[Unilateral paralysis of the vocal fold: correlation between laryngoscopy and electromyography]

From a clinical point of view, unilateral vocal fold paresis means that one of the vocal folds shows reduced mobility. Etiology may be mechanical or supranuclear, but in most cases it is a partial peripheral neurogenic lesion in the muscles innervated by one of the recurrent laryngeal nerves. On the one hand, a retrospective analysis was made of 71 cases with laryngoscopically reduced mobility of one vocal fold: 58 patients had electromyographic signs of partial denervation; 13 had normal electromyographic activity. Possible explanations are mechanical factors, paradoxical reinnervation, or central neurological pathology. On the other hand we reviewed 179 cases with an electromyographic diagnosis of unilateral partial peripheral neurogenic lesion in the muscles innervated by one of the recurrent laryngeal nerves: 119 patients showed a clinically immobile vocal fold, 2 a normally moving vocal fold and 58 a paretic vocal fold. A lot of immobile vocal folds are thus partial denervations. Insufficient amount of functional motor units and paradoxical reinnervation provide possible explanations.