Abstract Details

Title Median-ulnar Ratios in Differentiating Multifocal Motor Neuropathy From Amyotrophic Lateral Sclerosis

Topic Neuromuscular and Clinical Neurophysiology (EMG)

Presentation(s) P6 - Poster Session 6 (5:00 PM-6:00 PM)

Poster/Presentation
Number 9-003

Objective To determine whether median-to-ulnar compound muscle action potential (M/U) ratios can help differentiate between multifocal motor neuropathy (MMN) and amyotrophic lateral sclerosis (ALS).

Background Differentiating MMN from ALS is challenging, particularly in lower motor neuron (LMN)-predominant ALS, due to overlapping clinical and electrodiagnostic features. Prior studies comparing compound muscle action potential (CMAP) normalized ratios between the median and ulnar (M/U) motor nerves have suggested that the ratios are higher in MMN than in ALS, but it is unclear whether this holds across ALS subtypes.

Design/Methods We retrospectively analyzed 59 patients referred for EMG with suspected motor neuron disease. M/U ratios were calculated from median and ulnar CMAP amplitudes and compared across groups using t-tests, linear regression (with and without adjustment for age and sex), and density plots. ALS cases were stratified into LMN predominant and upper and lower limb onset.

Results

There were 16 patients with MMN, 30 with ALS, and 13 with LMN-ALS. Median M/U ratios were higher in MMN (1.85 [IQR 1.15–2.85]) compared with ALS (0.74 [0.42–1.07], p = 0.03). Arm- and leg-onset ALS had significantly lower ratios than MMN (p = 0.03 and p = 0.04). whereas the differences between LMN-ALS and MMN ratios were not significant. In regression models, both ALS and LMN-ALS were associated with lower M/U ratios vs. MMN. Density plots revealed overlap, but elevated ratios (>2) occurred almost exclusively in MMN.

Conclusions M/U ratios are higher in MMN than ALS and LMN-ALS and may be used to distinguish these conditions in ambiguous cases. In patients with focal LMN presentations, elevated ratios > 2 may identify those with MMN.

Authors/Disclosures
Jennifer Morganroth, MD, MBA (MGH) PRESENTER	Dr. Morganroth has nothing to disclose.
Sujata P. Thawani, MD (NYU Neurology Associates)	Dr. Thawani has nothing to disclose.
Holly Elser, MD, PhD (Hospital of the University of Pennsylvania)	Dr. Elser has nothing to disclose.
Kenneth C. Gorson, MD (Kenneth Gorson, MD)	Dr. Gorson has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Annexon. Dr. Gorson has received personal compensation in the range of $5,000-$9,999 for serving on a Scientific Advisory or Data Safety Monitoring board for UCB Pharma. Dr. Gorson has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for ArgenX. Dr. Gorson has received personal compensation in the range of $10,000-$49,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Pfizer.
Thomas Brannagan III, MD, FAAN (Columbia University)	Dr. Brannagan has received personal compensation in the range of $5,000-$9,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Sanofi. Dr. Brannagan has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Intellia. Dr. Brannagan has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Astra Zenica. Dr. Brannagan has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Annexon. The institution of Dr. Brannagan has received research support from Alnylam. The institution of Dr. Brannagan has received research support from Abcuro. The institution of Dr. Brannagan has received research support from Ionis. The institution of Dr. Brannagan has received research support from Vertex. The institution of Dr. Brannagan has received research support from NMD Pharma.

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