Functional electrical stimulation of the left recurrent laryngeal nerve using a vagus nerve stimulator in a normal horse.

This research demonstrates the successful use of a <a href="/equine-cranial-nerve-anatomy/" title="<a href="/equine-cranial-nerve-anatomy/" title="<a href="/equine-cranial-nerve-anatomy/" title="Cranial Nerves in Horses: Role in Sight, Hearing, Chewing & Balance”>Cranial Nerves in Horses: Role in Sight, Hearing, Chewing & Balance”>Cranial Nerves in Horses: Role in Sight, Hearing, Chewing & Balance”>vagus nerve stimulator (VNS) to stimulate the recurrent laryngeal nerve in a horse, resulting in controlled movement of the arytenoid, structures specific to the horse’s voice box.

Background

• The recurrent laryngeal nerve is a branch of the vagus nerve responsible for innervating certain muscles of the horse’s larynx or voice box.
• Issues with this nerve, such as paralysis, can cause equine laryngeal hemiplegia, a condition resulting in partial or complete paralysis of the larynx.
• The use of implantable vagus nerve stimulators (VNS) can often provide a means for direct stimulation of the recurrent laryngeal nerve, potentially mitigating the effects of conditions such as laryngeal hemiplegia.

Procedure

• In this study, a VNS electrode was surgically placed around the left recurrent laryngeal nerve at the cervical (neck) level in the horse and connected to a pulse generator.
• The purpose was to stimulate the nerve in a controlled manner, leading to targeted movements of the arytenoid, which are flaps in the larynx.
• The researchers monitored the displacement or movement of the arytenoid endoscopically, meaning they used an endoscope, a flexible tube with a light and camera attached to it. This was done without sedation and while the horse was standing.

Results and Conclusion

• The results revealed a complete and sustained abduction, or movement, of the arytenoid was achieved using a stimulation frequency of 25 Hz, an intensity of 1 mA, and a pulse width of 250 μs.
• This study suggests that functional electrical stimulation of the recurrent laryngeal nerve using a vagus nerve stimulator could be a feasible and effective therapeutic approach for the management of conditions such as equine laryngeal hemiplegia.