Dysosmia is a distortion or alteration of the perception of smell. It is considered a qualitative olfactory disorder because there is no measurable change in the ability to smell, but rather a change in how smells are perceived. Dysosmia can affect both nostrils at the same time or either nostril on its own (Kühn et al., 2013). Dysosmia can be characterized as either parosmia or phantosmia. Parosmia is when the brain misinterprets the natural smell of an odorant, and the smell is different from what a person remembers. This is considered an olfactory illusion and is more specifically characterized as cacosmia when natural odors are perceived as unpleasant aromas. Phantosmia is the perception of smell in the absence of any physical odorant and is considered to be an olfactory hallucination when the smell lasts only a few seconds.
Causes and Associations
Dysosmia is often considered to be a neurological disorder and other clinical associations have been made. Many cases have been associated with upper respiratory tract infections (URTIs) and nasal and paranasal sinus disease, like chronic rhinosinusitis. Dysosmia is also commonly associated with head trauma following an accident. Other clinical associations of dysosmia include toxic chemical exposure, nasal surgery, epilepsy, tumors on the frontal lobe or olfactory bulb, and neurological abnormalities (Nordin et al., 2011). Dysosmia has also been utilized to indicate the onset of neurodegenerative disorders such as Alzheimer’s and Parkinson’s diseases. Dysosmia in cases of neurodegenerative disorders presents itself about 20 years before other classic symptoms appear (Nordin et al., 2011). Smell disturbance with dysosmia is often associated with taste disturbance. People who suffer from smell and taste disturbance often have decreased food enjoyment, which results in significant weight loss and an impaired quality of life often leading to depression. Adverse effects of impaired life quality include deterioration of work life, sexual life, and social interactions (Nordin et al., 2011).
The causes of dysosmia are unclear but there are both peripheral and central theories behind the etiology of dysosmia (Leopold, 2002). In parosmia, the peripheral theory explains that the distortion is likely due to a number of olfactory primary neurons not functioning to create a complete characterization of an odorant. The central theory describes parosmia as a result of interpretive centers of the brain forming a distorted odor. Peripherally, phantosmia is theorized to be caused by primary olfactory neurons emitting abnormal signals to the brain, or due to the loss of inhibitory cells that are typically present in normal functioning. Phantosmia is explained centrally as hyperfunctioning cells in the brain generating the perception of odor.
Diagnosis and Tests
Diagnosing dysosmia requires taking an extensive medical history. A history will reveal past respiratory infection or head trauma, which is usually precedent to parosmia. On the other hand, cases of phantosmia typically occur spontaneously without a history of such events and are then considered idiopathic. Patients often have a difficult time distinguishing whether they have a taste or smell problem (Leopold, 2002). Physicians must identify whether the smell distortion is present when patients inhale an odorant (parosmia) or if an odor is present in the absence of a stimulus (phantosmia). A complete ear, nose, and throat (ENT) examination is important in observing nerves, nasal mucosa, and airways for obstructions and infections. Also, brain imaging should be used to rule out tumors.
Dysosmia is typically found in elderly people and symptoms tend to go away on their own. Waiting and watching is an appropriate treatment plan for dysosmia. However, if an individual is unwilling or unable to tolerate the olfactory distortions, there are medical and surgical treatments. Medical treatments include various types of nasal drops such as saline, Oxymetazoline HCl, and topical cocaine HCl, each with various advantages and side effects to consider (Leopold, 2002). There are surgical procedures to remove or excise olfactory bulbs, neurons, and olfactory epithelium in an attempt to eliminate phantosmia with the possibility of removing olfactory ability completely.
Darin T. Sisneros
See also: Anosmia; Odor Threshold; Olfactory Bulb; Olfactory Mucosa; Olfactory Nerve; Olfactory Sensory Neurons; Olfactory System; Phantosmia
Kühn, M., N. Abolmaali, M. Smitka, D. Podlesek, & T. Hummel. (2013). Dysosmia: Current aspects of diagnostics and therapy. HNO, 61(11), 975—984.
Leopold, Donald. (2002). Distortion of olfactory perception: Diagnosis and treatment. Chemical Senses, 27, 611—615.
Nordin, Steven, Ebba H. Blomqvist, Petter Olsson, Päär Stjäärne, & Anders Ehnhage. (2011). Effects of smell loss on daily life and adopted coping strategies in patients with nasal polyposis with asthma. Acta Oto-Laryngologica, 131(8), 826—832.