Transcranial magnetic stimulation: normal values of magnetic motor evoked potentials in 84 normal horses and influence of height, weight, age and sex.
Authors: Nollet H, Deprez P, van Ham L, Dewulf J, Decleir A, Vanderstraeten G
Journal: Equine veterinary journal
Summary
# Transcranial Magnetic Stimulation: Establishing Baseline Motor Function in the Equine Nervous System Cervical spinal cord disease represents a significant clinical challenge in equine practice, yet veterinarians lack objective neurophysiological tools to assess the functional integrity of descending motor pathways in living horses. Researchers recruited 84 healthy horses of varying heights and applied transcranial magnetic stimulation (TMS) to generate motor evoked potentials (MEPs), establishing normative values whilst investigating whether height, weight, age and sex influenced the measurements. The study found that MEP latencies and amplitudes remained relatively consistent across the population studied, with latency values varying minimally regardless of horse size or demographic variables—a crucial finding that allows clinicians to apply a single reference range rather than requiring height-adjusted standards. These baseline values provide the essential framework for distinguishing genuinely abnormal motor tract function from normal variation, offering farriers, veterinarians and rehabilitation specialists a quantifiable diagnostic parameter when evaluating horses presenting with ataxia, paresis or suspected spinal cord compromise. TMS could thereby shift assessment of cervical myelopathy from subjective clinical observation towards objective neurophysiological measurement, potentially enabling earlier detection and more informed prognosis in cases of conditions like wobbler syndrome.
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Practical Takeaways
- •TMS provides objective neurological assessment for horses with cervical spinal cord problems, filling a diagnostic gap where conventional tests lack functional information
- •Normal reference values from this study can be used to compare against affected horses and improve diagnostic accuracy for spinal cord dysfunction
- •Height, weight, age and sex should be considered when interpreting TMS results in clinical cases, as these factors influence normal values
Key Findings
- •Transcranial magnetic stimulation successfully generated motor evoked potentials in 84 healthy horses, establishing normal reference values for the species
- •Study identified TMS as an objective diagnostic tool for assessing integrity of descending motor tracts in horses with suspected spinal cord dysfunction
- •Analysis examined influences of height, weight, age and sex on motor evoked potential measurements in the normal population