RNA Foci in Two bi-Allelic RFC1 Expansion Carriers.

Cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS) is a late-onset, autosomal recessive neurodegenerative disorder caused by biallelic AAGGG/ACAGG repeat expansion (AAGGG-exp/ACAGG-exp) in RFC1. The recent identification of patients with CANVAS exhibiting compound heterozygosity for AAGGG-exp and truncating variants supports the loss-of-function of RFC1 in CANVAS patients. We investigated the pathological changes in 2 autopsied patients with CANVAS harboring biallelic ACAGG-exp and AAGGG-exp. RNA fluorescence in situ hybridization of the 2 patients revealed CCTGT- and CCCTT-containing RNA foci, respectively, in neuronal nuclei of tissues with neuronal loss. Our findings suggest that RNA toxicity may be involved in the pathogenesis of CANVAS. ANN NEUROL 2024;95:607-613.

Repeat conformation heterogeneity in cerebellar ataxia, neuropathy, vestibular areflexia syndrome.

Cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS) is a late-onset, slow-progressing multisystem neurodegenerative disorder. Biallelic AAGGG repeat expansion in RFC1 has been identified as causative of this disease, and repeat conformation heterogeneity (ACAGG repeat) was also recently implied. To molecularly characterize this disease in Japanese patients with adult-onset ataxia, we accumulated and screened 212 candidate families by an integrated approach consisting of flanking PCR, repeat-primed PCR, Southern blotting and long-read sequencing using Sequel II, GridION or PromethION. We identified 16 patients from 11 families, of whom seven had ACAGG expansions [(ACAGG)exp/(ACAGG)exp] (ACAGG homozygotes), two had ACAGG and AAGGG expansions [(ACAGG)exp/(AAGGG)exp] (ACAGG/AAGGG compound heterozygotes) and seven had AAGGG expansions [(AAGGG)exp/(AAGGG)exp] (AAGGG homozygotes). The overall detection rate was 5.2% (11/212 families including one family having two expansion genotypes). Long-read sequencers revealed the entire sequence of both AAGGG and ACAGG repeat expansions at the nucleotide level of resolution. Clinical assessment and neuropathology results suggested that patients with ACAGG expansions have similar clinical features to previously reported patients with homozygous AAGGG expansions, although motor neuron involvement was more notable in patients with ACAGG expansions (even if one allele was involved). Furthermore, a later age of onset and slower clinical progression were implied in patients with ACAGG/AAGGG compound heterozygous expansions compared with either ACAGG or AAGGG homozygotes in our very limited cohort. Our study clearly shows the occurrence of repeat conformation heterogeneity, with possible different impacts on the affected nervous systems. The difference in disease onset and progression between compound heterozygotes and homozygotes might also be suspected but with very limited certainty due to the small sample number of cases in our study. Studies of additional patients are needed to confirm this.

Clinical characterization of patients with leucine-rich repeat kinase 2 genetic variants in Japan.

Variants of leucine-rich repeat kinase 2 (LRRK2) are the most common genetic cause of familial Parkinson's disease (PD). We aimed to investigate the genetic and clinical features of patients with PD and LRRK2 variants in Japan by screening for LRRK2 variants in three exons (31, 41, and 48), which include the following pathogenic mutations: p.R1441C, p.R1441G, p.R1441H, p.G2019S, and p.I2020T. Herein, we obtained data containing LRRK2 variants derived from 1402 patients with PD (653 with sporadic PD and 749 with familial PD). As a result, we successfully detected pathogenic variants (four with p.R1441G, five with p.R1441H, seven with p.G2019S, and seven with p.I2020T) and other rare variants (two with p.V1447M, one with p.V1450I, one with p.T1491delT, and one with p.H2391Q). Two risk variants, p.P1446L and p.G2385R, were found in 10 and 146 patients, respectively. Most of the patients presented the symptoms resembling a common type of PD, such as middle-aged onset, tremor, akinesia, rigidity, and gait disturbance. Dysautonomia, cognitive decline, and psychosis were rarely observed. Each known pathogenic variant had a different founder in our cohort proven by haplotype analysis. The generation study revealed that the LRRK2 variants p.G2019S and p.I2020T were derived 3500 and 1300 years ago, respectively. Our findings present overviews of the prevalence and distribution of LRRK2 variants in Japanese cohorts.

GGC Repeat Expansion of NOTCH2NLC in Adult Patients with Leukoencephalopathy.

Leukoencephalopathies comprise a broad spectrum of disorders, but the genetic background of adult leukoencephalopathies has rarely been assessed. In this study, we analyzed 101 Japanese patients with genetically unresolved adult leukoencephalopathy using whole-exome sequencing and repeat-primed polymerase chain reaction for detecting GGC expansion in NOTCH2NLC. NOTCH2NLC was recently identified as the cause of neuronal intranuclear inclusion disease. We found 12 patients with GGC expansion in NOTCH2NLC as the most frequent cause of adult leukoencephalopathy followed by NOTCH3 variants in our cohort. Furthermore, we found 1 case with de novo GGC expansion, which might explain the underlying pathogenesis of sporadic cases. ANN NEUROL 2019;86:962-968.

A Japanese case of cerebellar ataxia, spastic paraparesis and deep sensory impairment associated with a novel homozygous TTC19 mutation.

Mitochondrial complex III (CIII) deficiency comprises a group of complex and heterogeneous genetic disorders. TTC19 mutations constitute a rare cause of CIII deficiency and are associated with neurological disorders in childhood and adulthood. Herein, we describe a 27-year-old Japanese man with cerebellar ataxia, spastic paraparesis, loss of deep sensation, mild frontal lobe dysfunction and transient psychiatric symptoms. Brain magnetic resonance imaging showed cerebellar atrophy and bilateral high-intensity signals in the inferior olives and regions adjacent to periaqueductal gray matter, on T2-weighted images. On whole-exome sequencing, we detected a novel homozygous frameshift mutation c.157_158dup [p.Pro54Alafs*48] in TTC19. Mitochondrial enzyme assays confirmed mild impairment of CIII enzymatic activity in lymphoblasts, which was consistent with TTC19-related CIII deficiency. His symptoms and radiological findings demonstrated an early stage or mild form of this disease, and further clarify the characteristics of patients with rare TTC19 mutations.

Molecular epidemiology and clinical spectrum of hereditary spastic paraplegia in the Japanese population based on comprehensive mutational analyses.

Hereditary spastic paraplegia (HSP) is one of the most genetically heterogeneous neurodegenerative disorders characterized by progressive spasticity and pyramidal weakness of lower limbs. Because >30 causative genes have been identified, screening of multiple genes is required for establishing molecular diagnosis of individual patients with HSP. To elucidate molecular epidemiology of HSP in the Japanese population, we have conducted mutational analyses of 16 causative genes of HSP (L1CAM, PLP1, ATL1, SPAST, CYP7B1, NIPA1, SPG7, KIAA0196, KIF5A, HSPD1, BSCL2, SPG11, SPG20, SPG21, REEP1 and ZFYVE27) using resequencing microarrays, array-based comparative genomic hybridization and Sanger sequencing. The mutational analysis of 129 Japanese patients revealed 49 mutations in 46 patients, 32 of which were novel. Molecular diagnosis was accomplished for 67.3% (33/49) of autosomal dominant HSP patients. Even among sporadic HSP patients, mutations were identified in 11.1% (7/63) of them. The present study elucidated the molecular epidemiology of HSP in the Japanese population and further broadened the mutational and clinical spectra of HSP.

The advances in the early and accurate diagnosis of Creutzfeldt-Jakob disease and other prion diseases: where are we today?

INTRODUCTION: Before the introduction of MRI diffusion-weighted images (DWI), the diagnosis of Creutzfeldt-Jakob disease (CJD) relied upon nonspecific findings including clinical symptoms, EEG abnormalities, and elevated levels of cerebrospinal fluid 14-3-3 protein. Subsequently, the use of DWI has improved diagnostic accuracy, but it sometimes remains difficult to differentiate CJD from encephalitis, epilepsy, and other dementing disorders. The revised diagnostic criteria include real-time quaking-induced conversion (RT-QuIC), detecting small amounts of CJD-specific prion protein, and clinically sensitive DWI. Combining these techniques has further improved diagnostic accuracy, enabling earlier diagnosis. AREAS COVERED: Herein, the authors review the recent advances in diagnostic methods and revised diagnostic criteria for sporadic CJD. They also discuss other prion diseases, such as variant CJD and chronic wasting disease, where the emergence of new types is a concern. EXPERT OPINION: Despite improvements in diagnostic methods and criteria, some subtypes of prion disease are still difficult to diagnose, and even the diagnosis using the most innovative RT-QuIC test remains a challenge in terms of accuracy and standardization. However, these revised criteria can be adapted to the emergence of new types of prion diseases. It is essential to continue careful surveillance and update information on the latest prion disease phenotypes.

Reduced likelihood of the Poggendorff illusion in cerebellar strokes: a clinical and neuroimaging study.

This study aimed to test our hypothesis that the cerebellum plays an important role in the generation of the optical-geometric illusion known as the Poggendorff illusion, the mechanism of which has been explained by accumulated experience with natural scene geometry. A total of 79 participants, comprising 28 patients with isolated cerebellar stroke, 27 patients with isolated cerebral stroke and 24 healthy controls, performed Poggendorff illusion tasks and 2 different control tasks. We also investigated core brain regions underpinning changes in the experience of the illusion effect using multivariate lesion-symptom mapping. Our results indicate that patients with isolated cerebellar stroke were significantly less likely to experience the Poggendorff illusion effect than patients with isolated cerebral stroke or healthy controls (74.6, 90.5 and 89.8%, respectively; F(2,76) = 6.675, P = 0.002). However, there were no inter-group differences in the control tasks. Lesion-symptom mapping analysis revealed that the brain lesions associated with the reduced frequency of the Poggendorff illusion effect were mainly centred on the right posteromedial cerebellar region, including the right lobules VI, VII, VIII, IX and Crus II. Our findings demonstrated, for the first time, that patients with cerebellar damage were significantly less likely to experience the Poggendorff illusion effect and that right posteromedial cerebellar lesions played an important role in this effect. These results provide new insight into alterations of a geometric illusion effect in patients with cerebellar disorders and pave the way for future clinical use of the illusion task to detect cerebellar abnormalities.

Relationship between motor learning and gambling propensity in Parkinson's disease.

INTRODUCTION: The basal ganglia and related dopaminergic cortical areas are important neural systems underlying motor learning and are also implicated in impulse control disorders (ICDs). Motor learning impairments and ICDs are frequently observed in Parkinson's disease (PD). Nevertheless, the relationship between motor learning ability and ICDs has not been elucidated. METHODS: We examined the relationship between motor learning ability and gambling propensity, a possible symptom for prodromal ICDs, in PD patients. Fifty-nine PD patients without clinical ICDs and 43 normal controls (NC) were administered a visuomotor rotation perturbation task and the Iowa Gambling Task (IGT) to evaluate motor learning ability and gambling propensity, respectively. Participants also performed additional cognitive assessments and underwent brain perfusion SPECT imaging. RESULTS: Better motor learning ability was significantly correlated with lower IGT scores, i.e., higher gambling propensity, in PD patients but not in NC. The higher scores on assessments reflecting prefrontal lobe function and well-preserved blood perfusion in prefrontal areas were correlated with lower IGT scores along with better motor learning ability. CONCLUSIONS: Our findings suggest that better motor learning ability and higher gambling propensity are based on better prefrontal functions, which are in accordance with the theory that the prefrontal cortex is one of the common essential regions for both motor learning and ICDs.

Rapid and comprehensive diagnostic method for repeat expansion diseases using nanopore sequencing.

We developed a diagnostic method for repeat expansion diseases using a long-read sequencer to improve currently available, low throughput diagnostic methods. We employed the real-time target enrichment system of the nanopore GridION sequencer using the adaptive sampling option, in which software-based target assignment is available without prior sample enrichment, and built an analysis pipeline that prioritized the disease-causing loci. Twenty-two patients with various neurological and neuromuscular diseases, including 12 with genetically diagnosed repeat expansion diseases and 10 manifesting cerebellar ataxia, but without genetic diagnosis, were analyzed. We first sequenced the 12 molecularly diagnosed patients and accurately confirmed expanded repeats in all with uniform depth of coverage across the loci. Next, we applied our method and a conventional method to 10 molecularly undiagnosed patients. Our method corrected inaccurate diagnoses of two patients by the conventional method. Our method is superior to conventional diagnostic methods in terms of speed, accuracy, and comprehensiveness.

Case Report: Extremely Early Detection of Preclinical Magnetic Resonance Imaging Abnormality in Creutzfeldt-Jakob Disease With the V180I Mutation.

The diagnosis of presymptomatic Creutzfeldt-Jakob disease (CJD) is challenging. The levels of total tau protein, 14-3-3 protein, and protease-resistant isoform of prion protein (PrPres) in the cerebrospinal fluid; periodic sharp wave complexes on electroencephalography; and diffusion-weighted imaging (DWI) of brain magnetic resonance imaging (MRI) have all been used to diagnose symptomatic CJD, but none of these markers have been established in the diagnosis of presymptomatic CJD. Here, we report a case of genetic CJD with the V180I mutation in which a small punctate cortical hyperintensity was detected on DWI 6 months before symptom onset and 9 months before diagnosis. Presymptomatic CJD is currently impossible to diagnose because of the lack of established early diagnostic markers. However, since MRI is increasingly used in daily clinical practice, the chance detection of such DWI abnormalities would have important implications in terms of providing a clue to examine a highly specific early diagnostic marker to be developed in the future for CJD. This will allow presymptomatic intervention by disease-modifying therapy in the near future.

Neural mechanisms of foreign accent syndrome: Lesion and network analysis.

BACKGROUND: Foreign accent syndrome (FAS) is a rare acquired speech disorder wherein an individual's spoken accent is perceived as "foreign." Most reported cases involve left frontal brain lesions, but it is known that various other lesions can also cause FAS. To determine whether heterogeneous FAS-causing lesions are localized to a common functional speech network rather than to a single anatomical site, we employed a recently validated image analysis technique known as "lesion network mapping." METHODS: We identified 25 published cases of acquired neurogenic FAS without aphasia, and mapped each lesion volume onto a reference brain. We next identified the network of brain regions functionally connected to each FAS lesion using a connectome dataset from normative participants. Network maps were then overlapped to identify common network sites across the lesions. RESULTS: Classical lesion overlap analysis showed heterogeneity in lesion anatomical location, consistent with prior reports. However, at least 80% of lesions showed network overlap in the bilateral lower and middle portions of the precentral gyrus and in the medial frontal cortex. The left lower portion of the precentral gyrus is suggested to be the location of lesions causing apraxia of speech (AOS), and the middle portion is considered to be a larynx-specific motor area associated with the production of vowels and stop/nasal consonants and with the determination of pitch accent. CONCLUSIONS: The lesions that cause FAS are anatomically heterogeneous, but they share a common functional network located in the bilateral posterior region of the frontal lobe. This network specifically includes not only the lower portion of the central gyrus, but also its middle region, which is referred to as the larynx motor cortex and is known to be associated with phonation. Our findings suggest that disrupted networks in FAS might be anatomically different from those in AOS.

Qualitative Deficits in Verbal Fluency in Parkinson's Disease with Mild Cognitive Impairment: A Clinical and Neuroimaging Study.

BACKGROUND: Mild cognitive impairment (MCI) in Parkinson's disease (PD) is considered a risk factor for PD with dementia (PDD). Verbal fluency tasks are widely used to assess executive function in PDD. However, in cases of PD with MCI (PD-MCI), the relative diagnostic accuracy of different qualitative verbal fluency measures and their related neural mechanisms remain unknown. OBJECTIVE: This study aimed to investigate the relative diagnostic accuracy of qualitative (clustering and switching) verbal fluency strategies and their correlates with functional imaging in PD-MCI. METHODS: Forty-five patients with PD (26 with MCI and 19 without MCI) and 25 healthy controls underwent comprehensive neurocognitive testing and resting-state functional magnetic resonance imaging. MCI in patients with PD was diagnosed according to established clinical criteria. The diagnostic accuracy of verbal fluency measures was determined via receiver operating characteristic analysis. Changes in brain functional connectivity between groups and across clinical measures were assessed using seed-to-voxel analyses. RESULTS: Patients with PD-MCI generated fewer words and switched less frequently in semantic and phonemic fluency tasks compared to other groups. Switching in semantic fluency showed high diagnostic accuracy for PD-MCI and was associated with reduced functional connectivity in the salience network. CONCLUSION: Our results indicate that reduced switching in semantic fluency tasks is a sensitive and specific marker for PD-MCI. Qualitative verbal fluency deficits and salience network dysfunction represent early clinical changes observed in PD-MCI.

Therapeutic efficacy of heparin and direct factor Xa inhibitors in cancer-associated cryptogenic ischemic stroke with venous thromboembolism.

BACKGROUND: Anticoagulation therapy, especially using heparin or recently developed oral direct factor Xa inhibitors (DiXals), is recommended as first-line treatment for cancer-related venous thromboembolism (VTE). However, the preventive efficacy of these anticoagulants for cancer-associated ischemic stroke is still unknown. We retrospectively investigated the efficacy of subcutaneous unfractionated heparin (UFH) and DiXals for preventing the recurrence of cancer-associated cryptogenic ischemic stroke with VTE. METHODS: We retrospectively studied consecutive patients with cancer-associated cryptogenic ischemic stroke and comorbid VTE who received subcutaneous UFH or oral DiXaIs at 9 hospitals. RESULT: Fifty-three patients (24 treated with UFH and 29 treated with DiXaIs) were enrolled. Of these, 47 demonstrated systemic metastasis (cancer stage IV). During 30-day follow-up after initiation of anticoagulation therapy, recurrent ischemic stroke was observed in only 1 patient (4%) in the UFH group and in 9 patients (31%) in the DiXal group. The incidence of major bleeding complications was similar between the 2 groups (4% and 10%, respectively). The cumulative risk of ischemic stroke recurrence within 30 days was lower with UFH than with DiXals (competing risk analysis, p = 0.008). In the DiXal group, patients who experienced recurrence showed significantly higher D-dimer levels than those without recurrence. CONCLUSION: In patients with cancer-associated cryptogenic ischemic stroke and comorbid VTE, UFH demonstrated a lower rate of recurrent ischemic stroke than DiXaIs, and there were no differences in bleeding risk between the 2 treatments. D-dimer levels at stroke onset increased the risk of recurrence in the DiXal group but not in the UFH group.

PLA2G6 variants associated with the number of affected alleles in Parkinson's disease in Japan.

This study aimed to evaluate genotype-phenotype correlations of Parkinson's disease (PD) patients with phospholipase A2 group V (PLA2G6) variants. We analyzed the DNA of 798 patients with PD, including 78 PD patients reported previously, and 336 in-house controls. We screened the exons and exon-intron boundaries of PLA2G6 using the Ion Torrent system and Sanger method. We identified 21 patients with 18 rare variants, such that 1, 9, and 11 patients were homozygous, heterozygous, and compound heterozygous, respectively, with respect to PLA2G6 variants. The allele frequency was approximately equal between patients with familial PD and those with sporadic PD. The PLA2G6 variants detected frequently were identified in the early-onset sporadic PD group. Patients who were homozygous for a variant showed more severe symptoms than those who were heterozygous for the variant. The most common variant was p.R635Q in our cohort, which was considered a risk variant for PD. Thus, the variants of PLA2G6 may play a role in familial PD and early-onset sporadic PD.

Adjustment of Subthalamic Deep Brain Stimulation Parameters Improves Wheeze and Dyspnea in Parkinson's Disease.

Subthalamic nucleus deep brain stimulation (STN-DBS) is an effective treatment for motor features in Parkinson's disease (PD). We present the case of a 56-year-old man with a 17-year history of PD. He underwent bilateral STN-DBS at the age of 51 years because of troublesome dyskinesia and wearing off. His motor features dramatically improved after the operation; however, he developed dysarthria and a refractory wheeze associated with dyspnea due to abnormal hyperadduction of the false vocal fold. By adjusting the stimulation site of STN, his severe wheeze, which was considered to be the result of the unfavorable spread of current to the corticobulbar tract, was significantly improved. This report provides concrete evidence that wheezing is caused by hyperadduction of the false vocal fold as an adverse effect of STN-DBS and can be reversed by adjusting the stimulation site for STN-DBS.

White matter hyperintensities on MRI in dementia with Lewy bodies, Parkinson's disease with dementia, and Alzheimer's disease.

BACKGROUND: In dementia with Lewy bodies (DLB) and Parkinson's disease with dementia (PDD), it is still debated whether white matter hyperintensities (WMH) on MRI reflect atherosclerotic cerebrovascular changes or Alzheimer's disease (AD)-related pathology such as cerebral amyloid angiopathy. To examine AD-related pathology in DLB and PDD, we compared the severity of WMH and medial temporal lobe atrophy among patients with DLB, PDD, non-demented PD (PDND), and AD. METHODS: We retrospectively studied sex- and age-matched outpatients with AD, DLB, PDD, and PDND, as well as subjects without central nervous system disorders as normal controls (n=50 each). All subjects underwent 1.5-T MRI examinations, and WMH detected by T2-weighted images or fluid-attenuated inversion recovery images were semiquantified according to the Fazekas method. Medial temporal lobe atrophy (MTA) was visually assessed by the MTA score. RESULTS: WMH were more prominent in AD, DLB, and PDD patients than in PDND patients and normal controls (NCs). DLB as well as AD showed more severe WMH than PDD. Visual assessment of medial temporal lobe atrophy showed that AD patients had the most severe atrophy, followed by DLB, PDD, and PDND patients, and NC subjects in that order. MTA scores showed significant correlations with WMH severity. CONCLUSION: Our results indicated that DLB was more similar to AD than to PDD in terms of MRI findings, suggesting that WMH in DLB may reflect mainly AD-related pathology rather than atherosclerotic cerebrovascular changes.