Clinical research on rehabilitation of olfaction

Analyzing the observed movements of the ’facial muscles’, we came to the conclusion that some movements actually result in a nasal airflow, which allows the odor molecules to reach the olfactory epithelium again. Refining these observed movements led to the conception of a nasal airflow inducing maneuver (NAIM) or so-called ’polite yawning’ technique [8]. This technique induces, basically, a rapid increase in volume of the oral cavity, while keeping the lips closed airtight. The potential vacuum, prompted by the ‘expansion’ of the oral cavity, has to be filled and the result is an airflow through the nasal cavity (see top animation). By repeating this maneuver rapidly, a ‘pumping’ effect is created and a sufficient airflow through the nose is established in order to be able to smell again.

This airflow can be visualized by means of a water manometer (see middle figures and video clips), which gives the patient (and the speech pathologist) an immediate visual feedback about the effectiveness of this maneuver.

The effectiveness of the NAIM was established in an intervention study and subsequently confirmed in a follow-up study [8, 9]. Approximately half of the patients were able to smell again after one half-hour training session. Also the 25 percent of the patients in this series, who were already able to smell with a personal technique, indicated an improvement: after the instruction by the speech pathologist, they were much better able to provoke a nasal airflow and could much better smell ‘at will’.

Traditional odor testing methods are time consuming and somewhat difficult for laryngectomized individuals, especially prior to the instruction of the NAIM. [2, 8] This testing appears to be somewhat easier when using the Zürcher Geruchstest, recently described by Simmen et al.[10]. The Zürcher Geruchstest contains 8 different odors with a multiple choice illustrated form (3 suggestions per odor). Olfaction is considered to be normal in case the patient identifies 7 or 8 of the odors correctly. Otherwise, the patient is considered to be anosmic or hyposmic. For initial testing of the olfactory acuity and assessing the results of the rehabilitation program, this is a quick (5 minutes) and easy method for patients to apply [9].