The loss of sense of smell is anosmia. Smell is closely aligned with taste. There is a safety factor involved because smell monitors inhaled chemicals, smoke, natural gas, and air pollutants. The cranial nerves that may be involved are olfactory nerve, trigeminal nerve, vagus nerve, and glossopharyngeal nerve.

Smell disorders are caused by conditions that interfere with odor access to the neuroepithelium (transport loss), injury to the receptor region (sensory loss), or damage to the central olfactory tract (neural loss). Etiologic factors associated with causes of loss of smell are as follows:

• Transport loss include: swollen nasal mucous membranes from allergies or bacterial rhinitis; acute viral upper respiratory infections; sinusitis or structural changes from polyps; deviated septum; or neoplasms. In addition, excessive mucus secretion may immerse the nasal cilia. These conditions result in a loss of ability to smell and taste.
• Sensory loss include: destruction of the nasoepithelium by viral infections; neoplasms; inhalation of toxic chemicals; or radiation therapy with a loss ability to smell and taste.
• Neural loss include: inability to smell and taste as an aftermath of head trauma; neurotoxic agents, such as topical cocaine; some endocrine disorders; Alzheimer's disease; neoplasms; or vitamin B12 deficiency.

Manifestations of the condition include: swollen nasal mucous membranes; loss of ability to smell in both nostrils; and loss of taste.

Diagnostic tests for this condition include: a physical examination that focuses on the upper aerodigestive tract and a complete neurological examination to assess cranial nerve function; computed tomography (CT) scan; and a forty-item sensory smell identification test. Patients with a total loss of smell usually correctly score only seven to nineteen of the forty items. A biopsy of the olfactory epithelium may be indicated.

Olfactory losses due to transport disorders are usually amenable to treatment with management of allergies by antibiotics or steroids (systemic and topical). Additionally, nasal polypectomy, septoplasty and sinus endoscopy may be quite effective in selected patients. There is no effective treatment for sensorineural losses. Sometimes spontaneous recovery occurs.

When traumatic anosmia develops, it is usually permanent; 10% improve or recover.

Special Considerations

• None. 

• Evaluation will be assigned under Diagnostic Codes 6275 or 6276 only if there is an anatomical or pathological basis for the condition. (38 CFR 4.87a [Schedule of ratings-other sense organs])