Dr. Antje Haehner and colleagues at the University of Dresden Medical School studied 20 patients with loss of sense of smell, or olfactory loss. Once during 2003-04 and again 13 to 19 months later the patients underwent a brain scan and an assessment of olfactory function.

At the first assessment, seven of the 20 patients had no sense of smell (anosmia) and 13 had a reduced sense of smell (hyposmia), while at the second assessment six had anosmia and 14 had hyposmia. In patients who initially had hyposmia, the volume of their olfactory bulb increased as olfactory function increased.

The correlation between olfactory bulb volume and olfactory function could be used to provide patients with information on the prognosis of their disease, the researchers said.

"Hypothetically, a multifactorial approach could be applied to eventually come up with a formula that would allow a more precise prognosis of olfactory function," they added.

The study appears in the June issue of the journal Archives of Otolaryngology -- Head & Neck Surgery.