Exploring the Mechanism of Phantosmia: Induction of odor phantoms through brain stimulation during radiotherapy
Wed-P2-062
Presented by: Yiling Mai
Aim. Our prospective study aimed to investigate the characteristics of phantosmias induced by RT, to identify factors that influence the occurrence, intensity and hedonic ratings of phantosmia.
Methods. A total of 106 patients (37 women) who underwent an RT in brain, ENT-related, and other body regions were included. Medical history and treatment parameters were collected in a structured medical interview. Olfactory function was measured using the Sniffin’ Stick Odor Identification Test at baseline. Phantosmias and also phosphenes were recorded based on a self-report questionnaire.
Results. There were 37% of the patients experiencing phantosmias, 51% experiencing phosphenes, and 29% simultaneously experiencing both sensations. Phantosmias were typically perceived as a chemical-like, metallic or burnt smell. Younger age (F = 7.81, p < 0.01), radiation in the brain region (χ2 = 14.05, p = 0.02), absence of taste problems (χ2 = 10.28, p = 0.01), and proton RT (χ2 = 10.57, p = 0.01) were related to these abnormal sensations. Phantosmias occurred in 10 out of 17 cases who underwent radiation in the temporal lobe, 22 out of 54 cases in the frontal lobe, 2 out of 7 cases in the occipital lobe, and 9 out of 41 cases in the parietal lobe. History of chemical/dust exposure predicted lower intensity (B = 1.52, p = 0.02) and lower unpleasantness (B = 0.49, p = 0.03) of phantosmia.
Conclusions. Phantosmias and phosphenes are common during RT. The treatment settings and individual arousal level influence the occurrence, intensity and hedonic of phantosmia and phosphene. Phantosmias and phosphenes may involve more central neural than peripheral mechanism, and they could be elicited with activation of areas that are not regarded to be part of the olfactory or visual network.
Keywords phantosmia, phosphene, radiation therapy, proton, photon
Methods. A total of 106 patients (37 women) who underwent an RT in brain, ENT-related, and other body regions were included. Medical history and treatment parameters were collected in a structured medical interview. Olfactory function was measured using the Sniffin’ Stick Odor Identification Test at baseline. Phantosmias and also phosphenes were recorded based on a self-report questionnaire.
Results. There were 37% of the patients experiencing phantosmias, 51% experiencing phosphenes, and 29% simultaneously experiencing both sensations. Phantosmias were typically perceived as a chemical-like, metallic or burnt smell. Younger age (F = 7.81, p < 0.01), radiation in the brain region (χ2 = 14.05, p = 0.02), absence of taste problems (χ2 = 10.28, p = 0.01), and proton RT (χ2 = 10.57, p = 0.01) were related to these abnormal sensations. Phantosmias occurred in 10 out of 17 cases who underwent radiation in the temporal lobe, 22 out of 54 cases in the frontal lobe, 2 out of 7 cases in the occipital lobe, and 9 out of 41 cases in the parietal lobe. History of chemical/dust exposure predicted lower intensity (B = 1.52, p = 0.02) and lower unpleasantness (B = 0.49, p = 0.03) of phantosmia.
Conclusions. Phantosmias and phosphenes are common during RT. The treatment settings and individual arousal level influence the occurrence, intensity and hedonic of phantosmia and phosphene. Phantosmias and phosphenes may involve more central neural than peripheral mechanism, and they could be elicited with activation of areas that are not regarded to be part of the olfactory or visual network.
Keywords phantosmia, phosphene, radiation therapy, proton, photon