Nanotube-Assisted Motor Neuron and Neuromuscular Junction Stabilization in Spinal Muscular Atrophy: A Hypothesis for Adjunctive Therapy.

Spinal muscular atrophy (SMA) therapies that restore SMN expression improve survival and motor function but often fail to fully stabilize distal motor units or sustain endurance. We propose a hypothesis-driven adjunctive approach, intended to complement SMN-restoring therapies, in which localized nanotube-enabled interfaces acting at or near the distal motor unit and neuromuscular junction enhance neuromuscular transmission reliability in surviving, remodeled motor units. The model predicts a temporal cascade: improved junctional reliability and reduced activity-dependent failure, followed by consistent motor unit output across repeated activation, and ultimately, enhanced endurance and functional reserve. Phenotype-specific responsiveness identifies patients most likely to benefit, specifically those with preserved-but-limited residual motor unit substrate accompanied by measurable neuromuscular junction instability. Drawing on shared mechanisms from ALS, spinal cord injury, and other neuromuscular disorders, we discuss mechanistic, translational, safety, regulatory, and ethical considerations. This framework links objective physiological constructs to functional outcomes, offering a mechanistically grounded path for adjunctive therapy development in SMA and related conditions.