Olfaction in rhinology--methods of assessing the sense of smell.

Olfactory disorders frequently occur in rhinological disease. Different subjective and objective test methods are available to assess the sense of olfaction. Among the subjective methods, screening tests and threshold measurements are commonly used to quantify hyposmia or anosmia. Qualitative methods are available using discrimination and identification tests. Objective methods are used in research and in some medicolegal situations. Objective tests include olfactory evoked potentials, functional Magnetic Resonance Imaging and functional Positron Emission Tomography. The measurement of the sense of smell helps to assess the whole spectrum of the effects of nasal disease. This is especially important before rhinological surgery, because a non-detected smell disorder in patients with rhinological disease is common. The assessment of a pre-existing hyposmia or anosmia helps to avoid a postoperative claim that this was caused by surgery. A variety of validated screening tests for olfaction is available and they are a useful tool to document whether a patient is able to smell.