an abnormal CAG repeat expansion in the androgen receptor gene. METHODS: We prospectively recruited and evaluated 11 patients with genetically confirmed SBMA and 9 patients with ALS diagnosed according to the revised El Escorial ALS criteria or the Awaji electrodiagnostic criteria. The C5-C7 cervical nerve roots and the median and ulnar nerves were evaluated ultrasonographically. RESULTS: The cross-sectional areas (CSAs) of the C6 and C7 nerve roots, the median nerve in the upper arm and forearm, and the ulnar nerve in the upper arm were smaller in patients with SBMA than those in patients with ALS (p < 0.05), whereas the CSAs of the C5 nerve root and the ulnar nerve in the forearm were not smaller. CONCLUSIONS: US showed that the peripheral nerves in patients with SBMA were thinner than those in patients with ALS despite similar degrees of weakness and motor neuron loss. Possible causes include additional sensory nerve involvement and longer disease duration in patients with SBMA than those in patients with ALS.

Effectiveness of Home-Based Exercises Without Supervision by Physical Therapists for Patients With Early-Stage Amyotrophic Lateral Sclerosis: A Pilot Study.

OBJECTIVE: To verify the effects of structured home-based exercises without supervision by a physical therapist in patients with early-stage amyotrophic lateral sclerosis (ALS). DESIGN: A historical controlled study that is part of a multicenter collaborative study. SETTING: Rehabilitation departments at general hospitals and outpatient clinics with a neurology department. PARTICIPANTS: Patients (N=21) with ALS were enrolled and designated as the home-based exercise (Home-EX) group, and they performed unsupervised home-based exercises. As a control group, 84 patients with ALS who underwent supervised exercise with a physical therapist for 6 months were extracted from a database of patients with ALS and matched with the Home-EX group in terms of their basic attributes and clinical features. INTERVENTION: The Home-EX group was instructed to perform structured home-based exercises without supervision by a physical therapist that consisted of muscle stretching, muscle training, and functional training for 6 months. MAIN OUTCOME MEASURES: The primary outcome was the score on the ALS Functional Rating Scale-Revised (ALSFRS-R), which is composed of 3 domains: bulbar function, limb function, and respiratory function. The score ranges from 0 to 48 points, with a higher score indicating better function. RESULTS: In the Home-EX group, 15 patients completed the home-based exercises for 6 months, and 6 patients dropped out because of medical reasons or disease progression. No adverse events were reported. The Home-EX group was found to have a significantly higher respiratory function subscore and total score on the ALSFRS-R than the control group at follow-up (P<.001 and P<.05, respectively). CONCLUSIONS: Structured home-based exercises without supervision by a physical therapist could be used to alleviate functional deterioration in patients with early-stage ALS.

Utility of Cystatin C for Estimating Glomerular Filtration Rate in Patients With Muscular Dystrophy.

Emerging concerns regarding heart failure, arrhythmia, and sudden death in patients with muscular dystrophy are of significant clinical importance. On the other hand, little attention has been paid to renal dysfunction because these patients have low serum creatinine levels. Serum cystatin C, unaffected by muscle quantity, is a potentially superior marker for estimating renal function. Here, we present cases with muscular dystrophy in which estimated glomerular filtration rate (GFR) by cystatin C (eGFRcys) provided good agreement with simultaneously measured GFR by inulin renal clearance (differences less than 20%). Sudden death with acute heart failure occurred in a patient with underlying renal dysfunction and elevated BNP. Neurologists and cardiologists should evaluate renal function using GFR with cystatin C in patients with muscular dystrophy.

Repeater F-waves are signs of motor unit pathology in polio survivors.

INTRODUCTION: The purpose of this study was to determine whether F-waves reveal electrophysiological features of anterior horn cells in polio survivors. METHODS: Forty-three polio survivors and 20 healthy controls underwent motor nerve conduction studies of the median and tibial nerves bilaterally, including sampling of F-waves elicited by 100 stimuli and the determination of motor unit number estimation (MUNE). RESULTS: A significant increase in abnormally stereotyped ("repeater") F-waves and a reduction of F-wave persistence were observed in both nerves in the polio group as compared with the control group. Repeater F-waves had a negative correlation with MUNE. CONCLUSIONS: These trends in F-wave persistence and repeater F-waves after motor unit loss are characteristic findings in polio survivors. Repeater F-waves are a sign of motor unit pathology.

Are multifocal motor neuropathy patients underdiagnosed? An epidemiological survey in Japan.

INTRODUCTION: Our objective was to do an epidemiologic survey of patients with multifocal motor neuropathy (MMN) in comparison with those with amyotrophic lateral sclerosis (ALS) in Japan. METHODS: In this retrospective study, we examined 46 patients with MMN and 1,051 patients with ALS from major neuromuscular centers in Japan from 2005 to 2009. Diagnosis was based on the European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS) and the revised El Escorial criteria. The efficacy of intravenous immunoglobulin (IVIg) was also taken into consideration in the diagnosis of MMN. RESULTS: The ratio of MMN to ALS patients (0­0.10) varied among the centers, but mostly converged to 0.05. The prevalence was estimated to be 0.29 MMN patients and 6.63 ALS patients per 100,000 population. CONCLUSIONS: The frequency of MMN patients was around 1 out of 20 ALS patients, and MMN was possibly underdiagnosed in some centers.

Reduction rate of body mass index predicts prognosis for survival in amyotrophic lateral sclerosis: a multicenter study in Japan.

Malnutrition in the early stage has been reported as an independent predictor of survival in amyotrophic lateral sclerosis (ALS). We analyzed retrospectively the effect of variation of body mass index (BMI) on survival in ALS patients. In total, 77 consecutive ALS patients were enrolled from nine hospitals in Japan. Reduction rate of BMI was calculated from BMI before the disease onset and at the time of the first visit to each hospital. We analyzed the correlation between BMI reduction rate and total disease duration. Results showed that the median BMI reduction rate was 2.5 per year (interquartile range 1.3-3.8). The BMI reduction rate was significantly correlated with survival length (p <0.0001). There was also a significant difference in survival between ALS patients with a BMI reduction rate ≥ and < 2.5 (Kaplan-Meier survival analysis and the log-rank test, p < 0.0001; hazard ratio by the Cox model, 2.9816). In conclusion, faster reduction of BMI at the initial stage before the first visit to hospital predicts shorter survival length also in Japanese ALS patients.

Tranilast for advanced heart failure in patients with muscular dystrophy: a single-arm, open-label, multicenter study.

BACKGROUND: The transient receptor potential cation channel subfamily V member 2 (TRPV2) is a stretch-sensitive calcium channel. TRPV2 overexpression in the sarcolemma of skeletal and cardiac myocytes causes calcium influx into the cytoplasm, which triggers myocyte degeneration. In animal models of cardiomyopathy and muscular dystrophy (MD), TRPV2 inhibition was effective against heart failure and motor function. Our previous pilot study showed that tranilast, a TRPV2 inhibitor, reduced brain natriuretic peptide (BNP) levels in two MD patients with advanced heart failure. Thus, this single-arm, open-label, multicenter study aimed to evaluate the safety and efficacy of tranilast for heart failure. METHODS: The study enrolled MD patients with advanced heart failure whose serum BNP levels were > 100 pg/mL despite receiving standard cardioprotective therapy. Tranilast was administered orally at 100 mg, thrice daily. The primary endpoint was the change in log (BNP) (Δlog [BNP]) at 6 months from baseline. The null hypothesis was determined based on a previous multicenter study of carvedilol results in a mean population Δlog (BNP) of 0.18. TRPV2 expression on peripheral blood mononuclear cell surface, cardiac events, total mortality, left ventricular fractional shortening, human atrial natriuretic peptide, cardiac troponin T, and creatine kinase, and pinch strength were also assessed. RESULTS: Because of the poor general condition of many patients, only 18 of 34 patients were included and 13 patients could be treated according to the protocol throughout the 6-month period. However, there were no serious adverse events related to tranilast except diarrhea, a known adverse effect, and the drug was administered safely. TRPV2 expression on the mononuclear cell surface was elevated at baseline and reduced after treatment. Cardiac biomarkers such as BNP, human atrial natriuretic peptide, and fractional shortening remained stable, suggesting a protective effect against the progression of heart failure. In the per protocol set group, Δlog [BNP] was - 0.2 and significantly lower than that in the null hypothesis. CONCLUSIONS: Tranilast is safe and effective in inhibiting TRPV2 expression, even in MD patients with advanced heart failure. Further trials are needed to evaluate the efficacy of tranilast in preventing myocardial damage, heart failure, motor impairment, and respiratory failure. Clinical trial registration The study was registered in the UMIN Clinical Trials Registry (UMIN-CTR: UMIN000031965, URL: http://www.umin.ac.jp/ctr/ ) [March 30, 2018] and the Japan Registry of Clinical Trials (jRCT, registration number: jRCTs031180038, URL: https://jrct.niph.go.jp/ ) [November 12, 2021]. Patient registration was started in December 19, 2018.

[Perspective on transition from pediatric to adult health care for patients with neurological disease: current situation and issues].

An improvement in efficacy treatment and development of the social support system has led to many patients with neurological disease being able to reach adulthood. Therefore health care for life from pediatrics to adulthood has become necessary. The Special Committee for Measures Against Transition from Pediatric to Adult Health Care of the Japanese Society of Neurology officially started to examine the current situation and issues of transition from pediatric to adult health care in July 2020. Pediatric neurologists and adult neurologists have an awareness of this issue of constructing a better transition from pediatric to adult health care. However, there are some tasks that need to be resolved in the medical system. We intend to improve the understanding of transition and assessment of medical service fees for transition in cooperation with the Japanese Society of Neurology and the Japanese Society of Child Neurology.

A novel mutation of ALK2, L196P, found in the most benign case of fibrodysplasia ossificans progressiva activates BMP-specific intracellular signaling equivalent to a typical mutation, R206H.

Fibrodysplasia ossificans progressiva (FOP) is a rare autosomal dominant congenital disorder characterized by progressive heterotopic ossification in muscle tissues. Constitutively activated mutants of a bone morphogenetic protein (BMP) receptor, ALK2, have been identified in patients with FOP. Recently, a novel ALK2 mutation, L196P, was found in the most benign case of FOP reported thus far. In the present study, we examined the biological activities of ALK2(L196P) in vitro. Over-expression of ALK2(L196P) induced BMP-specific activities, including the suppression of myogenesis, the induction of alkaline phosphatase activity, increased BMP-specific luciferase reporter activity, and increased phosphorylation of Smad1/5 but not Erk1/2 or p38. The activities of ALK2(L196P) were higher than those of ALK2(G356D), another mutant ALK2 allele found in patients with FOP and were equivalent to those of ALK2(R206H), a typical mutation found in patients with FOP. ALK2(L196P) was equally or more resistant to inhibitors in comparison to ALK2(R206H). These findings suggest that ALK2(L196P) is an activated BMP receptor equivalent to ALK2(R206H) and that ALK2(L196P) activity may be suppressed in vivo by a novel molecular mechanism in patients with this mutation.

Infection control in the respiratory care of coronavirus disease-19 patients with neuromuscular diseases.

Close contact is unavoidable in the care of patients with neuromuscular diseases (NMD). In addition, respiratory physiotherapy and noninvasive ventilation generate massive amounts of aerosols. Caring for a patient suffering from coronavirus disease-19 raises concerns about the risk of infection not only to the caregiver and/or medical staff but also to other individuals in contact with these personnel. We reviewed the points to be noted in infection control when a patient with neuromuscular diseases receiving respiratory care is infected with COVID-19 and summarizes the recommendation. Infected patients must be isolated in a negative-pressure or actively ventilated room. Clear zoning separating clean and infected areas should be performed for pathogen containment. Caregivers should wear appropriate personal protective equipment and thoroughly clean their hands. Leak-prevention measures and the use of proper respiratory circuits and filters with virus-removal performance are crucial to reducing aerosols in noninvasive ventilation. Although respiratory physiotherapy is essential, treatment should be minimized in consideration of the infection state and sputum status, and alternative therapies such as postural drainage should be carefully considered. Infection control is distinctly obligate; however, it impairs the quality of life and activity of daily living significantly. We should implement it with enough ethical consideration, adequate explanation, and patient consent. We hope that this paper will contribute to appropriate COVID-19 infection control in patients with neuromuscular diseases requiring respiratory care.

Electrophysiological assessment of corticorespiratory pathway function in amyotrophic lateral sclerosis.

Respiratory muscle paralysis is inevitable in the clinical course of amyotrophic lateral sclerosis (ALS). Our objective was to electrophysiologically assess the function of the phrenic nerve and diaphragm motor cortex in ALS. Phrenic nerve M waves, diaphragm motor evoked potentials (MEPs) induced by transcranial magnetic stimulation, and their clinical correlations were analyzed in 29 ALS patients. The M wave amplitude was significantly lower in patients than in healthy control subjects (p<0.001). The MEP amplitudes both in the expiratory and inspiratory phases were significantly decreased in patients (p<0.01). In particular, 15 patients showed no MEPs in the expiratory phase, six of whom also showed no MEPs in the inspiratory phase. Five of them had no respiratory complaints. There was a weak, non-significant correlation between the inspiratory MEP amplitude and forced vital capacity (p=0.052). We conclude that the loss of MEP might reflect the subclinical involvement of the voluntary respiratory drive from the diaphragm motor cortex, potentially leading to further respiratory deterioration.

[Anti-NMDA receptor encephalitis during pregnancy].

A 19-year-old female in her 2nd trimester (17 weeks) of pregnancy became irritable a few days before admission. She became unable to open her mouth and could not talk. She was admitted to the psychiatric hospital due to a rapid change in behavior and a consciousness disturbance. She was diagnosed as having schizophrenia by a psychiatrist. Her EEG showed diffuse high voltage and slow waves. Acute encephalitis was then suspected. Her past and family histories were not suggestive of viral infection. On physical examination, she had a low grade fever. She had hyperhidrosis, autophagia, and repeated oral dyskinesia. Her consciousness level fluctuated from somnolence to stupor. Although her blood CRP level was mildly elevated and she had mild pleocytosis, HSV-PCR was negative in the cerebrospinal fluid (CSF). Abdominal ultrasound examination and MRI showed no ovarian teratoma. Computed tomography (CT) and magnetic resonance imaging (MRI) showed no brain abnormalities. Before analysis for specific nervous system antibodies, the initial diagnosis was non-herpetic limbic encephalitis. She was twice treated with a 6-day course of methylprednisolone (500 mg/day) infusion. She was also given phenobarbital since she had a tonic-clonic seizure about 1 month after admission. Finally, she had a normal delivery at 37 weeks. The baby was healthy, and the patient was discharged without sequelae. We concluded that her diagnosis was anti-N-methyl-D-aspartate (NMDA) receptor (anti-NMDAR) encephalitis based on the presence of anti-NMDAR antibody in the CSF. This report is the first description of a patient with anti-NMDAR antibody encephalitis. The precise mechanism of this encephalitis is not clear, although there have been several reports of autoimmune encephalitis during pregnancy. The patient's CSF anti-NMDAR antibody titer during treatment was measured. Before treatment, the CSF anti-NMDAR antibody titer was strongly positive, but it decreased during treatment and then disappeared after delivery. We hypothesized that the presence of the embryo or placenta may have triggered an antigenic signal and/or antibody through inappropriate immunological modulation.

[A case of motor and sensory polyneuropathy and respiratory failure with novel heterozygous mutation of the senataxin gene].

The patient was a 29-year-old male. He took his first steps at two-and-a-half years old, but his physical strength deteriorated and he became non-ambulatory at 12 years old. He had respiratory failure at the age of 20, and finally underwent tracheostomy with invasive positive-pressure ventilation (TPPV). He showed distal dominant muscle weakness and atrophy, including the face. Spinal scoliosis was recognized. He had peripheral predominance of sensory disorders. Nerve conduction studies showed a decrease of compound muscle action potential and a reduction of motor nerve conduction velocity. Sensory nerve action potential was not evoked. In genetic analysis, c.23 C> T (p. T8M) heterozygous mutation was found in the senataxin gene (SETX). Although SETX is a causative gene of familial amyotrophic lateral sclerosis type 4 (ALS4), this case suggests that SETX mutation can also cause motor and sensory polyneuropathy.

Non-aqueous, zwitterionic solvent as an alternative for dimethyl sulfoxide in the life sciences.

Dimethyl sulfoxide (DMSO) is widely used as a solvent in the life sciences, however, it is somewhat toxic and affects cell behaviours in a range of ways. Here, we propose a zwitterionic liquid (ZIL), a zwitterion-type ionic liquid containing histidine-like module, as a new alternative to DMSO. ZIL is not cell permeable, less toxic to cells and tissues, and has great potential as a vehicle for various hydrophobic drugs. Notably, ZIL can serve as a solvent for stock solutions of platinating agents, whose anticancer effects are completely abolished by dissolution in DMSO. Furthermore, ZIL possesses suitable affinity to the plasma membrane and acts as a cryoprotectant. Our results suggest that ZIL is a potent, multifunctional and biocompatible solvent that compensates for many shortcomings of DMSO.

Aldose reductase inhibitor ranirestat significantly improves nerve conduction velocity in diabetic polyneuropathy: A randomized double-blind placebo-controlled study in Japan.

AIMS/INTRODUCTION: Diabetic polyneuropathy is one of the most frequent diabetic complications, and impairs patients' quality of life. We evaluated the efficacy and safety of ranirestat (40 mg/day) in patients with diabetic polyneuropathy. MATERIALS AND METHODS: This was a multicenter, placebo-controlled, randomized double-blind, parallel-group, phase III study in which 557 patients were randomly assigned to either the ranirestat or placebo group and assessed for 52 weeks. The co-primary end-points were the changes in tibial motor nerve conduction velocity and total modified Toronto Clinical Neuropathy Score as a measure of clinical symptoms. RESULTS: There was a significant increase in tibial motor nerve conduction velocity in the ranirestat group compared with the placebo group. The difference between groups in the change at last observation was 0.52 m/s (P = 0.021). Increases in nerve conduction velocity in the ranirestat group were found not only in the tibial motor nerves, but also in the median motor nerves, proximal median sensory nerves and distal median sensory nerves. No significant differences in modified Toronto Clinical Neuropathy Score or safety parameters were found between the two groups. CONCLUSIONS: Ranirestat (40 mg/day) was well tolerated and improved nerve conduction velocity. Regarding symptoms and signs, no detectable benefits over the placebo were observed in the ranirestat group during the 52 weeks of treatment.

A unique mutation of ALK2, G356D, found in a patient with fibrodysplasia ossificans progressiva is a moderately activated BMP type I receptor.

Fibrodysplasia ossificans progressiva (FOP) is a rare autosomal dominant congenital disorder characterized by progressive heterotopic bone formation in muscle tissues. A common mutation among FOP patients has been identified in ALK2, ALK2(R206H), which encodes a constitutively active bone morphogenetic protein (BMP) receptor. Recently, a unique mutation of ALK2, ALK2(G356D), was identified to be a novel mutation in a Japanese FOP patient who had unique clinical features. Over-expression of ALK2(G356D) induced phosphorylation of Smad1/5/8 and activated Id1-luc and alkaline phosphatase activity in myoblasts. However, the over-expression failed to activate phosphorylation of p38, ERK1/2, and CAGA-luc activity. These ALK2(G356D) activities were weaker than those of ALK2(R206H), and they were suppressed by a specific inhibitor of the BMP-regulated Smad pathway. These findings suggest that ALK2(G356D) induces heterotopic bone formation via activation of a BMP-regulated Smad pathway. The quantitative difference between ALK2(G356D) and ALK2(R206H) activities may have caused the phenotypic differences in these patients.

Operation of a P300-based brain-computer interface in patients with Duchenne muscular dystrophy.

A brain-computer interface (BCI) or brain-machine interface is a technology that enables the control of a computer and other external devices using signals from the brain. This technology has been tested in paralysed patients, such as those with cervical spinal cord injuries or amyotrophic lateral sclerosis, but it has not been tested systematically in Duchenne muscular dystrophy (DMD), which is a severe type of muscular dystrophy due to the loss of dystrophin and is often accompanied by progressive muscle weakness and wasting. Here, we investigated the efficacy of a P300-based BCI for patients with DMD. Eight bedridden patients with DMD and eight age- and gender-matched able-bodied controls were instructed to input hiragana characters. We used a region-based, two-step P300-based BCI with green/blue flicker stimuli. EEG data were recorded, and a linear discriminant analysis distinguished the target from other non-targets. The mean online accuracy of inputted characters (accuracy for the two-step procedure) was 71.6% for patients with DMD and 80.6% for controls, with no significant difference between the patients and controls. The P300-based BCI was operated successfully by individuals with DMD in an advanced stage and these findings suggest that this technology may be beneficial for patients with this disease.

Operation of a P300-based brain-computer interface by patients with spinocerebellar ataxia.

OBJECTIVE: We investigated the efficacy of a P300-based brain-computer interface (BCI) for patients with spinocerebellar ataxia (SCA), which is often accompanied by cerebellar impairment. METHODS: Eight patients with SCA and eight age- and gender-matched healthy controls were instructed to input Japanese hiragana characters using the P300-based BCI with green/blue flicker. All patients depended on some assistance in their daily lives (modified Rankin scale: mean 3.5). The chief symptom was cerebellar ataxia; no cognitive deterioration was present. A region-based, two-step P300-based BCI was used. During the P300 task, eight-channel EEG data were recorded, and a linear discriminant analysis distinguished the target from other nontarget regions of the matrix. RESULTS: The mean online accuracy in BCI operation was 82.9% for patients with SCA and 83.2% for controls; no significant difference was detected. CONCLUSION: The P300-based BCI was operated successfully not only by healthy controls but also by individuals with SCA. SIGNIFICANCE: These results suggest that the P300-based BCI may be applicable for patients with SCA.

The measurement and estimation of total energy expenditure in Japanese patients with ALS: a doubly labelled water method study.

Appropriate nutritional therapy has not been established for patients with amyotrophic lateral sclerosis (ALS). Our objective was to measure the total energy expenditure (TEE) and determine an equation to estimate the energy requirements for Japanese patients with ALS. Twenty-six Japanese patients with ALS participated in the study. The TEE was measured using the doubly labelled water (DLW) method for a 14-day period. Using a range of clinical parameters and multiple regression analyses, we determined an adequate equation to calculate TEE. Results showed that the median value of total energy intake (TEI) was 1581 (interquartile 1278-1782) kcal/d. TEE and TEE/body weight were 1628 kcal/d (1352-1865) and 31.3 kcal/kg (29.2-34.4), respectively. The ratio of TEE/estimated TEE by the Harris-Benedict equation was 1.14 (1.09-1.26). The difference between TEI and TEE was -63 kcal (-221 - 122), and 15 patients (57.7%) showed a negative balance. From regression analyses, we determined an equation to estimate TEE using the resting metabolic rate estimated by the Harris-Benedict equation (RMR-HB) and scores of the revised ALS Functional Rating Scale (ALSFRS-R): TEE = (1.67 × RMR-HB) + (11.8 × ALSFRS-R) - 680 (p < 0.0001). In conclusion, energy expenditure of Japanese patients with ALS was higher than expected, and we proposed a preliminary equation to estimate TEE for future nutritional intervention.

Effects of low frequency filtering on distal compound muscle action potential duration for diagnosis of CIDP: A Japanese-European multicenter prospective study.

OBJECTIVE: The duration of the distal compound muscle action potential (DCMAP) is a useful index to detect demyelination in the distal nerve segments. However in published electrodiagnostic criteria for chronic inflammatory demyelinating polyneuropathy (CIDP), the cut-off values of DCMAP duration are defined using an EMG low frequency filter of only 20 Hz. We aimed to provide widely-available reference data using several low cut filters. METHODS: In 13 Japanese and European tertiary centers, DCMAP duration data using 2, 5, 10, and 20 Hz low frequency filters were prospectively collected from 147 normal controls, 59 patients with typical CIDP, and 100 with diabetic polyneuropathy. Optimal cut-off values were calculated with receiver-operating characteristic curves, offering 100% specificity versus normal controls. RESULTS: The higher low frequency filter was associated with significantly shorter DCMAP duration in all groups. For CIDP diagnosis, the calculated cut-off values had a sensitivity ranging from 51% to 66%, and a specificity versus diabetic neuropathy from 96% to 98%. CONCLUSIONS: Our results show that DCMAP duration is largely dependent on low frequency filter settings, but is a useful index for CIDP diagnosis when the cut-off values are properly determined at each filter setting. SIGNIFICANCE: Our data provide the systematic reference values of DCMAP duration for CIDP diagnosis available for most EMG laboratories.