Taste Dysfunction

Geriatric Essentials

• Decreased olfactory function contributes greatly to age-related taste reductions.

Taste decreases only slightly with aging, usually blunting a specific taste quality (ie, sweet, sour, salty, bitter). However, olfactory function decreases greatly, even in healthy people, and contributes greatly to age-related taste reductions.

Non-age-related causes include neuropathies (eg, from diabetes, stroke, multiple sclerosis); cognitive disorders (eg, dementia, stroke, Parkinson's disease), gastroesophageal reflux, and upper respiratory infections; oral disorders (eg, periodontal abscesses, ulcerations); drugs (see Table 104-2); surgical or other trauma to the 7th (facial), 9th (glossopharyngeal), or 10th (vagus) cranial nerve (which subserve taste sensation to the tongue, soft palate, and oral pharynx); other oral or maxillofacial trauma (ie, trauma that results in edema, subcutaneous hemorrhage, or infection and subsequently in taste abnormalities); dental or alveolar surgery (eg, extractions, periodontal surgery, biopsies); craniomandibular surgery; intraoral infections that produce a purulent discharge; and poor oral hygiene. Poor oral hygiene, particularly of teeth with extensive restorations or of dentures, may result in chronic unpleasant taste sensations and may lead to gingivitis or bacterial and fungal infections, which contribute to taste dysfunction. Finally, saliva is responsible for dissolving tastants and transporting them directly to the taste buds. In the absence of adequate salivary function, taste function can become impaired.

Symptoms and Signs

Patients experience a decreased ability to taste (hypogeusia) or a persistent bad taste (dysgeusia). Taste loss (ageusia) is uncommon. In most patients, changes occur slowly and insidiously.

Diagnosis

Taste dysfunction should be characterized by patient history. Patients can be asked whether they can taste the saltiness of a potato chip, the sweetness of ice cream, the sourness of lemon juice, and the bitterness of coffee; affirmative answers indicate that any deficit is probably olfactory rather than gustatory.

Diagnosis is by history and examination. If a patient reports an unpleasant taste that is usually associated with meals or that can be rinsed away with water, the cause may be oral pathology, including trauma and poor hygiene.

The patient should be asked about systemic disorders, drug use, head trauma, and upper respiratory infections. Sudden taste loss may be attributable to a cranial tumor. If a tumor is suspected, evaluation must include the 1st (olfactory), 7th, 9th, and 10th cranial nerves. Patients with a sudden change in taste that has no obvious cause should be referred to a neurologist, and MRI or CT of the head should be done to rule out a cranial tumor. In the absence of a definitive diagnosis, referral to a chemosensory center for intensive testing may be necessary.

Treatment

Treatment is tailored to any underlying condition. If no cause is identified, treatment is empirical and difficult; no therapies are established. Unproven interventions include antireflux therapies, zinc, and clonazepam.

Meticulously documenting symptoms and reassuring patients that distinct sensory deficits have been diagnosed often helps. Patients may need counseling and behavioral therapy to learn how to live with persistent idiopathic taste disturbance. Adding strong flavorings, herbs, and spices to foods can stimulate weak receptors and enhance the olfactory component of flavor sensation and improve mealtime satisfaction.

This topic was last updated September 2005.