Unusual olfactory perception during radiation sessions for primary brain tumors: a retrospective study

During irradiation sessions for brain tumors or head and neck cancers, some patients experience abnormal olfactory sensations. To date, the frequency of such sensations during these treatment sessions has not been investigated. We analyzed abnormal olfactory sensations in patients who underwent radiation therapy at our institution for primary brain tumors, excluding malignant lymphoma, between January 2009 and January 2018. A total of 191 patients who were awake during radiation treatment and capable of communicating were analyzed in this retrospective medical study. Of these patients, 7 were aware of olfactory sensations during irradiation. The median age of these 7 patients was 13 (range 8-47) years, Six were <20 years of age, accounting for 10% of the total population of similar age (n = 60). However, only 1 of 131 patients aged ≥20 years complained of strange olfactory sensations. Four of seven patients had germ cell tumors, but none had a medulloblastoma. We investigated patients who experienced light sensation, as an internal standard to ascertain the accuracy of this study. Only 10 patients experienced light sensation during their irradiation sessions. This suggests that the frequency of these sensations was possibly underestimated in our study. In conclusion, a considerable number of patients experienced unusual olfactory sensations during radiation treatment. Further prospective studies on abnormal olfactory sensations during irradiation are needed to clarify the underlying mechanism of this sensation.