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

Abstract

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.

Evidence of peripheral large nerve involvement in fibromyalgia: a retrospective review of EMG and nerve conduction findings in 55 FM subjects

“…As a result, prior to data analyses, we elected to reclassify two subjects as non-CIDP: one "FM Only, " and one "FM+RA. " Finally, the accuracy and consistency of cursor placement for all motor NCS, including during measurement of distal CMAP duration, was optimized by having our elctromyographer (RGG) visually identify the onset of the initial negative deflection for each nerve and manually adjust the cursor setting as required (sensitivity=2 mV/division; see Methods) (14)(15)(16).…”

“…Our electromyographer measured all NCS motor parameters, including distal CMAP duration, by visually identifying the onset of the initial negative deflection and the return to baseline of the last negative deflection (display setting at 2mV/division); cursor placement was adjusted manually, as necessary (14)(15)(16)(17)(18). All sensory NCS were measured to the peak of the negative wave.…”

“…Two subjects (one "FM Only" and one "FM+RA") who originally met criteria for "Possible CIDP" were reclassified as non-CIDP subjects due to the potential influence of a change in our low filter settings (see Electrodiagnostic Studies above) on determining prolongation of the distal CMAP duration (14,15,17). No other study subject required reclassification.…”

An electrophysiological classification associated with Guillain–Barré syndrome outcomes

“…Patients were classified as having AIDP pattern when they had one of the following in two or more nerves: (1) motor nerve conduction velocity \90 % of the lower limit of normal if amplitude of distal CMAP is [50 % of lower limit of normal, \85 % if amplitude is \50 % of lower limit of normal; (2) DML [110 % of the upper limit of normal if amplitude is more than lower limit of normal,[120 % of upper limit of normal if amplitude is less than lower limit of normal; (3) evidence of unequivocal temporal dispersion; and (4) F-wave latency [120 % upper limit of normal. Because how much temporal dispersion of CMAP should be considered 'unequivocal' was not defined in Ho's criteria, we used a distal CMAP duration of more than 6.6 ms in the median, 6.7 ms in the ulnar, 7.6 ms in the peroneal, and 8.8 ms in the tibial nerves [24] or a [30 % increased duration of the proximal CMAP when compared with distal CMAP in all nerves [25]. Patients were classified as having AMAN pattern when had no evidence of the demyelination as defined for AIDP pattern and had decrease in distal CMAP amplitude to \80 % of lower limit of normal in at least two nerves.…”

Demyelinating Neuropathy and Autoimmune Hemolytic Anemia in a Patient with Pancreatic Cancer

“…Nerve conduction studies were performed as previously described (10,11). The tests revealed a prolongation of distal latencies, an increased distal compound muscle action potential duration (12) and slowing of the sensory nerve conduction velocities in the bilateral median nerves (Table). Neither temporal dispersion nor conduction block of the compound muscle action potentials between the proximal and distal sites of stimulation was observed (13).…”