To test the hypothesis that functional cortico-muscular connectivity reflects the compensatory neural communication in cortical and spinal networks in spinal muscular atrophy(SMA), in over 50% of the Irish adult SMA population. 

Spinal Muscular Atrophy is a pure lower motor neuron disorder with onset occurring usually in infancy or childhood.  Breakthroughs in the treatment of SMA with anti-sense oligonucleotide has been shown to be effective in infants. However, the benefit of this therapy in adults remains unclear.

Recent MRI studies¹ in adult SMA have provided convincing evidence of re-organization of the motor cortex, raising the possibility that loss of anterior horn cells in childhood leads to upstream changes in neuronal structure and function.

10 patients with spinal muscular and 10 healthy controls were studied during the performance of tailored isometric precision grip tasks for those patients with minimal hand muscle function. Simultaneous recordings of  High-density 128-channel EEG and 8 bipolar surface EMG recordings from extrinsic and intrinsic hand muscles were taken. Time-series analyses captured communication pathways between cortical brain regions, and oscillatory motor drives to muscles were quantified  during specific motor tasks. 

Analysis of the SMA patient group showed pathological presence of cortico-muscular coherence(CMC) between EMG and EEG signals recorded from frontal and parietal brain regions in abnormal frequency bands. This included alpha-band increases over the parietal (Pz) region which extend to other frequency bands in the frontal (Fz) and central (Cz) regions.

EEG-EMG coherence during functional motor tasks shows pathological changes in the central-peripheral communication in SMA Patients. Pathological locations of CMC suggest  compensatory changes in the motor cortex, which involves broader cortical regions with synchronous activity to muscles, in those affected with SMA. CMC has potential as a biomarker in SMA with the potential to be used to monitor drug efficacy in future clinical trials.

¹Querin,G Neuroimage Clin. 2019