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

Abstract

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.

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

“…Finally, previous reports ( Thaisetthawatkul et al, 2002 ; Cleland et al, 2003; 2006 ) and this study measured CMAP duration with setting EMG filter as 20 Hz to 20 kHz. Because the CMAP duration would be largely affected by the low cut filter setting, future studies will be required to assess the effects of the low cut filter.…”

Thromboembolic complications of intravenous immunoglobulin therapy in patients with neuropathy: A two-year study

“…Twenty-one patients had GBS. All met the following clinical diagnostic criteria for GBS: (i) maximum time from onset to nadir ≤4 weeks (ii) weakness, hypo/areflexia, with or without sensory involvement in ≥2 limbs [12]. Only fulfillment of clinical criteria was required for inclusion in the current analysis, as several patients with GBS had electrophysiology performed after initiation of IVIg treatment.…”

Electrodiagnosis of GBS subtypes by a single study: not yet the squaring of the circle

“…We looked to the data on distal CMAP duration in 19 patients with final diagnosis of axonal GBS. CMAPs were recorded with 2 Hz–10 kHz filter setting, at least three motor nerves were studied in each patient, and the cut-off value of 8.5 ms of duration for all nerves was adopted 13. At the first study (within 3 weeks from onset), distal CMAP duration was prolonged in one nerve in three (16%) patients (2 AMAN with RCF and 1 AMAN with axonal degeneration).…”