Neuroplasticity after olfactory training in post-surgical olfactory impaired patients, using functional magnetic resonance imaging. A randomized pilot study

Abstract Objectives: Treatment for olfactory dysfunction is challenging due to limited therapeutic options. Olfactory training has shown improvement in smell identification, discrimination, and threshold for odor detection. The primary objective is to assess the effect of olfactory training in patients with olfactory dysfunction after pituitary surgery, using functional Magnetic Resonance Imaging (fMRI). Design: This study was designed as a two-arm pilot clinical trial. Setting: Chilean tertiary hospital providing endoscopic pituitary surgery and olfactory evaluation and treatment. Participants: We included two cohorts of subjects: healthy subjects, and patients with post-surgical olfactory dysfunction. Healthy patients were recruited voluntarily at the ENT clinic to assess fMRI testing paradigms and as a control group for the olfactory dysfunction group. Main outcome measures: The main outcome measures were functional activation analysis obtained by fMRI. Olfactory test assessment scores were also obtained during each testing session. Results: 119 patients that underwent an endoscopic transsphenoidal approach were contacted and surveyed for olfactory dysfunction. Twelve patients met inclusion criteria, but six of them declined to participate. Six patients were randomized using computer-generated random numbers. The patients in the trained group showed a significant improvement in the olfactory test results after olfactory training compared to the no-training group (P < 0.05). The group that underwent olfactory training showed more areas of activation after training than in baseline analysis (P < 0.05). Conclusion: Patients that underwent olfactory training showed significant improvement in olfactory testing. fMRI results showed more activated areas in the olfactory training group, which could be compatible with neuroplasticity.