Substitution of human olfaction by the trigeminal system.

Smell loss is a sensory impairment that has major consequences in many areas of daily life and for which current therapies are insufficient. A prosthesis-type technology enabling patients to sample their olfactory environment has not yet been developed. The aim of our study was, therefore, to test whether stimulation of the intranasal trigeminal system by a device combining an artificial nose with an intranasal electrical stimulator will enable patients to detect and discriminate odorant molecules. Four experiments involving normosmic individuals (n = 13) and patients with olfactory loss (n = 52) showed that individuals were able to detect their olfactory environment using the device. For discrimination, the results are less clear-cut but show that most patients can distinguish between two external stimuli. Although this substitution approach does not allow patients to smell real odors, it is a genuine first substitution solution that we could imagine offering to patients in the future.