Fabry disease (FD) is a rare X-linked disorder characterised by abnormal progressive lysosomal deposition of globotriaosylceramide in a large variety of cell types. The central nervous system (CNS) is often involved in FD, with a wide spectrum of manifestations ranging from mild symptoms to more severe courses related to acute cerebrovascular events. In this review we present the current knowledge on brain imaging for this condition, with a comprehensive and critical description of its most common neuroradiological imaging findings. Moreover, we report results from studies that investigated brain physiopathology underlying this disorder by using advanced imaging techniques, suggesting possible future directions to further explore CNS involvement in FD patients.Teaching Points • Conventional neuroradiological findings in FD are aspecific. • White matter hyperintensities represent the more consistent brain imaging feature of FD • Abnormalities of the vasculature wall of posterior circulation are also consistent features. • The pulvinar sign is not reliable as a finding pathognomonic for FD. • Advanced imaging techniques have increased our knowledge about brain involvement in FD.

BACKGROUND AND PURPOSE: Deep gray matter involvement is a consistent feature in multiple sclerosis. The aim of this study was to evaluate the relationship between different deep gray matter alterations and the development of subcortical atrophy, as well as to investigate the possible different substrates of volume loss between phenotypes. MATERIALS AND METHODS: Seventy-seven patients with MS (52 with relapsing-remitting and 25 with progressive MS) and 41 healthy controls were enrolled in this cross-sectional study. MR imaging investigation included volumetric, DTI, PWI and Quantitative Susceptibility Mapping analyses. Deep gray matter structures were automatically segmented to obtain volumes and mean values for each MR imaging metric in the thalamus, caudate, putamen, and globus pallidus. Between-group differences were probed by ANCOVA analyses, while the contribution of different MR imaging metrics to deep gray matter atrophy was investigated via hierarchic multiple linear regression models. RESULTS: Patients with MS showed a multifaceted involvement of the thalamus and basal ganglia, with significant atrophy of all deep gray matter structures (P Ͻ .001). In the relapsing-remitting MS group, WM lesion burden proved to be the main contributor to volume loss for all deep gray matter structures (P Յ .006), with a minor role of local microstructural damage, which, in turn, was the main determinant of deep gray matter atrophy in patients with progressive MS (P Յ .01), coupled with thalamic susceptibility changes (P ϭ .05). CONCLUSIONS: Our study confirms the diffuse involvement of deep gray matter in MS, demonstrating a different behavior between MS phenotypes, with subcortical GM atrophy mainly determined by global WM lesion burden in patients with relapsing-remitting MS, while local microstructural damage and susceptibility changes mainly accounted for the development of deep gray matter volume loss in patients with progressive MS. ABBREVIATIONS: DD ϭ disease duration; DGM ϭ deep gray matter; DMT ϭ disease-modifying treatment; EDSS ϭ Expanded Disability Status Scale; FA ϭ fractional anisotropy; HC ϭ healthy controls; LL ϭ lesion load; MD ϭ mean diffusivity; PMS ϭ progressive MS; QSM ϭ Quantitative Susceptibility Mapping; rCBV ϭ relative CBV; RRMS ϭ relapsing-remitting MS

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Atrophy of specific cerebellar lobules explains different aspects of motor and cognitive disability in patients with progressive MS. Investigation of cerebellar involvement provides further insight into the pathophysiological basis of clinical disability in progressive MS.

The pulvinar sign has a significantly lower incidence in Fabry disease than previously described. This finding, coupled with a lack of significant differences in quantitative MR imaging, allows hypothesizing that selective involvement of the pulvinar is a rare neuroradiologic sign of Fabry disease.