Anosmia Diagnosis and Treatment

OlfactionIf you have experienced a loss in your sense of smell, you should seek evaluation by a board-certified otolaryngologist (ear, nose and throat specialist), preferably at a large university medical center, to determine if the cause can be identified and if you may respond to treatment.

Anosmia is a diverse disorder having many possible causes. Unfortunately, at the present time, there are relatively few forms of smell problems for which the underlying cause can be conclusively identified. And without knowing exactly what caused the smell loss, treatment options are limited. Finally, it often is difficult to predict who will and who won’t respond to treatment.

Nasal-Sinus Disease

Your doctor will evaluate whether you have a physical blockage that prevents odors form reaching your olfactory epithelium, the part of the nose that contains the cells that actually help the brain recognize odors. In some patients, polyps grow to block the nasal passages. These polyps can be treated with oral corticosteroids or with surgery—unfortunately, they often return after treatment and require more surgery or lifelong medical therapy.

Your doctor will also check for signs of chronic rhinosinusitis or nasal inflammation. Chronic rhinosinusitis can be treated through medicines such as antibiotics or through surgery. Smell function may improve after such treatments if the system has not been permanently damaged.

Viral Upper Respiratory Disease

Many times, your doctor will not be able to determine an exact cause for your loss of smell but your medical history may reveal that the loss was preceded by a cold or other upper respiratory infection (URI). Viruses are believed to be the most common causes of smell loss. These viruses appear to directly injure the olfactory epithelium, the tissue that contains the smell receptor cells.

Typically, smell loss is noticed after other URI symptoms have disappeared. If the smell loss is treated with oral corticosteroids very soon after the initial URI, some patients with such losses can regain their sense of smell.

Even if patients do not receive immediate treatment following a URI-related smell loss, there is hope for recovery. The olfactory system is resilient, with smell receptor cells being continually replaced throughout an individual’s life span. Our studies indicate that 2/3 to 3/4 of patients with a suspected viral-induced smell loss show spontaneous improvement, but the recovery typically is delayed and gradual, often taking two or more years.

Head Trauma

In some circumstances, your evaluation may uncover a head injury that preceded your smell loss. In such injuries the connections between the smell receptors in the nose and the smell centers in the brain are severed. Recovery from such losses is delayed and gradual and occurs only in about 1/3 of such cases.

Other Causes

Finally, losses in the ability to distinguish odors can signal the onset of Alzheimer’s Disease, Parkinson’s Disease or other neurological disorders. Your doctor may order a magnetic resonance imaging scan or computed tomography scan to evaluate this possibility further.

Smell Training

Can losses in the sense of smell be reversed through other means? According to the US National Institutes of Health, there currently are no evidence-based preventive measures, interventions, or treatments available for anosmia. However, there now are a number of lines of evidence suggesting that regular, intermittent exposure to odors, with efforts to identify smells, can lead to improvements in olfaction. Just as athletic injuries and stroke-induced disabilities can be improved through early rehabilitation, smell loss can be helped through olfactory retraining.

Those who have lost their smell can put together a set of four or five non-irritating odors (e.g., perfumes, coffee grounds, flavor extracts) and try to smell, discriminate and identify them a couple of times each day. In other words, stimulating and trying to re-train the olfactory system may help, especially if begun within 12 months after the onset of the disorder.

Monell scientists unfortunately cannot provide advice on diagnosis or potential treatment options. As part of our anosmia project, we will develop educational material on anosmia and other smell disorders to distribute to physicians.