[Etiology, diagnostic and therapeutic management of taste disorders]

Taste disorders can be subdivided in ageusia, which is the inability to detect any qualitative gustatory sensation and hypogeusia, which is a decreased sensitivity to all tastants. Dysgeusia or pargeusia is a distortion or perversion in the perception of a tastant in contrast to phantosmia, which is a perception of taste that occurs in the absence of a tastant. The site of lesion can usually be determined by history and clinical examination. History taking should always include the assessment of current and former medication. Conditions that interfere with access of a tastant to the taste bud are differentiated from conditions that either injure the receptor cell or damage the gustatory afferent nerves and the central pathways. Psychophysical taste evaluation includes identification of quality using sprays or taste strips and testing of intensity perception measuring threshold using the 3-drop technique. Moreover, measurement of taste in localized areas can be performed either with conventional chemicals or using an electrogustometer. Gustatory evoked potentials are not yet routinely elicited. Therapy has to be planned according to the cause of the disorder.