To the Editor:
I enjoyed reading the letters in the March issue. The one about hominids having stone weapons 2.6 million years ago rang a bell regarding the value of the paranasal sinuses. The paranasal sinuses may provide a buffer against facial trauma. Just think of the many zygomatic fractures resulting from fights that are seen in emergency departments. The sinuses may bubble pack the brain like highway compression barriers. Handheld weapons used for striking would have been a new type of peril, and during this long period new defenses may well have developed. There has to be some value to the paranasal sinuses!
Mary C. Darken, MD
New Orleans, Louisiana
Dr. Altemeier's response:
Dr. Darken presents an interesting hypothesis. A brief literature review found that others have speculated about this same issue. Blanton and Biggs reviewed the significance of the paranasal sinuses and discussed evidence that they "absorb shock applied to the head for protection of sensory organs."1 They review that as a whole, the sinuses form a pyramid with the base anteriorly and the apex deep at the sphenoid. They further comment that this structure seems suited to protect endocranial structures from facial impacts and that the absorption of such energy by sinuses could hinder expansion of a cranial fracture. And a model to test shock absorption by sinuses experimentally has suggested that energy absorption was reduced when sinuses were filled with fluid as opposed to air. The main argument against this as a sinus function has been that sinuses vary in size between animals. Some horned ungulates, such as moose and elk, lack these air spaces, whereas others (goats, sheep, and elephants) have air spaces over the cranial vault that extend into the horns. Because both those with and those without these air spaces endure the shock of butting impact without concussion or obvious damage, this seems to be against a role for the sinuses to distribute or dissipate the stress of impact in ungulates, anyway. But your speculations about sinuses having been selected to protect us from the facial blows of other humans is new and insightful, in my view. Thanks!
1. Blanton PL, Biggs NL. Eighteen hundred years of controversy: the paranasal sinuses. American Journal of Anatomy. 1969;124: 135-148.