Chemosensory interaction: acquired olfactory impairment is associated with decreased taste function

Olfaction, taste and trigeminal function are three distinct modalities. However, in daily life they are often activated concomitantly. In health and disease, it has been shown that in two of these senses, the trigeminal and olfactory senses, modification of one sense leads to changes in the other sense and vice versa. The objective of the study was to investigate whether and (if so) how, the third modality, taste, is influenced by olfactory impairment. We tested 210 subjects with normal (n=107) or impaired (n=103) olfactory function for their taste identification capacities. Validated tests were used for olfactory and gustatory testing (Sniffin' Sticks, Taste Strips). In an additional experiment, healthy volunteers underwent reversible olfactory cleft obstruction to investigate short-time changes of gustatory function after olfactory alteration. Mean gustatory identification (taste strip score) for the subjects with impaired olfaction was 19.4±0.6 points and 22.9±0.5 points for those with normal olfactory function (t=4.6, p<0.001). The frequencies of both, smell and taste impairments interacted significantly (Chi2, F=16.4, p<0.001), and olfactory and gustatory function correlated (r 210=0.30, p<0.001). Neither age nor olfactory impairment cause effects interfered with this olfactory-gustatory interaction. In contrast, after short-lasting induced olfactory decrease, gustatory function remained unchanged. The present study suggests that longstanding impaired olfactory function is associated with decreased gustatory function. These findings seem to extend previously described mutual chemosensory interactions also to smell and taste. It further raises the question whether chemical senses in general decrease mutually after acquired damag

Clinical aspects of olfaction

The most important aims of this thesis were: (1) to investigate the prevalence of olfactory dysfunction in an adult Swedish population and to relate dysfunction to factors of possible impact on olfaction, (2) to present our experience with patients seeking medical attention for olfactory disorders, (3) to describe the relationship between detection and identification tests for olfactory disorders, (4) to assess olfactory event-related potentials (OERPs) in patients with olfactory impairment and in healthy controls, thereby exploring possibilities and limitations regarding to the clinical utility of the method, and (5) to evaluate the effect on the sense of smell of radiation in patients treated for head and neck cancer. Materials and methods: In the population-based study, 1900 adult subjects were drawn from the municipal register (I). Of these, 1387 were tested for olfactory impairment and questioned with regard to their sense of smell and relevant medical conditions. Three hundred and three patients seeking medical care for olfactory disturbances were clinically examined and tested with detection and identification tests: 102 of these patients also answered a questionnaire with regard to quality of life (II). OERPs were obtained after stimulation with an olfactometer in 23 patients and 24 healthy controls (III). The effect of radiation on the olfactory organ was investigated in 71 patients with head and neck tumors, before and after radiotherapy (IV). Results: The overall prevalence of olfactory dysfunction in adults was 19.1%, with 13.3% suffering hyposmia and 5.8% anosmia (I). Olfactory dysfunction (hyposmia and anosmia), was related to high age, male gender, and nasal polyps. Prevalence of anosmia in particular was found to be related to high age, nasal polyps, and diabetes mellitus. In neither case was there a relation to smoking (I). Upper respiratory tract infection was the most likely cause of olfactory disorder in close to 30% of the cases, followed by nasal polyposis, head trauma, and aging. However, the suggested etiology was not possible to determine in one third of the cases. Clinically, a strong relationship was found between the detection and identification tests (II). Patients with olfactory disorders have reduced quality of life relating to paid employment, household work, and social and family life (II). The OERPs in patients showed reduced amplitude and longer latencies compared to controls. Increasing concentration of the stimulant odor increased the OERPs (III). Patients who were exposed to a high dose of radiation against the olfactory organ showed reduced olfactory capability compared to those exposed to a low dose (IV). Conclusions: Olfactory dysfunction is common in society. Patients seeking medical attention for olfactory disorders should be investigated for both quantitative and qualitative disorders with reliable tests because impaired olfactory function is associated with a reduced quality of life. Patients who will be treated with radiation for tumors near the olfactory region should be informed of the risk of olfactory deterioration. Key words: olfactory disorders, epidemiology, quality of life, diagnosis, event-related potentials, radiation therapy

"Taste Strips" - a rapid, lateralized, gustatory bedside identification test based on impregnated filter papers

OBJECTIVE: To elaborate normative values for a clinical psychophysical taste test ("Taste Strips"). BACKGROUND: The "Taste Strips" are a psychophysical chemical taste test. So far, no definitive normative data had been published and only a fairly small sample size has been investigated. In light of this shortcoming for this easy, reliable and quick taste testing device, we attempted to provide normative values suitable for the clinical use. SETTING: Normative value acquisition study, multicenter study. METHODS: The investigation involved 537 participants reporting a normal sense of smell and taste (318 female, 219 male, mean age 44 years, age range 18-87 years). The taste test was based on spoon-shaped filter paper strips ("Taste Strips") impregnated with the four (sweet, sour, salty, and bitter) taste qualities in four different concentrations. The strips were placed on the left or right side of the anterior third of the extended tongue, resulting in a total of 32 trials. With their tongue still extended, patients had to identify the taste from a list of four descriptors, i. e., sweet, sour, salty, and bitter (multiple forced-choice). To obtain an impression of overall gustatory function, the number of correctly identified tastes was summed up for a "taste score". RESULTS: Taste function decreased significantly with age. Women exhibited significantly higher taste scores than men which was true for all age groups. The taste score at the 10(th) percentile was selected as a cut-off value to distinguish normogeusia from hypogeusia. Results from a small series of patients with ageusia confirmed the clinical usefulness of the proposed normative values. CONCLUSION: The present data provide normative values for the "Taste Strips" based on over 500 subjects tested