The presence of hypertrophied or chronically infected lymphoid tissue in the nasopharynx has long been recognized as the cause of many ills related to the upper air passages, such as repeated colds, sinusitis, ear infections and deafness.
Since the adenoids form an integral part of the mucous membrane of the nasopharynx, it is usually impossible to remove them completely by surgical operation, and nodules which are left often rapidly hypertrophy, so that within a few months there is recurrence of the original condition. In cases of deafness resulting from obstruction of the eustachian tubes, surgical removal of the adenoids is often unsuccessful in relieving the condition, because often the offending lymphoid tissue is within or close to the orifice of the eustachian tubes and thus is inaccessible for surgical removal. Such tissue, when chronically infected, will cause edema of the surrounding mucous membrane and thus impair the drainage and ventilation
CROWE SJ, WALZL EM. IRRADIATION OF HYPERPLASTIC LYMPHOID TISSUE IN THE NASOPHARYNX. JAMA. 1947;134(2):124-127. doi:10.1001/jama.1947.02880190012004