Off-resonance saturation as an MRI method to quantify mineral- iron in the post-mortem brain.

PURPOSE: To employ an off-resonance saturation method to measure the mineral-iron pool in the postmortem brain, which is an endogenous contrast agent that can give information on cellular iron status. METHODS: An off-resonance saturation acquisition protocol was implemented on a 7 Tesla preclinical scanner, and the contrast maps were fitted to an established analytical model. The method was validated by correlation and Bland-Altman analysis on a ferritin-containing phantom. Mineral-iron maps were obtained from postmortem tissue of patients with neurological diseases characterized by brain iron accumulation, that is, Alzheimer disease, Huntington disease, and aceruloplasminemia, and validated with histology. Transverse relaxation rate and magnetic susceptibility values were used for comparison. RESULTS: In postmortem tissue, the mineral-iron contrast colocalizes with histological iron staining in all the cases. Iron concentrations obtained via the off-resonance saturation method are in agreement with literature. CONCLUSIONS: Off-resonance saturation is an effective way to detect iron in gray matter structures and partially mitigate for the presence of myelin. If a reference region with little iron is available in the tissue, the method can produce quantitative iron maps. This method is applicable in the study of diseases characterized by brain iron accumulation and can complement existing iron-sensitive parametric methods.

MR imaging for the quantitative assessment of brain iron in aceruloplasminemia: A postmortem validation study.

AIMS: Non-invasive measures of brain iron content would be of great benefit in neurodegeneration with brain iron accumulation (NBIA) to serve as a biomarker for disease progression and evaluation of iron chelation therapy. Although magnetic resonance imaging (MRI) provides several quantitative measures of brain iron content, none of these have been validated for patients with a severely increased cerebral iron burden. We aimed to validate R2* as a quantitative measure of brain iron content in aceruloplasminemia, the most severely iron-loaded NBIA phenotype. METHODS: Tissue samples from 50 gray- and white matter regions of a postmortem aceruloplasminemia brain and control subject were scanned at 1.5 T to obtain R2*, and biochemically analyzed with inductively coupled plasma mass spectrometry. For gray matter samples of the aceruloplasminemia brain, sample R2* values were compared with postmortem in situ MRI data that had been obtained from the same subject at 3 T - in situ R2*. Relationships between R2* and tissue iron concentration were determined by linear regression analyses. RESULTS: Median iron concentrations throughout the whole aceruloplasminemia brain were 10 to 15 times higher than in the control subject, and R2* was linearly associated with iron concentration. For gray matter samples of the aceruloplasminemia subject with an iron concentration up to 1000 mg/kg, 91% of variation in R2* could be explained by iron, and in situ R2* at 3 T and sample R2* at 1.5 T were highly correlated. For white matter regions of the aceruloplasminemia brain, 85% of variation in R2* could be explained by iron. CONCLUSIONS: R2* is highly sensitive to variations in iron concentration in the severely iron-loaded brain, and might be used as a non-invasive measure of brain iron content in aceruloplasminemia and potentially other NBIA disorders.

Quantification of different iron forms in the aceruloplasminemia brain to explore iron-related neurodegeneration.

AIMS: Aceruloplasminemia is an ultra-rare neurodegenerative disorder associated with massive brain iron deposits, of which the molecular composition is unknown. We aimed to quantitatively determine the molecular iron forms in the aceruloplasminemia brain, and to illustrate their influence on iron-sensitive MRI metrics. METHODS: The inhomogeneous transverse relaxation rate (R2*) and magnetic susceptibility obtained from 7 T MRI were combined with Electron Paramagnetic Resonance (EPR) and Superconducting Quantum Interference Device (SQUID) magnetometry. The basal ganglia, thalamus, red nucleus, dentate nucleus, superior- and middle temporal gyrus and white matter of a post-mortem aceruloplasminemia brain were studied. MRI, EPR and SQUID results that had been previously obtained from the temporal cortex of healthy controls were included for comparison. RESULTS: The brain iron pool in aceruloplasminemia detected in this study consisted of EPR-detectable Fe3+ ions, magnetic Fe3+ embedded in the core of ferritin and hemosiderin (ferrihydrite-iron), and magnetic Fe3+ embedded in oxidized magnetite/maghemite minerals (maghemite-iron). Ferrihydrite-iron represented above 90% of all iron and was the main driver of iron-sensitive MRI contrast. Although deep gray matter structures were three times richer in ferrihydrite-iron than the temporal cortex, ferrihydrite-iron was already six times more abundant in the temporal cortex of the patient with aceruloplasminemia compared to the healthy situation (162 µg/g vs. 27 µg/g), on average. The concentrations of Fe3+ ions and maghemite-iron in the temporal cortex in aceruloplasminemia were within the range of those in the control subjects. CONCLUSIONS: Iron-related neurodegeneration in aceruloplasminemia is primarily associated with an increase in ferrihydrite-iron, with ferrihydrite-iron being the major determinant of iron-sensitive MRI contrast.

Effects of iron chelation therapy on the clinical course of aceruloplasminemia: an analysis of aggregated case reports.

BACKGROUND: Aceruloplasminemia is a rare genetic iron overload disorder, characterized by progressive neurological manifestations. The effects of iron chelation on neurological outcomes have only been described in case studies, and are inconsistent. Aggregated case reports were analyzed to help delineate the disease-modifying potential of treatment. METHODS: Data on clinical manifestations, treatment and neurological outcomes of treatment were collected from three neurologically symptomatic Dutch patients, who received deferiprone with phlebotomy as a new therapeutic approach, and combined with other published cases. Neurological outcomes of treatment were compared between patients starting treatment when neurologically symptomatic and patients without neurological manifestations. RESULTS: Therapeutic approaches for aceruloplasminemia have been described in 48 patients worldwide, including our three patients. Initiation of treatment in a presymptomatic stage of the disease delayed the estimated onset of neurological manifestations by 10 years (median age 61 years, SE 5.0 vs. median age 51 years, SE 0.6, p = 0.001). Although in 11/20 neurologically symptomatic patients neurological manifestations remained stable or improved during treatment, these patients were treated significantly shorter than patients who deteriorated neurologically (median 6 months vs. median 43 months, p = 0.016). Combined iron chelation therapy with deferiprone and phlebotomy for up to 34 months could be safely performed in our patients without symptomatic anemia (2/3), but did not prevent further neurological deterioration. CONCLUSIONS: Early initiation of iron chelation therapy seems to postpone the onset of neurological manifestations in aceruloplasminemia. Publication bias and significant differences in duration of treatment should be considered when interpreting reported treatment outcomes in neurologically symptomatic patients. Based on theoretical grounds and the observed long-term safety and tolerability in our study, we recommend iron chelation therapy with deferiprone in combination with phlebotomy for aceruloplasminemia patients without symptomatic anemia.

New insights in the neurological phenotype of aceruloplasminemia in Caucasian patients.

INTRODUCTION: The diagnosis aceruloplasminemia is usually made in patients with advanced neurological manifestations of the disease. In these patients prognosis is poor, disabilities are severe and patients often die young. The aim of our study was to facilitate recognition of aceruloplasminemia at a disease stage at which treatment can positively influence outcome. Currently, the neurological phenotype of aceruloplasminemia has been mainly described in Japanese patients. This 'classical' phenotype consists of cerebellar ataxia, hyperkinetic movement disorders and cognitive decline. In this study we describe the spectrum of neurological disease in Caucasian patients. METHODS: Data on neurological presentation and follow-up were gathered from both our patients, homozygous for the G631R mutation in the CP gene, and other published Caucasian cases. Neurological features of aceruloplasminemia in Caucasian patients were compared to those summarized in Japanese patients. RESULTS: 21 Caucasian patients, both ours and the described cases, displayed a wide range of movement disorders with predominant chorea, parkinsonism and ataxia, and also tremor and dystonia. In addition to cognitive decline, nearly half of the Caucasian patients presented with psychiatric changes, including depression, anxiety and behavioral changes. In one-third of the neurologically symptomatic Caucasian patients, cognitive- or psychiatric changes were the first neurological manifestations of aceruloplasminemia. CONCLUSIONS: Aceruloplasminemia in Caucasian patients can present with a wider range and a different order of neurological symptoms than previously described in Japanese patients. Psychiatric changes and parkinsonism can be added to the spectrum of neurological disease. Cognitive- or psychiatric changes may be the first neurological manifestations of aceruloplasminemia.