The olfactory system and its disorders.

The sense of smell is greatly underappreciated, despite the fact that it monitors the intake of airborne agents into the human respiratory system and determines to a large degree the flavor and palatability of foods and beverages. In addition to enhancing quality of life, this primary sensory system warns of spoiled foods, leaking natural gas, polluted air and smoke, and mediates basic elements of communication (e.g.

Olfaction in Parkinson's disease.

It has become increasingly apparent that Parkinson's disease (PD) can no longer be considered purely a motor disease, as numerous sensory alterations accompany this disorder either before or early in its clinical progression. Most notable among such disturbances are decrements in smell function. Such anomalies have been documented in approximately 90% of patients with early-stage sporadic PD and appear to progress little, if at all, with the development of the more classic PD-related motor symptoms.

Estrogen replacement therapy induces functional asymmetry on an odor memory/discrimination test.

The secondary afferents of the olfactory system largely project to the ipsilateral cortex without synapsing in the thalamus, making unilateral olfactory testing a useful probe of ipsilateral hemispheric activity. In light of evidence that lateralized performance on some perceptual tasks may be influenced by estrogen, we assessed left:right nostril differences in two measures of olfactory function in 14 post-menopausal women receiving estrogen replacement therapy (ERT) and 48 post-menopausal women receiving no such therapy. Relative to women not taking ERT, those receiving ERT exhibited better performance in the left nostril and poorer performance in the right nostril on an odor memory/discrimination test.

Drug-induced taste disorders.

Numerous drugs have the potential to adversely influence a patient's sense of taste, either by decreasing function or producing perceptual distortions or phantom tastes. In some cases, such adverse effects are long lasting and cannot be quickly reversed by drug cessation. In a number of cases, taste-related adverse effects significantly alter the patient's quality of life, dietary choices, emotional state and compliance with medication regimens.

The olfactory vector hypothesis of neurodegenerative disease: is it viable?

Environmental agents, including viruses, prions, and toxins, have been implicated in the cause of a number of neurodegenerative diseases, most notably Alzheimer's and Parkinson's diseases. The presence of smell loss and the pathological involvement of the olfactory pathways in the formative stages of Alzheimer's and Parkinson's diseases, together with evidence that xenobiotics, some epidemiologically linked to these diseases, can readily enter the brain via the olfactory mucosa, have led to the hypothesis that Alzheimer's and Parkinson's diseases may be caused or catalyzed by agents that enter the brain via this route. Evidence for and against this concept, the "olfactory vector hypothesis," is addressed in this review.

Accuracy of self-report in detecting taste dysfunction.

Objective: To determine the sensitivity, specificity, and positive and negative predictive value of responses to the following questionnaire statements in detecting taste loss: "I can detect salt in chips, pretzels, or salted nuts," "I can detect sourness in vinegar, pickles, or lemon," "I can detect sweetness in soda, cookies, or ice cream," and "I can detect bitterness, in coffee, beer, or tonic water." Responses to an additional item, "I can detect chocolate in cocoa, cake or candy," was examined to determine whether patients clearly differentiate between taste loss and flavor loss secondary to olfactory dysfunction.

Methods: A total of 469 patients (207 men, mean age = 54 years, standard deviation = 15 years; and 262 women, mean age = 54 years, standard deviation = 14 years) were administered a questionnaire containing these questions with the response categories of "easily," "somewhat," and "not at all," followed by a comprehensive taste and smell test battery.

Predictors of prognosis in patients with olfactory disturbance.

Objective: Although olfaction is often compromised by such factors as head trauma, viruses, and toxic agents, the olfactory epithelium and sectors of the olfactory bulb have the potential for regeneration. This study assessed the degree to which olfactory function changes over time in patients presenting to a university-based smell and taste center with complaints of olfactory dysfunction and the influences of etiology (eg, head trauma, upper respiratory infection), sex, age, smoking behavior, degree of initial dysfunction, and other factors on such change.

Methods: Well-validated odor identification tests were administered to 542 patients on 2 occasions separated from one another by 3 months to 24 years.

Office procedures for quantitative assessment of olfactory function.

Background: Despite the importance of the sense of smell for establishing the flavor of foods and beverages, as well as protecting against environmental dangers, this primary sensory system is commonly ignored by the rhinologist.

Methods: In this article basic issues related to practical measurement of olfactory function in the clinic are described and examples of the application of the two most common paradigms for such measurement--odor identification and detection--are presented. A listing is made of the 27 olfactory tests currently used clinically, along with their strengths and weaknesses.

San Francisco/Oakland Bay Bridge Welder Study: olfactory function.

Background: The sense of smell can be damaged by airborne xenobiotics, including aerosolized heavy metals, reflecting the direct exposure of its receptors to the outside environment.

Objectives: To determine whether professional welders working in confined spaces exhibit olfactory dysfunction. To determine whether such dysfunction, if present, is related to indices of metal exposure associated with welding, as well as measures of neurologic and neuropsychological function.

Sniff magnitude test: relationship to odor identification, detection, and memory tests in a clinic population.

Recently a novel measure of olfactory function, the Sniff Magnitude Test (SMT), was developed that relies on changes in inhalation in response to an odor. The relationship of this unique test to that of other olfactory tests has received little investigation. In this study, we assessed, in 132 patients presenting to a chemosensory disorders clinic, the relationship of SMT scores to those from 3 standardized psychophysical tests: the University of Pennsylvania Smell Identification Test (UPSIT), a phenyl ethyl alcohol odor detection threshold test, and a short-term odor memory/discrimination test.

Antifreeze ingestion by dogs and rats: influence of stimulus concentration.

Ingestive responses of 50 rats and 4 gastric-cannulated dogs to ethylene glycol-based antifreeze (AF) were found to be inversely related to concentration. The antifreeze was never preferred to water. Do thirsty animals that encounter weak AF solutions drink them solely for their water content, water-related oral tactile sensations, or both, being inadvertently poisoned in the process?

Olfactory dysfunction in leprosy.

Leprosy (Hansen's disease) is associated with a high incidence of nasal pathology. Despite this fact, the influence of this disorder on the sense of smell is poorly understood. In this study, we administered a standardized 12-item odor identification test to 77 patients with three types of leprosy: tuberculoid (n = 9), borderline (n = 42), and lepromatous (n = 26).

Olfactory dysfunction and its measurement in the clinic and workplace.

Objectives: To provide an overview of practical means for quantitatively assessing the sense of smell in both the clinic and workplace. To address basic measurement issues, including those of test sensitivity, specificity, and reliability. To describe and discuss factors that influence olfactory function, including airborne toxins commonly found in industrial settings.

Utility of a three-item smell identification test in detecting olfactory dysfunction.

Objective: Physicians rarely assess smell function, largely because of time considerations. Therefore, there is clinical need for very brief cranial nerve I screening tests. Although a few such tests exist, none have been adequately validated.

Objective assessment of terbinafine-induced taste loss.

Objectives: Terbinafine (Lamisil), a widely prescribed oral antifungal agent, reportedly induces taste loss in 0.6% to 2.8% of those taking the drug.

Episodic odor memory: influences of handedness, sex, and side of nose.

It is not known whether, or to what degree, odor memory is influenced by lateralized brain processes. In this study, we administered a 12-item match-to-sample odor memory test separately to the left and right sides of the nose of 30 left- and 30 right-handed subjects of equivalent age, sex distribution, and overall general smell ability. For each test item, one of three delay intervals (10-, 30-, and 60-s) was interspersed between smelling the target stimulus and smelling the first of four response alternatives.

Effects of drugs on olfaction and taste.

The fact that so many varied medications reportedly affect taste and smell is a testament to the complexity of the gustatory and olfactory systems. The reception, transduction, propagation, and perception of a chemical tastant or odorant requires the effective operation of numerous mechanisms--all of which may be susceptible in one way or another to a prescribed medication. Just as a diuretic may block the apical ion channels on a taste bud, or an antifungal can inhibit cytochrome p450-dependent enzymes at the level of the receptors, a chemotherapeutic agent can destroy mitosis in a replicating receptor cell and a steroid can lead to candidal overgrowth on the tongue surface.

Posttonsillectomy taste distortion: a significant complication.

Objective/hypothesis: Tonsillectomy is among the most commonly performed procedures. As with any surgery, head and neck surgeons must be aware of possible complications and their potential affects. At our smell and taste center, we have been referred several patients in a 6-month period with the complaint of taste distortion after tonsillectomy.

Marijuana odor perception: studies modeled from probable cause cases.

The 4th Amendment of the United States Constitution protects American citizens against unreasonable search and seizure without probable cause. Although law enforcement officials routinely rely solely on the sense of smell to justify probable cause when entering vehicles and dwellings to search for illicit drugs, the accuracy of their perception in this regard has rarely been questioned and, to our knowledge, never tested. In this paper, we present data from two empirical studies based upon actual legal cases in which the odor of marijuana was used as probable cause for search.

Effects of stimulation duration on electrogustometric thresholds.

The ability to detect low electrical currents presented to the lingual surface is widely used to assess taste function in humans. Despite this fact, the influence of stimulus duration on electrical taste thresholds is not well established. In this study, we evaluated the effects of current duration (0.

Comparison of detection threshold values determined using glass sniff bottles and plastic squeeze bottles.

Olfactory threshold measures are influenced by such factors as odorant species, diluent type, psychophysical paradigm, and stimulus-presentation procedure. In this study, we compared phenyl ethyl alcohol odor-detection thresholds obtained using 120-ml glass sniff bottles to those obtained using 120-ml plastic squeeze bottles. Although these presentation media are commonly employed in published studies, there has never been a formal comparison of values obtained using them.

Olfactory dysfunction occurs in transgenic mice overexpressing human tau protein.

Disorders of olfaction are among the first clinical signs of neurodegenerative diseases such as Alzheimer's disease (AD) and idiopathic Parkinson's disease (PD). In this study, we employed an odor habituation paradigm to evaluate the olfactory function of T alpha 1-3RT transgenic mice that overexpress tau, a key pathogenic protein in AD, and compared such function to that of wild-type controls who do not overexpress this protein. The T alpha 1-3RT mice, but not the controls, exhibited responses indicative of decreased olfactory function.

Olfactory dysfunction in degenerative ataxias.

Several lines of evidence suggest that the cerebellum may play a role in higher-order olfactory processing. In this study, we administered the University of Pennsylvania Smell Identification Test (UPSIT), a standardised test of olfactory function, to patients with ataxias primarily due to cerebellar pathology (spinocerebellar ataxias and related disorders) and to patients with Friedreich ataxia, an ataxia associated mainly with loss of afferent cerebellar pathways. UPSIT scores were slightly lower in both patient groups than in the control subjects, but no differences were noted between the scores of the Friedreich and the other ataxia patients.

Impairment of odor hedonics in men with schizophrenia.

Objective: Olfactory deficits in patients with schizophrenia, including those of odor identification, detection threshold sensitivity, discrimination, and memory, have been well described. Deficits in emotional perception, processing, and experience have also been reported, with anhedonia being one of the core features. While anatomical connections testify to the relationship between olfaction and emotion, there has been little investigation of the hedonic properties of odors in schizophrenia.

Influences of antihypertensive and antihyperlipidemic drugs on the senses of taste and smell: a review.

According to the Physicians' Desk Reference (PDR), 36% of modern antihypertensive and antihyperlipidemic drugs produce untoward alterations in chemosensory perception. Such disturbances can adversely affect the quality of life, produce non-compliance to medication schedules, and may result in decreased food intake, loss of appetite, weight decrement, and depression. This review lists the primary antihypertensive and antihyperlipidemic drugs that adversely alter chemosensory function, provides information on better defining the nature of the dysfunction, outlines testing strategies and available tests that could be used to better define the prevalence of the dysfunction, and summarizes means for mitigating such alterations.