Anatomy of the tonsillar bed: topographical relationship between the palatine tonsil and the lingual branch of the glossopharyngeal nerve.

Taste disturbance may result from injury to the lingual branch of the glossopharyngeal nerve (LBGN) during tonsillectomy. Because an understanding of the anatomy of this nerve is required in order to avoid injuring it, a gross, histologic anatomic study was undertaken of the topographical relationship between the LBGN and the muscle layer of the palatine tonsillar bed. Evaluation of 107 sides of 83 Japanese adult cadavers (aged 27-88 years) confirmed that the muscular composition and lamination of the tonsillar bed do not change with age or pathological conditions such as inflammation. In about a quarter (23.4%) of cases, the LBGN traveled inferior to the styloglossus muscle and lateral to the superior constrictor pharyngeal muscle over its whole course to the base of the tongue, so that the palatine tonsil was clearly separated from the LBGN. In 55.1% of cases, however, the muscle lining of the tonsillar bed was discontinuous and thin muscle bundles, derived from the stylopharyngeus, palatopharyngeus or superior constrictor pharyngeal muscle, partially covered the tonsillar capsule externally. Moreover, in 21.5% of cases the LBGN was firmly adherent to the tonsillar capsule, due to the complete absence of muscles lining the tonsillar bed. In these cases, and also probably in a similar percentage of patients undergoing tonsillectomy, taste disturbance may occur on removal of the hypertrophic tonsillar capsule. Therefore, minimal disturbance of the tonsillar bed is recommended in all cases of tonsillectomy.