Considerations for pacing of the cricoarytenoid dorsalis muscle by neuroprosthesis in horses.
Authors: Ducharme N G, Cheetham J, Sanders I, Hermanson J W, Hackett R P, Soderholm L V, Mitchell L M
Journal: Equine veterinary journal
Summary
# Editorial Summary: Functional Electrical Stimulation for Equine Laryngeal Neuropathy Recurrent laryngeal neuropathy (RLN) remains a significant clinical problem in horses, with conventional prosthetic laryngoplasty offering limited success and nerve-muscle pedicle transplantation requiring extended recovery periods. Ducharme and colleagues investigated whether electrical stimulation of the recurrent laryngeal nerve could achieve reliable arytenoid cartilage abduction in seven mature horses, implanting programmable nerve cuff electrodes and delivering stimulation at 24 Hz over a 12-month study period. Excellent abduction was attained in five horses, with mean arytenoid angles of 52.7 degrees maintained for periods up to one year, though two severely affected (grade IV) animals showed poor response; notably, tissue impedance roughly doubled between one and two months post-implantation before stabilising, and continuous 60-minute stimulation produced no muscular fatigue despite consistent maximal abduction. Technical implant failures limited long-term success in six horses, yet the proof-of-concept remains compelling—optimal stimulation intensities ranged from 0.65–7.2 mA, marginally higher than those required in humans and dogs. For equine practitioners managing RLN cases, neuroprosthetic stimulation represents a promising future alternative to conventional approaches, though device reliability and refinement will be critical before clinical application becomes viable.
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Practical Takeaways
- •Neuroprosthetic stimulation of the recurrent laryngeal nerve can restore effective airway opening in horses with laryngeal paralysis, offering an alternative to conventional prosthetic laryngoplasty
- •Expect increasing tissue impedance in the first 2 months post-implantation; device programming may need adjustment during this period
- •This approach may be particularly suitable for horses with grades I-III laryngeal dysfunction; results in grade IV cases were poor
Key Findings
- •Functional electrical stimulation of the recurrent laryngeal nerve achieved excellent arytenoid abduction (mean 52.7°) in 6 of 7 horses with laryngeal grades I-III
- •Tissue impedance doubled from 1.06 kOhm at one week to 2.32 kOhm at 2 months post-implantation, then stabilized
- •Maximal arytenoid abduction was achieved at stimulation amplitudes of 0.65-7.2 mA with no evidence of muscle fatigue during 60 minutes of continuous stimulation
- •Technical implant failures resulted in loss of abduction in 6 horses between one week and 11 months post-operatively