FM Patients’ Difficulty Smelling May Be Linked to Decreased Olfactory Bulb Volume

FM Patients’ Difficulty Smelling May Be Linked to Decreased Olfactory Bulb Volume

Patients with fibromyalgia (FM) may have reduced volume of the olfactory bulb, a key structure in how we perceive and distinguish smell, a study found. That finding may help explain why some patients report impairments in olfactory perception.

The study, “Decreased olfactory bulb volumes in patients with fibromyalgia syndrome,” was published in the journal Clinical Rheumatology.

Olfactory perception, including being able to identify and distinguish different types of odors, is a feature often reported to be impaired in FM patients.

The olfactory bulb is the first structure involved in our perception of smell. It is composed of two types of nerve cells that receive input from cells in the nasal cavity. But, while “self-reported olfactory functions have been studied with olfactory tests, olfactory bulb volumes have not been studied” in FM patients, the research team wrote.

The volume of the olfactory bulb is known to be reduced in other diseases, too, including Alzheimer’s disease, Parkinson’s disease, schizophrenia, and depression. Some of these patients also experience olfactory dysfunction.

To determine the volume of the olfactory bulb in a group of FM patients, researchers used magnetic resonance imaging (MRI). In total, the study enrolled 62 female participants — 30 with FM and 32 healthy controls — with mean ages of 44.2 and 41.7, respectively.

MRI analyses showed that the olfactory bulbs of patients with FM had a reduced volume compared to healthy controls. Specifically, the mean volumes of the right olfactory bulbs were 74.9 mm3 in the FM group and 92.6 mm3 in the control group. The mean volumes of the left olfactory bulbs were 74.3 mm3 and 92.8 mm3, respectively.

The mean of total olfactory bulb volume (the volume of both right and left) was 146.6 mm3 in the FM group and 186.5 mm3 in the healthy control group, a 1.2 ratio difference.

The team suggested that the decrease detected in FM patients is the potential result of alterations in neuronal structures in patients’ brains, evidence that may support the notion defended by some that FM is a brain disorder.

Overall, the team concluded that patients with fibromyalgia are at risk of having decreased olfactory bulb volumes.

“Outcomes of the present study should be kept in mind for proper and reasonable management of this tough syndrome and for future studies,” the team wrote.