Structural magnetic resonance imaging in dystonia: A systematic review of methodological approaches and findings

Abstract

Background and purpose: Structural magnetic resonance techniques have been widely applied in neurological disorders to better understand tissue changes, probing characteristics such as volume, iron deposition and diffusion. Dystonia is a hyperkinetic movement disorder, resulting in abnormal postures and pain. Its pathophysiology is poorly understood, with normal routine clinical imaging in idiopathic forms. More advanced tools provide an opportunity to identify smaller scale structural changes which may underpin pathophysiology. This review aims to provide an overview of methodological approaches undertaken in structural brain imaging of dystonia cohorts, and to identify commonly identified pathways, networks or regions that are implicated in pathogenesis.Methods: Structural magnetic resonance imaging studies of idiopathic and genetic forms of dystonia were systematically reviewed. Adhering to strict inclusion and exclusion criteria, PubMed and Embase databases were searched up to January 2022, with studies reviewed for methodological quality and key findings. Results:Seventy-seven studies were included, involving 1945 participants. The majority of studies employed diffusion tensor imaging (DTI) (n = 45) or volumetric analyses (n = 37), with frequently implicated areas of abnormality in the brainstem, cerebellum, basal ganglia and sensorimotor cortex and their interconnecting white matter pathways. Genotypic and motor phenotypic variation emerged, for example fewer cerebellothalamic tractography streamlines in genetic forms than idiopathic and higher grey matter volumes in task-specific than non-task-specific dystonias.Discussion: Work to date suggests microstructural brain changes in those diagnosed with dystonia, although the underlying nature of these changes remains undetermined.Employment of techniques such as multiple diffusion weightings or multi-exponential relaxometry has the potential to enhance understanding of these differences.

Blood neurofilament light chain as a surrogate marker for dystonia

“…In line with our findings, recent studies applying diffusion tensor imaging (DTI), which is an MRI-based axonal injury imaging marker that enables in vivo mapping of the diffusion of water molecules in brains to characterize changes in white matter integrity specific to axons [26], demonstrated that patients with idiopathic adult-onset focal dystonia have significantly reduced fractional anisotropy in the basal ganglia and cerebellum compared to controls, suggesting a process of axonal loss [27,28]. A recent study reviewing 1945 participants with dystonia undergoing DTI revealed fewer cerebello-thalamic tractography streamlines in genetic forms of dystonia than in idiopathic dystonia, suggesting more profound microstructural brain changes in those diagnosed with genetic dystonia [29]. However, few DTI-based studies have been performed in patients with generalized dystonia or combined dystonia syndrome due to its rarity.…”

White matter microstructural changes in adult-onset idiopathic focal cervical dystonia using ultra-strong diffusion gradient MRI

“…White matter analysis in AOIFCD has predominantly involved diffusion MRI, using relatively non-specific measures, coupled with heterogenous approaches and findings. Some have demonstrated localised higher, lower or unchanged diffusion tensor measures such as fractional anisotropy (FA) and mean diffusivity (MD) within motor pathways (5,(7)(8)(9)(10).…”

Macro- and micro-structural insights into primary dystonia: a UK Biobank study

“…Volumetric MRI has indicated higher volumes in task-specific forms of dystonia, most notably in the cerebellar, basal ganglia and sensorimotor grey matter regions [ 34 ], with variable findings in non-task-specific forms. Findings from diffusion MRI (dMRI) studies have been mixed, although cerebellar white matter projections, and white matter deep to the primary sensorimotor cortices have been highlighted [ 23 ]. There is also evidence for genotypic and phenotypic variation, including more widespread changes in genetic dystonias and intermediate changes in non-motor manifesting gene carriers.…”