MRI T2 and T2* relaxometry to visualize neuromelanin in the dorsal substantia nigra pars compacta

Visualizing gradual changes in neuromelanin distribution within the substantia nigra is an important metric used to monitor the progression of Parkinsonism. This study aimed to identify the origin of the mismatch region between magnetic resonance transverse relaxation times (T2 and T2*) in the substantia nigra and investigate its feasibility and implications for in vivo detection of neuromelanin as a clinical biomarker. The relationships between neuromelanin distribution assessed by histological staining and the area of T2 and T2* mismatch determined by high- and low-resolution magnetic resonance relaxometry at 7T were directly compared in two normal and one depigmented substantia nigra collected at postmortem. In vivo feasibility of assessing T2 and T2* mismatch, clinically, was investigated using 3T magnetic resonance imaging. In the normal postmortem substantia nigra tissue, the T2 and T2* mismatch region exhibiting a linear pattern was strongly colocalized with neuromelanin distribution along the dorsal substantia nigra pars compacta, but a negligible amount of dorsal mismatch was observed in the depigmented brain. The regions of T2 and T2* mismatch from MRI, neuromelanin pigments from histology, and elevated iron signals from mass spectrometry were spatially overlapped for a normal postmortem brain. In preliminary in vivo studies, a similar, linear T2 and T2* mismatch region was observed in the dorsal area of the substantia nigra in eight normal subjects; this mismatch was significantly obscured in eight Parkinson???s disease patients. The length of the dorsal linear mismatch line based on the T2*-T2 mask was significantly shorter in the Parkinson???s disease patients compared to normal controls; this result was corroborated by reduced striatal uptake of [18F] FP-CIT dopamine transporters assessed by positron emission tomography scans. In conclusion, the measurement of T2 and T2* mismatch could serve as a complementary imaging biomarker to visualize the dorsal region of the substantia nigra pars compacta, which contains large amounts of neuromelanin

Susceptibility-related phase contrast associated with the alterations of myelo- architecture in adult-onset leukoencephalopathy with neuroaxonal spheroids and pigmented glia

To investigate the origin of susceptibility-weighted imaging (SWI) contrast in frontal white matters of adult-onset leukoencephalopathy with neuroaxonal spheroids and pigmented glia (ALSP), we performed a combined post-mortem magnetic resonance imaging (MRI) and histological study of ALSP pathology. The myelin architectural changes, marked central myelin loss with preserved U-fibers beneath cortical gray matter, mainly contributed to the susceptibility contrast

Comparison Study between T2*, Quantitative Susceptibility Mapping, and Histology for Postmortem Human Substantia Nigra

Selective iron deposition in the substantia nigra (SN) along with the gradual loss of neuromelanin cell (NMC) is known to be associated with neurodegenerative diseases, such as Parkinson's disease. Postmortem 40-year-old male and 70-year-old female SN tissues were scanned at various spatial resolutions with 7T MRI. The association of T2* and QSM-derived susceptibility values with quantitative NMC and iron from Perl's Prussian blue staining were investigated with precise co-registration of MRI and histology. We identified that T2* and susceptibility values for NMC and iron regions, which were segmented from histology were significantly different from corresponding values of background tissue area

Neuropsychological, neuroimaging and autopsy findings of butane encephalopathy

Abstract Background Butane is an aliphatic hydrocarbon used in various commercial products. While numerous reports of sudden cardiac-related deaths from butane inhalation have been described, butane-associated acute encephalopathy has rarely been reported. Case presentation A 38-year-old man presented with cognitive dysfunction after butane gas inhalation. Neuropsychological test results showed impairments in verbal and visual memory, and frontal executive function. Diffusion weighted MRI revealed symmetric high-signal changes in the bilateral hippocampus and globus pallidus. FDG-PET demonstrated decreased glucose metabolism in the bilateral precuneus and occipital areas and the left temporal region. At the 8-month follow-up, he showed still significant deficits in memory and frontal functions. Diffuse cortical atrophy with white matter hyperintensities and extensive glucose hypometabolism were detected on follow-up MRI and FDG-PET, respectively. Brain autopsy demonstrated necrosis and cavitary lesions in the globus pallidus. Conclusions Only a few cases of butane encephalopathy have been reported to date. Brain lesions associated with butane encephalopathy include lesions in the bilateral thalamus, insula, putamen, and cerebellum. To the best of our knowledge, this is the first report on bilateral hippocampal and globus pallidal involvement in acute butane encephalopathy. The pathophysiology of central nervous system complications induced by butane intoxication is not yet fully understood. However, the direct toxic effects of butane or anoxic injury secondary to cardiac arrest or respiratory depression have been suggested as possible mechanisms of edematous changes in the brain after butane intoxication