Afferent input and sensory function after human spinal cord injury

Area of Science:

• Neuroscience
• Rehabilitation Medicine
• Clinical Electrophysiology

Background:

• Spinal cord injury (SCI) frequently impairs sensory axon integrity in the dorsal columns.
• Assessing ascending sensory tract function is vital for monitoring SCI extent and recovery.
• Electrophysiological methods offer objective measures of sensory pathway function post-injury.

Purpose of the Study:

• To review common electrophysiological techniques for evaluating afferent input transmission to the brain following human SCI.
• To discuss the role of afferent input in modulating corticospinal excitability and its implications for upper and lower limb function.
• To highlight the limitations of current sensory examinations in characterizing SCI severity and the need for functional assessments.

Main Methods:

• Review of electrophysiological techniques including afferent input-induced facilitation/inhibition, somatosensory evoked potentials (SSEPs), dermatomal SSEPs, and electrical perceptual thresholds.
• Analysis of how afferent input timing influences corticospinal excitability through cortical and spinal mechanisms.
• Discussion of the application of these techniques in control versus SCI participants.

Main Results:

• Electrophysiological techniques can detect differences between control and SCI individuals.
• Current sensory exams may be suboptimal for precise SCI level and severity characterization.
• Afferent input modulation of corticospinal excitability depends on timing and limb specificity.

Conclusions:

• The timing of afferent input arrival at sensory and motor cortices is critical for plasticity-induced protocols in SCI.
• Future research should incorporate electrophysiological assessments during functional behaviors to understand impaired afferent input's role in motor control.
• Considering the effects of afferent input transmission on multiple functions is essential for managing SCI patients.