The human nucleus accumbens suffers parkinsonism-related shrinkage: a novel finding

The human nucleus accumbens (NA) plays an important role in motivation and emotional processes and is involved in some of the most disabling neuropsychiatric disorders such as Parkinson's disease (PD). The purpose of our study was to check out the potential existence of a statistically significant difference in NA size between parkinsonian and non-parkinsonian individuals, through studying brain magnetic resonance images (MRIs).

For our study we used 52 NAs from 26 cerebral MRIs from neurosurgical patients. Of these MRIs, 15 were preoperative from patients with advanced PD who underwent bilateral deep brain stimulation of the subthalamic nucleus. The group of non-parkinsonian MRIs came from the rest 11 individuals. We measured the absolute and relative NA maximum transverse diameter (D (max)), and absolute and relative NA width at a specific transverse plane.

We found a statistically significant difference of the mean value of the D (max) (absolute and relative) between the two groups. The mean percentage reduction of the NA size was 11.77% represented by the relative D (max).

To our knowledge, this is the first report of parkinsonism-related shrinkage of the human NA. Further research is needed to identify whether a respective shrinkage is also observed in patients with early PD and whether this atrophy is correlated with dopaminergic neuropsychiatric symptoms (perhaps mediated by a malfunctioning NA) that occur in PD.