Genotype-related respiratory progression in Duchenne muscular dystrophy-A multicenter international study.

INTRODUCTION/AIMS: Mutations amenable to skipping of specific exons have been associated with different motor progression in Duchenne muscular dystrophy (DMD). Less is known about their association with long-term respiratory function. In this study we investigated the features of respiratory progression in four DMD genotypes relevant in ongoing exon-skipping therapeutic strategies. METHODS: This was a retrospective longitudinal study including DMD children followed by the UK NorthStar Network and international AFM Network centers (May 2003 to October 2020). We included boys amenable to skip exons 44, 45, 51, or 53, who were older than 5 years of age and ambulant at first recorded visit. Subjects who were corticosteroid-naive or enrolled in interventional clinical trials were excluded. The progression of respiratory function (absolute forced vital capacity [FVC] and calculated as percent predicted [FVC%]) was compared across the four subgroups (skip44, skip45, skip51, skip53). RESULTS: We included 142 boys in the study. Mean (standard deviation) age at first visit was 8.6 (2.5) years. Median follow-up was 3 (range, 0.3-8.3) years. In skip45 and skip51, FVC% declined linearly from the first recorded visit. From the age of 9 years, FVC% declined linearly in all genotypes. Skip44 had the slowest (2.7%/year) and skip51 the fastest (5.9%/year) annual FVC% decline. The absolute FVC increased progressively in skip44, skip45, and skip51. In skip53, FVC started declining from 14 years of age. DISCUSSION: The progression of respiratory dysfunction follows different patterns for specific genotype categories. This information is valuable for prognosis and for the evaluation of exon-skipping therapies.

Rimeporide as a first- in-class NHE-1 inhibitor: Results of a phase Ib trial in young patients with Duchenne Muscular Dystrophy.

Rimeporide, a first-in-class sodium/proton exchanger Type 1 inhibitor (NHE-1 inhibitor) is repositioned by EspeRare for patients with Duchenne Muscular Dystrophy (DMD). Historically, NHE-1 inhibitors were developed for cardiac therapeutic interventions. There is considerable overlap in the pathophysiological mechanisms in Congestive Heart Failure (CHF) and in cardiomyopathy in DMD, therefore NHE-1 inhibition could be a promising pharmacological approach to the cardiac dysfunctions observed in DMD. Extensive preclinical data was collected in various animal models including dystrophin-deficient (mdx) mice to characterise Rimeporide's anti-fibrotic and anti-inflammatory properties and there is evidence that NHE-1 inhibitors could play a significant role in modifying DMD cardiac and also skeletal pathologies, as the NHE-1 isoform is ubiquitous. We report here the first study with Rimeporide in DMD patients. This 4-week treatment, open label phase Ib, multiple oral ascending dose study, enrolled 20 ambulant boys with DMD (6-11 years), with outcomes including safety, pharmacokinetic (PK) and pharmacodynamic (PD) biomarkers. Rimeporide was safe and well-tolerated at all doses. PK evaluations showed that Rimeporide was well absorbed orally reaching pharmacological concentrations from the lowest dose, with exposure increasing linearly with dose and with no evidence of accumulation upon repeated dosing. Exploratory PD biomarkers showed positive effect upon a 4-week treatment, supporting its therapeutic potential in patients with DMD, primarily as a cardioprotective treatment, and provide rationale for further efficacy studies.

Persistent microglial activation and synaptic loss with behavioral abnormalities in mouse offspring exposed to CASPR2-antibodies in utero.

Gestational transfer of maternal antibodies against fetal neuronal proteins may be relevant to some neurodevelopmental disorders, but until recently there were no proteins identified. We recently reported a fivefold increase in CASPR2-antibodies in mid-gestation sera from mothers of children with intellectual and motor disabilities. Here, we exposed mice in utero to purified IgG from patients with CASPR2-antibodies (CASPR2-IgGs) or from healthy controls (HC-IgGs). CASPR2-IgG but not HC-IgG bound to fetal brain parenchyma, from which CASPR2-antibodies could be eluted. CASPR2-IgG exposed neonates achieved milestones similarly to HC-IgG exposed controls but, when adult, the CASPR2-IgG exposed progeny showed marked social interaction deficits, abnormally located glutamatergic neurons in layers V-VI of the somatosensory cortex, a 16% increase in activated microglia, and a 15-52% decrease in glutamatergic synapses in layers of the prefrontal and somatosensory cortices. Thus, in utero exposure to CASPR2-antibodies led to permanent behavioral, cellular, and synaptic abnormalities. These findings support a pathogenic role for maternal antibodies in human neurodevelopmental conditions, and CASPR2 as a potential target.

Dystrophinopathies and Limb-Girdle Muscular Dystrophies.

Muscular dystrophies are a heterogeneous group of inherited diseases. The natural history of these disorders along with their management have changed mainly due to a better understanding of their pathophysiology, the evolution of standards of care, and new treatment options. Dystrophinopathies include both Duchenne's and Becker's muscular dystrophies, but in reality they are a spectrum of muscle diseases caused by mutations in the gene that encodes the protein dystrophin. Duchenne's muscular dystrophy is the most common form of inherited muscle disease of childhood. The current standards of care considerably prolong independent ambulation and survival. Several therapeutic options either aiming at substituting/correcting the primary protein defect or limiting the progression of the dystrophic process are currently being explored in clinical trials.Limb-girdle muscular dystrophies (LGMDs) are rare and heterogeneous conditions, characterized by weakness and wasting of the pelvic and shoulder girdle muscles. Originally classified into dominant and recessive, > 30 genetic forms of LGMDs are currently recognized. Further understanding of the pathogenic mechanisms of LGMD will help identifying novel therapeutic approaches that can be tested in clinical trials.

Characteristics of Neuro-Behçet's Disease in a Case-Series from a Single Centre in Northern Portugal.

INTRODUCTION: Behçet's disease (BD) is a multisystem inflammatory disease of unknown etiology that may affect the CNS - Neuro-Behçet (NB). Our aim was to evaluate the frequency of neurological involvement and characterize a cohort of our NB patients. METHODS: We retrospectively revised the clinical, laboratory and imaging data of a cohort of BD patients, followed in our hospital outpatient clinic. RESULTS: We identified 138 BD patients. Twenty-five out of 138 had NB (15 female). Four patients presented with neurological symptoms. We identified a total of 37 attacks. Twenty-one attacks were classified as parenchymatous, four non-parenchymatous and 12 as other syndromes. Seventeen patients had CSF analysis performed (20 samples). Five samples were normal, 15 showed CSF pleocytosis. The most frequent finding on MRI performed in the acute phase was extensive lesions involving the brainstem. Two patients died due to the neurological involvement of BD. CONCLUSION: We found 18.1% prevalence of NB and a higher female-to-male ratio in our group than in other series. Gastrointestinal and vascular involvement was more frequent in the NB group. The fact that neurological involvement may be the first manifestation of BD with therapeutic implications and associated morbidity points out the relevance of an early diagnosis.

The prevalence of familial hemiplegic migraine with cerebellar ataxia and spinocerebellar ataxia type 6 in Portugal.

BACKGROUND: CACNA1A gene disorders present a variable familial phenotype of ataxia, migraine with aura, and/or hemiplegic migraine. Prevalence data for these conditions are scarce. OBJECTIVE: The aim of this study is to report a minimal prevalence estimate for familial hemiplegic migraine with cerebellar ataxia and spinocerebellar ataxia type 6 in Portugal. METHODS: This is a multisource population-based prevalence study. Patients and families with spinocerebellar ataxia type 6 and familial hemiplegic migraine and cerebellar ataxia identified through the Portuguese survey of hereditary ataxias and spastic paraplegias were re-evaluated. Prevalent patients were confirmed to be alive and affected at the 1st of January 2013. RESULTS: One family with spinocerebellar ataxia type 6 and 2 families with other CACNA1A gene mutations were identified. From these families, 23 patients were alive and living in Portugal in the prevalence day, for an estimated national prevalence per 100,000 inhabitants of 0.21 for familial hemiplegic migraine with cerebellar ataxia and of 0.01 for spinocerebellar ataxia type 6. CONCLUSION: The prevalence of familial hemiplegic migraine with cerebellar ataxia and spinocerebellar ataxia type 6 are both probably low in Portugal.

Monozygotic twin sisters discordant for familial hemiplegic migraine.

BACKGROUND: The high concordance rate of migraine in monozygotic twin pairs has long been recognised. In the current study, we present a monozygotic twin pair discordant for familial hemiplegic migraine (FHM). CASE PRESENTATIONS: We evaluated 12 adult family members in 2012. The twin pair was separately examined by neurologists at different time points. Mutation screening was performed for known FHM-related genes. The monozygosity of the twins was verified. Eleven individuals had a history of migraine or paroxysmal neurological symptoms, including four patients with motor aura. No mutations were detected in the CACNA1A, ATP1A2, SCN1A, PRRT2 or NOTCH3 genes. The monozygotic twin sisters, aged 52, were discordant for age of onset, motor aura and neuropsychological aura (forced thinking). Overall, the family members presented a wide range of phenotypical features. CONCLUSIONS: Familial hemiplegic migraine is a monogenic disorder that is distinct from migraine with typical aura. However, in certain families with motor aura, such as this one, it is possible that the most severe phenotype is caused by an unlikely combination of polygenic traits and non-genetic factors. In these kindreds, we propose that hemiplegic aura is only a severe and complex form of typical aura.

Determining minimal clinically important differences in the North Star Ambulatory Assessment (NSAA) for patients with Duchenne muscular dystrophy.

The North Star ambulatory assessment (NSAA) is a functional motor outcome measure in Duchenne muscular dystrophy (DMD), widely used in clinical trials and natural history studies, as well as in clinical practice. However, little has been reported on the minimal clinically important difference (MCID) of the NSAA. The lack of established MCID estimates for NSAA presents challenges in interpreting the significance of the results of this outcome measure in clinical trials, natural history studies and clinical practice. Combining statistical approaches and patient perspectives, this study estimated MCID for NSAA using distribution-based estimates of 1/3 standard deviation (SD) and standard error of measurement (SEM), an anchor-based approach, with six-minute walk distance (6MWD) as the anchor, and evaluation of patient and parent perception using participant-tailored questionnaires. The MCID for NSAA in boys with DMD aged 7 to 10 years based on 1/3 SD ranged from 2.3-2.9 points, and that on SEM ranged from 2.9-3.5 points. Anchored on the 6MWD, the MCID for NSAA was estimated as 3.5 points. When the impact on functional abilities was considered using participant response questionnaires, patients and parent perceived a complete loss of function in a single item or deterioration of function in one to two items of the assessment as an important change. Our study examines MCID estimates for total NSAA scores using multiple approaches, including the impact of patient and parent perspective on within scale changes in items based on complete loss of function and deterioration of function, and provides new insight on evaluation of differences in these widely used outcome measure in DMD.

T Cell Responses to Dystrophin in a Natural History Study of Duchenne Muscular Dystrophy.

Duchenne muscular dystrophy (DMD) is caused by the lack of dystrophin, but many patients have rare revertant fibers that express dystrophin. The skeletal muscle pathology of DMD patients includes immune cell infiltration and inflammatory cascades. There are several strategies to restore dystrophin in skeletal muscles of patients, including exon skipping and gene therapy. There is some evidence that dystrophin restoration leads to a reduction in immune cells, but dystrophin epitopes expressed in revertant fibers or following genome editing, cell therapy, or microdystrophin delivery after adeno-associated viral gene therapy may elicit T cell production in patients. This may affect the efficacy of the therapeutic intervention, and potentially lead to serious adverse events. To confirm and extend previous studies, we performed annual enzyme- linked immunospot interferon-gamma assays on peripheral blood mononuclear cells from 77 pediatric boys with DMD recruited into a natural history study, 69 of whom (89.6%) were treated with corticosteroids. T cell responses to dystrophin were quantified using a total of 368 peptides spanning the entire dystrophin protein, organized into nine peptide pools. Peptide mapping pools were used to further localize the immune response in one positive patient. Six (7.8%) patients had a T cell-mediated immune response to dystrophin at at least one time point. All patients who had a positive result had been treated with corticosteroids, either prednisolone or prednisone. Our results show that ∼8% of DMD individuals in our cohort have a pre-existing T cell-mediated immune response to dystrophin, despite steroid treatment. Although these responses are relatively low level, this information should be considered a useful immunological baseline before undertaking clinical trials and future DMD studies. We further highlight the importance for a robust, reproducible standard operating procedure for collecting, storing, and shipping samples from multiple centers to minimize the number of inconclusive data.

High-Throughput Digital Image Analysis Reveals Distinct Patterns of Dystrophin Expression in Dystrophinopathy Patients.

Duchenne muscular dystrophy (DMD) is an incurable disease caused by out-of-frame DMD gene deletions while in frame deletions lead to the milder Becker muscular dystrophy (BMD). In the last decade several antisense oligonucleotides drugs have been developed to induce a partially functional internally deleted dystrophin, similar to that produced in BMD, and expected to ameliorate the disease course. The pattern of dystrophin expression and functionality in dystrophinopathy patients is variable due to multiple factors, such as molecular functionality of the dystrophin and its distribution. To benchmark the success of therapeutic intervention, a clear understanding of dystrophin expression patterns in dystrophinopathy patients is vital. Recently, several groups have used innovative techniques to quantify dystrophin in muscle biopsies of children but not in patients with milder BMD. This study reports on dystrophin expression using both Western blotting and an automated, high-throughput, image analysis platform in DMD, BMD, and intermediate DMD/BMD skeletal muscle biopsies. Our results found a significant correlation between Western blot and immunofluorescent quantification indicating consistency between the different methodologies. However, we identified significant inter- and intradisease heterogeneity of patterns of dystrophin expression in patients irrespective of the amount detected on blot, due to variability in both fluorescence intensity and dystrophin sarcolemmal circumference coverage. Our data highlight the heterogeneity of the pattern of dystrophin expression in BMD, which will assist the assessment of dystrophin restoration therapies.

Increased dystrophin production with golodirsen in patients with Duchenne muscular dystrophy.

OBJECTIVE: To report safety, pharmacokinetics, exon 53 skipping, and dystrophin expression in golodirsen-treated patients with Duchenne muscular dystrophy (DMD) amenable to exon 53 skipping. METHODS: Part 1 was a randomized, double-blind, placebo-controlled, 12-week dose titration of once-weekly golodirsen; part 2 is an ongoing, open-label evaluation. Safety and pharmacokinetics were primary and secondary objectives of part 1. Primary biological outcome measures of part 2 were blinded exon skipping and dystrophin protein production on muscle biopsies (baseline, week 48) evaluated, respectively, using reverse transcription PCR and Western blot and immunohistochemistry. RESULTS: Twelve patients were randomized to receive golodirsen (n = 8) or placebo (n = 4) in part 1. All from part 1 plus 13 additional patients received 30 mg/kg golodirsen in part 2. Safety findings were consistent with those previously observed in pediatric patients with DMD. Most of the study drug was excreted within 4 hours following administration. A significant increase in exon 53 skipping was associated with ∼16-fold increase over baseline in dystrophin protein expression at week 48, with a mean percent normal dystrophin protein standard of 1.019% (range, 0.09%-4.30%). Sarcolemmal localization of dystrophin was demonstrated by significantly increased dystrophin-positive fibers (week 48, p < 0.001) and a positive correlation (Spearman r = 0.663; p < 0.001) with dystrophin protein change from baseline, measured by Western blot and immunohistochemistry. CONCLUSION: Golodirsen was well-tolerated; muscle biopsies from golodirsen-treated patients showed increased exon 53 skipping, dystrophin production, and correct dystrophin sarcolemmal localization. CLINICALTRIALSGOV IDENTIFIER: NCT02310906. CLASSIFICATION OF EVIDENCE: This study provides Class I evidence that golodirsen is safe and Class IV evidence that it induces exon skipping and novel dystrophin as confirmed by 3 different assays.

Blood-derived biomarkers correlate with clinical progression in Duchenne muscular dystrophy.

BACKGROUND: Duchenne Muscular Dystrophy is a severe, incurable disorder caused by mutations in the dystrophin gene. The disease is characterized by decreased muscle function, impaired muscle regeneration and increased inflammation. In a clinical context, muscle deterioration, is evaluated using physical tests and analysis of muscle biopsies, which fail to accurately monitor the disease progression. OBJECTIVES: This study aims to confirm and asses the value of blood protein biomarkers as disease progression markers using one of the largest longitudinal collection of samples. METHODS: A total of 560 samples, both serum and plasma, collected at three clinical sites are analyzed using a suspension bead array platform to assess 118 proteins targeted by 250 antibodies in microliter amount of samples. RESULTS: Nine proteins are confirmed as disease progression biomarkers in both plasma and serum. Abundance of these biomarkers decreases as the disease progresses but follows different trajectories. While carbonic anhydrase 3, microtubule associated protein 4 and collagen type I alpha 1 chain decline rather constantly over time, myosin light chain 3, electron transfer flavoprotein A, troponin T, malate dehydrogenase 2, lactate dehydrogenase B and nestin plateaus in early teens. Electron transfer flavoprotein A, correlates with the outcome of 6-minutes-walking-test whereas malate dehydrogenase 2 together with myosin light chain 3, carbonic anhydrase 3 and nestin correlate with respiratory capacity. CONCLUSIONS: Nine biomarkers have been identified that correlate with disease milestones, functional tests and respiratory capacity. Together these biomarkers recapitulate different stages of the disorder that, if validated can improve disease progression monitoring.

Cardiorespiratory Progression Over 5 Years and Role of Corticosteroids in Duchenne Muscular Dystrophy: A Single-Site Retrospective Longitudinal Study.

BACKGROUND: Corticosteroids (CSs) have prolonged survival and respiratory function in boys with Duchenne muscular dystrophy (DMD) when compared with CSs-naïve boys. RESEARCH QUESTION: The differential impact of frequently used CSs and their regimens on long-term (> 5 years) cardiorespiratory progression in children with DMD is unknown. STUDY DESIGN AND METHODS: This was a retrospective longitudinal study including children with DMD followed at Dubowitz Neuromuscular Centre, Great Ormond Street Hospital London, England, from May 2000 to June 2017. Patients enrolled in any interventional clinical trials were excluded. We collected patients' anthropometrics and respiratory (FVC, FVC % predicted and absolute FVC, and noninvasive ventilation requirement [NIV]) and cardiac (left ventricular shortening function [LVFS%]) function. CSs-naïve patients had never received CSs. Patients who were treated with CSs took either deflazacort or prednisolone, daily or intermittently (10 days on/10 days off) for > 1 month. Average longitudinal models were fitted for yearly respiratory (FVC % predicted) and cardiac (LVFS%) progression. A time-to-event analysis to FVC % predicted < 50%, NIV start, and cardiomyopathy (LVFS% < 28%) was performed in CS-treated (daily and intermittent) vs CS-naïve patients. RESULTS: There were 270 patients, with a mean age at baseline of 6.2 ± 2.3 years. The median follow-up time was 5.6 ± 3.5 years. At baseline, 263 patients were ambulant. Sixty-six patients were treated with CSs daily, 182 patients underwent CSs intermittent > 60% treatment, and 22 were CS-naïve patients. Yearly FVC % predicted declined similarly from 9 years (5.9% and 6.9% per year, respectively; P = .27) in the CSs-daily and CSs-intermittent groups. The CSs-daily group declined from a higher FVC % predicted than the CSs-intermittent group (P < .05), and both reached FVC % predicted < 50% and NIV requirement at a similar age, > 2 years later than the CS-naïve group. LVFS% declined by 0.53% per year in the CSs-treated group irrespective of the CSs regimen, significantly slower (P < .01) than the CSs-naïve group progressing by 1.17% per year. The age at cardiomyopathy was 16.6 years in the CSs-treated group (P < .05) irrespective of regimen and 13.9 years in the CSs-naïve group. INTERPRETATION: CSs irrespective of the regimen significantly improved respiratory function and delayed NIV requirement and cardiomyopathy.

Novel free-circulating and extracellular vesicle-derived miRNAs dysregulated in Duchenne muscular dystrophy.

Aim: To perform cross-sectional and longitudinal miRNA profiling in plasma from Duchenne muscular dystrophy (DMD) subjects and find non-invasive biomarkers in DMD. Subjects/materials & methods: Plasma was collected from 14 age and sex matched controls and 46 DMD subjects. Free-circulating and extracellular vesicle (EV)-derived miRNA expression was measured by RT-qPCR. Results: Free-circulating and EVs derived miR-29c-3p and miR-133a-3p are dysregulated in DMD subjects. Free-circulating and EV-derived miR-29c-3p are reduced in DMD subjects undergoing daily corticosteroid treatment. Free-circulating miR-1-3p and miR-122-5p are longitudinally upregulated in ambulant DMD subjects. Conclusion: We detected novel free-circulating and EV-derived dysregulated miRNAs in plasma from DMD subjects and characterized the longitudinal profile of free-circulating miRNA on plasma from DMD subjects.

Categorising trajectories and individual item changes of the North Star Ambulatory Assessment in patients with Duchenne muscular dystrophy.

Functional variability among boys with Duchenne muscular dystrophy (DMD) is well recognised and complicates interpretation of clinical studies. We hypothesised that boys with DMD could be clustered into groups sharing similar trajectories of ambulatory function over time, as measured by the North Star Ambulatory Assessment (NSAA) total score. We also explored associations with other variables such as age, functional abilities, and genotype. Using the NorthStar Clinical Network database, 395 patients with >1 NSAA assessment were identified. We utilised latent class trajectory analysis of longitudinal NSAA scores, which produced evidence for at least four clusters of boys sharing similar trajectories versus age in decreasing order of clinical severity: 25% of the boys were in cluster 1 (NSAA falling to ≤ 5 at age ~10y), 35% were in cluster 2 (NSAA ≤ 5 ~12y), 21% in were cluster 3 (NSAA≤ 5 ~14y), and 19% in cluster 4 (NSAA > 5 up to 15y). Mean ages at diagnosis of DMD were similar across clusters (4.2, 3.9, 4.3, and 4.8y, respectively). However, at the first NSAA assessment, a significant (p<0.05) association was observed between earlier declining clusters and younger age, worse NSAA, slower rise from supine, slower 10 metre walk/run times, and younger age of steroid initiation. In order to assess the probability of observing complete loss of function for individual NSAA items, we examined the proportion of patients who shifted from a score of 1 or 2 at baseline to a score of 0. We also assessed the probability of gain of function using the inverse assessment and stratified the probability of deterioration, improvement-or static behavior-by age ranges and using baseline functional status. Using this tool, our study provides a comprehensive assessment of the NSAA in a large population of patients with DMD and, for the first time, describes discrete clusters of disease progression; this will be invaluable for future DMD clinical trial design and interpretation of findings.

Downregulation of miRNA-29, -23 and -21 in urine of Duchenne muscular dystrophy patients.

AIM: To study the signature of 87 urinary miRNAs in Duchenne muscular dystrophy (DMD) patients, select the most dysregulated and determine statistically significant differences in their expression between controls, ambulant (A) and nonambulant (NA) DMD patients, and patients on different corticosteroid regimens. Patients/materials & methods: Urine was collected from control (n = 20), A (n = 31) and NA (n = 23) DMD patients. miRNA expression was measured by reverse transcription-quantitative PCR. RESULTS: miR-29c-3p was significantly downregulated in A DMD patients while miR-23b-3p and miR-21-5p were significantly downregulated in NA DMD patients compared with age-matched controls. CONCLUSION: miR-29c-3p, miR-23b-3p and miR-21-5p are promising novel noninvasive biomarkers for DMD, and miR-29c-3p levels are differentially affected by different steroid regimens, supporting the antifibrotic effect of steroid therapy.

Vascular Pathology Causing Late Onset Generalized Chorea: A Clinico-Pathological Case Report.

BACKGROUND: Chorea may occur as a manifestation of an acute stroke. Patients with vascular-related chorea typically present with an acute or subacute onset of hemichorea, contralateral to the lesion. METHODS AND FINDINGS: In this clinico-pathological case, we report a 90-year-old female who presented, at age 81, with a transient episode of generalized chorea. Over the years, the patient continued to have intermittent episodes of generalized chorea or hemichorea, followed by a progressive dementia syndrome with gait and sphincter disturbance. There was no family history of chorea or dementia. Laboratory tests for paraneoplastic or autoimmune disorders and genetic testing for Huntington's disease were normal or negative. Magnetic resonance imaging showed subcortical and basal ganglia atrophy associated with ischemic leukoencephalopathy and lacunar infarcts. The post-mortem examination identified multiple lacunar infarcts (cortex, white matter, thalamus, basal ganglia) and minor Alzheimer's disease neuropathological changes. CONCLUSIONS: Vascular disease, affecting the basal ganglia, is included in most lists of causes of generalized chorea. Proven cases are difficult to find. We present a rare case of vascular pathology causing late onset generalized and intermittent chorea. We highlight the intermittent nature of the chorea that could be explained by cumulative vascular lesions or functional disconnection in a previous deficient circuit.