European Section

European Literature Review

Decreased olfactory bulb volume in idiopathic Parkinson's disease detected by 3.0-Tesla magnetic resonance imaging

Author: Dr. Stefan Brodoehl and colleagues
Source: Hans Berger Department of Neurology, Jena University Hospital, Jena, Germany; Brain Imaging Center, University of Jena, Jena, Germany.
Mov Disord. 2012 Jul;27(8):1019-25. doi: 10.1002/mds.25087. Epub 2012 Jun 21 ©The Movement Disorder Society



A number of neuropathological studies have demonstrated that the olfactory system is among the first brain regions affected in Parkinson's disease (PD). These findings correlate with pathophysiological and pathological data that show a loss in olfactory bulb (OB) volume in patients with PD. However, to date, MRI has not been a reliable method for the in vivo detection of this volumetric loss in PD. Using a 3.0-Tesla MRI constructive interference in the steady-state sequence, OB volume was evaluated in patients with PD (n = 16) and healthy control subjects (n = 16). A significant loss of OB volume was observed in patients with PD, compared to the healthy control group (91.2 ± 15.72 versus 131.4 ± 24.56 mm(3) , respectively). Specifically, decreased height of the left OB appears to be a reliable parameter that is adaptable to clinical practice and significantly correlates with OB volume loss in patients with idiopathic PD. Measuring both the volume and height of the OB by MRI may be a valuable method for the clinical investigation of PD. © 2012 Movement Disorder Society.


MDS-ES Web Editor's commentary by Carlo Colosimo, MD, PhD
Sapienza University of Rome, Italy

The diagnosis of Parkinson’s disease (PD) is based on clinical grounds alone and requires the presence of the typical motor symptoms associated with this condition. Nevertheless, a variety of non-motor symptoms are an integral part of the clinical spectrum of PD, and may even be present before the first appearance of the classical motor disorder.

In particular, large population-based studies have consistently shown that not only 80% of patients with PD are hyposmic, but also that healthy subjects with smell dysfunction are at increased risk to develop PD with an odds ratio for this association of around 5. The interesting study by Brodoehl and colleagues, looked at the presence of MRI abnormalities at the level of the olfactory bulb (OB) in 16 patients with mild-to-moderate PD. These German researchers were able to find, using 3T MRI, a significant asymmetric loss of olfactory bulb volume in patients (who were all hypo- or anosmic) as compared to normosmic controls. They concluded by claiming that OB MRI changes, which were directly related to olfactory dysfunction objectively detected in the patients, could prove useful in distinguishing between PD and other neurological disorders.

In my opinion there is also another possible spin-off from these data. The current challenge is, indeed, to have reliable markers of PD in a very early phase, in order to test a new neuroprotective strategy which could delay or prevent the onset of clinical disease.

The findings from this imaging study open the door to further studies aimed at establishing the role of this neuroimaging technique as a reliable surrogate marker of olfactory loss that could allow earlier diagnosis during the premotor stages of the illness.