Standardization of transcranial magnetic stimulation in the horse.
Authors: Nollet H, Van Ham L, Dewulf J, Vanderstraeten G, Deprez P
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Standardization of Transcranial Magnetic Stimulation in the Horse Transcranial magnetic stimulation (TMS) offers potential for assessing motor pathway function in horses, but optimal technique parameters had not been established. Nollet and colleagues tested seven different forehead coil positions, two stimulation intensities (80% and 100% of maximal output), and current directions in both clockwise and counter-clockwise configurations, recording motor evoked potentials from the extensor carpi radialis and cranial tibial muscles in seven horses. Placement at the median forehead consistently produced the shortest onset latencies and largest peak-to-peak amplitudes for both muscles, with no meaningful difference between left and right recordings or between current directions. These findings provide a practical standardization protocol for equine neurological assessment, establishing the midline forehead position as the optimal site for reliable and reproducible measurements when investigating upper motor neuron function—particularly valuable for evaluating spinal cord disease, ataxia, and other central nervous system conditions affecting performance or safety.
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Practical Takeaways
- •When performing transcranial magnetic stimulation in horses for neurophysiological assessment, consistently place the coil at the median forehead position to obtain reliable and reproducible measurements
- •Either coil current direction can be used interchangeably without affecting latency measurements, simplifying standardization protocols
- •Bilateral recordings yield comparable results, reducing need for duplicate measurements across sides in clinical neurophysiological evaluation
Key Findings
- •Median forehead coil placement produced shortest onset latency and largest peak-to-peak amplitude for motor evoked potentials in both extensor carpi radialis and cranial tibial muscles
- •No significant difference in recordings between left and right side stimulation sites
- •Current direction (clockwise vs counter-clockwise) had no influence on onset latency of motor evoked potentials
- •Standardized coil positioning on the forehead is essential for consistent transcranial magnetic stimulation measurements in horses