Immunohistochemical and histomorphometric study of human uvula innervation: a comparative analysis of non-snorers versus apneic snorers

The objective of this study was to verify a possible correlation between the etiology of uvulopalatal ptosis and decrease in palatopharyngeal muscle tone, due to a reduction of the number of nerve fibers in surgical specimens obtained from snoring patients. We have designed a comparative retrospective, case-control, double-blind, immunohistochemical and histomorphometric study of human uvula innervation in 51 apneic snoring patients who underwent uvulopalatopharyngoplasty (UPPP) and 47 normal subjects collected in a 5-year-long period in the Departments of Otolaryngology of Desio and ForlAnot sign Hospital, Italy. Case study was chosen in patients who underwent UPPP, variably associated with other disobstructive surgical procedures for treatment of obstructive sleep apnea syndrome, classified according to current clinical, polysomnographic, endoscopic, and imaging criteria. Control subjects were recruited at the Institute of Legal Medicine, University of Milan, according to strong inclusion and exclusion criteria. The main outcome measure of the study was the number of nerve fibers in the patients' uvula evaluated histologically and repeated two times by two different people, in all the areas of the specimens. Finally, we correlated the area of the histological section with the number of fibers contained therein. The number of nerve fibers varied from a minimum of 58 to a maximum of 163 in normal subjects. In the snoring patient population, the number of nerve fibers varied from a minimum of 22 to a maximum of 126 (statistically significant difference, p < 0.0001). In conclusion, our results direct toward a clear neurogenetic predisposition to uvulopalatal ptosis, marked ab initio by a lower set of motor nerve fibers, which may be the initial stage of another subsequent morphological and functional abnormality.