Abstract Details

Title Cervical Spinal Cord Gray Matter Area is Associated with Motor Unit Number Index in Spinal Muscular Atrophy

Topic Neuromuscular and Clinical Neurophysiology (EMG)

Presentation(s) S33 - ALS and Motor Neuron Diseases (2:24 PM-2:36 PM)

Poster/Presentation
Number 008

Background There is an unmet need for valid imaging markers to monitor the disease course and therapeutic outcome in SMA. The novel rAMIRA (radially sampled Averaged Magnetization Inversion Recovery Acquisitions) method enables high in-plane resolution MR-imaging with improved contrast of SC GM in clinically feasible acquisition times. MUNIX is an established quantitative neurophysiological measure that provides an index of the number of functioning lower motor neurons that supply a muscle. The association between SC GM area and MUNIX has not been investigated in SMA yet.

Objective To evaluate the association between spinal cord (SC) gray matter (GM) atrophy and Motor Unit Number Index (MUNIX) in patients with 5q-Spinal Muscular Atrophy (SMA).

Design/Methods Using axial 2D rAMIRA imaging, we prospectively investigated 21 patients with 5q-SMA, types 2 and 3 (mean age/SD 41.3/11.6y, 9 women) and 21 age- and sex-matched healthy controls (HC) (mean age/SD 41.7/11.4y, 9 women) at the intervertebral disc level C5/C6 perpendicular to the spinal cord. SC GM areas were determined using a semi-automated approach. MUNIX of the biceps brachii (BB) was measured following the ENCALS protocol. The association between SC GM area and MUNIX was assessed using multivariable regression analysis covarying for age and sex.

Results SC GM area at C5/6 was significantly reduced in patients compared to HC (mean GM area in mm² (SD): SMA 17.5 (2.2); HC 21.1 (2.3); relative reduction: 17.1% (p<0.0001)). In multivariable regression analysis SC GM area at C5/6 explained 53% of MUNIX variance of the BB in SMA patients.

Conclusions In patients with SMA, SC GM area is strongly associated with motor neuron function quantitated by MUNIX in the corresponding myotome, indicating the functional relevance of this structural marker. Further longitudinal studies are necessary to evaluate the potential of this novel imaging marker for monitoring the disease course and therapeutic outcome.

Authors/Disclosures
Eva M. Kesenheimer, MD (University Hospital Basel) PRESENTER	Dr. Kesenheimer has nothing to disclose.
Maria Janina Wendebourg, MD (University Hospital Switzerland)	Dr. Wendebourg has nothing to disclose.
	No disclosure on file
Laura Sander, MD (Universitätsspital Basel)	Dr. Sander has nothing to disclose.
Matthias Weigel, PhD	The institution of Matthias Weigel, PhD has received research support from Biogen. Matthias Weigel, PhD has received intellectual property interests from a discovery or technology relating to health care.
	No disclosure on file
Dirk Fischer	The institution of Dirk Fischer has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Hoffmann La Roche AG. The institution of Dirk Fischer has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Hoffmann La Roche AG.
	No disclosure on file
	No disclosure on file
Markus Weber, MD (Kantonsspital St. Gallen)	Dr. Weber has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Biogen Idec. Dr. Weber has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Mitsubishi Tanabe.
Cristina Granziera, MD, PhD (Basel University Hospital)	Dr. Granziera has nothing to disclose.
Michael Sinnreich, MD, PhD (Basel University Hospital)	Prof. Sinnreich has nothing to disclose.
	No disclosure on file
Regina Schlaeger, MD (University Hospital Basel, Neurology)	The institution of Dr. Schlager has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for sobi. The institution of Dr. Schlager has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Allergan. The institution of Dr. Schlager has received research support from Gottfried and Julia Bangerter Rhyner Foundation. The institution of Dr. Schlager has received research support from Freiwillige Akademische Gesellschaft. The institution of Dr. Schlager has received research support from Stiftung zur Förderung der gastroenterologischen Forschung und allgemeinen Klinischen Forschung sowie der medizinischen Bildgebung. The institution of Dr. Schlager has received research support from Lorenzo Piaggio Foundation. The institution of Dr. Schlager has received research support from Biogen Inc.