Comparison of Cerebellar Grey Matter Alterations in Bipolar and Cerebellar Patients: Evidence from Voxel-Based Analysis

Abstract

The aim of this study was to compare the patterns of cerebellar alterations associated with bipolar disease with those induced by the presence of cerebellar neurodegenerative pathologies to clarify the potential cerebellar contribution to bipolar affective disturbance. Twenty-nine patients affected by bipolar disorder, 32 subjects affected by cerebellar neurodegenerative pathologies, and 37 age-matched healthy subjects underwent a 3T MRI protocol. A voxel-based morphometry analysis was used to show similarities and differences in cerebellar grey matter (GM) loss between the groups. We found a pattern of GM cerebellar alterations in both bipolar and cerebellar groups that involved the anterior and posterior cerebellar regions (p = 0.05). The direct comparison between bipolar and cerebellar patients demonstrated a significant difference in GM loss in cerebellar neurodegenerative patients in the bilateral anterior and posterior motor cerebellar regions, such as lobules I-IV, V, VI, VIIIa, VIIIb, IX, VIIb and vermis VI, while a pattern of overlapping GM loss was evident in right lobule V, right crus I and bilateral crus II. Our findings showed, for the first time, common and different alteration patterns of specific cerebellar lobules in bipolar and neurodegenerative cerebellar patients, which allowed us to hypothesize a cerebellar role in the cognitive and mood dysregulation symptoms that characterize bipolar disorder.

Keywords: bipolar disorder; cerebellar atrophy; cerebellar grey matter volume; voxel-based morphometry.

Figure 1

Cerebellar regions showing patterns of significantly reduced cerebellar grey matter (GM) are reported and superimposed on the spatially unbiased infratentorial template (SUIT) [51] in coronal (y), axial (z) and sagittal (x) sections. (a) BD < HS (in blue); (b) CD < HS (in red); (c) CD < BD (in green). The results are considered significant at p-values < 0.05 FWE corrected at the cluster level. Images are shown in the radiological convention.

Figure 2

(a) Clusters of reduced cerebellar GM in BD and CD compared to HSs are reported in blue and red, respectively. Regions of overlapped cerebellar GM loss between BD and CD are shown in violet on the spatially unbiased infratentorial template (SUIT) [51]. (b) Only cerebellar regions showing patterns of significantly reduced GM in both BD and CD patients are shown in violet and superimposed on the probabilistic SUIT cerebellar atlas [51], which provides anatomical subdivision of cerebellar lobules (in greyscale). Images are shown according to radiological convention in coronal (y), axial (z) and sagittal (x) sections.