Pathology of the cerebellar dentate nucleus in sporadic olivopontocerebellar atrophy: a morphometric investigation

Quantifying iron deposition in the cerebellar subtype of multiple system atrophy and spinocerebellar ataxia type 6 by quantitative susceptibility mapping

We used quantitative susceptibility mapping (QSM) to assess the brain iron deposition in 28 patients with the cerebellar subtype of multiple system atrophy (MSA-C), nine patients with spinocerebellar ataxia type 6 (SCA6), and 23 healthy controls. Two reviewers independently measured the mean QSM values in brain structures including the putamen, globus pallidus, caudate nucleus, red nucleus, substantia nigra, and cerebellar dentate nucleus. A receiver operating characteristics (ROC) analysis was performed to assess the diagnostic usefulness of the QSM measurements. The QSM values in the substantia nigra were significantly higher in the MSA-C group compared to the HC group (p = .007). The QSM values in the cerebellar dentate nucleus were significantly higher in MSA-C than those in the SCA6 and HC groups (p < .001), and significantly lower in the SCA6 patients compared to the HCs (p = .027). The QSM values in the cerebellar dentate nucleus were correlated with disease duration in MSA-C, but inversely correlated with disease duration in SCA6. In the ROC analysis, the QSM values in the cerebellar dentate nucleus showed excellent accuracy for differentiating MSA-C from SCA6 (area under curve [AUC], 0.925), and good accuracy for differentiating MSA-C from healthy controls (AUC 0.834). QSM can identify increased susceptibility of the substantia nigra and cerebellar dentate nucleus in MSA-C patients. These results suggest that an increase in iron accumulation in the cerebellar dentate nucleus may be secondary to the neurodegeneration associated with MSA-C.

The genetics and pathology of mitochondrial disease

Mitochondria are double-membrane-bound organelles that are present in all nucleated eukaryotic cells and are responsible for the production of cellular energy in the form of ATP. Mitochondrial function is under dual genetic control - the 16.6-kb mitochondrial genome, with only 37 genes, and the nuclear genome, which encodes the remaining ∼1300 proteins of the mitoproteome. Mitochondrial dysfunction can arise because of defects in either mitochondrial DNA or nuclear mitochondrial genes, and can present in childhood or adulthood in association with vast clinical heterogeneity, with symptoms affecting a single organ or tissue, or multisystem involvement. There is no cure for mitochondrial disease for the vast majority of mitochondrial disease patients, and a genetic diagnosis is therefore crucial for genetic counselling and recurrence risk calculation, and can impact on the clinical management of affected patients. Next-generation sequencing strategies are proving pivotal in the discovery of new disease genes and the diagnosis of clinically affected patients; mutations in >250 genes have now been shown to cause mitochondrial disease, and the biochemical, histochemical, immunocytochemical and neuropathological characterization of these patients has led to improved diagnostic testing strategies and novel diagnostic techniques. This review focuses on the current genetic landscape associated with mitochondrial disease, before focusing on advances in studying associated mitochondrial pathology in two, clinically relevant organs - skeletal muscle and brain. © 2016 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Corticobasal degeneration with olivopontocerebellar atrophy and TDP-43 pathology: an unusual clinicopathologic variant of CBD

Corticobasal degeneration (CBD) is a disorder affecting cognition and movement due to a progressive neurodegeneration associated with distinctive neuropathologic features, including abnormal phosphorylated tau protein in neurons and glia in cortex, basal ganglia, diencephalon, and brainstem, as well as ballooned neurons and astrocytic plaques. We identified three cases of CBD with olivopontocerebellar atrophy (CBD-OPCA) that did not have α-synuclein-positive glial cytoplasmic inclusions of multiple system atrophy (MSA). Two patients had clinical features suggestive of progressive supranuclear palsy (PSP), and the third case had cerebellar ataxia thought to be due to idiopathic OPCA. Neuropathologic features of CBD-OPCA are compared to typical CBD, as well as MSA and PSP. CBD-OPCA and MSA had marked neuronal loss in pontine nuclei, inferior olivary nucleus, and Purkinje cell layer. Neuronal loss and grumose degeneration in the cerebellar dentate nucleus were comparable in CBD-OPCA and PSP. Image analysis of tau pathology showed greater infratentorial tau burden, especially in pontine base, in CBD-OPCA compared with typical CBD. In addition, CBD-OPCA had TDP-43 immunoreactive neuronal and glial cytoplasmic inclusions and threads throughout the basal ganglia and in olivopontocerebellar system. CBD-OPCA met neuropathologic research diagnostic criteria for CBD and shared tau biochemical characteristics with typical CBD. These results suggest that CBD-OPCA is a distinct clinicopathologic variant of CBD with olivopontocerebellar TDP-43 pathology.

Cerebellar pathology in sporadic and familial Alzheimer's disease including APP 717 (Val-->Ile) mutation cases: a morphometric investigation

Familial Alzheimer's disease (FAD) tends to present with more prominent neurological symptoms including cerebellar signs than sporadic Alzheimer's disease (SAD). In order to elucidate the pathological differences in the cerebellum, which may be associated with the cerebellar symptoms, we have investigated morphometrically beta-amyloid deposits, atrocytosis, Purkinje cells and dentate neurons in the cerebellum of 10 FAD patients including two cases with the beta-amyloid precursor protein (APP) gene mutation (APP717 Val-->Ile), 10 SAD patients and 10 non-demented age-matched controls. The regions examined included the molecular, Purkinje cell and granular cell layers, the cerebellar white matter and the dentate nucleus. Purkinje cell density in FAD was significantly lower than in SAD. There were no significant differences in the density of dentate neurons among the three groups. The density of astrocytes in FAD was significantly greater than that in SAD in the granular cell and Purkinje cell layers and in the white matter. There were no significant differences in the amount and subtypes of beta-amyloid deposits (extracellular, vascular and perivascular) between FAD and SAD in all the regions investigated. In two cases with the APP mutation, both Purkinje cell loss and beta-amyloid deposition in the cerebellum were greater than the mean for FAD and SAD cases. Astrocytosis in the mutation cases was not greater than the mean for FAD cases except for the dentate nucleus in one case. Extracellular beta-amyloid deposits were not seen in any of the control cases although amyloid angiopathy was observed in one case. This study demonstrates for the first time that Purkinje cell loss and reactive astrocytosis of the cerebellum in FAD are more severe than in SAD, but that beta-amyloid deposition in the cerebellum in both FAD and SAD are similar. The more prominent neurological signs observed in FAD may be explained by more severe neurodegeneration than are found in sporadic cases.