White matter integrity correlates with cognition and disease severity in Fabry disease

Effects of Current Therapies on Disease Progression in Fabry Disease: A Narrative Review for Better Patient Management in Clinical Practice

Fabry disease (FD) is a rare lysosomal storage disorder that is characterized by renal, neurological, and cardiovascular dysfunction. Four treatments are currently available for patients with FD; three enzyme replacement therapies (ERTs; agalsidase alfa, agalsidase beta, and pegunigalsidase alfa) and one pharmacological chaperone (migalastat). This review focuses on the evidence for the benefits of ERTs and migalastat, and provides an overview of their impact on disease manifestations and quality of life (QoL). Agalsidase beta is associated with renal, neurological, and cardiovascular benefits, and may prevent renal disease progression. Agalsidase alfa provides stabilizing effects across all main organ systems, although minor sex-specific differences exist in patients with more advanced baseline disease. The benefits of agalsidase alfa and agalsidase beta are similar but depend on the extent of baseline disease. Some data indicate that agalsidase beta may be preferable over the longer term. Both agalsidase alfa and agalsidase beta are associated with improved gastrointestinal and pain symptoms, as well as improved QoL. Patients with advanced end-organ damage tend not to respond as optimally to ERTs as those who initiate ERTs before irreversible organ fibrosis develops, highlighting the need for early treatment initiation. Migalastat, which is only approved for patients with amenable missense gene variants, generally stabilizes renal parameters and provides cardiovascular benefits. Migalastat also improves diarrhea and pain, and stabilizes QoL (although ERT may be more effective for pain management), but the neurological effects of migalastat have not been studied. Real-world data raise concerns about effective in vivo amenability of some genetic variants. Future studies with direct treatment comparisons in patients with FD are needed.

Clinical and Pathophysiologic Correlates of Basilar Artery Measurements in Fabry Disease

BACKGROUND AND PURPOSE

Alterations of the basilar artery (BA) anatomy have been suggested as a possible MRA feature of Fabry disease (FD). Nonetheless, no information about their clinical or pathophysiologic correlates is available, limiting our comprehension of the real impact of vessel remodeling in FD.

MATERIALS AND METHODS

Brain MRIs of 53 subjects with FD (mean age, 40.7 [SD, 12.4] years; male/female ratio = 23:30) were collected in this single-center study. Mean BA diameter and its tortuosity index were calculated on MRA. Possible correlations between these metrics and clinical, laboratory, and advanced imaging variables of the posterior circulation were tested. In a subgroup of 20 subjects, a 2-year clinical and imaging follow-up was available, and possible longitudinal changes of these metrics and their ability to predict clinical scores were also probed.

RESULTS

No significant association was found between MRA metrics and any clinical, laboratory, or advanced imaging variable (P values ranging from -0.006 to 0.32). At the follow-up examination, no changes were observed with time for the mean BA diameter (P = .84) and the tortuosity index (P = .70). Finally, baseline MRA variables failed to predict the clinical status of patients with FD at follow-up (P = .42 and 0.66, respectively).

CONCLUSIONS

Alterations of the BA in FD lack of any meaningful association with clinical, laboratory, or advanced imaging findings collected in this study. Furthermore, this lack of correlation seems constant across time, suggesting stability over time. Taken together, these results suggest that the role of BA dolichoectasia in FD should be reconsidered.

Investigation of serum neurofilament light chain as a biomarker in Fabry disease

Fabry disease (FD) constitutes a rare, X-linked lysosomal storage disorder affecting multiple organ systems, most notably heart, kidneys, and the central nervous system. Neurofilament light chains (NfL) have emerged as a prime candidate for a body fluid biomarker reflecting neuro-axonal injury. We aimed to evaluate its addition to the diagnostic and monitoring armamentarium in FD. Serum NfL concentrations (sNfL) were measured in 50 people with FD (PwFD) and 30 healthy control subjects (HC) using the Simoa© technology, followed by calculation of Z-scores adjusted for age and body mass index. In addition, clinical disease severity in PwFD was measured using the FOS-MSSI (Fabry outcome study - Mainz severity score index), which comprises clinical and paraclinical parameters. PwFD show elevated sNfL Z-scores compared to HC (PwFD: 1.12 [SD 1.5], HC: 0.01 [SD 1.2], p < 0.001). In PwFD, males showed higher sNfL Z-scores than females (1.75 [SD 1.5] vs. 0.73 [SD 1.4]). Importantly, sNfL Z-scores were increased in PwFD with ischemic white matter lesions of the CNS (1.5, SD 2.2 vs. 0.5, SD 2.9, p = 0.03). In our small cohort, sNfL Z-scores correlated fairly with FOS-MSSI (Kendall's-Tau [τ] = 0.25, p = 0.01), and, interestingly with serum creatinine (τ = 0.28, p = 0.005) and estimated glomerular filtration rate (eGFR, τ =-0.28, p = 0.005). Based on these exploratory results, sNfL might provide value as a biomarker of neuroaxonal damage in FD, possibly reflecting cerebrovascular injury. Additionally, the correlation of sNfL with renal function warrants further investigation.

Expanding the Neurological Phenotype of Anderson-Fabry Disease: Proof of Concept for an Extrapyramidal Neurodegenerative Pattern and Comparison with Monogenic Vascular Parkinsonism

Anderson-Fabry disease (AFD) is a genetic sphingolipidosis involving virtually the entire body. Among its manifestation, the involvement of the central and peripheral nervous system is frequent. In recent decades, it has become evident that, besides cerebrovascular damage, a pure neuronal phenotype of AFD exists in the central nervous system, which is supported by clinical, pathological, and neuroimaging data. This neurodegenerative phenotype is often clinically characterized by an extrapyramidal component similar to the one seen in prodromal Parkinson's disease (PD). We analyzed the biological, clinical pathological, and neuroimaging data supporting this phenotype recently proposed in the literature. Moreover, we compared the neurodegenerative PD phenotype of AFD with a classical monogenic vascular disease responsible for vascular parkinsonism and cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). A substantial difference in the clinical and neuroimaging features of neurodegenerative and vascular parkinsonism phenotypes emerged, with AFD being potentially responsible for both forms of the extrapyramidal involvement, and CADASIL mainly associated with the vascular subtype. The available studies share some limitations regarding both patients' information and neurological and genetic investigations. Further studies are needed to clarify the potential association between AFD and extrapyramidal manifestations.

Assessing brain involvement in Fabry disease with deep learning and the brain-age paradigm

While neurological manifestations are core features of Fabry disease (FD), quantitative neuroimaging biomarkers allowing to measure brain involvement are lacking. We used deep learning and the brain-age paradigm to assess whether FD patients' brains appear older than normal and to validate brain-predicted age difference (brain-PAD) as a possible disease severity biomarker. MRI scans of FD patients and healthy controls (HCs) from a single Institution were, retrospectively, studied. The Fabry stabilization index (FASTEX) was recorded as a measure of disease severity. Using minimally preprocessed 3D T1-weighted brain scans of healthy subjects from eight publicly available sources (N = 2160; mean age = 33 years [range 4-86]), we trained a model predicting chronological age based on a DenseNet architecture and used it to generate brain-age predictions in the internal cohort. Within a linear modeling framework, brain-PAD was tested for age/sex-adjusted associations with diagnostic group (FD vs. HC), FASTEX score, and both global and voxel-level neuroimaging measures. We studied 52 FD patients (40.6 ± 12.6 years; 28F) and 58 HC (38.4 ± 13.4 years; 28F). The brain-age model achieved accurate out-of-sample performance (mean absolute error = 4.01 years, R2 = .90). FD patients had significantly higher brain-PAD than HC (estimated marginal means: 3.1 vs. -0.1, p = .01). Brain-PAD was associated with FASTEX score (B = 0.10, p = .02), brain parenchymal fraction (B = -153.50, p = .001), white matter hyperintensities load (B = 0.85, p = .01), and tissue volume reduction throughout the brain. We demonstrated that FD patients' brains appear older than normal. Brain-PAD correlates with FD-related multi-organ damage and is influenced by both global brain volume and white matter hyperintensities, offering a comprehensive biomarker of (neurological) disease severity.

Lysosomal storage diseases

Lysosomal storage disorders (LSDs) are a group of inherited metabolic diseases caused by dysfunction of the lysosomal system, with subsequent progressive accumulation of macromolecules, activation of inflammatory response, and cell death. Neurologic damage is almost always present, and it is usually degenerative. White matter (WM) involvement may be primary or secondary. Diseases with primary WM involvement are leukodystrophies, demyelinating (Krabbe disease and metachromatic leukodystrophy), and hypomyelinating leukodystrophies (free sialic acid storage disease, fucosidosis, and mucolipidosis type IV). LSDs with secondary WM involvement are classified as leukoencephalopathies and include gangliosidosis, mucopolysaccharidosis (MPS), ceroid neuronal lipofuscinosis, multiple sulfatase deficiency, alpha-mannosidosis, Pompe disease, and Fabry disease. Neurologic manifestations may overlap among LSDs and include developmental delays, motor, cognitive and speech impairments, seizures, visual failure, ataxia, and extrapyramidal signs. Most of LSDs are typically present in early or late infancy, but juvenile and adult forms also exist and are associated with predominantly neuropsychiatric and behavioral symptoms. The outcome of these disorders is generally poor and specific treatments (enzyme replacement therapy, hematopoietic stem cell transplantation, or gene therapy) are only available in a small number of them.

Progressive Changes in Cerebral Apparent Diffusion Values in Fabry Disease: A 5-Year Follow-up MRI Study

BACKGROUND AND PURPOSE

White matter lesions are commonly found in patients with Fabry disease. Existing studies have shown elevated diffusivity in healthy-appearing brain regions that are commonly associated with white matter lesions, suggesting that DWI could help detect white matter lesions at an earlier stage This study explores whether diffusivity changes precede white matter lesion formation in a cohort of patients with Fabry disease undergoing yearly MR imaging examinations during a 5-year period.

MATERIALS AND METHODS

T1-weighted anatomic, FLAIR, and DWI scans of 48 patients with Fabry disease (23 women; median age, 44 years; range, 15-69 years) were retrospectively included. White matter lesions and tissue probability maps were segmented and, together with ADC maps, were transformed into standard space. ADC values were determined within lesions before and after detection on FLAIR images and compared with normal-appearing white matter ADC. By means of linear mixed-effects modeling, changes in ADC and ΔADC (relative to normal-appearing white matter) across time were investigated.

RESULTS

ADC was significantly higher within white matter lesions compared with normal-appearing white matter (P < .01), even before detection on FLAIR images. ADC and ΔADC were significantly affected by sex, showing higher values in men (60.1 [95% CI, 23.8-96.3] ×10-6mm2/s and 35.1 [95% CI, 6.0-64.2] ×10-6mm2/s), respectively. ΔADC increased faster in men compared with women (0.99 [95% CI, 0.27-1.71] ×10-6mm2/s/month). ΔADC increased with time even when only considering data from before detection (0.57 [95% CI, 0.01-1.14] ×10-6mm2/s/month).

CONCLUSIONS

Our results indicate that in Fabry disease, changes in diffusion precede the formation of white matter lesions and that microstructural changes progress faster in men compared with women. These findings suggest that DWI may be of predictive value for white matter lesion formation in Fabry disease.

Compromised white matter is related to lower cognitive performance in adults with phenylketonuria

Despite increasing knowledge about the effects of phenylketonuria on brain structure and function, it is uncertain whether white matter microstructure is affected and if it is linked to patients' metabolic control or cognitive performance. Thus, we quantitatively assessed white matter characteristics in adults with phenylketonuria and assessed their relationship to concurrent brain and blood phenylalanine levels, historical metabolic control and cognitive performance. Diffusion tensor imaging and ¹H spectroscopy were performed in 30 adults with early-treated classical phenylketonuria (median age 35.5 years) and 54 healthy controls (median age 29.3 years). Fractional anisotropy and mean, axial and radial diffusivity were investigated using tract-based spatial statistics, and white matter lesion load was evaluated. Brain phenylalanine levels were measured with ¹H spectroscopy whereas concurrent plasma phenylalanine levels were assessed after an overnight fast. Retrospective phenylalanine levels were collected to estimate historical metabolic control, and a neuropsychological evaluation assessed the performance in executive functions, attention and processing speed. Widespread reductions in mean diffusivity, axial diffusivity and fractional anisotropy occurred in patients compared to controls. Mean diffusivity and axial diffusivity were decreased in several white matter tracts and were most restricted in the optic radiation (effect size r_rb = 0.66 to 0.78, P < 0.001) and posterior corona radiata (r_rb = 0.83 to 0.90, P < 0.001). Lower fractional anisotropy was found in the optic radiation and posterior corona radiata (r_rb = 0.43 to 0.49, P < 0.001). White matter microstructure in patients was significantly associated with cognition. Specifically, inhibition was related to axial diffusivity in the external capsule (r_s = -0.69, P < 0.001) and the superior (r_s = -0.58, P < 0.001) and inferior longitudinal fasciculi (r_s = -0.60, P < 0.001). Cognitive flexibility was associated with mean diffusivity of the posterior limb of the internal capsule (r_s = -0.62, P < 0.001), and divided attention correlated with fractional anisotropy of the external capsule (r_s = -0.61, P < 0.001). Neither concurrent nor historical metabolic control was significantly associated with white matter microstructure. White matter lesions were present in 29 out of 30 patients (96.7%), most often in the parietal and occipital lobes. However, total white matter lesion load scores were unrelated to patients' cognitive performance and metabolic control. In conclusion, our findings demonstrate that white matter alterations in early-treated phenylketonuria persist into adulthood, are most prominent in the posterior white matter and are likely to be driven by axonal damage. Furthermore, diffusion tensor imaging metrics in adults with phenylketonuria were related to performance in attention and executive functions.

Fabry Disease and Central Nervous System Involvement: From Big to Small, from Brain to Synapse

Fabry disease (FD) is an X-linked lysosomal storage disorder (LSD) secondary to mutations in the GLA gene that causes dysfunctional activity of lysosomal hydrolase α-galactosidase A and results in the accumulation of globotriaosylceramide (Gb3) and globotriaosylsphingosine (lyso-Gb3). The endothelial accumulation of these substrates results in injury to multiple organs, mainly the kidney, heart, brain and peripheral nervous system. The literature on FD and central nervous system involvement is scarce when focusing on alterations beyond cerebrovascular disease and is nearly absent in regard to synaptic dysfunction. In spite of that, reports have provided evidence for the CNS’ clinical implications in FD, including Parkinson’s disease, neuropsychiatric disorders and executive dysfunction. We aim to review these topics based on the current available scientific literature.

Structural disconnection and functional reorganization in Fabry disease: a multimodal MRI study

Central nervous system involvement in Fabry disease, a rare systemic X-linked lysosomal storage disorder, is characterized by the presence of heterogeneous but consistent functional and microstructural changes. Nevertheless, knowledge about the degree and extension of macro-scale brain connectivity modifications is to date missing. In this work, we performed connectomic analyses of diffusion and resting-state functional MRI to investigate changes of both structural and functional brain organization in Fabry disease, as well as to explore the relationship between the two and their clinical correlates. In this retrospective cross-sectional study, 46 patients with Fabry disease (28F, 42.2 ± 13.2years) and 49 healthy controls (21F, 42.3 ± 16.3years) were included. All subjects underwent an MRI examination including anatomical, diffusion and resting-state functional sequences. Images were processed to obtain quantitative structural and functional connectomes, where the connections between regions of interest were weighted by the total intra-axonal signal contribution of the corresponding bundle and by the correlation between blood-oxygen level–dependent time series, respectively. We explored between-group differences in terms of both global network properties, expressed with graph measures and specific connected subnetworks, identified using a network-based statistics approach. As exploratory analyses, we also investigated the possible association between cognitive performance and structural and functional connectome modifications at both global and subnetwork level in a subgroup of patients (n = 11). Compared with healthy controls, patients with Fabry disease showed a significantly reduced global efficiency (P = 0.005) and mean strength (P &lt; 0.001) in structural connectomes, together with an increased modularity (P = 0.005) in functional networks. As for the network-based statistics analysis, a subnetwork with decreased structural connectivity in patients with Fabry disease compared with healthy controls emerged, with eight nodes mainly located at the level of frontal or deep grey-matter areas. When probing the relation between altered global network metrics and neuropsychological tests, correlations emerged between the structural and functional disruption with results at verbal and working memory tests, respectively. Furthermore, structural disruption at subnetwork level was associated with worse executive functioning, with a significant moderation effect of functional changes suggesting a compensation mechanism. Taken together, these results further expand the current knowledge about brain involvement in Fabry disease, showing widespread structural disconnection and functional reorganization, primarily sustained by loss in axonal integrity and correlating with cognitive performance.

Cognitive dysfunction and white matter hyperintensities in Fabry disease

Fabry disease (FD) is an X-linked lysosomal storage disorder with multi-system involvement including cerebrovascular disease. Patients with FD also have a high risk of ischaemic stroke and TIA. White matter hyperintensities are common, but their clinical impact on cognition remains uncertain. Previous studies have examined the neuropsychological profile of FD, but have been inconclusive in part due to methodological limitations including small sample sizes. We sought to address these limitations in a case-control study of 26 patients with Fabry disease with mild to moderate disease symptoms matched with 18 healthy controls for age and premorbid intellectual level. We obtained detailed neuropsychological data and MRI neuroimaging data on the severity of white matter changes. Mood was accounted for as a possible confounder. Our results showed significant compromise of executive functions and information processing speed for the FD group. Error analyses suggested that the compromise of executive functions could not be entirely accounted for by slowed information processing speed. We demonstrated significant correlations between cognitive decline and the overall volume of white matter hyperintensities in the FD group. Our results point to significant compromise of cognition in FD even without stroke or mood difficulties. This suggests that neuropsychological assessment and rehabilitation should be routinely offered to patients with FD.

Gardenia jasminoides J. Ellis extract alleviated white matter damage through promoting the differentiation of oligodendrocyte precursor cells via suppressing neuroinflammation

Increasing evidence has highlighted the role of white matter damage in the pathology of Alzheimer's disease (AD). Previous research has shown that a mixture of crocin analogues (GJ-4), Gardenia jasminoides J. Ellis extract, improved cognition in several AD mouse models, but the mechanism remains unclear. The aim of the present study was to investigate the effects and underlying mechanisms of GJ-4 on white matter damage. Proteomic analysis and western blotting results suggested that the level of myelin-related proteins, including myelin basic protein (MBP), myelin associated glycoprotein (MAG) and myelin associated oligodendrocyte basic protein (MOBP), was significantly decreased in the brain of PrP-hAβPPswe/PS1ΔE9 (APP/PS1) transgenic mice, and GJ-4 treatment increased the expressions of these proteins. This result revealed that GJ-4 could ameliorate myelin injury, suggesting that this might be a possible mechanism of GJ-4 on cognition. To validate the effects of GJ-4 on myelin, a metabolite of GJ-4, crocetin, which can pass through the blood-brain barrier, was applied in in vitro experiments. A mechanistic study revealed that crocetin significantly promoted the differentiation of primary cultured oligodendrocyte precursor cells to oligodendrocytes through up-regulation of nuclear Ki67 and transcription factor 2 (Olig2). Oligodendrocytes, the myelin-forming cells, have been reported to be lifelong partners of neurons. Therefore, to investigate the effects of crocetin on myelin and neurons, lysophosphatidylcholine (LPC)-treated primary mixed midbrain neuronal/glial culture was used. Immunofluorescence results indicated that crocetin treatment protected neurons and suppressed microglial activation against LPC-induced injury. To further discern the effects of GJ-4 on white matter injury and neuroinflammation, an LPC-induced mouse model was developed. GJ-4 administration increased oligodendrocyte proliferation, differentiation, and myelin repair. The mechanistic study indicated that GJ-4 improved white matter injury through the regulation of neuroinflammatory dysfunction. These data indicated that GJ-4 effectively repaired white matter damage in the LPC-treated mice. Thus, the present study supported GJ-4 as a potential therapeutic agent for AD and white matter related diseases.

The central vein sign helps in differentiating multiple sclerosis from its mimickers: lessons from Fabry disease

OBJECTIVES

Although the use of specific MRI criteria has significantly increased the diagnostic accuracy of multiple sclerosis (MS), reaching a correct neuroradiological diagnosis remains a challenging task, and therefore the search for new imaging biomarkers is crucial. This study aims to evaluate the incidence of one of the emerging neuroradiological signs highly suggestive of MS, the central vein sign (CVS), using data from Fabry disease (FD) patients as an index of microvascular disorder that could mimic MS.

METHODS

In this retrospective study, after the application of inclusion and exclusion criteria, MRI scans of 36 FD patients and 73 relapsing-remitting (RR) MS patients were evaluated. Among the RRMS participants, 32 subjects with a disease duration inferior to 5 years (early MS) were also analyzed. For all subjects, a Fazekas score (FS) was recorded, excluding patients with FS = 0. Different neuroradiological signs, including CVS, were evaluated on FLAIR T2-weighted and spoiled gradient recalled echo sequences.

RESULTS

Among all the recorded neuroradiological signs, the most striking difference was found for the CVS, with a detectable prevalence of 78.1% (57/73) in RRMS and of 71.4% (25/32) in early MS patients, while this sign was absent in FD (0/36).

CONCLUSIONS

Our results confirm the high incidence of CVS in MS, also in the early phases of the disease, while it seems to be absent in conditions with a different etiology. These results corroborate the possible role of CVS as a useful neuroradiological sign highly suggestive of MS.

KEY POINTS

• The search for new imaging biomarkers is crucial to achieve a correct neuroradiological diagnosis of MS. • The CVS shows an incidence superior to 70% in MS patients, even in the early phases of the disease, while it appears to be absent in FD. • These findings further corroborate the possible future central role of CVS in distinguishing between MS and its mimickers.

Diffusion tensor imaging reveals neuronal microstructural changes in myalgic encephalomyelitis/chronic fatigue syndrome

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) patients suffer from a variety of physical and neurological complaints indicating the central nervous system plays a role in ME/CFS pathophysiology. Diffusion tensor imaging (DTI) has been used to study microstructural changes in neurodegenerative diseases. In this study, we evaluated DTI parameters to investigate microstructural abnormalities in ME/CFS patients. We estimated DTI parameters in 25 ME/CFS patients who met Fukuda criteria (ME/CFS_Fukuda ), 18 ME/CFS patients who met International Consensus Criteria (ICC) (ME/CFS_ICC ) only and 26 healthy control (HC) subjects. In addition to voxel-based DTI-parameter group comparisons, we performed voxel-based DTI-parameter interaction-with-group regressions with clinical and autonomic measures to test for abnormal regressions. Group comparisons between ME/CFS_ICC and HC detected significant clusters (a) with decreased axial diffusivity (p = .001) and mean diffusivity (p = .01) in the descending cortico-cerebellar tract in the midbrain and pons and (b) with increased transverse diffusivity in the medulla. The mode of anisotropy was significantly decreased (p = .001) in a cluster in the superior longitudinal fasciculus region. Voxel-based group comparisons between ME/CFS_Fukuda and HC did not detect significant clusters. For ME/CFS_ICC and HC, DTI parameter interaction-with-group regressions were abnormal for the clinical measures of information processing score, SF36 physical, sleep disturbance score and respiration rate in both grey and white matter regions. Our study demonstrated that DTI parameters are sensitive to microstructural changes in ME/CFS_ICC and could potentially act as an imaging biomarker of abnormal pathophysiology in ME/CFS. The study also shows that strict case definitions are essential in investigation of the pathophysiology of ME/CFS.

Brain MRI in Monogenic Cerebral Small Vessel Diseases: A Practical Handbook

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Monogenic cerebral small vessel diseases are a topic of growing interest, as several genes responsible have been recently described and new sequencing techniques such as Next generation sequencing are available. Brain imaging is a key exam in these diseases. First, since it is often the first exam performed, an MRI is key in selecting patients for genetic testing and for interpreting Next generation sequencing reports. In addition, neuroimaging can be helpful in describing the underlying pathological mechanisms involved in cerebral small vessel disease. With this review, we aim to provide Neurologists and Stroke physicians with an up-to date overview of the current neuroimaging knowledge on monogenic small vessel diseases.