Assessment of Olfactory Function

Rombaux, Philippe [UCL] Huart, Caroline [UCL] Collet, Stéphanie [Mont-Godinne]

Evaluation of olfactory function in humans remained poorly explored for a long time. This was mostly due to the difficulty of producing selective and controlled olfactory stimuli. Recently, the development of reliable techniques to investigate olfactory system has led to an increasing interest on the research on this field. Opposite to what has been assumed for many years, our chemosensory systems were shown to be an essential factor in terms of our behavior and well-being. In the last years, several authors have reported that olfactory disorders occurs at a much higher frequency than previously assumed; and it has been reported that 20% of the population suffers from olfactory disorders. Hence, the field of research on olfaction is not only on interest for basic scientists but also for clinicians. It is widely assumed that a precise clinical work-up procedure is mandatory in order to assess the olfactory function of patients suffering from smell disorders. Indeed it is essential to (1) accurately assess their olfactory deficit and, hence, provide them appropriate counseling and prognosis, (2) assess recovery from or progression of the olfactory dysfunction, (3) evaluate a therapeutic success. The direct way to monitor olfactory function is self-assessment. Nevertheless, self-assessment is biased by unspecific factors (i.e. nasal airway patency, mood…); and it seems to be uncorrelated to results from olfactory testings. Several methods have been developed and validated to quantify the olfactory function. Today, we dispose of reliable psychophysical testing, electrophysiological testing of chemosensory function, and high performance imaging. This chapter will focus on techniques related to evaluation of olfactory function.