Magnetic Motor Evoked Potential Recording in Horses Using Intramuscular Needle Electrodes and Surface Electrodes.
Authors: Rijckaert Joke, Pardon Bart, Van Ham Luc, van Loon Gunther, Deprez Piet
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Surface Electrodes as a Non-Invasive Alternative for Equine Motor Evoked Potential Recording Assessing the integrity of the equine spinal cord and motor pathways has traditionally relied on intramuscular needle electrodes for transcranial motor evoked potential (MEP) recording, a technique that carries practical limitations around electrode placement, patient discomfort, and handling requirements. Rijckaert and colleagues compared adhesive surface electrodes against the conventional intramuscular needle approach in ten sedated warmblood horses, measuring motor latency times (MLTs) and amplitudes across all four limbs to evaluate feasibility, repeatability, and agreement between methods. Motor latency times demonstrated excellent concordance between electrode types—thoracic limb latencies averaged 20.8 ms (needle) versus 21.2 ms (surface), whilst pelvic limb latencies were 39.4 ms and 39.2 ms respectively—with good repeatability for both recording methods; however, amplitude measurements showed insufficient agreement and excessive test-to-test variation (ranging 3.8–8.3 mV across limbs) to establish surface electrodes as interchangeable for this parameter. The painless application and reliable latency data position surface electrodes as a pragmatic alternative for detecting conduction delays indicative of spinal cord dysfunction, particularly valuable in clinical settings where needle placement proves challenging or when repeated assessments are required. Until amplitude standardisation is resolved through larger studies examining electrode contact variables and anatomical factors, practitioners should view surface-electrode MEP primarily as a screening tool for abnormal conduction times rather than a complete substitute for needle-based recordings in diagnostic protocols.
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Practical Takeaways
- •Surface electrodes can be used as a viable alternative to needle electrodes for motor latency assessment in clinical equine neurological examinations without causing discomfort
- •If using surface electrodes for MEP in your practice, focus on motor latency times as the reliable measurement; amplitude values require further validation before clinical interpretation
- •This methodology could reduce stress on sedated horses during neurological workups, though the technique requires further standardization before widespread clinical adoption
Key Findings
- •Surface electrode MEP recording is feasible and well-tolerated in sedated horses with motor latency times of 20.8±1.5 ms (thoracic) and 39.4±3.8 ms (pelvic limbs)
- •Motor latency times showed good agreement and repeatability between surface and intramuscular needle electrodes (Bland-Altman analysis)
- •Amplitude measurements demonstrated insufficient agreement and repeatability between recording methods due to large test-to-test variations
- •Surface electrodes offer a painless, easy-to-place alternative to intramuscular needle electrodes for MLT measurement in equine neurological assessment