Morphology of the Cricopharyngeal Muscle in Zenker and Control Specimens

Abstract

The cricopharyngeal muscle (CPM) is essential for normal deglutition. Pharyngeal dysphagia commonly results from impaired or uncoordinated CPM dilation. Dysfunction of the CPM has also been implicated in the genesis of Zenker's (pharyngoesophageal) diverticulum. Despite the CPM's significance, little is understood about its morphology. We studied CPM biopsy specimens from 20 patients with Zenker's diverticulum and from 5 fresh cadaver patients with detailed histologic techniques to include fiber size and shape and adenosine triphosphatase, reduced nicotinamide adenine dinucleotide, trichrome, succinate dehydrogenase, cytochrome C oxidase, periodic acid-Schiff reaction, oil red O, acid phosphatase, Congo red, crystal violet, and monoadenylate deaminase stains. The normal CPM has unique morphological characteristics, with some myofibers having staining properties that are a hybrid between striated muscle and muscle spindle. The variable orientation of the muscle fibers is also different from that of most other striated musculature. Of the 20 Zenker CPM specimens, 4 specimens did not reveal any significant differences from controls (2 of which had insufficient amounts of tissue for complete analysis). In the remaining 16 specimens, several abnormalities existed, including excessive size variation (16/16), grouping of atrophic fibers (9/16), target or targetoid formations (4/16), cores (2/16), and ragged red fibers (2/16). The final pathological pattern of the 16 specimens was neurogenic in 7, myopathic in 4, and mixed (with neurogenic predominance) in the remaining 5. Two specimens contained significant lymphocytic inflammatory infiltrates. We conclude that the unique neuromuscular function of the CPM in deglutition is likely due to its fiber orientation and the hybrid nature of some of the myofibers. Morphological disturbances of the CPM impair its dilation and may account for the development of Zenker's diverticulum. This disturbance is most often due to progressive denervation of the CPM.

Myosin Heavy Chain Composition and Fiber Size of the Cricopharyngeus Muscle in Patients with Achalasia and Normal Subjects

“…The type I predominance in the CA patients in this study is consistent with other studies of the normal CPM. 7,12 Fiber size, a significant determinant of muscle fiber strength, may also be altered in the diseased state. In this investigation, the dominant type I fibers were not significantly different between the CA patients and normal controls.…”

Botulinum Toxin Injection for the Treatment of Upper Esophageal Sphincter Dysfunction

“…and were classified as showing predominantly neurogenic, myopathic, or mixed neurogenic and myopathic changes in accordance with previously detailed criteria. 9,28 …”

“…8 Few studies have evaluated the muscle fiber subtype histology of the CP muscle, but it appears to have a unique ade nosine triphosphatase staining pattern indicating the highly oxidative nature of the tissue. This feature is more characteristic of fetal musculature than of adult striated muscle 9 and allows maintenance of basal tonicity, with occlusion of the esophageal lumen at rest and relaxation during swallowing to allow passage of the food bolus. 8 Dysphagia can result from failed relaxation or hypertrophy of the CP muscle and/or altered coordination between pharyngeal peristalsis and opening of the UES.…”

The anatomy and physiology of normal and abnormal swallowing in oropharyngeal dysphagia

“…A pharyngeal diverticulum is a herniation of tissue between two muscles which form the inferior pharyngeal constrictors . These are the thyropharyngeus and cricopharyngeus muscles . The herniation occurs at a point of weakness between the two muscles caused Killian's Dehiscence.…”