Examination of the sense of smell

Olfactory disorders are common. Functional anosmia is present in about 5-6% of the general population, while from the age of about 55 years the olfactory sense is restricted in about 25% of cases. A precise examination is necessary to describe the patients symptoms and ascertain possible reasons for them. As far as diagnosis and possible treatment of olfactory or gustatory disorders are concerned, the main advantage allowing progress is the availability of standardised methods of testing the chemical senses. In this article procedures for orthonasal and retronasal psychophysical examination of the olfactory sense and the derivation of potentials evoked by olfactory stimuli are described. In addition, possible ways of examining the intranasal sensitivity of the trigeminal nerve and measuring the volume of the olfactory bulb, and also for immunochemical investigation of biopsies from the olfactory region, are discussed as possible means of reaching a diagnosis.