Cerebral circulation in aging.

Cerebral circulation is known to be protected by the regulatory function against the hypoperfusion that will affect the cognitive function as a result of brain ischemia and energy failure. The regulatory function includes cerebrovascular autoregulation, chemical control, metabolic control, and neurogenic control, and those compensatory mechanisms can be influenced by hypertension, atherosclerosis, cardiac diseases, cerebrovascular diseases and aging. On the other hand, large and/or small infarction, intracranial hemorrhage, subarachnoid hemorrhage, atherosclerosis, amylod angiopathy are also more directly associated with cognitive decline not only in those with vascular cognitive impairment or vascular dementia but also those with Alzheimer's disease.

A single blind randomized controlled clinical trial of mexiletine in amyotrophic lateral sclerosis: Efficacy and safety of sodium channel blocker phase II trial.

Fasciculations are characteristic features of amyotrophic lateral sclerosis (ALS), and suggest motor nerve hyperexcitability. Recent reports have shown that an increase in persistent nodal sodium current is associated with shorter survival in ALS patients. This objective of this trial is to study the efficacy and safety of mexiletine, a sodium channel blocker, for ALS. Sixty eligible participants were randomly allocated (1:1) to riluzole 100 mg or riluzole plus mexiletine 300 mg. The primary endpoint was change in the revised ALS functional rating scale (ALSFRS-R) scores during six months. We also monitored strength-duration time constant (SDTC, a measure of persistent sodium current) in median motor axons. Results showed that during six months of treatment, changes in the ALSFRS-R score and SDTC were -7.0 ± 7.1 and -0.04 ± 0.1, respectively, in the riluzole group and -6.9 ± 6.4 and 0.04 ± 0.1, respectively, in the mexiletine group (p = 0.96 and 0.049). Adverse events amounted 20% in the riluzole and 33% in the mexiletine groups. In conclusion, the results suggest that daily 300 mg mexiletine has no effects on axonal sodium current and ALSFRS-R deterioration in ALS. We have to attempt another trial using a higher dose of mexiletine or other agents to suppress sodium currents and ALS progression in the future.

Complex fasciculation potentials and survival in amyotrophic lateral sclerosis.

OBJECTIVE: We investigated the relationship between fasciculation potentials (FPs) and survival in patients with ALS. METHODS: In 85 ALS patients, we prospectively performed needle EMG in five to seven muscles of each patient. The shape of the detected FPs was analyzed by inspection, and FPs with >4 phases were judged as complex FPs. We analyzed the correlation between complex FPs and survival period using the Cox proportional hazard model. RESULTS: Complex FPs were observed in 47 patients, more frequently in the muscles with normal strength or mild weakness. The presence of complex FPs was associated with shorter survival (hazard ratio 3.055; p=0.004). The greater the number of muscles with complex FPs, the shorter the survival and the faster the progression speed. CONCLUSION: Wide distribution of complex FPs is associated with shorter survival in ALS. SIGNIFICANCE: Complex FPs are useful to predict prognosis of ALS patients and should be evaluated in the EMG examination.

Bortezomib-induced neuropathy: axonal membrane depolarization precedes development of neuropathy.

OBJECTIVE: Bortezomib is a proteasome inhibitor with high efficacy for multiple myeloma but with severe peripheral neurotoxicity, leading to dose modification and severe neurological disability. This study aimed to investigate the pathophysiology of bortezomib-induced neuropathy. METHODS: Threshold tracking was used to assess the excitability of sensory and motor axons. Measurements were sequentially performed before and after bortezomib treatment in nine patients with newly diagnosed multiple myeloma. RESULTS: In total, 67% of patients finally developed symptomatic neuropathy. Changes in sensory axonal excitability indices readily occurred after the first course of administration. Patterns of changes in excitability indices suggest membrane depolarization (decreased superexcitability, P<0.001; decreased depolarizing threshold electrotonus 90-100ms, P=0.02). Abnormalities in nerve conduction parameters suggestive of axonal degeneration appeared after the second course of treatment. CONCLUSIONS: Bortezomib induces a depolarizing shift in resting membrane potential prior to the development of neuropathy. Membrane depolarization could be associated with impairment of electrogenic Na(+)-K(+)-ATPase-dependent pump caused by toxic effects of bortezomib on mitochondria. SIGNIFICANCE: Axonal depolarization and hyperexcitability might enhance neurodegeneration in bortezomib-induced neuropathy.

Markedly upregulated serum interleukin-12 as a novel biomarker in POEMS syndrome.

OBJECTIVE: To systematically study abnormalities in cytokine profiles in polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin changes (POEMS) syndrome, which has been increasingly recognized as a cause of demyelinating neuropathy associated with plasma cell dyscrasia and elevated serum level of vascular endothelial growth factor (VEGF). METHODS: In this case-control study, we measured serum levels of 27 cytokines in patients with POEMS syndrome using a multiplex suspension array system, and compared them with those of controls. In 10 patients, serial changes after treatment were analyzed. RESULTS: Interleukin (IL)-12 as well as VEGF levels were markedly increased (p < 0.0001) in all the patients (n = 23). Ten kinds of other proinflammatory cytokines such as IL-6 and tumor necrosis factor-α were also significantly increased in the POEMS syndrome group, but in some patients the serum levels of such cytokines remained within the normal ranges. After treatments, the IL-12 as well as VEGF levels significantly decreased with clinical improvements (p > 0.01 and p > 0.05, respectively). CONCLUSIONS: Our findings suggest that serum IL-12 is a biomarker of the disease activity in POEMS syndrome. The overproduction of IL-12, as well as VEGF, is likely to play an important role in the pathogenesis of the disorder, and could contribute to the peripheral nerve demyelination in POEMS syndrome.

Motor axonal excitability properties are strong predictors for survival in amyotrophic lateral sclerosis.

OBJECTIVE: The aim of this study was to investigate whether axonal excitability indices are associated with survival in patients with amyotrophic lateral sclerosis (ALS). Previous nerve excitability studies suggested increased persistent sodium currents in motor axons of patients with ALS, which lead to axonal hyperexcitability and potentially enhance neuronal death. METHODS: 112 patients with sporadic ALS were followed up until endpoint (death or tracheostomy). Multivariate analyses were performed using the Cox proportional hazard model. Threshold tracking was used to measure multiple axonal excitability indices in median motor axons, such as strength-duration time constant (SDTC; a measure of nodal persistent sodium current). Latent addition was also used to estimate the magnitude of persistent sodium currents. RESULTS: The overall median tracheostomy-free survival from onset was 37 months. Prolonged SDTC was strongly associated with shorter survival (adjusted HR 4.07; 95% CI 1.7 to 9.8; p=0.0018) compared with older onset age (>60 years; HR=1.80) and bulbar onset (HR=1.80). Estimated median survival was 34 months in the longer SDTC group and 51 months in the shorter SDTC group. This index was highly statistically significant even after multiple testing adjustments with age and site of onset (bulbar or limb). Latent addition study results were consistent with these findings. CONCLUSIONS: Axonal persistent sodium currents, estimated by SDTC and latent addition, are strong and independent predictors for shorter survival in patients with ALS. Membrane hyperexcitability is possibly associated with motor neuronal death, and modulation of excessive sodium currents could be a novel therapeutic option for ALS.

Different neurological and physiological profiles in POEMS syndrome and chronic inflammatory demyelinating polyneuropathy.

BACKGROUND: POEMS (polyneuropathy, organomegaly, endocrinopathy, M protein and skin changes) syndrome, a rare cause of demyelinating neuropathy associated with multiorgan involvement, has been increasingly recognised. Polyneuropathy is often an initial manifestation and therefore the disorder can be misdiagnosed as chronic inflammatory demyelinating polyneuropathy (CIDP). Objective To elucidate whether POEMS syndrome and CIDP are differentiated based on profiles of neuropathy. METHODS: Clinical and electrophysiological data were reviewed in consecutive POEMS syndrome (n=51) and typical CIDP (n=46) patients in a single Japanese hospital between 2000 and 2010. RESULTS: Both POEMS and CIDP patients showed symmetric polyneuropathy, physiological evidence of demyelination (70% of POEMS patients fulfilled the electrodiagnostic criteria for definite CIDP) and albuminocytological dissociation; 49% of the POEMS syndrome patients had neuropathy onset and 60% of them were initially diagnosed as having CIDP by neurologists. Clinically, POEMS neuropathy more frequently showed severe leg pain (76% vs 7%; p<0.001), muscle atrophy (52% vs 24%; p=0.005) and distal dominant muscle weakness. Electrophysiologically, POEMS syndrome was characterised by less prolonged distal motor latency (mean 5.6 ms vs 8.1 ms; p<0.001) and higher terminal latency index (0.42 vs 0.33; p=0.006) in the median nerves, and unrecordable tibial and sural responses (p<0.001), suggesting demyelination predominant in the nerve trunk rather than in the distal nerve terminals, and axonal loss in the lower limb nerves. CONCLUSIONS: Before development of typical systemic manifestations, POEMS neuropathy can be distinguished from CIDP by the clinical profile and patterns of nerve conduction abnormalities. Recognition of these features leads to early diagnosis and proper treatment for POEMS syndrome.

Awaji ALS criteria increase the diagnostic sensitivity in patients with bulbar onset.

OBJECTIVE: To assess whether Awaji criteria improve the sensitivity of diagnosis for amyotrophic lateral sclerosis (ALS). In Awaji ALS criteria, fasciculation potentials are regarded as evidence of acute denervation in the presence of chronic neurogenic changes on needle electromyography. METHODS: We reviewed clinical and neurophysiological data of 113 consecutive patients who were suspected as suffering ALS. The six muscles (trapezius, biceps, first dorsal interosseous, T10-paraspinalis, vastus lateralis, and tibialis anterior muscles) were examined by EMG, focusing on the presence of fasciculation potentials. The sensitivity of revised El Escorial (R-EEC) and Awaji criteria was compared. RESULTS: Probable or definite ALS was diagnosed in 61% of the patients by R-EEC and 71% by Awaji criteria. By applying Awaji criteria; (1) 17 of the 44 patients categorized as possible ALS by R-EEC reached to probable/definite ALS, 11 of whom had bulbar onset, (2) in 48 patients with bulbar onset, the proportion of probable/definite ALS increased from 59% to 82%, (3) in 62 patients with limb onset, the proportion of probable/definite ALS was 61% (63% by R-EEC). CONCLUSIONS: Awaji criteria improve the sensitivity of ALS diagnosis in patients with bulbar onset, but not in those with limb onset. SIGNIFICANCE: Accepting fasciculation potentials as evidence of acute denervation increases the diagnostic sensitivity of ALS, particularly in patients with bulbar onset, and contributes to early diagnosis.

Antiganglioside antibodies are associated with axonal Guillain-Barré syndrome: a Japanese-Italian collaborative study.

BACKGROUND: Whether or not antiganglioside antibodies are related to axonal or demyelinating Guillain-Barré syndrome (GBS) is still a matter of controversy, as detailed in previous studies conducted in Western and Asian countries. OBJECTIVE: To clarify whether antiganglioside antibodies are associated with axonal dysfunction in Japanese and Italian GBS patient cohorts. METHODS: Clinical and electrophysiological profiles were reviewed for 156 GBS patients collected from Japan (n=103) and Italy (n=53). Serum IgG antibodies against GM1, GM1b, GD1a and GalNAc-GD1a were measured by ELISA in the same laboratory. Electrodiagnostic criteria and results of serial electrophysiological studies were used for classification of GBS subtypes: acute inflammatory demyelinating polyneuropathy (AIDP) and acute motor axonal neuropathy (AMAN). RESULTS: In both Japanese and Italian cohorts, any of the antibodies were positive in 36% of the patients, and antibody positivity had a significant association with the AMAN electrodiagnosis. Approximately 30% of Japanese and Italian antiganglioside positive patients showed the AIDP pattern at the first examination whereas sequential studies showed that most finally showed the AMAN pattern. Clinically, seropositive patients more frequently had preceding diarrhoea and pure motor neuropathy in both Japanese and Italian cohorts; vibratory sensation was normal in 97% of Japanese and in 94% of Italian seropositive patients. CONCLUSIONS: In GBS, clinical and electrophysiological features appear to be determined by antiganglioside antibodies, and the antibodies are associated with motor axonal GBS in both Japan and Italy. Classification of the GBS subtypes as a disease entity should be made, combining the results of antiganglioside assays and serial electrodiagnostic studies.

Differences in excitability between median and superficial radial sensory axons.

OBJECTIVE: The aim of this study was to investigate differences in excitability properties of human median and superficial radial sensory axons (e.g., axons innervating the glabrous and hairy skin in the hand). Previous studies have shown that excitability properties differ between motor and sensory axons, and even among sensory axons between median and sural sensory axons. METHODS: In 21 healthy subjects, threshold tracking was used to examine excitability indices such as strength-duration time constant, threshold electrotonus, supernormality, and threshold change at the 0.2 ms inter-stimulus interval in latent addition. In addition, threshold changes induced by ischemia for 10 min were compared between median and superficial radial sensory axons. RESULTS: Compared with radial sensory axons, median axons showed shorter strength-duration time constant, greater threshold changes in threshold electrotonus (fanning-out), greater supernormality, and smaller threshold changes in latent addition. Threshold changes in both during and after ischemia were greater for median axons. CONCLUSIONS: These findings suggest that membrane potential in human median sensory axons is more negative than in superficial radial axons, possibly due to greater activity of electrogenic Na(+)/K(+) pump. These results may reflect adaptation to impulses load carried by median axons that would be far greater with a higher frequency. SIGNIFICANCE: Biophysical properties are not identical in different human sensory axons, and therefore their responses to disease may differ.

Markedly reduced axonal potassium channel expression in human sporadic amyotrophic lateral sclerosis: an immunohistochemical study.

Fasciculations are characteristic features of amyotrophic lateral sclerosis (ALS), suggesting abnormally increased excitability of motor axons. Previous nerve excitability studies have shown reduced axonal potassium currents in ALS patients that may contribute to the hyperexcitability and thereby generation of fasciculations. To clarify changes in axonal ion channel expression in motor axons of ALS, we performed immunohistochemistry of potassium and sodium channels in the C7 and L5 ventral/dorsal roots obtained from five autopsy cases of sporadic ALS. Compared to controls, the immunoreactivity of potassium channels (Kv1.2) was markedly reduced in the ventral roots, but normal in the dorsal roots of all the ALS patients. Nodal sodium channel expression was not significantly different in ALS patients and control subjects. Our results show prominently reduced expression of axonal potassium channels, and provide the neuropathological and biological basis for decreased accommodative potassium currents in motor axons of ALS patients. The axonal hyperexcitability would lead to generation of fasciculations, and possibly enhances motor neuron death in ALS.

Detection of bone lesions by CT in POEMS syndrome.

OBJECTIVE: To study the utility of CT for detection of small bone lesions in POEMS (polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin changes) syndrome. For patients with a solitary bone lesion, irradiation is a first-line treatment, whereas systemic chemotherapy is indicated for patients with multiple bone lesions. Therefore it is important to correctly identify the number of bone lesions. METHODS: We studied the sensitivity of chest/abdomen/pelvic CT to detect bone lesions in 28 patients with POEMS syndrome. (99m)Tc-HMDP bone scintigraphy was performed in 14 patients, and the results were compared with CT. RESULTS: CT showed multiple bone lesions in 68% of the 28 patients, and 71% of the lesions had a diameter <10 mm. In 14 patients who underwent both CT and scintigraphy, bone lesions were detected in 57% by CT and in 79% by scintigraphy, but the location and nature of the identified lesions were considerably different; CT frequently showed small lesions (diameter <10 mm) in the vertebrae and pelvis, which were not detected by scintigraphy, whereas scintigraphy could show lesions in the skull and long bones. Overall, by using both examinations, multiple bone lesions were found for 86% of patients. CONCLUSION: CT is particularly useful to detect small bone lesions. CT and bone scintigraphy are complementary, and therefore both should be performed for bone survey in POEMS syndrome.

Activity-dependent changes in impulse conduction of single human motor axons: a stimulated single fiber electromyography study.

OBJECTIVE: The aim of this study is to develop a novel method to assess activity-dependent hyperpolarization in human single motor axons at a constant stimulus frequency by using intra-muscular axonal stimulating single fiber electromyography (s-SFEMG). METHODS: We performed s-SFEMG in the extensor digitorum communis (EDC) muscle of 10 normal subjects, and measured changes in latencies for single muscle fiber action potentials (MAPs) during 500 stimuli delivered at 5, 10 and 20 Hz. The data were analyzed with a repeated measurement analysis, and multiple comparisons were performed. RESULTS: A total of 585 MAPs were examined at 5 Hz (n=190), 10 Hz (n=210), and 20 Hz (n=185) steady stimulation. There was a progressive linear prolongation of latencies, as the stimulus rate increased (F=95.6, p<0.001); the least square means (SEM) of latency change were 100.7 (0.28)% at 5 Hz, 102.3 (0.27)% at 10 Hz and 105.3 (0.28)% at 20 Hz. There were statistically significant differences between frequencies by Tukey-Kramer's method. Despite the significant latency prolongation, no activity-dependent conduction block developed. A 20 Hz electric stimulation to intramuscular axons was well-tolerated in all the subjects. CONCLUSIONS: Tetanic stimulation at a constant rate results in significant latency increase in single human motor axons, the extent of which depends on the stimulus frequency. The findings imply that physiological discharge rates will activate the Na(+)/K(+) pump and thereby produce axonal hyperpolarization in single motor axons. SIGNIFICANCE: This technique may detect activity-dependent conduction block if the safety margin of impulse transmission is significantly reduced by demyelination or increased branching due to collateral sprouting in a variety of neuromuscular disorders.

Distal motor axonal dysfunction in amyotrophic lateral sclerosis.

Nerve conduction slowing in amyotrophic lateral sclerosis (ALS) is usually caused by loss of fast motor axons. We studied the frequency, extent, and distribution of prominently prolonged distal motor latencies in ALS. We reviewed results of median, ulnar, and tibial nerve conduction studies in 91 patients with ALS, 24 with lower motor neuron disorders, and 36 with axonal neuropathy. Coincidental carpal tunnel syndrome was found for 4 (4.4%) of the ALS patients who were excluded from analyses. Markedly prolonged distal latencies (>125% of the upper limit of normal) were found only in the median nerve of ALS patients (9%), and in none of the disease controls. Excitability studies suggested membrane depolarization in some ALS patients. Our results show that approximately 10% of ALS patients shows prominently prolonged median distal latency, which cannot be explained by axonal loss and carpal tunnel lesion. The distal nerve conduction slowing may partly be caused by membrane depolarization possibly due to motor neuronal degeneration in ALS. We suggest that recognition of the pattern of distal motor axonal dysfunction predominant in the median nerve is clinically important, and could provide additional insights into the pathophysiology of ALS.

Altered axonal excitability properties in juvenile muscular atrophy of distal upper extremity (Hirayama disease).

OBJECTIVE: Juvenile muscular atrophy of distal upper extremity (Hirayama disease) is characterized by juvenile-onset of asymmetric amyotrophy, but the pathophysiology has not been fully clarified. "Cold paresis", aggravation of muscle weakness with exposure to cold, is a characteristic feature of this disease. The aim of this study was to investigate changes in axonal excitability properties in Hirayama disease. METHODS: Threshold tracking was used to measure strength-duration time constant (SDTC), threshold electrotonus, refractoriness, and supernormality in median motor axons at the wrist of 14 patients and 10 age-matched normal controls. The measurements were performed at room temperature and after cooling. RESULTS: Patients showed prolonged SDTC, fanning-out of threshold electrotonus curves, and increased refractoriness and supernormality. After cooling, there were similar changes in patients and normal subjects, compatible with axonal depolarization possibly due to paralysis of sodium-potassium pump. CONCLUSIONS: Motor axonal excitability in Hirayama disease were characterized by increased persistent sodium currents, and dysfunction of transient sodium and potassium channels possibly associated with prominent collateral sprouting in young individuals. Further studies will be required to elucidate mechanisms for cold paresis. SIGNIFICANCE: Assessment of axonal excitability could provide characteristic features of ionic mechanisms in diseases with neurogenic amyotrophy such as Hirayama disease.

Elevated CSF TDP-43 levels in amyotrophic lateral sclerosis: specificity, sensitivity, and a possible prognostic value.

TAR DNA binding protein of 43 kDa (TDP-43) is likely to be the major pathogenetic protein in amyotrophic lateral sclerosis (ALS). A previous study has shown that levels of TDP-43 in CSF measured by an ELISA are significantly higher for ALS patients than for controls. The aim of this study was to investigate whether elevated CSF TDP-43 levels are specific to ALS, and are associated with clinical profiles in ALS patients. We measured CSF TDP-43 levels by the same ELISA in 27 ALS patients and 50 neurodegenerative or inflammatory disease controls such as Parkinson's disease, multiple sclerosis, and Guillain-Barré syndrome. Results showed that the CSF TDP-43 levels were increased only in ALS patients. Receiver operating characteristic (ROC) analyses showed a sensitivity of 59.3% and a specificity of 96.0%. We also found that lower CSF TDP-43 levels may be associated with shorter survival time. In conclusion, the CSF TDP-43 is a potential biomarker that supports a diagnosis of ALS. Moreover, among ALS patients, lower levels of CSF TDP-43 may reflect the accumulation of TDP-43 in the cortical and spinal motor neurons and thereby shorter survival time, although this should be confirmed in larger prospective studies.

Multifocal conduction blocks in sarcoid peripheral neuropathy.

Peripheral neuropathy is a rare manifestation of sarcoidosis, and previous studies have shown axonal degeneration as the main pathology. We herein report three patients with sarcoidosis who presented with multiple mononeuropathy as the initial manifestation. Nerve conduction studies showed prominent multifocal conduction blocks in the intermediate nerve trunk. In all three patients, corticosteroid treatment resulted in a dramatic clinical improvement associated with rapid resolution of conduction blocks. The sequential electrodiagnostic findings suggest that demyelinative or ischemic-functional conduction block is responsible for their neuropathy. To date, only three cases of acute conduction block neuropathy associated with sarcoidosis have been reported, but it may occur more frequently than expected.

Mexiletine suppresses nodal persistent sodium currents in sensory axons of patients with neuropathic pain.

OBJECTIVE: To investigate changes in axonal persistent Na(+) currents in patients with neuropathic pain and the effects of mexiletine, an analogue of lidocaine, on axonal excitability properties. METHODS: The technique of latent addition was used to estimate nodal persistent Na(+) currents in superficial radial sensory axons of 17 patients with neuropathic pain/paresthesias before and after mexiletine treatment. Brief hyperpolarizing conditioning currents were delivered, and threshold change at the conditioning-test interval of 0.2 ms was measured as an indicator of the magnitude of persistent Na(+) currents. RESULTS: Threshold changes at 0.2 ms in latent addition were greater in the neuropathic patients than in the normal controls (p<0.001). After mexiletine treatment, there was a reduction in clinical pain scores (p<0.001), associated with decreased threshold changes at 0.2 ms (p<0.001). CONCLUSIONS: In patients with neuropathy, nodal persistent Na(+) currents in large sensory fibers increase, and the abnormal currents can be suppressed by mexiletine. Pain reduction after mexiletine treatment raises the possibility that excessive Na(+) currents are also suppressed in small fibers mediating neuropathic pain. SIGNIFICANCE: Latent addition can be used for indirect in vivo monitoring of nodal Na(+) currents in large sensory fibers, and future studies using this approach in small fibers would provide new insights into the peripheral mechanism of neuropathic pain.

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.

Utility of the distal compound muscle action potential duration for diagnosis of demyelinating neuropathies.

To assess the significance of distal compound muscle action potential (CMAP) duration for diagnosis of demyelinating neuropathies, electrophysiologic data were reviewed from 471 subjects, including 145 normal controls, 60 patients with chronic inflammatory demyelinating polyneuropathy (CIDP), 205 with other neuropathy, and 61 with amyotrophic lateral sclerosis (ALS). The duration of distally evoked CMAP was measured in the median, ulnar, tibial, and peroneal nerves. Optimal cut-off values were calculated with receiver-operating characteristic (ROC) curves. In comparison of normal controls and CIDP patients, ROC analyses showed the sufficient area under the curves (82-93%). When the cut-off values in the detection of demyelination were determined as the point with 98% specificity vs. normal on the ROC curves (median, 6.6 ms; ulnar, 6.7 ms; peroneal, 7.6 ms; tibial, 8.8 ms), the sensitivity was 77% for CIDP, with a specificity of 90% vs. ALS and 95% vs. diabetic neuropathy. The distal CMAP duration is a useful index for the detection of distal demyelination. We suggest the above cut-off values for each nerve as one of the electrodiagnostic criteria for demyelinating neuropathies, preferentially affecting the distal nerve terminals, such as CIDP.