Distal Compound Muscle Action Potential Duration Research Articles

Electrodiagnostic data-driven clustering identifies a prognostically different subgroup of patients with chronic inflammatory demyelinating polyneuropathy

ObjectiveThis study aimed to explore the correlations between electrodiagnostic (EDX) features in patients with chronic inflammatory demyelinating polyneuropathy (CIDP) and to investigate whether EDX data-driven clustering can identify a distinct...

Electrophysiological demyelinating features in hereditary ATTR amyloidosis

Objective: To elucidate the electrophysiological demyelinating features in patients with hereditary ATTR amyloidosis that may lead to a misdiagnosis of chronic inflammatory demyelinating polyneuropathy (CIDP).Methods: In 102 patients with hereditary ATTR amyloidosis (85 Val30Met and 17 non-Val30Met; 37 and 65 from endemic and non-endemic areas, respectively), results of motor nerve conduction studies (MNCSs) with a 2-Hz low-cut filter in the unilateral ulnar and tibial nerves were retrospectively investigated to assess whether each MNCS parameter demonstrated demyelinating features that fulfil the European Federation of Neurological Societies/Peripheral Nerve Society electrodiagnostic (EFNS/PNS EDX) criteria for CIDP.Results: Thirteen patients with low compound muscle action potential (CMAP) amplitude in the tibial nerve (0.7 ± 0.7 mV) and prolonged distal CMAP duration in the ulnar nerve satisfied the definite EFNS/PNS EDX criteria for CIDP. Abnormal temporal dispersion and prolongation of distal latency in the tibial nerve were observed in 5 of 13 patients. However, only one of the 13 patients presented with the reduction of motor conduction velocity in each nerve. No patient exhibited conduction block in any nerve.Conclusion: Patients with hereditary ATTR amyloidosis occasionally show electrophysiological demyelinating features without conduction block following severe axonal degeneration.

Diagnostic Significance of Distal Compound Muscle Action Potential (CMAP) Duration-A Case Report

The diagnostic criteria of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) are based on clinical findings and auxiliary investigations, of which the most important ones are neurophysiological findings. Since the European Federation of Neurological Societies/ Peripheral Nerve Society (EFNS/PNS) incorporated distal CMAP duration into the neurophysiological diagnostic criteria, their sensitivity increased to 81.3% and specificity to 96.2%. We describe a case of a 58-year-old man who was referred to our electromyography (EMG) laboratory for a second opinion regarding his diagnosis. The patient exhibited sensory-motor polyneuropathy with prominent hypotrophy of the calf muscles. Electrodiagnostic testing prior to admission had revealed a probable axonal neuropathy. In our EMG laboratory, we accomplished nerve conduction studies (NCS) of both hands and legs and we noted a prominent increase of distal CMAP duration, whereas distal motor latencies (DML) were within normal limits. As the CMAP amplitude in the tibial and peroneal nerves was less than 1 millivolt (mV), the existence of myelinopathy could not be inferred from any other parameters identified in the lower extremities. Neurophysiological investigation of both hands was necessary, even though the clinical picture of polyneuropathy was substantially more prominent in the legs. It is important to distinguish between axonal and myelin sheath lesions in order to understand the pathogenetic aspects of neuropathy. In addition, treatment of demyelinating autoimmune neuropathies can be offered and it is effective. In our patient, distal CMAP duration was the main discriminating parameter among the various neurophysiological parameters of the CIDP diagnostic criteria.

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

ObjectiveThe 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 20Hz. We aimed to provide widely-available reference data using several low cut filters. MethodsIn 13 Japanese and European tertiary centers, DCMAP duration data using 2, 5, 10, and 20Hz 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. ResultsThe 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%. ConclusionsOur 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. SignificanceOur data provide the systematic reference values of DCMAP duration for CIDP diagnosis available for most EMG laboratories.

104. Assessment of distal compound muscle action potential duration (DCMAPD) in paediatric chronic inflammatory demyelinating polyneuropathy (CIDP)

To evaluate if duration of distal compound muscle action potential duration (DCMAPD) could represent a sensitive parameter in clinical practice to add to established electrophysiological diagnostic criteria in paediatric chronic inflammatory demyelinating polyneuropathy (CIDP) and its rule in patient’s follow-up. We retrospectively reviewed records of 8 children affected by CIDP (6/8 possible CIDP, 2/8 confirmed CIDP) according to established diagnostic criteria of the 88th ENMC International Workshop (2000), before consideration of DCMAPD prolongation. Patients were studied with EMG equipment with low-cut filter settings ⩽10 Hz. Using adult cut-offs to define DCMAPD prolongation it was present in 8/8 patients for peroneal nerve, in 6/8 for median nerve and in all five patients in which we recorded tibial nerve. During follow-up time clinical worsening corresponded always to a greater DCMAPD prolongation compared with other electrophysiological parameters (amplitude, distal latency and nerve conduction velocity). Appropriate evaluation of DCMAPD appears an essential criterion to consider in assessing suspected CIDP and to support clinical worsening in follow-up, which may be helpful in limiting extensiveness and duration of electrophysiological testing, thereby reducing patient discomfort, especially in children.

Duration of the distal compound muscle action potential for diagnosis of chronic inflammatory demyelinating polyneuropathy: effects of low-cut filters.

In current electrodiagnostic criteria for chronic inflammatory demyelinating polyneuropathy, the cutoff values of distal compound muscle action potential (DCMAP) duration are defined using electromyogram low-cut filter setting of 20 Hz. We aimed to assess effects of low-cut filter on DCMAP duration (10 vs. 20 Hz). We prospectively measured DCMAP duration in 130 normal controls and 42 patients, fulfilling diagnostic criteria for typical chronic inflammatory demyelinating polyneuropathy by European Federation of Neurological Societies/Peripheral Nerve Society. Distal compound muscle action potential duration was significantly shortened with 20-Hz than 10-Hz filtering. When the cutoff values were defined as the upper limit of normal (ULN, mean + 2.5SD), the sensitivity/specificity was 67%/95% in 10-Hz recordings, and 69%/95% in 20-Hz recordings. This diagnostic accuracy was similar to that defined by receiver operating characteristic analyses. Distal compound muscle action potential duration significantly affected by the low-cut electromyogram filter setting, but with at least 10 and 20 Hz, the diagnostic accuracy is similar.

Is total duration of distal compound muscle action potential better than negative peak duration in the diagnosis of chronic inflammatory demyelinating polyneuropathy?

The diagnosis of chronic inflammatory demyelinating polyneuropathy (CIDP) is difficult, and the role of electrophysiology is crucial. Distal compound muscle action potential (CMAP) duration is a useful tool that is assessed by measuring negative peak duration (NP). The value of total distal CMAP duration (T), which seems more precise from a physiological standpoint, has not been studied. We reviewed retrospectively the records of 50 patients with CIDP and 50 controls with chronic axonal neuropathy. We constructed ROC curves for NP and T. Comparison of AUC for T vs. NP showed an advantage for the former (P=0.026 for the fibular nerve). Our derived cut-offs offered a sensitivity of 42.3% for T vs. 35.3% for NP. This study suggests a slight advantage for T over NP duration of the distal CMAP in the diagnosis of CIDP. However, the clinical relevance of this result must be weighed against the feasibility of this measurement.

Neuroprotective effects of folic acid on experimental diabetic peripheral neuropathy

Diabetic peripheral neuropathy (DPN) is widely considered as a degenerative complication of diabetic patients. The clinical effectiveness of folic acid (FA) on DPN is uncertain. The objective of the present study was to determine the effect of FA in DPN using electromyography (EMG), histopathological examination, immunohistochemistry, inclined plane test, and malondialdehyde (MDA) levels as a marker for lipid peroxidation in experimental diabetic rats. A total of 21 Sprague Dawley rats were randomly divided into 3 groups: control group, diabetes group, and FA-treated group. In EMG, compound muscle action potential (CMAP) amplitude in the sciatic nerve was lower in the diabetes group compared with the control group. CMAP amplitude in the sciatic nerve was higher in the FA-treated group when compared with the diabetes group. Distal latency and CMAP duration in the sciatic nerve were lower in the FA-treated group when compared with the diabetes group. In histopathological examination of the sciatic nerve, peripheral fibrosis was present in the diabetic group; the fibrosis was lower in the FA-treated group. In comparison with the diabetes group, the expression of nerve growth factor (NGF) was higher in the FA-treated group. The scores for the inclined plane test were lower in the diabetes group and higher in the FA-treated group than the control group. The MDA levels were significantly lower in the FA-treated group when compared with the diabetes group.The study suggests that FA can protect diabetic rats against DPN and that the underlying mechanism for this may be related to improvement of the expression of NGF and lower MDA levels.

P1-37. Distal compound muscle action potential dispersion would commonly occur in patients with anti-MAG/SGPG antibody associated neuropathy

The prolonged distal compound muscle action potential (CMAP) duration (i.e. distal temporal dispersion) has been recently validated as a measure of distal demyelination in chronic inflammatory demyelinating polyneuropathy (CIDP) patients. In previous reports, distal temporal dispersion was rare in patients with anti-MAG/SGPG antibody associated neuropathy. Here, to test this notion, we studied distal CMAP duration in our patients. Subjects were 5 patients with anti-MAG and/or anti-SGPG antibody associated neuropathy. We performed conventional motor conduction studies in unilateral median, ulnar and tibial nerves. The cut-off point of distal temporal dispersion was set at 9ms based on a previous report. Distal CMAP duration was prolonged in 4 of 5 patients. Among 13 responses, 50% (median), 60% (ulnar) and 75% (tibial) presented distal temporal dispersion. There were negative correlation between distal CMAP duration and conduction velocity (R[2] = 0.63, p = 0.0012), and positive correlation between distal CMAP duration and distal latency (R[2] = 0.75, p = 0.0001). Our findings suggest that distal temporal dispersion is not rare in patients with anti-MAG/SGPG antibody associated neuropathy, which is in contrast to previous reports.

A European multicentre reappraisal of distal compound muscle action potential duration in chronic inflammatory demyelinating polyneuropathy

The electrodiagnostic value of distal compound muscle action potential duration (DCMAPD) has been studied rarely in chronic inflammatory demyelinating polyneuropathy (CIDP). Cut-offs proposed have not been widely evaluated. The influence of low-cut EMG filter settings ≤ 10 Hz as used in Europe is uncertain. We retrospectively reviewed records of 110 patients with typical, treatment-responsive CIDP, from Leicester, U.K., Paris and Angers, France. All fulfilled revised European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS) clinical and electrodiagnostic criteria for typical CIDP (2010), before consideration of DCMAPD prolongation. Results were compared with those of 110 controls with chronic sensory/sensory-motor axonal neuropathy. We constructed receiver operating characteristic (ROC) curves for each nerve and derived cut-offs for DCMAPD prolongation, offering specificity of ≥ 98% vs. controls. DCMAPD was significantly greater in all nerves for CIDP patients, compared with controls (P < 0.001). ROC curves allowed derivation of cut-offs of sensitivities ranging from 27.1% (ulnar nerve) to 60% (tibial nerve). Using these cut-offs to define DCMAPD prolongation in any studied motor nerve offered a sensitivity of 69.1% for CIDP and specificity of 97.3% vs. controls. Cut-offs for DCMAPD are dependent on EMG filter settings. DCMAPD prolongation in any motor nerve, using our derived cut-offs, represents a sensitive and specific marker of CIDP in patients studied with EMG equipment with low-cut filter settings ≤ 10 Hz. Appropriate use of this parameter appears an essential criterion to consider in assessing suspected CIDP, which may be helpful in limiting extensiveness and duration of electrophysiological testing, thereby reducing patient discomfort.

Value of distal compound muscle action potential duration prolongation in acute inflammatory demyelinating polyneuropathy: A European perspective

The value of distal compound muscle action potential duration (DCMAPD) has not been widely studied in acute inflammatory demyelinating polyneuropathy (AIDP) with electromyography (EMG) equipment at low-cut filter settings <10 Hz, as used in Europe. We retrospectively reviewed the records of 40 patients with AIDP and 40 controls with axonal neuropathy, from Leicester, UK, and Angers, France. The best combination of sensitivity/specificity for AIDP using DCMAPD prolongation in any one nerve was offered by cut-offs from two other studies (sensitivity: 90% and 87.5%, respectively; specificity: 92.5% for both). Independent DCMAPD prolongation in any one nerve was better than, or equivalent to, other criteria. DCMAPD prolongation in any one nerve, at cut-offs suggested by prior studies, represents a sensitive and specific marker to aid/simplify electrodiagnosis of AIDP in patients studied with EMG equipment with low-cut filter settings of <10 Hz.

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.

Dispersion of compound muscle action potential in hereditary neuropathies and chronic inflammatory demyelinating polyneuropathy

Distal compound muscle action potential (DCMAP) dispersion, defined as a DCMAP duration > or = 9 ms, and proximal-distal (P-D) CMAP dispersion are considered useful in the electrodiagnosis of chronic inflammatory demyelinating polyneuropathy (CIDP). Distal and P-D CMAP dispersion have not been fully studied in hereditary neuropathies, and it is not known whether these measures distinguish hereditary from acquired demyelination. We compared DCMAP duration and P-D CMAP dispersion in 91 genetically characterized hereditary neuropathies and 33 subjects with CIDP. DCMAP dispersion was more frequent in nerves affected by CIDP (41.5%) than in Charcot-Marie-Tooth disease (CMT)1A (24.4%), CMT1B (7.4%), hereditary neuropathy with liability to pressure palsies (HNPP) (10.5%), or CMTX (9.8%). P-D CMAP dispersion was more frequent in CIDP (27.7% of nerves) than in hereditary neuropathies (16.3%) when applying American Academy of Neurology (AAN) criteria; however, its frequency was similar in CIDP and the hereditary neuropathies using the more restrictive criteria of the American Association of Neuromuscular and Electrodiagnostic Medicine (AANEM). Although dispersion is more common in CIDP than in the hereditary neuropathies, DCMAP and P-D dispersion occur in at least one motor nerve in a significant proportion of hereditary neuropathies, and cannot be used in isolation to distinguish acquired from hereditary demyelination.

Acute inflammatory demyelinating polyneuropathy: Contribution of a dispersed distal compound muscle action potential to electrodiagnosis

Prolonged duration of the distal compound muscle action potential (DCMAP) ("DCMAP dispersion") is useful in the electrodiagnosis of chronic inflammatory demyelinating polyneuropathy (CIDP) with good specificity in distinguishing CIDP from amyotrophic lateral sclerosis (ALS) and diabetic polyneuropathy, but its role in the electrodiagnosis of acute inflammatory demyelinating polyneuropathy (AIDP) is unclear. This study addresses this issue by determining the optimal cutoff for DCMAP duration using receiver operating characteristic (ROC) analysis in 207 motor nerves from 53 clinically defined AIDP patients compared to 148 motor nerves from 55 ALS patients. We also determined whether the presence of DCMAP dispersion improves the sensitivity of four of the most sensitive published sets of electrodiagnostic criteria for AIDP. Using the ROC-derived optimal DCMAP duration cutoff of 8.5 ms, DCMAP dispersion was found in at least one motor nerve in 66% of subjects with AIDP compared to 9% of subjects with ALS. DCMAP dispersion improved the sensitivity of the four tested criteria sets to 76%-87% from 43%-77%. Moreover, of 13 AIDP patients who met none of the four published criteria sets, 5 (38%) had at least one dispersed DCMAP. These findings indicate that the presence of DCMAP dispersion adds electrodiagnostic sensitivity to the currently published criteria sets, while maintaining reasonably high specificity against a prototypical disorder of the primary motor neuron with axon loss.