Olfactory sensations produced by high-energy photon irradiation of the olfactory receptor mucosa in humans

During irradiation of volumes that incorporate the olfactory system, a proportion of patients have complained of a pungent smell. A retrospective study was carried out to determine the prevalence of this side-effect. A questionnaire was sent to 40 patients whose treatment volumes included the olfactory region and also to a control group treated away from this region. The irradiated tumor volumes included the frontal lobe, whole brain, nasopharynx, pituitary fossa, and maxillary antrum. Of the 25 patients who replied, 60% experienced odorous symptoms during irradiation. They described the odor as unpleasant and consistent with ozone. Stimulation of olfactory receptors is considered to be caused by the radiochemical formation of ozone and free radicals in the mucus overlying the olfactory mucosa.