Disorders of Taste and Smell

This article aims to educate clinical neurologists on the importance of taste and smell disorders in clinical neurology. These disorders commonly occur in head trauma, multiple sclerosis, seizure disorders, and neurodegenerative diseases such as idiopathic Parkinson disease and dementia, mild cognitive impairment, and Alzheimer disease, just to name a few. This article covers the basic anatomy of smell and taste, notes the important points of taking a proper history, and discusses smell and taste testing, which are inexpensive, minimally time-consuming procedures. Recurrent bad smells and tastes are not uncommon in these disorders, which cause major impairment in quality of life, including loss of appetite, decreased eating, and weight loss. The diagnosis and treatment of these disorders will also be discussed.

Despite past widespread negative prognoses of taste and smell disorders, more recent work in the last 10 years has shown an improved prognosis for smell and taste recovery in most disorders, and recommendations for changes in food preparation have helped many patients enjoy their food and increase their appetite. Recent experimental evidence has shown that smell loss and testing can assist in separating idiopathic Parkinson disease from other parkinsonian syndromes, can suggest which patients with rapid eye movement (REM) sleep behavior disorder will more likely develop Parkinson disease, and can be predictive of the progression of cognitive impairment and Alzheimer dementia.

This article discusses the common smell and taste disorders that a clinical neurologist will encounter in practice. The anatomy and function of smell and taste will be reviewed, followed by office evaluation and testing. The common disorders will be reviewed, along with their prognosis and management.