Characteristics of ipsilateral corticomotor pathways in people with cervical Spinal Cord injury.

Objective: Understanding motor neurophysiology is important for developing effective upper limb treatments for people with tetraplegia following cervical spinal cord injury (SCI). While literature has primarily focused on contralateral motor pathways, neurophysiology of ipsilateral pathways remains largely unexplored in tetraplegia. We aimed to investigate ipsilateral physiology and its relationship to upper limb function in individuals with tetraplegia.

Methods: Twenty-three individuals with tetraplegia and 24 age-matched controls underwent transcranial magnetic stimulation to assess ipsilateral and contralateral motor physiology in the biceps muscle of the weaker arm. We also evaluated upper limb function and spasticity in tetraplegia.

Results: There were no differences in ipsilateral motor evoked potential (iMEP) features (amplitudes, onsets, offsets, durations, and areas) between participants with tetraplegia and controls (all p > 0.05). However, participants with tetraplegia who had larger iMEP amplitudes also had larger contralateral MEP amplitudes (p = 0.008) and better proximal arm motor function (p = 0.031).

Conclusion: Ipsilateral motor physiology is associated with contralateral physiology and proximal arm motor function in tetraplegia.

Significance: Ipsilateral pathways may play a role in proximal arm function in tetraplegia. However, injury-specific adaptations were missed due to preserved biceps strength in our sample. Future studies should investigate iMEPs in non-preserved muscles to establish injury-specific relevance for rehabilitation.