The reason for the presence of the paranasal sinuses has been a controversial subject since the time of Galen, 130–201 A.D. In a review of the literature, the diversity of the numerous functions ascribed to these air-filled cavities was found to be astounding. Many functions were ascribed only on the basis of opinion rather than scientific investigation and recent studies have illustrated the fallacy of these opinions. To date, not one proposed function has been universally accepted to be the essential reason for their existence.

This review of the literature deals mainly with those theories of anatomical and physiological significance of the paranasal sinuses having received the most consideration and many of which are currently considered tenable. These are, as follows: (1) impart resonance to the voice; (2) humidify and warm inspired air; (3) increase the area of the olfactory membrane; (4) absorb shock applied to the head for protection of sensory organs; (5) secrete mucus for keeping the nasal chambers moist; (6) thermally insulate the nervous centers; (7) aid facial growth and architecture; (8) exist as evolutionary remains and/or unwanted air spaces; and (9) lighten the bones of the skull for maintenance of proper balance of the head.