Magnetic resonance imaging detection of deep gray matter iron deposition in multiple sclerosis: A systematic review

Excessive iron accumulation in the striatum associated with addictive behaviors of medication-overuse headache: a prospective study

BACKGROUND

Abnormal iron deposition may be a biomarker for a disrupted central antinociceptive neuronal network, and the relationship between iron deposition and the pathophysiological mechanisms of chronic migraine (CM) with medication overuse (MOH) remains unclear. We investigated iron deposition in the deep gray matter (DGM) of the brain in CM patients with and without MOH using quantitative susceptibility mapping (QSM).

METHODS

Forty-eight healthy controls (HCs) and 69 CM patients (36 with MOH; 33 without MOH) were recruited. QSM data were acquired using a 3.0 T Magnetic resonance imaging (MRI). Regions of interest (ROI) in the DGM, including the bilateral caudate, putamen, globus pallidus (GP), hippocampus, nucleus accumbens, and amygdala, were segmented from the T1-weighted images (T1WI) of the whole brain of each individual patient using FreeSurfer. QSM images were registered to T1WI. QSM values within each ROI were extracted and compared between CM and HCs, as well as between CM with MOH and CM without MOH. Correlations between QSM values and clinical assessment scale scores were calculated. Receiver operating characteristic (ROC) analysis was used to assess the diagnostic performance of QSM values in these DGM for detecting CM and CM with MOH.

RESULTS

Compared to HCs, CM patients exhibited increased iron deposition in the caudate (p = 0.013) and putamen (p < 0.001). In the CM without MOH group, headache duration correlated positively with iron deposition in the caudate (r = 0.502, p = 0.010) and putamen (r = 0.514, p = 0.009). CM with MOH patients showed greater iron deposition in the caudate (p < 0.001), putamen (p < 0.001), and GP (p = 0.049) than those without MOH, with medication use frequency correlating positively with iron deposition in the caudate (r = 0.427, p = 0.023) and putamen (r = 0.445, p = 0.018). ROC curve analysis indicated that the caudate (AUC = 0.736) and putamen (AUC = 0.729) exhibited high sensitivity and specificity in diagnosing CM with MOH.

CONCLUSIONS

CM patients with MOH had excessive iron deposition in basal ganglia regions, including the caudate, putamen, and GP, which may be related to the medication overuse behavior. Iron deposition in the caudate and putamen may be a potential biomarker for CM with MOH. These findings provide insight into the common pathophysiological mechanisms underlying MOH and potential addiction.

Thalamic iron in multiple sclerosis: Waning support for the early-rise late-decline hypothesis

BACKGROUND

Studies of thalamic iron levels in multiple sclerosis (MS) have yielded variable findings, potentially due to differences in study cohorts. For example, studies in relatively young cohorts (average ages below 40 years) have reported elevated susceptibility in people with MS (pwMS), whereas studies in older cohorts (above 40 years) found decreased susceptibility.

OBJECTIVE

To test the "early-rise late-decline" hypothesis, which posits that age differences in study cohorts are responsible for conflicting findings regarding thalamic susceptibility in MS.

METHODS

We chose to replicate one of the previous studies that showed evidence of elevated thalamic iron concentrations in younger pwMS (Rudko et al., 2014). We also replicated a study involving older pwMS (Pudlac et al., 2020) to serve as a control. We assessed thalamic susceptibility using the QSM processing and analysis methodology outlined by Rudko et al. RESULTS: Although cohort characteristics, QSM processing, and analytical methods were closely matched, we found significantly lower thalamic susceptibility in the younger pwMS compared to controls (-1.1 ± 7.8 vs. 5.4 ± 6.1 ppb; effect sizes: -0.35 to -0.91). Study outcomes were robust across a wide range of regularization parameters, with effect size differences influenced by background field removal regularization. A similar pattern was observed in the older cohort, where thalamic susceptibility was again lower in pwMS compared to controls (4.0 ± 9.5 vs. 9.6 ± 10.7 ppb; effect size: -0.55).

CONCLUSIONS

Our findings contradict the "early rise" hypothesis of thalamic iron levels in pwMS. The consistency of our results across multiple analyses suggests that QSM processing artifacts are unlikely to explain previous reports of increased thalamic iron. Instead, these variations may stem from demographic or clinical differences, such as geographical factors and treatment regimens.

Cerebral iron accumulation in multiple sclerosis: Pathophysiology and therapeutic implications

Multiple sclerosis (MS) is a chronic autoimmune disorder of the central nervous system characterized by demyelination, neuroinflammation, and neurodegeneration. Recent studies highlight the role of cerebral iron (Fe) accumulation in exacerbating MS pathophysiology. Fe, essential for neural function, contributes to oxidative stress and inflammation when dysregulated, particularly in the brain's gray matter and demyelinated lesions. Advanced imaging techniques, including susceptibility-weighted and quantitative susceptibility mapping, have revealed abnormal Fe deposition patterns in MS patients, suggesting its involvement in disease progression. Iron's interaction with immune cells, such as microglia, releases pro-inflammatory cytokines, further amplifying neuroinflammation and neuronal damage. These findings implicate Fe dysregulation as a significant factor in MS progression, contributing to clinical manifestations like cognitive impairment. Therapeutic strategies targeting Fe metabolism, including Fe chelation therapies, show promise in reducing Fe-related damage, instilling optimism about the future of MS treatment. However, challenges such as crossing the blood-brain barrier and maintaining Fe homeostasis remain. Emerging approaches, such as Fe-targeted nanotherapeutics and biologics, offer new possibilities for personalized treatments. However, the journey is far from over. Continued research into the molecular mechanisms of Fe-induced neuroinflammation and oxidative damage is essential. Through this research, we can develop effective interventions that could slow MS progression and improve patient outcomes.

Quantitative Susceptibility Mapping Values Quantification in Deep Gray Matter Structures for Relapsing-Remitting Multiple Sclerosis: A Systematic Review and Meta-Analysis

BACKGROUND/OBJECTIVES

This systematic review and meta-analysis aimed to investigate the role of magnetic susceptibility (χ) in deep gray matter (DGM) structures, including the putamen (PUT), globus pallidus (GP), caudate nucleus (CN), and thalamus, in the most common types of multiple sclerosis (MS) and relapsing-remitting MS (RRMS), using quantitative susceptibility mapping (QSM).

METHODS

The literature was systematically reviewed up to November 2023, adhering to PRISMA guidelines. This study was conducted using a random-effects model to calculate the standardized mean difference (SMD) in QSM values between patients with RRMS and healthy controls (HCs). Publication bias and risk of bias were also assessed.

RESULTS

Nine studies involving 1074 RRMS patients with RRMS and 640 HCs were included in the meta-analysis. The results showed significantly higher QSM (χ) values in the PUT (SMD = 0.40, 95% confidence interval [CI] = 0.22-0.59, p = .000), GP (SMD = 0.60, 95% CI = 0.50-0.70, p = .00), and CN (SMD = 0.40, 95% CI = 0.15-0.66, p = .005) of RRMS patients compared to HCs. However, there were no significant differences in the QSM values in the thalamus between patients with RRMS and HCs (SMD = -0.33, 95% CI -0.67-0.01, p = .026). Age- and sex-based subgroup analysis demonstrated that younger patients (< 40 years) in the PUT, GP, and CN groups and larger male populations (> 25%) in the PUT and GP groups had more significant χ. Interestingly, thalamic QSM values were found to decrease in RRMS patients over 40 years of age and in higher male populations. Sex-based subgroup analysis indicated higher iron levels in the PUT and GP of RRMS patients regardless of sex. QSM values were higher in certain brain regions (PUT, GP, and CN) during the early stages (disease duration < 9.6 years) of RRMS, but lower in the thalamus during the later stages (disease duration > 9.6 years) than HCs.

DISCUSSION/CONCLUSION

QSM may serve as a biomarker for understanding χ value alterations such as iron dysregulation and its contribution to neurodegeneration in RRMS, especially in the basal ganglia nuclei including PUT, GP, and CN.

Postencephalitic Parkinsonism: Unique Pathological and Clinical Features-Preliminary Data

Postencephalitic parkinsonism (PEP) is suggested to show a virus-induced pathology, which is different from classical idiopathic Parkinson's disease (PD) as there is no α-synuclein/Lewy body pathology. However, PEP shows a typical clinical representation of motor disturbances. In addition, compared to PD, there is no iron-induced pathology. The aim of this preliminary study was to compare PEP with PD regarding iron-induced pathology, using histochemistry methods on paraffin-embedded post-mortem brain tissue. In the PEP group, iron was not seen, except for one case with sparse perivascular depositions. Rather, PEP offers a pathology related to tau-protein/neurofibrillary tangles, with mild to moderate memory deficits only. It is assumed that this virus-induced pathology is due to immunological dysfunctions causing (neuro)inflammation-induced neuronal network disturbances as events that trigger clinical parkinsonism. The absence of iron deposits implies that PEP cannot be treated with iron chelators. The therapy with L-Dopa is also not an option, as L-Dopa only leads to an initial slight improvement in symptoms in isolated cases.

Decoding Gray Matter Involvement in Multiple Sclerosis via Imaging

Multiple sclerosis (MS) is increasingly understood not only as a white matter disease but also involving both the deep and cortical gray matter (GM). GM pathology in people with MS (pwMS) includes the presence of lesions, leptomeningeal inflammation, atrophy, altered iron concentration, and microstructural changes. Studies using 7T and 3T MR imaging with optimized protocols established that GM damage is a principal driver of disease progression in pwMS. Future work is needed to incorporate the assessment of these GM imaging biomarkers into the clinical workup of pwMS and the assessment of treatment efficacy.