Multiple Sensory Illusions Are Evoked During the Course of Proton Therapy

Abstract Visual illusions from astronauts in space have been reported to be associated with the passage of high energy charged particles through visual structures (retina, optic nerve, brain). This prompted us to investigate whether protons during the course of clinical radiotherapy could also evoke similar perceptions and whether other sensory systems were similarly affected. A retrospective review of proton radiotherapy patient records at Loma Linda University identified 29 reports from 19 patients who spontaneously reported visual, olfactory, auditory and gustatory illusions during treatment. Our results suggest that small numbers of protons can evoke neuronal responses on a 0.1 second time scale sufficient to elicit conscious sensory illusion experiences analogous to those from normal sensory inputs. The regions of the brain receiving the highest doses corresponded with the anatomical structures associated with each type of illusion. Our findings suggest that more detailed queries about sensory illusions during proton therapy are warranted, possibly integrated with quantitative effect descriptions (such as electroencephalography) and can provide additional physiological basis for understanding the effects of protons on central nervous system tissues, needed for radiation risk assessment in advance of deep space human exploration.