Nagahisa Murakami

Reduced alpha-synuclein in cerebrospinal fluid in synucleinopathies: Evidence from a meta-analysis

Alpha‐synuclein plays a key role in the pathology of synucleinopathies including Parkinsons disease (PD) and multiple system atrophy (MSA). However, whether alpha‐synuclein level in cerebrospinal fluid (CSF) could distinguish synucleinopathies from progressive supranuclear palsy (PSP) is still a contentious issue. A comprehensive literature search yielded nine eligible studies. We expressed the between‐group difference of the concentration of alpha‐synuclein in CSF as the standardized mean difference. The proportion of variation attributable to heterogeneity was computed and expressed as I2. Nine studies involved 537 controls, 843 PD, 130 MSA, and 98 PSP patients. The overall effect of PD on alpha‐synuclein in CSF was significantly different from normal control or disease control (standardized mean difference = –0.67, P < 0.00001). These studies were heterogeneous (I2 = 40%). Alpha‐synuclein in CSF in MSA was significantly reduced relative to controls with heterogeneous studies (standardized mean difference = –0.75, P < 0.0001; I2 = 62%). In contrast, no significant difference of alpha‐synuclein in CSF was observed between PSP and controls with heterogeneous studies (standardized mean difference = –0.28, P = 0.13; I2 = 53%). Alpha‐synuclein in CSF was significantly reduced in synucleinopathies compared with PSP (“PD vs. PSP”: standardized mean difference = –0.38, P = 0.001; “MSA vs. PSP”: standardized mean difference = –0.66, P < 0.00001). The included studies were homogeneous (I2 = 0%). Our study showed that alpha‐synuclein levels in CSF in synucleinopathies was significantly lower than in PSP. This finding provides insights into the pathophysiological difference between synucleinopathies and PSP as well as possibility of development of a tool for differential diagnosis between MSA and PSP using enzyme‐linked immunosorbent assay (ELISA) and similar methods.

Neurofilament light chain level in cerebrospinal fluid can differentiate Parkinson's disease from atypical parkinsonism: Evidence from a meta-analysis

A reliable test that facilitates the accurate diagnosis of Parkinsons and disorders will help with both, clinical management and therapeutic research. In this context, neurofilament light chain (NFL) is candidate for a biomarker in cerebrospinal fluid (CSF). A comprehensive literature search yielded 4 eligible studies. We expressed between-group difference of NFL concentration in CSF as the standardized mean difference. Four studies involved 166 Parkinsons disease (PD), 116 multiple system atrophy (MSA) and 73 progressive supranuclear palsy (PSP) patients. Patients with MSA showed higher concentration of NFL concentration in CSF than those with PD (standardized mean difference=1.60, P<0.0001). These studies were homogeneous (P=0.17). NFL in CSF in PSP was significantly elevated relative to PD with homogeneous studies (standardized mean difference=2.04, P<0.0001; P=0.99). The present meta-analysis suggested that NFL concentration in CSF in MSA and PSP was significantly increased relative to PD, and that this could help us to separate PD from atypical parkinsonian syndromes.

Exome sequencing reveals a novel ANO10 mutation in a Japanese patient with autosomal recessive spinocerebellar ataxia

To the Editor : Spinocerebellar ataxia autosomal recessive type 10 (SCAR10, OMIM 613728) is caused by the mutation of ANO10 (1). The clinical phenotype was characterized by ataxia, hyper-reflexia, normal plantar reflex, downbeat nystagmus and lower motor neuron involvement. Here, we report a novel ANO10 mutation in a patient with autosomal recessive spinocerebellar ataxia (ARSCA), using exome sequencing. The research procedure was approved by the Ethics Committee of Hiroshima University. All of the examinations were performed after obtaining informed consent from the patient. Control exomes were obtained from patients undergoing exome analysis for diseases other than SCA. A Japanese patient with cerebellar ataxia born to consanguineous parents had a homozygous nonsense ANO10 (c.609C>G, p.Y203X) mutation. The identified mutation was validated with conventional Sanger sequencing. This mutation was not detected in our control exomes. A 58-year-old man had presented with loss of consciousness at age 42 and was treated with 800 mg of sodium valproate (further information could not be obtained). He had noticed a tendency to fall at age 46 and dysarthria at age 54. However, he continued to satisfactorily function at work. At age of 58, he presented with saccadic eye movement, hyper-reflexia, decreased vibration sense and constipation. Muscle atrophy, nystagmus and tortuosity of the conjunctival vessels were not observed. Electromyography was normal. His MiniMental State Examination score was 29. Brain magnetic resonance imaging (MRI) showed mild cerebellar atrophy, and brain stem was slightly atrophic at age 57 (Fig. 1). Single photon emission computed tomography showed a decrease in cerebellar flow. Previously reported SCAR10 cases have originated from the Netherlands, Serbia and France (1, 2), and this is the first case reported outside Europe. In contrast to our case, previous reported cases also presented muscle atrophy, nystagmus, tortuosity of the conjunctival vessels and intellectual deficit. In addition, in our case, decreased vibration sense and constipation were detected and the age of onset was relatively late. These characteristics should be considered when diagnosing SCAR10. Previously, homozygous missense mutation, homozygous frame-shift mutation and compound Fig. 1. Brain magnetic resonance imaging at age of 57: T1 sagittal image. Mild cerebellar atrophy was observed.

Exome sequencing reveals a novel MRE11 mutation in a patient with progressive myoclonic ataxia

Progressive myoclonic ataxia (PMA) is a clinical syndrome defined as progressive ataxia and myoclonus and infrequent seizures in the absence of progressive dementia. Due to the extremely heterogeneous nature of PMA, a large proportion of PMA cases remain molecularly undiagnosed. The aim of this study was to clarify the molecular etiology of PMA. The patient was a 52-year-old female from consanguineous parents. She developed a jerking neck movement at age 9, which gradually expanded to her entire body. On physical examination at age 47, she exhibited generalized, spontaneous myoclonus that occurred continuously. She also presented with mild limb and truncal ataxia. An electroencephalogram revealed no abnormalities. A brain MRI displayed no atrophy of the cerebellum. Electrophysiological studies suggested myoclonus of a subcortical origin. For further evaluation, we performed exome sequencing, and we identified a novel homozygous missense mutation in the MRE11 gene (NM_005590:c.140C>T:p.A47V). Subsequently, we analyzed the expression of MRE11 and related proteins (RAD50 and NBS1) via Western blot, and they were markedly decreased compared to a healthy control. Mutations in the MRE11 gene have been known to cause an ataxia-telangiectasia-like (ATLD) disorder. Accumulating evidence has indicated that its wide phenotypic variations in ATLD correspond to genotypic differences. Interestingly, our case exhibited a relatively mild decrease in NBS1 compared to previously reported cases of a homozygous missense mutation, which may account for the milder phenotype in this patient. Moreover, together with a recently reported case of an MRE11 mutation, it is suggested that MRE11 mutations can present as PMA.

Imaging-based differential diagnosis between multiple system atrophy and Parkinson's disease

There are many tools for differentiating between multiple system atrophy with predominant parkinsonian features (MSA-P) and Parkinsons disease (PD). These include middle cerebellar peduncle (MCP) width, apparent diffusion coefficient (ADC) value of the putamen and cerebellum, and (123)I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy images. We aimed to directly compare the above-mentioned methods, and to determine the optimal tool for differential diagnosis. Eleven patients with MSA-P and 36 patients with PD were enrolled. Of these, 7 patients with MSA-P and 14 patients with PD were chosen as background-matched subjects. We measured MCP width, ADC value of the putamen and cerebellum, and MIBG myocardial scintigraphy images. Area under curve (AUC) of receiver operating characteristic (ROC) was assessed to compare the above-mentioned methods. MCP width and ADC value of the putamen may be helpful for differentiating between MSA-P and PD relative to other methods in background-matched patients (MCP, AUC=0.95; putamen ADC, AUC=0.88; cerebellar ADC, AUC=0.70; MIBG, AUC=0.78). Similar AUCs were seen in all patients with different backgrounds. Our findings suggested that MCP width and ADC value of the putamen could be superior to ADC value of the cerebellum and MIBG uptake for differentiating between MSA-P and PD.

The effect of tremor onset on middle cerebellar peduncle of Parkinson's disease

The majority of studies of Parkinsons disease (PD) focused on basal ganglia initially; however, accumulating evidence suggests cerebellar involvement in pathophysiology. We aimed to investigate the effects of tremor onset on middle cerebellar peduncle (MCP) width of PD patients and of disease duration on differential diagnosis. We measured MCP width of 81 PD, 34 multiple system atrophy (MSA) and 16 normal controls, using MRI. A meta-analysis was performed including two previous and the present studies. We carried out correlation analysis between disease duration and MCP width separately in subgroup of PD with or without tremor onset. Receiver operating characteristic curves were analyzed. Our meta-analysis indicated that MCP width was significantly smaller in MSA relative to PD with homogeneous studies. There was significant correlation between disease duration and MCP width in PD without tremor onset. In contrast, there was no correlation observed in PD with tremor onset. Subclassification according to disease duration showed improved area under curve of PD vs. MSA with predominant parkinsonian features. MCP width could be a valuable tool for differential diagnosis. Our finding suggested that MCP was impaired in advanced stage of PD without tremor onset as part of the abnormality of the cerebellar system.

Val66Met polymorphism of brain-derived neurotrophic factor is associated with idiopathic dystonia

The Val66Met (G196A; rs6265) single nucleotide polymorphism of brain-derived neurotrophic factor (BDNF) affects morphology and neuronal activity, and is expected to be associated with central nervous system disorders. However, it remains controversial whether Val66Met polymorphism is a risk factor for idiopathic dystonia. We aimed to clarify the impact of BDNF polymorphism on idiopathic dystonia. A literature search of PubMed was carried out. A random-effects model was employed for the meta-analysis. A pooled odds ratio (OR) was calculated along with 95% confidence intervals (CI) to reflect the risk of idiopathic dystonia in each genotype (GG, AG, AA) or minor allele. The proportion of variation due to heterogeneity was computed and expressed as I(2). Five case-control studies, comprising a total sample size of 1804 subjects (784 idiopathic dystonia patients, 1020 normal controls), were included in this meta-analysis. AA genotype was significantly more frequent in patients with idiopathic dystonia (OR=1.47, 95% CI 1.09-1.99, p=0.01, four studies, n=1716). This finding was derived from homogeneous studies (p=0.97, I(2)=0%). Our meta-analysis has revealed a significant overall effect of the AA genotype on the development of idiopathic dystonia.

The effect of istradefylline for Parkinson’s disease: A meta-analysis

Adenosine A2A receptor antagonists are an alternative treatment strategy for Parkinson’s disease. Several randomized placebo controlled studies have tested the effect of A2A receptor antagonist istradefylline, and more robust evidence has been acquired. This meta-analysis aimed to provide evidence for its efficacy and safety on patients with Parkinson’s disease. After a systematic literature search, we calculated the pooled standardized mean difference and risk ratio for continuous and dichotomous variables, respectively. Further, sensitivity analyses were performed to confirm the effect estimated by meta-analyses. Publication bias was assessed by funnel plot and deviation of intercept. Six studies satisfied our inclusion criteria. Istradefylline (40 mg/day) decreased off time and improved motor symptoms of Parkinson’s disease in homogeneous studies. Istradefylline at 20 mg/day decreased off time and improved motor symptoms, but heterogeneity was found in the analysis of the former among studies. There was a significant effect of istradefylline on dyskinesia in homogeneous studies. Publication bias, however, was observed in the comparison of dyskinesia. Other adverse events showed no significant difference. The present meta-analysis suggests that istradefylline at 40 mg/day could alleviate off time and motor symptoms derived from Parkinson’s disease. Dyskinesia might be worsened, but publication bias prevents this from being clear.

Proteasome impairment in neural cells derived from HMSN-P patient iPSCs

Hereditary motor and sensory neuropathy with proximal dominant involvement (HMSN-P) is caused by a heterozygous mutation (P285L) in Tropomyosin-receptor kinase Fused Gene (TFG), histopathologically characterized by progressive spinal motor neuron loss with TFG cytosolic aggregates. Although the TFG protein, found as a type of fusion oncoprotein, is known to facilitate vesicle transport from endoplasmic reticulum (ER) to Golgi apparatus at ER exit site, it is unclear how mutant TFG causes motor neuron degeneration. Here we generated induced pluripotent stem cells (iPSCs) from HMSN-P patients, and differentiated the iPSCs into neural cells with spinal motor neurons (iPS-MNs). We found that HMSN-P patient iPS-MNs exhibited ubiquitin proteasome system (UPS) impairment, and HMSN-P patient iPS-MNs were vulnerable to UPS inhibitory stress. Gene correction of the mutation in TFG using the CRISPR-Cas9 system reverted the cellular phenotypes of HMSN-P patient iPS-MNs. Collectively, these results suggest that our cellular model with defects in cellular integrity including UPS impairments may lead to identification of pathomechanisms and a therapeutic target for HMSN-P.

Extranodal NK/T-cell lymphoma, nasal type, manifesting as rapidly progressive dementia without any mass or enhancing brain lesion

Among the many potential etiologies for rapidly progressive dementia (RPD), primary central nervous system extranodal NK/T‐cell lymphoma, nasal‐type (ENKL) is a rare entity. We present the first reported case of autopsy‐proven RPD due to ENKL without any mass or enhancing lesion of the brain. A 54‐year‐old immunocompetent man presented with RPD, myoclonus and ataxia. The mini‐mental state examination (MMSE) score was 22/30. His brain MRI revealed progressive brain atrophy without gadolinium enhancement or mass lesion. Five months after the initial evaluation, cognitive impairment further worsened with an MMSE score of 3/30. At the advanced stage, lumbar MRI showed swollen cauda equina with gadolinium enhancement. The number of Epstein‐Barr virus (EBV) DNA in cerebrospinal fluid had gradually increased. Twelve months after onset, the patient died of respiratory failure. Pathological findings revealed that lymphoma cells had diffusely invaded the meninges, parenchyma of the brain, spinal cord and cauda equina. Cells were positive for CD3, CD56 and EBV‐encoded small RNAs and negative for CD20. No evidence of malignancy was identified in the visceral organs. This report indicates that ENKL should be recognized as one of the rare causes of RPD. Early testing for EBV‐DNA in cerebrospinal fluid and imaging of cauda equina would be useful diagnostic tools.