The olfactory bulb in the brain appears to change in size in a way that corresponds to individual alterations in sense of smell, according to an article in the June issue of Archives of Otolaryngology—Head & Neck Surgery.
Investigators have studied the size of the olfactory bulb in patients who have lost their sense of smell as a result of injury, infection, congenital conditions or neurodegenerative diseases, as well as in those with a normal sense of smell, the authors wrote. Research indicates that the size of the olfactory bulb changes throughout adult life.
Antje Haehner, MD, and colleagues at University of Dresden Medical School, Germany, studied 20 patients with a loss of sense of smell (olfactory loss). Between 2003 and 2004 and then 13 to 19 months later, patients underwent an assessment that included magnetic resonance imaging of the brain and nasal endoscopy. The researchers tested their olfactory function by using a kit that measures an individual’s threshold for detecting odors and ability to discriminate between odors and identify particular odors.
At the first assessment, seven of the 20 patients had no sense of smell (anosmia) and 13 had a reduced sense of smell (hyposmia). At the second assessment, six patients had anosmia and 14 had hyposmia. In patients who had hyposmia initially, the volume of the olfactory bulb increased as olfactory function increased. However, the researchers found no correlation between the volume of the olfactory bulb and the patient’s ability to distinguish between odors or identify specific odors.
"The correlation between olfactory bulb volume and olfactory function may potentially be used in combination with other factors influencing olfaction such as remaining olfactory function, age and duration of olfactory loss as a means to provide patients with individual information on the prognosis of their disease," the authors wrote.
"Hypothetically, a multifactorial approach could be applied to eventually come up with a formula that would allow a more precise prognosis of olfactory function," the authors continued. "Especially since therapeutic options in patients with olfactory loss are limited, at present, this type of information is of high clinical significance."
