Dispersion of the distal compound muscle action potential as a diagnostic criterion for chronic inflammatory demyelinating polyneuropathy

Abstract

Quantitation of DCMAP dispersion shows promise as a sensitive and specific adjunctive electrodiagnostic criterion for CIDP.

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

“…During the second portion of our study (when we were using a 20 Hz low filter setting) identification of an abnormal distal CMAP duration followed a previously proposed definition (16). During the early portion of our study (when we were using a 2 Hz low filter setting) identification of an abnormal distal CMAP duration followed the suggestions of Rajabally et al (15) for low filter settings of ≤ 10 Hz.…”

“…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.…”

“…When there was a significant reduction in motor amplitude, axonopathy was deemed present. Demyelination was deemed present when abnormal prolongation of the distal CMAP duration was observed (16,17). Temporal dispersion, as a further sign of demyelination, was also reported when detected for motor nerves (16).…”

“…Demyelination was deemed present when abnormal prolongation of the distal CMAP duration was observed (16,17). Temporal dispersion, as a further sign of demyelination, was also reported when detected for motor nerves (16). Median nerves were excluded from these determinations because of the potential for coincident demyelination if carpal tunnel syndrome (CTS) was present (20).…”