Primary dystonia: conceptualizing the disorder through a structural brain imaging lens

Abstract

Background: Dystonia is a hyperkinetic movement disorder characterized by involuntary, repetitive twisting movements. The anatomical structures and pathways implicated in its pathogenesis and their relationships to the neurophysiological paradigms of abnormal surround inhibition, maladaptive plasticity, and impaired sensorimotor integration remain unclear.

Objective: We review the use of high-resolution structural brain imaging using voxel-based morphometry (VBM) and diffusion tensor imaging (DTI) techniques for evaluating brain changes in primary torsion dystonia and their relationships to the pathophysiology of this disorder.

Methods: A PubMed search was conducted to identify relevant literature.

Results: VBM and DTI studies produced somewhat conflicting results across different forms of primary dystonia and reported increases, decreases, or both in gray matter volume and white matter integrity. However, despite the discrepancies, these studies are consistent in revealing brain abnormalities in dystonia that extend beyond the basal ganglia and involve the sensorimotor cortex and cerebellum.

Discussion: Although limited to date, structural magnetic resonance imaging (MRI) studies combined with functional brain imaging and neurophysiological modalities begin to establish structural-functional relationships at different levels of the abnormal basal ganglia, cortical, and cerebellar networks and provide clues into the pathophysiological mechanisms that underlie primary dystonia. Cross-disciplinary studies are needed for further investigations of the interplay between structural-functional brain abnormalities and environmental and genetic risk factors in dystonia patients.

Keywords: MRI; Primary dystonia; diffusion tensor imaging; voxel-based morphometry.

Figure 1. Differences in Increases in GMV in Patients with SD compared to Healthy Controls are Dependent on Sample Size. The color bar represents F values and reflects the significance of changes in patients compared to controls.

Figure 2. Impact of the Choice of T1-weighted Sequence on Brain Tissue Segmentation for VBM analysis. The segmented gray matter images were acquired using MPRAGE (magnetization-prepared rapid acquisition with gradient echo, left column) and SPGR (spoiled gradient recalled echo, right column) sequences. Fully automated segmentation into gray matter, white matter, and CSF was performed using SPM8 software. The red arrows indicate the over-segmented primary motor cortex and basal ganglia.