Motor Innervation of the Human Cricopharyngeus Muscle

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Abstract
Innervation of the human cricopharyngeus muscle remains historically controversial and unclear, encouraging numerous treatments inconsistently designed to pharmacologically or mechanically alter the contractile state of this muscle. Neuroanatomic controversy results from and is perpetuated by 1) use of nonhuman models, 2) observational misinterpretation of small-diameter, overlapping nerve fibers, and, most importantly, 3) lack of real-time verification of neural projections. We sought to overcome these difficulties by performing microdissections in 27 patients undergoing laryngectomy and using real-time electromyographic verification. We demonstrated 1) dual ipsilateral innervation by the pharyngeal plexus and recurrent laryngeal nerve, 2) segmental projection of the recurrent laryngeal nerve to anterior motor units, 3) pharyngeal plexus projection to posterior motor units, 4) absence of a sympathetic or external superior laryngeal nerve contribution, and 5) absence of contralateral innervation. Suchdual ipsilateral innervation, segmentally projected, has not been previously described in any other form of neuromuscular organization. Neuroanatomic accuracy should improve diagnostic and therapeutic strategies for future management of pharyngeal dysphagia.