Background

Parkinsonian features have been used as a minor diagnostic criterion for fragile X-associated tremor/ataxia syndrome (FXTAS). However, prior studies have examined parkinsonism (defined as having bradykinesia with at least rest tremor or postural instability) mostly in premutation carriers without a diagnosis of FXTAS. The current study was intended to elaborate this important aspect of the FXTAS spectrum, and to quantify the relationships between parkinsonism, FXTAS clinical staging and genetic/molecular measures.

Methods

Thirty eight (38) FXTAS patients and 10 age-matched normal controls underwent a detailed neurological examination that included all but one item (i.e. rigidity) of the motor section of the Unified Parkinson's Disease Rating Scale (UPDRS).

Results

The FXTAS patient group displayed substantially higher prevalence of parkinsonian features including body bradykinesia (57%) and rest tremor (26%), compared to the control group. Furthermore, parkinsonism was identified in 29% of FXTAS patients. Across all patients, body bradykinesia scores significantly correlated with FXTAS clinical stage, FMR1 mRNA level, and ataxic gait of cerebellar origin, while postural instability was associated with intention tremor.

Interpretation

Parkinsonian features in FXTAS appear to be characterized as bradykinesia concurrent with cerebellar gait ataxia, postural instability accompanied by intention tremor, and frequent rest tremor, representing distinctive patterns that highlight the need for further clinical studies including genetic testing for the FMR1 premutation. The association between FMR1 mRNA level and bradykinesia implicates pathophysiological mechanisms which may link FMR1 mRNA toxicity, dopamine deficiency and parkinsonism in FXTAS.

Objective

To investigate the nature of cognitive impairments and underlying brain mechanisms in older female fragile X premutation carriers with and without fragile X-associated tremor/ataxia syndrome (FXTAS).

Methods

Extensive neuropsychological testing and cognitive event-related brain potentials (ERPs; particularly, the auditory P300) were examined in 84 female participants: 33 fragile X premutation carriers with FXTAS (mean age = 62.8 years), 25 premutation carriers without FXTAS (mean age = 55.4 years), and 26 normal healthy controls (mean age = 59.3 years).

Results

Both premutation groups exhibited executive dysfunction on the Behavioral Dyscontrol Scale, with subtle impairments in inhibition and performance monitoring in female carriers without FXTAS, and more substantial deficits in FXTAS women. However, the female carrier group without FXTAS showed more pronounced deficiencies in working memory. Abnormal ERPs were recorded over the frontal lobes, where FXTAS patients showed both P300 amplitude reduction and latency prolongation, whereas only decreased frontal P300 amplitudes were found in carriers without FXTAS. These frontal P300 measures correlated with executive function and information processing speed.

Interpretation

The neuropsychological testing and ERP results of the present study provide support for the hypothesis that executive dysfunction is the primary cognitive impairment among older female premutation carriers both with and without FXTAS, although these deficits are relatively mild compared to those in FXTAS males. These findings are consistent with a synergistic effect of the premutation and aging on cognitive impairment among older female fragile X premutation carriers, even in those without FXTAS symptoms.

We sought cognitive event-related potential (ERP) biomarkers of "Preclinical Alzheimer's disease" (Pre-AD) using an incidental verbal learning paradigm with high sensitivity to prodromal AD. Seven elderly persons, with normal cognition at the time of ERP recordings, but who showed subsequent cognitive decline or AD pathology at autopsy (n = 5, mean Braak stage = 2.8), were compared to 12 "robust" normal elderly (RNE) persons who remained cognitively normal (Mfollow-up = 9.0 years). EEG was recorded during a word repetition paradigm (semantically congruous (50%) and incongruous target words repeat ~10-140 seconds later). The RNE P600 congruous word repetition ERP effects (New minus Old congruous words) were significantly larger than in Pre-AD (mean amplitudes = 3.28 vs. 0.10 μV, p = .04). High group discrimination (84%) was achieved (by a P600 amplitude cutoff of ~1.5 μV). Abnormal P600 word repetition effects in cognitively normal elderly persons may be an important sign of synaptic dysfunction and Preclinical AD.

Older FMR1 premutation carriers may develop fragile X-associated tremor/ataxia syndrome (FXTAS), a neurodegenerative disorder manifesting cognitive deficits that often subsequently progress to dementia. To date, there is no specific treatment available for FXTAS. Studies have demonstrated the premutation-associated overactivation of glutamatergic receptors in neurons. Memantine, a NMDA receptor antagonist approved for treatment of Alzheimer's disease, thus was tested in the first placebo-controlled, double-blind, randomized clinical trial in FXTAS. Prior event-related brain potential (ERP) studies in FXTAS found reduced N400 repetition effect, a glutamate-related electrophysiological marker of semantic priming, and verbal memory processes. This substudy of the randomized clinical trial of memantine in FXTAS sought to use the N400 repetition effect to evaluate effects of chronic memantine treatment on verbal memory. Subsequent recall and recognition memory tests for the experimental stimuli were administered to characterize verbal memory. Data from 41 patients who completed the 1-year memantine trial (21 on memantine) and also completed longitudinal ERP studies were analyzed. Results showed treatment-associated benefits on both cued-recall memory and N400 repetition effect amplitude. Importantly, improvement in cued recall was positively correlated with amplitude increase of the N400 repetition effect. The placebo group, in contrast, displayed a significant reduction of the N400 repetition effect after 1 year. These results suggest that memantine treatment may have beneficial effects on verbal memory in FXTAS. Additional studies of memantine, perhaps in combination with other therapeutic agents, appear warranted, as symptomatic treatments and neuroprotective treatments are both needed for this recently recognized neurodegenerative disorder.

Progressive cognitive deficits are common in patients with fragile X-associated tremor/ataxia syndrome (FXTAS), with no targeted treatment yet established. In this substudy of the first randomized controlled trial for FXTAS, we examined the effects of NMDA antagonist memantine on attention and working memory. Data were analyzed for patients (24 in each arm) who completed both the primary memantine trial and two EEG recordings (at baseline and follow-up) using an auditory "oddball" task. Results demonstrated significantly improved attention/working memory performance after one year only for the memantine group. The event-related potential P2 amplitude elicited by non-targets was significantly enhanced in the treated group, indicating memantine-associated improvement in attentional processes at the stimulus identification/discrimination level. P2 amplitude increase was positively correlated with improvement on the behavioral measure of attention/working memory during target detection. Analysis also revealed that memantine treatment normalized the P2 habituation effect at the follow-up visit. These findings indicate that memantine may benefit attentional processes that represent fundamental components of executive function/dysfunction, thought to comprise the core cognitive deficit in FXTAS. The results provide evidence of target engagement of memantine, as well as therapeutically relevant information that could further the development of specific cognitive or disease-modifying therapies for FXTAS.

The fragile X-associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative disorder affecting a subset of carriers of the FMR1 (fragile X mental retardation 1) premutation. Penetrance and expression appear to be significantly higher in males than females. Although the most obvious aspect of the phenotype is the movement disorder that gives FXTAS its name, the disorder is also accompanied by progressive cognitive impairment. In this review, we address the cognitive neuropsychological and neurophysiological phenotype for males and females with FXTAS, and for male and female unaffected carriers. Despite differences in penetrance and expression, the cognitive features of the disorder appear similar for both genders, with impairment of executive functioning, working memory, and information processing the most prominent. Deficits in these functional systems may be largely responsible for impairment on other measures, including tests of general intelligence and declarative learning. FXTAS is to a large extent a white matter disease, and the cognitive phenotypes observed are consistent with what some have described as white matter dementia, in contrast to the impaired cortical functioning more characteristic of Alzheimer's disease and related disorders. Although some degree of impaired executive functioning appears to be ubiquitous among persons with FXTAS, the data suggest that only a subset of unaffected carriers of the premutation - both female and male - demonstrate such deficits, which typically are mild. The best-studied phenotype is that of males with FXTAS. The manifestations of cognitive impairment among asymptomatic male carriers, and among women with and without FXTAS, are less well understood, but have come under increased scrutiny.

Changes in the fragile X mental retardation 1 gene (FMR1) have been associated with specific phenotypes, most specifically those of fragile X syndrome (FXS), fragile X tremor/ataxia syndrome (FXTAS), and fragile X primary ovarian insufficiency (FXPOI). Evidence of increased risk for additional medical, psychiatric, and cognitive features and conditions is now known to exist for individuals with a premutation, although some features have been more thoroughly studied than others. This review highlights the literature on medical, reproductive, cognitive, and psychiatric features, primarily in females, that have been suggested to be associated with changes in the FMR1 gene. Based on this review, each feature is evaluated with regard to the strength of evidence of association with the premutation. Areas of need for additional focused research and possible intervention strategies are suggested.

Objective: To examine cognitive deficits and associated brain activity in fragile X-associated tremor/ataxia syndrome (FXTAS) patients with parkinsonism (FXTp+), in relation to FXTAS patients without parkinsonism (FXTp-), and normal elderly controls (NC). Methods: Retrospective reviews were performed in 65 FXTAS patients who participated in the event-related brain potential (ERP) study and also had either a videotaped neurological examination or a neurological examination for extrapyramidal signs. Parkinsonism was defined as having bradykinesia with at least one of the following: rest tremor, postural instability, hypermyotonia, or rigidity. Eleven FXTp+ patients were identified and compared to 11 matched FXTp- and 11 NC. Main ERP measures included the N400 congruity effect, N400 repetition effect, and the late positive component (LPC) repetition effect. Results: When compared with FXTp- and NC, the FXTp+ group showed more severe deficits in executive function, cued-recall, recognition memory, along with a significantly reduced N400 repetition effect (thought to index semantic processing and verbal learning/memory) which was correlated with poorer verbal memory. Across all patients, FMR1 mRNA levels were inversely correlated with delayed recall on the California Verbal Learning Test (CVLT). Interpretation: The findings of more prominent executive dysfunction and verbal learning/memory deficits in FXTp+ than FXTp- are consistent with findings in Parkinson's disease (PD), and may indicate that concomitant and/or synergistic pathogenetic mechanisms associated with PD play a role in FXTAS. These results have implications not only for understanding the cognitive impairments associated with the parkinsonism subtype of FXTAS, but also for the development of new interventions for these patients.

Background

Fragile X-associated tremor/ataxia syndrome (FXTAS), a neurodegenerative disorder caused by FMR1 gene premutations, typically associated with frontal-subcortical type cognitive impairments. High prevalence (~50%) of superimposed Alzheimer׳s pathology has been reported in FMR1 premutation carriers, and standardized neuropsychological tests have not yielded any robust discriminators between FXTAS and Alzheimer׳s disease (AD) dementia. The similarities/differences in memory processes between FXTAS and early AD remain underexplored.

Methods

32-channel event-related potentials (ERPs) were obtained from a semantic judgment task in which semantically congruous (50%) and incongruous pairs repeat pseudorandomly. The N400 and late positive component (LPC) of 25 FXTAS patients (M(age)=71.2, MMSE=26.6) were compared to a matched group of 25 patients with MCI or early AD (1 mild AD dementia, 24 amnestic MCI, of whom 18 later converted to AD; M(age)=73.4, MMSE=26.4), and 25 healthy elderly.

Results

Both patient groups showed similar reductions in the N400 repetition effect and N400 congruity effect amplitudes, compared to controls, reflecting abnormal semantic priming and repetition priming. The MCI/AD group, however, had significantly smaller LPC word repetition effects and poorer learning and memory on the CVLT than FXTAS. The LPC and N400 repetition effects both correlated with verbal memory across all subjects, but only N400 correlated with memory in FXTAS.

Conclusion

FXTAS patients show relative sparing of the LPC repetition effect, and less disruption of explicit memory than prodromal/early AD. N400 abnormalities in FXTAS appear to account for much of their mild impairments in verbal learning and memory.

Background and Purpose- Although there are no trials or large cohorts to inform clinical care, current guidelines caution against giving intravenous tPA (tissue-type plasminogen activator) to patients with acute ischemic stroke who are taking non-vitamin K antagonist oral anticoagulants (NOACs). We performed a literature review of intravenous tPA in patients treated with NOACs preceding stroke. Methods- A literature search of PubMed was performed encompassing January 2010 to March 2018. Patient characteristics, timing of last medication intake, laboratory testing, use of reversal, and outcomes ≤3 months after discharge were summarized. Results- We identified 55 studies with 492 NOAC patients receiving tPA (dabigatran, 181; rivaroxaban, 215; apixaban, 40; and unspecified NOAC, 56). Among patients with complete data, the median time from the last NOAC intake to symptom onset was 8 hours (interquartile range, 2.5-14.5), with 55.2% (80/145) within 12 hours. Few patients underwent sensitive laboratory tests, such as thrombin time, diluted thrombin time, or anti-Xa assays before tPA administration. The overall observed rates of symptomatic intracranial hemorrhage, mortality, and favorable outcomes (National Institutes of Health Stroke Scale score, ≤1; modified Rankin Scale score, 0-2; or neurological improvement in the National Institutes of Health Stroke Scale score, ≥8 points) were 4.3% (20/462), 11.3% (48/423), and 43.7% (164/375), respectively. Among dabigatran-treated patients, reversal with idarucizumab was associated with fewer symptomatic intracranial hemorrhage (4.5% [2/44] versus 7.4% [8/108]; unadjusted odds ratio, 0.60; 95% CI, 0.12-2.92), death (4.5% [2/44] versus 12.0% [13/108]; unadjusted odds ratio, 0.35; 95% CI, 0.08-1.61), and more favorable outcomes (79.1% [34/43] versus 39.2% [29/74]; unadjusted odds ratio, 5.86; 95% CI, 2.45-14.00), although the differences were not statistically significant for symptomatic intracranial hemorrhage and death. Conclusions- These preliminary observations suggest that tPA may be reasonably well tolerated without prohibitive risks of bleeding complications in selected patients on NOACs. Reversal of anticoagulant effects by idarucizumab for dabigatran-treated patients before tPA is an emerging strategy that was associated with more favorable outcomes.