Chapter 030. Disorders of Smell, Taste, and Hearing (Part 3)

Approach to the Patient: Disorders of the Sense of Smell Unilateral anosmia is rarely a complaint and is only recognized by testing of smell in each nasal cavity separately. Bilateral anosmia, on the other hand, brings patients to medical attention. Anosmic patients usually complain of a loss of the sense of taste even though their taste thresholds may be within normal limits. In actuality, they are complaining of a loss of flavor detection, which is mainly an olfactory function. The physical examination should include a thorough inspection of the ears, upper respiratory tract, and head and neck. A neurologic...
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Chapter 030. Disorders of Smell, Taste, and Hearing (Part 3) Chapter 030. Disorders of Smell, Taste, and Hearing (Part 3) Approach to the Patient: Disorders of the Sense of Smell Unilateral anosmia is rarely a complaint and is only recognized by testingof smell in each nasal cavity separately. Bilateral anosmia, on the other hand,brings patients to medical attention. Anosmic patients usually complain of a lossof the sense of taste even though their taste thresholds may be within normallimits. In actuality, they are complaining of a loss of flavor detection, which ismainly an olfactory function. The physical examination should include a thoroughinspection of the ears, upper respiratory tract, and head and neck. A neurologicexamination emphasizing the cranial nerves and cerebellar and sensorimotorfunction is essential. Any signs of depression should be noted. Sensory olfactory function can be assessed by several methods. The OdorStix test uses a commercially available odor-producing magic marker–like penheld approximately 8–15 cm (3–6 in.) from the patients nose. The 30-cm alcoholtest uses a freshly opened isopropyl alcohol packet held ~30 cm (12 in.) from thepatients nose. There is a commercially available scratch-and-sniff card containingthree odors available for gross testing of olfaction. A superior test is the Universityof Pennsylvania Smell Identification Test (UPSIT). This consists of a 40-item,forced choice, scratch-and-sniff paradigm. For example, one of the items reads,This odor smells most like (a) chocolate, (b) banana, (c) onion, or (d) fruitpunch. The test is highly reliable, is sensitive to age and sex differences, andprovides an accurate quantitative determination of the olfactory deficit. TheUPSIT, which is a forced-choice test, can also be used to identify malingerers whotypically report fewer correct responses than would be expected by chance. Theaverage score for total anosmics is slightly higher than that expected on the basisof chance because of the inclusion of some odorants that act by trigeminalstimulation. Olfactory threshold testing is another method of assessing olfactoryfunction. Following assessment of sensory olfactory function, the detectionthreshold for an odorant such as methyl ethyl carbinol is established usinggraduated concentrations for each side of the nose. Nasal resistance can also bemeasured with anterior rhinomanometry for each side of the nose. CT or MRI of the head is required to rule out paranasal sinusitis; neoplasmsof the anterior cranial fossa, nasal cavity, or paranasal sinuses; or unsuspectedfractures of the anterior cranial fossa. Bone abnormalities are best seen with CT.MRI is the most sensitive method to visualize olfactory bulbs, ventricles, andother soft tissue of the brain. Coronal CT is optimal for assessing cribriform plate,anterior cranial fossa, and sinus anatomy. Biopsy of the olfactory epithelium is possible. However, given thewidespread degeneration of the olfactory epithelium and intercalation ofrespiratory epithelium in the olfactory area of adults with no apparent olfactorydysfunction, biopsy results must be interpreted with caution. Disorders of the Sense of Smell: Treatment Therapy for patients with transport olfactory losses due to allergic rhinitis,bacterial rhinitis and sinusitis, polyps, neoplasms, and structural abnormalities ofthe nasal cavities can be undertaken with a high likelihood for improvement.Allergy management; antibiotic therapy; topical and systemic glucocorticoidtherapy; and surgery for nasal polyps, deviation of the nasal septum, and chronichyperplastic sinusitis are frequently effective in restoring the sense of smell. There is no proven treatment for sensorineural olfactory losses.Fortunately, spontaneous recovery often occurs. Zinc and vitamin therapy(especially with vitamin A) are advocated by some. Profound zinc deficiency canproduce loss and distortion of the sense of smell but is not a clinically importantproblem except in very limited geographic areas (Chap. 71). The epithelialdegeneration associated with vitamin A deficiency can cause anosmia, but inwestern societies the prevalence of vitamin A deficiency is low. Exposure tocigarette smoke and other airborne toxic chemicals can cause metaplasia of theolfactory epithelium, and spontaneous recovery can occur if the insult is removed.Counseling of patients is therefore helpful in such cases. More than half of people over age 60 suffer from olfactory dysfunction. Noeffective treatment exists for presbyosmia, but patients are often reassured to learnthat this problem is common in their age group. In addition, early recognition andcounseling can help patients to compe ...