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Muscle Nerve. 2014 May;49(5):636-44. doi: 10.1002/mus.23967.

The motor neuron response to SMN1 deficiency in spinal muscular atrophy.

Author information

1
Department of Neurology, Boston Children's Hospital and Harvard Medical School, 300 Longwood Avenue, Boston, Massachusetts, 02115, USA.

Abstract

INTRODUCTION:

The purpose of this study was to measure and analyze motor unit number estimation (MUNE) values longitudinally in spinal muscular atrophy (SMA).

METHODS:

Sixty-two children with SMA types 2 and 3 were observed prospectively for up to 42 months. Longitudinal electrophysiological data were collected, including compound motor action potential (CMAP), single motor unit action potential (SMUP), and MUNE.

RESULTS:

Significant motor neuron loss and compensatory collateral reinnervation were noted at baseline. Over time, there was a significant mean increase in MUNE (4.92 units/year, P = 0.009), a mean decrease in SMUP amplitude (-6.32 μV/year, P = 0.10), and stable CMAP amplitude.

CONCLUSIONS:

The unexpected longitudinal results differ from findings in amyotrophic lateral sclerosis studies, perhaps indicating that compensatory processes in SMA involve new motor unit development. A better understanding of the mechanisms of motor unit decline and compensation in SMA is important for assessing novel therapeutic strategies and for providing key insights into disease pathophysiology.

KEYWORDS:

compound motor action potential; electrophysiology; motor neuron disease; motor unit number estimation; spinal muscular atrophy

PMID:
23893312
PMCID:
PMC4090017
DOI:
10.1002/mus.23967
[Indexed for MEDLINE]
Free PMC Article

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