Electromyographic investigation of human vocal cord paralysis

Vocal cord paralysis following carotid endarterectomy: the paradox of return of function

In a series of 411 consecutive carotid endarterectomies 29 patients were identified with vocal cord paralysis. All patients were symptomatic, although in many these symptoms were subtle and rapidly resolved. There was a statistically significant predominance of left-sided paralysis. Excluding three patients who died during the initial year of follow-up return of normal voice was noted in 22 patients, but complete return of vocal cord function was present in only 15. Apposition of the contralateral vocal cord against a paralyzed vocal cord allowed for production of normal voice in five patients. Less than 1% of patients remained with symptoms at one year following endarterectomy. We conclude that vocal cord paralysis is a common complication of carotid endarterectomy; the voice becomes an unreliable guide as to its resolution. We recommend laryngoscopic examination of all patients who undergo bilateral carotid endarterectomy.

Laryngeal synkinesis: its significance to the laryngologist

Basic research and surgical cases have shown that the injured recurrent laryngeal nerve (RLN) may regenerate axons to the larynx that inappropriately innervate both vocal cord adductors and abductors. Innervation of vocal cord adductor muscles by those axons that depolarize during inspiration is particularly devastating to laryngeal function, since it produces medial vocal cord movement during inspiration. Many patients thought to have clinical bilateral vocal cord paralysis can be found to have synkinesis on at least one side. This will make the glottic airway smaller, particularly during inspiration, than would true paralysis of all the intrinsic laryngeal muscles. Patients with bilateral vocal cord paralysis should undergo laryngeal electromyography. If inspiratory innervation of the adductor muscles is present, simple reinnervation of the posterior cricoarytenoid muscle will fail. The adductor muscles also must be denervated by transection of the adductor division of the regenerated RLN.

Treatment of spasmodic dysphonia by means of resection of the recurrent laryngeal nerve

Over the last twelve years 44 patients suffering from spasmodic dysphonia have been seen at Huddinge hospital. There were 34 women and 10 men. 22 of these patients were for various reasons not regarded as candidates for surgery. The opposite applied to the remaining 22 patients. The outcome of a temporary nerve block guided us (the surgeons and the patients) whether to operate or not. 12 patients were thus operated upon by means of resection of the right recurrent laryngeal nerve. The immediate post-operative result was excellent in 11 of 12 patients but the voice deteriorated in 4 patients. They had revision surgery with a successful result in 3 of them. Also the other 7 patients deteriorated to some extent but not to the degree that revision surgery was necessary. It is our hypothesis that recurrencies are caused by reinnervation of the sectioned nerve.

Reinnervation of skeletal muscle with a neuromuscular pedicle

In the past decade the otolaryngologist has become interested in the problem of muscle reinnervation as it relates to laryngeal and facial paralysis. Although reinnervation by neuromuscular pedicle transfer has shown promising results in the laboratory and clinic, some investigators have had difficulty in achieving reliable results with this procedure. To further assess the technique's validity, we investigated the neuromuscular pedicle. This study utilized a strap muscle neuromuscular pedicle transfer to a contralateral strap muscle in the rabbit. The results were analyzed by the use of a number of independent measures, including electrical stimulation of the nerve, muscle contractibility, electromyography, enzyme histochemistry, reduced-silver staining for normal fibers, and the retrograde transport of the enzyme marker horseradish peroxidase. The physiologic and anatomic results demonstrated that morphologic and functional reinnervation of the experimentally isolated muscle by the transferred neuromuscular pedicle occurred. The most convincing data were produced by gross electrical stimulation, twitch and tetanic contraction, and horseradish peroxidase labeling. Electromyographic activity and other histologic findings supported the above conclusions.

Selective reinnervation of vocal cord adductors in unilateral vocal cord paralysis

Laryngeal reinnervation procedures were performed in a series of dogs. An attempt was made to reinnervate the vocal cord adductors with one nerve graft, while a different nerve was grafted to the abductors. The recurrent laryngeal nerve was dissected distally to its terminal branches, where the abductor-adductor sorting out occurs. The abductor branch was reinnervated with a phrenic nerve graft as previously described. The adductor division was grafted with one of the following nerves: proximal recurrent laryngeal, external branch of superior laryngeal, or ansa hypoglossi. Results revealed that in most cases it was indeed possible to reinnervate the adductive and abductive vocal cord muscles separately. Recurrent laryngeal nerve anastomosis to the distal adductor division produced strong reinnervation, but appeared to inhibit in some way the phrenic reinnervation of the abductor branch. Ansa hypoglossi anastomosis to the adductor division seemed to induce satisfactory reinnervation of the adductor musculature with the least noticeable donor deficit.