Novel clinicopathological characteristics differentiate dementia with Lewy bodies from Parkinson's disease dementia.

Dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD) known as Lewy body dementias have overlapping clinical and neuropathological features. Neuropathology in both includes combination of Lewy body and Alzheimer's disease (AD) pathology. Cerebral amyloid angiopathy (CAA), often seen in AD, is increasingly recognized for its association with dementia. AIMS: This study investigated clinical and neuropathological differences between DLB and PDD. METHODS: 52 PDD and 16 DLB cases from the Queen Square Brain Bank (QSBB) for Neurological disorders were included. Comprehensive clinical data of motor and cognitive features were obtained from medical records. Neuropathological assessment included examination of CAA, Lewy body and AD pathology. RESULTS: CAA was more common in DLB than in PDD (P = 0.003). The severity of CAA was greater in DLB than in PDD (P = 0.009), with significantly higher CAA scores in the parietal lobe (P = 0.043), and the occipital lobe (P = 0.008), in DLB than in PDD. The highest CAA scores were observed in cases with APOE ε4/4 and ε2/4. Survival analysis showed worse prognosis in DLB, as DLB reached each clinical milestone sooner than PDD. Absence of dyskinesia in DLB is linked to the significantly lower lifetime cumulative dose of levodopa in comparison with PDD. CONCLUSIONS: This is the first study which identified prominent concurrent CAA pathology as a pathological substrate of DLB. More prominent CAA and rapid disease progression as measured by clinical milestones distinguish DLB from PDD.

Review: Clinical, neuropathological and genetic features of Lewy body dementias.

Lewy body dementias are the second most common neurodegenerative dementias after Alzheimer's disease and include dementia with Lewy bodies and Parkinson's disease dementia. They share similar clinical and neuropathological features but differ in the time of dementia and parkinsonism onset. Although Lewy bodies are their main pathological hallmark, several studies have shown the emerging importance of Alzheimer's disease pathology. Clinical amyloid-ß imaging using Pittsburgh Compound B (PiB) supports neuropathological studies which found that amyloid-ß pathology is more common in dementia with Lewy bodies than in Parkinson's disease dementia. Nevertheless, other co-occurring pathologies, such as cerebral amyloid angiopathy, TDP-43 pathology and synaptic pathology may also influence the development of neurodegeneration and dementia. Recent genetic studies demonstrated an important role of APOE genotype and other genes such as GBA and SNCA which seem to be involved in the pathophysiology of Lewy body dementias. The aim of this article is to review the main clinical, neuropathological and genetic aspects of dementia with Lewy bodies and Parkinson's disease dementia. This is particularly relevant as future management for these two conditions may differ.

Exploring the putative role of kallikrein-6, calpain-1 and cathepsin-D in the proteolytic degradation of α-synuclein in multiple system atrophy.

AIMS: There is evidence that accumulation of α-synuclein (α-syn) in Parkinson's disease (PD) and dementia with Lewy bodies (DLB) results from impaired removal of α-syn rather than its overproduction. Kallikrein-6 (KLK6), calpain-1 (CAPN1) and cathepsin-D (CTSD) are among a small number of proteases that cleave α-syn and are dysregulated in PD and DLB. Our aim in this study was to determine whether protease activity is altered in another α-synucleinopathy, multiple system atrophy (MSA), and might thereby modulate the regional distribution of α-syn accumulation. METHODS: mRNA and protein level and/or activity of KLK6, CAPN1 and CTSD were measured and assessed in relation to α-syn load in multiple brain regions (posterior frontal cortex, caudate nucleus, putamen, occipital cortex, pontine base and cerebellar white matter), in MSA (n = 20) and age-matched postmortem control tissue (n = 20). RESULTS: CTSD activity was elevated in MSA in the pontine base and cerebellar white matter. KLK6 and CAPN1 levels were elevated in MSA in the putamen and cerebellar white matter. However, the activity or level of these proteolytic enzymes did not correlate with the regional distribution of α-syn. CONCLUSIONS: Accumulation of α-syn in MSA is not due to reduced activity of the proteases we have studied. We suggest that their upregulation is likely to be a compensatory response to increased α-syn in MSA.

Histological heterogeneity in a large clinical cohort of juvenile idiopathic inflammatory myopathy: analysis by myositis autoantibody and pathological features.

AIM: Juvenile idiopathic inflammatory myopathies have been recently reclassified into clinico-serological subgroups. Myopathological correlates of the subgroups are incompletely understood. METHODS: We studied muscle biopsies from 101 children with clinically and serologically defined juvenile idiopathic inflammatory myopathies from the UK JDM Cohort and Biomarker Study by applying the international JDM score tool, myopathological review and C5b-9 complement analysis. RESULTS: Autoantibody data were available for 90/101 cases with 18/90 cases positive for anti-TIF1γ, 15/90 anti-NXP2, 11/90 anti-MDA5, 5/90 anti-Mi2 and 6/90 anti-PmScl. JDM biopsy severity scores were consistently low in the anti-MDA5 group, high in the anti-Mi2 group, and widely distributed in the other groups. Biopsies were classified histologically as perifascicular atrophy (22/101), macrophage-rich necrosis (6/101), scattered necrosis (2/101), clustered necrosis (2/101), inflammatory fibre invasion (2/101), chronic myopathic change (1/101), diffuse endomysial macrophage infiltrates (40/101) and minimal change (24/101). MDA5 cases segregated with the minimal change group and showed no capillary C5b-9-deposition. The Mi2 group displayed high severity scores and a tendency towards sarcolemmal complement deposition. NXP2 and TIF1γ groups showed a variety of pathologies with a high proportion of diffuse endomysial macrophage infiltrates and a high proportion of capillary C5b-9 deposition. CONCLUSION: We have shown that juvenile idiopathic inflammatory myopathies have a spectrum of histopathological phenotypes and show distinct complement attack complex deposition patterns. Both correlate in some cases with the serological subtypes. Most cases do not show typical histological features associated with dermatomyositis (e.g. perifascicular atrophy). In contrast, more than half show relatively mild histopathological changes.

Neuropathology of Beta-propeller protein associated neurodegeneration (BPAN): a new tauopathy.

INTRODUCTION: Beta-propeller protein associated neurodegeneration (BPAN) is associated with mutations in the WD repeat domain 45 (WDR45) gene on chromosome Xp11 resulting in reduced autophagic flux. This study describes the clinical and neuropathological features of a female 51 year old BPAN case. The clinical history includes learning disability and progressive gait abnormalities since childhood followed by progressive dystonic features in young adulthood. Brain imaging revealed generalised brain atrophy and bilateral mineralisation of the globus pallidus and substantia nigra. RESULTS: The major pathological findings were observed in the substantia nigra with excess iron deposition, gliosis, axonal swellings and severe neuronal loss. Iron deposition was also observed in the globus pallidus. There was extensive hyperphosphorylated-tau deposition in the form of neurofibrillary tangles, pre-tangles and neuropil threads. Furthermore, histological studies and immunoblotting confirmed a mixed Alzheimer type 3-and 4-repeat tau pathology. Microtubule-associated protein 1A/1B-light chain 3 (LC3) immunoblotting of brain homogenates indicated autophagic activity and may support the role of WDR45 in autophagy. CONCLUSIONS: The widespread Alzheimer-type tau pathology in this disease indicates that this should be considered as a tauopathy and adds further support to the proposal that impaired autophagy may have a role in tauopathies.

Zebra body myopathy is caused by a mutation in the skeletal muscle actin gene (ACTA1).

We present follow up data on the original case of 'zebra body myopathy' published by Lake and Wilson in 1975. Pathological features in a second biopsy performed at the age of 29 years included a wide variation in fibre size, multiple split fibres, excess internal nuclei and endomysial connective tissue, rimmed vacuoles, accumulation of myofibrillar material and large 'wiped out' areas lacking stain for oxidative enzymes. The presence of nemaline rods and actin-like filaments in addition to small zebra bodies suggested ACTA1 as a candidate gene. This has been confirmed by the identification of a novel c.1043T.p.Leu348Gln mutation, which probably occurred de novo. This case illustrates that the myopathy associated with zebra bodies is part of the spectrum of myopathies associated with the ACTA1 gene. It also highlights that accumulation of actin filaments is not confined to severe neonatal ACTA1 cases and that progression of weakness can occur in congenital myopathies, as the patient is now wheelchair bound and can only stand with the aid of a walking frame.

Oculoleptomeningeal Amyloidosis associated with transthyretin Leu12Pro in an African patient.

Oculoleptomeningeal amyloidosis is a rare manifestation of hereditary transthyretin (TTR) amyloidosis. Here, we present the first case of leptomeningeal amyloidosis associated with the TTR variant Leu12Pro mutation in an African patient. A 43-year-old right-handed Nigerian man was referred to our centre with rapidly progressive neurological decline. He presented initially with weight loss, confusion, fatigue, and urinary and erectile dysfunction. He then suffered recurrent episodes of slurred speech with right-sided weakness. He went on to develop hearing difficulties and painless paraesthesia. Neurological examination revealed horizontal gaze-evoked nystagmus, brisk jaw jerk, increased tone, brisk reflexes throughout and bilateral heel-shin ataxia. Magnetic resonance imaging showed extensive leptomeningeal enhancement. Cerebrospinal fluid analysis showed a raised protein of 6.4 g/dl. Nerve conduction studies showed an axonal neuropathy. Echocardiography was characteristic of cardiac amyloid. TTR gene sequencing showed that he was heterozygous for the leucine 12 proline mutation. Meningeal and brain biopsy confirmed widespread amyloid angiopathy. TTR amyloidosis is a rare cause of leptomeningeal enhancement, but should be considered if there is evidence of peripheral or autonomic neuropathy with cardiac or ocular involvement. The relationship between different TTR mutations and clinical phenotype, disease course, and response to treatment remains unclear.

Neuropathological features of multiple system atrophy with cognitive impairment.

Cognitive impairment (CI) is an exclusion criterion for the diagnosis of multiple system atrophy (MSA), according to the second consensus statement. This view was recently challenged by patients with pathologically confirmed MSA who were reported to have dementia. With an aim to investigate the pathological substrate of CI in MSA, quantitative assessment of the glial and neuronal cytoplasmic inclusions and semiquantitative assessment of neuronal loss in the cortical and limbic regions was performed. No differences in the severity of these MSA-related pathological findings were identified between nine MSA cases with CI and nine MSA cases with normal cognition. Alzheimer's-related pathological changes, cerebral amyloid angiopathy, and cerebrovascular disease did not differ between the two MSA groups. MSA-specific α-synuclein and secondary pathological conditions were not more severe in MSA cases with CI, suggesting that although CI may be intrinsic to the MSA disease process, further investigation into the pathological basis of cognitive impairment in MSA is warranted.

Characteristics of progressive supranuclear palsy presenting with corticobasal syndrome: a cortical variant.

AIMS: Since the first description of the classical presentation of progressive supranuclear palsy (PSP) in 1963, now known as Richardson's syndrome (PSP-RS), several distinct clinical syndromes have been associated with PSP-tau pathology. Like other neurodegenerative disorders, the severity and distribution of phosphorylated tau pathology are closely associated with the clinical heterogeneity of PSP variants. PSP with corticobasal syndrome presentation (PSP-CBS) was reported to have more tau load in the mid-frontal and inferior-parietal cortices than in PSP-RS. However, it is uncertain if differences exist in the distribution of tau pathology in other brain regions or if the overall tau load is increased in the brains of PSP-CBS. METHODS: We sought to compare the clinical and pathological features of PSP-CBS and PSP-RS including quantitative assessment of tau load in 15 cortical, basal ganglia and cerebellar regions. RESULTS: In addition to the similar age of onset and disease duration, we demonstrated that the overall severity of tau pathology was the same between PSP-CBS and PSP-RS. We identified that there was a shift of tau burden towards the cortical regions away from the basal ganglia; supporting the notion that PSP-CBS is a 'cortical' PSP variant. PSP-CBS also had less severe neuronal loss in the dorsolateral and ventrolateral subregions of the substantia nigra and more severe microglial response in the corticospinal tract than in PSP-RS; however, neuronal loss in subthalamic nucleus was equally severe in both groups. CONCLUSIONS: A better understanding of the factors that influence the selective pathological vulnerability in different PSP variants will provide further insights into the neurodegenerative process underlying tauopathies.

Pantothenate kinase-associated neurodegeneration is not a synucleinopathy.

AIMS: Mutations in the pantothenate kinase 2 gene (PANK2) are responsible for the most common type of neurodegeneration with brain iron accumulation (NBIA), known as pantothenate kinase-associated neurodegeneration (PKAN). Historically, NBIA is considered a synucleinopathy with numerous reports of NBIA cases with Lewy bodies and Lewy neurites and some cases reporting additional abnormal tau accumulation. However, clinicopathological correlations in genetically proven PKAN cases are rare. We describe the clinical, genetic and neuropathological features of three unrelated PKAN cases. METHODS: All three cases were genetically screened for the PANK2 gene mutations using standard Sanger polymerase chain reaction sequencing. A detailed neuropathological assessment of the three cases was performed using histochemical and immunohistochemical preparations. RESULTS: All cases had classical axonal swellings and Perls' positive iron deposition in the basal ganglia. In contrast to neuroaxonal dystrophies due to mutation of the phospholipase A2, group VI (PLA2G6) gene, in which Lewy body pathology is widespread, no α-synuclein accumulation was detected in any of our PKAN cases. In one case (20-year-old male) there was significant tau pathology comprising neurofibrillary tangles and neuropil threads, with very subtle tau pathology in another case. CONCLUSIONS: These findings indicate that PKAN is not a synucleinopathy and, hence the cellular pathways implicated in this disease are unlikely to be relevant for the pathomechanism of Lewy body disorders.

Review: genetics and neuropathology of primary pure dystonia.

Neuropathology has been the key to understanding the aetiology of many neurological disorders such as Alzheimer's disease, Parkinson's disease, frontotemporal degeneration and cerebellar ataxias. Dystonia shares many clinical features with these conditions but research in general, has been unrewarding in providing information on disease processes. Neuropathological studies are few in number and only limited morphological abnormalities have been described. In the genetic literature, dystonia loci are represented as DYT and are assigned ascending numerals chronologically as they are identified. This review will concentrate on the neuropathology of primary pure dystonia, focusing on DYT1 and DYT6 and the correlation between clinical and genetic findings. Research in this area is incomplete and confounded by the rarity of post mortem brain tissue. However, recent findings, indicating a direct interaction between the torsinA (TOR1A) gene responsible for DYT1 and the thanatos-associated domain-containing apoptosis-associated protein 1 (THAP1) gene responsible for DYT6, have important implications in understanding these two entities and also for other members of this group of disorders.

The neuropathology, pathophysiology and genetics of multiple system atrophy.

Multiple system atrophy (MSA) is an unrelenting, sporadic, adult-onset, neurodegenerative disease of unknown aetiology. Its clinically progressive course is characterized by a variable combination of parkinsonism, cerebellar ataxia and/or autonomic dysfunction. Neuropathological examination often reveals gross abnormalities of the striatonigral and/or olivopontocerebellar systems, which upon microscopic examination are associated with severe neuronal loss, gliosis, myelin pallor and axonal degeneration. MSA is a member of a diverse group of neurodegenerative disorders termed α-synucleinopathies, due to the presence of abnormal α-synuclein positive cytoplasmic inclusions in oligodendrocytes, termed glial cytoplasmic inclusions. These are the hallmark neuropathological lesion of MSA and are thought to play a central role in the pathogenesis of the disease. In this review, neuropathological features of MSA are described in detail, along with recent advances in the pathophysiology and genetics of the disease. Our current knowledge of the expression and accumulation of α-synuclein, and efforts to model the disease in vitro and in vivo, are emphasized in this paper and have helped formulate a working hypothesis for the pathogenesis of MSA.

High resolution MR anatomy of the subthalamic nucleus: imaging at 9.4 T with histological validation.

Using conventional MRI the subthalamic nucleus (STN) is not clearly defined. Our objective was to define the anatomy of the STN using 9.4 T MRI of post mortem tissue with histological validation. Spin-echo (SE) and 3D gradient-echo (GE) images were obtained at 9.4 T in 8 post mortem tissue blocks and compared directly with corresponding histological slides prepared with Luxol Fast Blue/Cresyl Violet (LFB/CV) in 4 cases and Perl stain in 3. The variability of the STN anatomy was studied using internal reference points. The anatomy of the STN and surrounding structures was demonstrated in all three anatomical planes using 9.4 T MR images in concordance with LFB/CV stained histological sections. Signal hypointensity was seen in 6/8 cases in the anterior and medial STN that corresponded with regions of more intense Perl staining. There was significant variability in the volume, shape and location of the borders of the STN. Using 9.4 T MRI, the internal signal characteristics and borders of the STN are clearly defined and significant anatomical variability is apparent. Direct visualisation of the STN is possible using high field MRI and this is particularly relevant, given its anatomical variability, for planning deep brain stimulation.

Does levodopa accelerate the pathologic process in Parkinson disease brain?

BACKGROUND: Several in vitro studies have suggested levodopa (L-dopa) to be toxic to dopaminergic neurons and that it can modulate the aggregation process of α-synuclein. We investigated the relationship between cumulative lifetime dose of l-dopa and nigral neuronal count and Lewy body (LB) pathology in Parkinson disease (PD). METHODS: Density of pigmented neurons was measured unilaterally in a single section of substantia nigra (SN) with delineation of the dorsal and ventral tiers in 96 cases of PD with well-documented clinical records relating to antiparkinsonian drug treatment. Cortical and nigral LB densities were determined using a morphometric approach. RESULTS: Mean lifetime dose of L-dopa correlated significantly (p < 0.001) with duration of PD in the entire study population (n = 96) and it was not possible to disentangle their individual effect. This was not the case in a subgroup analysis of younger onset patients with a longer duration of PD (n = 40) who showed no significant correlation between L-dopa and total SN neuronal density (p = 0.07), after adjustment for duration of illness. There was, however, a lower neuronal density in the ventral (p = 0.02) but not in the dorsal (p = 0.27) tier detected with the cumulative dose of L-dopa. We found no difference in L-dopa dose between Braak PD stages (p = 0.58). Furthermore, the subgroup analysis showed no relationship of L-dopa dose to either cortical (p = 0.47) or nigral (p = 0.48) LB density. CONCLUSION: Chronic use of L-dopa in PD does not enhance progression of PD pathology as far as can be determined by our observations with SN neuronal counts and LB densities.

LRRK2 expression in idiopathic and G2019S positive Parkinson's disease subjects: a morphological and quantitative study.

AIMS: Mutations in the gene encoding leucine-rich repeat kinase-2 (LRRK2) have been established as a common genetic cause of Parkinson's disease (PD). The distribution of LRRK2 mRNA and protein in the human brain has previously been described, although it has not been reported in PD cases with the common LRRK2 G2019S mutation. METHODS: To further elucidate the role of LRRK2 in PD, we determined the localization of LRRK2 mRNA and protein in post-mortem brain tissue from control, idiopathic PD (IPD) and G2019S positive PD cases. RESULTS: Widespread neuronal expression of LRRK2 mRNA and protein was recorded and no difference was observed in the morphological localization of LRRK2 mRNA or protein between control, IPD and G2019S positive PD cases. Using quantitative real-time polymerase chain reaction, we demonstrated that there is no regional variation in LRRK2 mRNA in normal human brain, but we have identified differential expression of LRRK2 mRNA with significant reductions recorded in limbic and neocortical regions of IPD cases compared with controls. Semi-quantitative analysis of LRRK2 immunohistochemical staining demonstrated regional variation in staining intensity, with weak LRRK2 immunoreactivity consistently recorded in the striatum and substantia nigra. No clear differences were identified in LRRK2 immunoreactivity between control, IPD and G2019S positive PD cases. LRRK2 protein was identified in a small proportion of Lewy bodies. CONCLUSIONS: Our data suggest that widespread dysregulation of LRRK2 mRNA expression may contribute to the pathogenesis of IPD.

Cerebral amyloidosis: amyloid subunits, mutants and phenotypes.

Cerebral amyloid diseases are part of a complex group of chronic and progressive entities bracketed together under the common denomination of protein folding disorders and characterized by the intra- and extracellular accumulation of fibrillar aggregates. Of the more than 25 unrelated proteins known to produce amyloidosis in humans only about a third of them are associated with cerebral deposits translating in cognitive deficits, dementia, stroke, cerebellar and extrapyramidal signs, or a combination thereof. The familial forms reviewed herein, although infrequent, provide unique paradigms to examine the role of amyloid in the mechanism of disease pathogenesis and to dissect the link between vascular and parenchymal amyloid deposition and their differential contribution to neurodegeneration.