Key result
Adult SMN1-linked SMA exhibits significant anterior-posterior cervical spinal cord atrophy versus healthy controls.
Why the study?
The mechanisms underlying the topography of motor deficits in SMN1-linked spinal muscular atrophy remain unknown.
What is the profile of cervical spinal cord atrophy in adult SMN1-linked SMA compared to healthy controls, and does it correlate with muscle weakness?
Case-Control (n=36)
No
What is the profile of cervical spinal cord atrophy in adult SMN1-linked SMA compared to healthy controls, and does it correlate with muscle weakness?
p-value: p=<10^-5
Spinal cord atrophy in adult SMN1-linked SMA predominates in segments innervating proximal muscles, but does not correlate directly with strength and disability scores, suggesting additional mechanisms for weakness.
SCA predominates at C3–C6 in SMA III/IV without correlating to weakness; leaves open non-neuronal contributors to motor topography.
PURPOSE: The mechanisms underlying the topography of motor deficits in spinal muscular atrophy (SMA) remain unknown. We investigated the profile of spinal cord atrophy (SCA) in SMN1-linked SMA, and its correlation with the topography of muscle weakness. MATERIALS AND METHODS: Eighteen SMN1-linked SMA patients type III/V and 18 age/gender-matched healthy volunteers were included. Patients were scored on manual muscle testing and functional scales. Spinal cord was imaged using 3T MRI system. Radial distance (RD) and cord cross-sectional area (CSA) measurements in SMA patients were compared to those in controls and correlated with strength and disability scores. RESULTS: CSA measurements revealed a significant cord atrophy gradient mainly located between C3 and C6 vertebral levels with a SCA rate ranging from 5.4% to 23% in SMA patients compared to controls. RD was significantly lower in SMA patients compared to controls in the anterior-posterior direction with a maximum along C4 and C5 vertebral levels (p-values < 10-5). There were no correlations between atrophy measurements, strength and disability scores. CONCLUSIONS: Spinal cord atrophy in adult SMN1-linked SMA predominates in the segments innervating the proximal muscles. Additional factors such as neuromuscular junction or intrinsic skeletal muscle defects may play a role in more complex mechanisms underlying weakness in these patients.
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Mendili et al. (2016) conducted a case-control in SMN1-linked Spinal Muscular Atrophy (SMA) type III/IV (n=36). SMN1-linked SMA vs. Healthy volunteers was evaluated on Cervical spinal cord radial distance (RD) and cross-sectional area (CSA) (p=<10^-5). Adult patients with SMN1-linked SMA exhibited significant cervical spinal cord atrophy predominantly in the anterior-posterior direction between C3 and C6 vertebral levels compared to healthy controls.