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
examination emphasizing the cranial nerves and cerebellar and sensorimotor
function is essential. Any signs of depression should be noted.
Sensory olfactory function can be assessed by several methods. The Odor
Stix test uses a commercially available odor-producing magic marker–like pen
held approximately 8–15 cm (3–6 in.) from the patient's nose. The 30-cm alcohol
test uses a freshly opened isopropyl alcohol packet held ~30 cm (12 in.) from the
patient's nose. There is a commercially available scratch-and-sniff card containing
three odors available for gross testing of olfaction. A superior test is the University
of 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) fruit
punch." The test is highly reliable, is sensitive to age and sex differences, and
provides an accurate quantitative determination of the olfactory deficit. The
UPSIT, which is a forced-choice test, can also be used to identify malingerers who
typically report fewer correct responses than would be expected by chance. The
average score for total anosmics is slightly higher than that expected on the basis
of chance because of the inclusion of some odorants that act by trigeminal
stimulation.
Olfactory threshold testing is another method of assessing olfactory

Counseling of patients is therefore helpful in such cases.
More than half of people over age 60 suffer from olfactory dysfunction. No
effective treatment exists for presbyosmia, but patients are often reassured to learn
that this problem is common in their age group. In addition, early recognition and
counseling can help patients to compensate for the loss of smell. The incidence of
natural gas–related accidents is disproportionately high in the elderly, perhaps due
in part to the gradual loss of smell. Mercaptan, the pungent odor in natural gas, is
an olfactory stimulant that does not activate taste receptors. Many elderly with
olfactory dysfunction experience a decrease in flavor sensation and find it
necessary to hyperflavor food, usually by increasing the amount of salt in their
diet.
Taste
Compared with disorders of smell, gustatory disorders are uncommon. Loss
of olfactory sensitivity is often accompanied by complaints of loss of the sense of
taste, usually with normal detection thresholds for taste.