Are cognitive changes progressive in prediagnostic HD?

Safer Attitude to Risky Decision-Making in Premanifest Huntington's Disease Subjects

Huntington’s disease (HD) is an inherited neurodegenerative disorder characterized by involuntary, jerky movements, incoordination, behavioral changes and subtle executive and cognitive impairment starting before motor symptoms. Our study aimed to assess the risky decision-making process in premanifest (pre) HD subjects, by means Game of Dice Task (GDT). As dependent variables, several GDT outcomes have been taken into consideration. We recruited 30 subjects (15 females) with preHD (i.e., Diagnosis Confidence Level < 4; Total Motor Score < 10), and 21 age, gender and education matched neurologically normal subjects (11 females). GDT is a computer-guided task where subjects are invited to watch the digits on which to bet and to evaluate the related potential risk to win or loss. Our results showed that decision and feedback times were longer in preHD than in neurologically normal group in both disadvantageous and advantageous choices. PreHD subjects provided a greater number of “safe” strategies, taken with longer decision-making time than neurologically normal subjects, showing a reduced propensity to risk. Such behavior, characterized by increased slowness in acting and providing answers, might contribute to delineate a behavioral and cognitive profile in preHD.

A Novel Ecological Approach Reveals Early Executive Function Impairments in Huntington's Disease

Introduction: Impairments in executive functions are common in neurogenetic disorders such as Huntington's disease (HD) and are thought to significantly influence the patient's functional status. Reliable tools with higher ecological validity that can assess and predict the impact of executive dysfunction in daily-life performance are needed. This study aimed to develop and validate a novel non-immersive virtual reality task ("EcoKitchen") created with the purpose of capturing cognitive and functional changes shown by HD carriers without clinical manifestations of the disease (Premanifest HD), in a more realistic setting. Materials and Methods: We designed a virtual reality task with three blocks of increasing executive load. The performance of three groups (Controls, CTRL; Premanifest HD individuals, HP; Early Manifest HD patients, HD) was compared in four main components of the study protocol: the EcoKitchen; a subjective (self-report) measure - "The Adults and Older Adults Functional Assessment Inventory (IAFAI)"; the "Behavioural Assessment of Dysexecutive Syndrome battery (BADS)"; and a conventional neuropsychological test battery. We also examined statistical associations between EcoKitchen and the other executive, functional and clinical measures used. Results: The HD group showed deficits in all the assessment methods used. In contrast, the HP group was only found to be impaired in the EcoKitchen task, particularly in the most cognitively demanding blocks, where they showed a higher number of errors compared to the CTRL group. Statistically significant correlations were identified between the EcoKitchen, measures of the other assessment tools, and HD clinical features. Discussion: The EcoKitchen task, developed as an ecological executive function assessment tool, was found to be sensitive to early deficits in this domain. Critically, in premanifest HD individuals, it identifies dysfunction prior to symptom onset. Further it adds a potential tool for diagnosis and management of the patients' real-life problems.

Developing stem cell therapies for juvenile and adult-onset Huntington's disease

Stem cell therapies have been explored as a new avenue for the treatment of neurologic disease and damage within the CNS in part due to their native ability to mimic repair mechanisms in the brain. Mesenchymal stem cells have been of particular clinical interest due to their ability to release beneficial neurotrophic factors and their ability to foster a neuroprotective microenviroment. While early stem cell transplantation therapies have been fraught with technical and political concerns as well as limited clinical benefits, mesenchymal stem cell therapies have been shown to be clinically beneficial and derivable from nonembryonic, adult sources. The focus of this review will be on emerging and extant stem cell therapies for juvenile and adult-onset Huntington's disease.

Tracking motor impairments in the progression of Huntington's disease

The Unified Huntington's Disease Rating Scale is used to characterize motor impairments and establish motor diagnosis. Little is known about the timing of diagnostic confidence level categories and the trajectory of motor impairments during the prodromal phase. Goals of this study were to estimate the timing of categories, model the prodromal trajectory of motor impairments, estimate the rate of motor impairment change by category, and provide required sample size estimates for a test of efficacy in clinical trials. In total, 1010 gene-expanded participants from the Neurobiological Predictors of Huntington's Disease (PREDICT-HD) trial were analyzed. Accelerated failure time models were used to predict the timing of categories. Linear mixed effects regression was used to model the longitudinal motor trajectories. Age and length of gene expansion were incorporated into all models. The timing of categories varied significantly by gene expansion, with faster progression associated with greater expansion. For the median expansion, the third diagnostic confidence level category was estimated to have a first occurrence 1.5 years before diagnosis, and the second and first categories were estimated to occur 6.75 years and 19.75 years before diagnosis, respectively. Motor impairments displayed a nonlinear prodromal course. The motor impairment rate of change increased as the diagnostic confidence level increased, with added acceleration for higher progression scores. Motor items can detect changes in motor impairments before diagnosis. Given a sufficiently high progression score, there is evidence that the diagnostic confidence level can be used for prodromal staging. Implications for Huntington's disease research and the planning of clinical trials of efficacy are discussed.

Cognitive reserve and brain reserve in prodromal Huntington's disease

Huntington disease (HD) is associated with decline in cognition and progressive morphological changes in brain structures. Cognitive reserve may represent a mechanism by which disease-related decline may be delayed or slowed. The current study examined the relationship between cognitive reserve and longitudinal change in cognitive functioning and brain volumes among prodromal (gene expansion-positive) HD individuals. Participants were genetically confirmed individuals with prodromal HD enrolled in the PREDICT-HD study. Cognitive reserve was computed as the composite of performance on a lexical task estimating premorbid intellectual level, occupational status, and years of education. Linear mixed effects regression (LMER) was used to examine longitudinal changes on four cognitive measures and three brain volumes over approximately 6 years. Higher cognitive reserve was significantly associated with a slower rate of change on one cognitive measure (Trail Making Test, Part B) and slower rate of volume loss in two brain structures (caudate, putamen) for those estimated to be closest to motor disease onset. This relationship was not observed among those estimated to be further from motor disease onset. Our findings demonstrate a relationship between cognitive reserve and both a measure of executive functioning and integrity of certain brain structures in prodromal HD individuals.

The relationship between cortisol and verbal memory in the early stages of Huntington's disease

Hypothalamic pituitary adrenal (HPA) axis hyperactivity has been linked to learning and memory difficulties in a range of neurodegenerative and neuropsychiatric conditions. In Huntington's disease (HD), both declines in learning and memory and HPA axis dysfunction are present early in the disease. However, the relationship between specific learning and memory deficits and HPA axis functioning in HD has not been examined. The aim of this study was to investigate cortisol levels in relation to verbal learning and memory in pre-diagnosed (pre-HD) participants and patients at the early stages of diagnosed HD (early-HD). Cortisol concentration was assayed in saliva samples from 57 participants (17 early-HD, 20 pre-HD, and 20 controls) at four time-points across a 24-h period. Verbal memory was assessed using the California Verbal Learning Test-Second Edition (CVLT-II). We focused statistical analyses on the late evening cortisol concentration, and examined cortisol levels and verbal memory function in relation to diagnostic group (control, pre-HD, early-HD), and in a separate set of analyses combining pre-HD and early-HD (and excluding controls) we also examined cortisol and verbal memory performance in relation to the severity of HD-related motor signs. Of these two classification approaches, HD motor sign severity was more strongly associated with high evening cortisol levels and both reduced information encoding and memory retrieval. Separately, there was also a trend of higher cortisol levels in pre-HD. The findings suggest hypercortisolism and the underlying pathological changes may begin many years before a clinical diagnosis is made, but the memory decline associated with HPA axis disturbance may only become detectable once motor signs become pronounced.

Deficient sustained attention to response task and P300 characteristics in early Huntington's disease

Evidence for the extent and nature of attentional impairment in premanifest and manifest Huntington’s disease (HD) is inconsistent. Understanding such impairments may help to better understand early functional changes in HD and could have consequences concerning care for HD patients. We investigated attentional control in both early and premanifest HD. We studied 17 early HD subjects (mean age: 51 years), 12 premanifest HD subjects (mean age: 43 years), and 15 healthy controls (mean age: 51 years), using the sustained attention to response task (SART), a simple Go/No-go test reflecting attentional and inhibitory processes through reaction time (RT) and error rates. Simultaneously recorded EEG yielded P300 amplitudes and latencies. The early HD group made more Go errors (p < 0.001) and reacted slower (p < 0.005) than the other groups. The RT pattern during the SART was remarkably different for early HD subjects compared to the other two groups (p < 0.005), apparent as significant post-error slowing. P300 data showed that for early HD the No-go amplitude was lower than for the other two groups (p < 0.05). Subjects with early HD showed a reduced capacity to effectively control attention. They proved unable to resume the task directly after having made an error, and need more time to return to pre-error performance levels. No attentional control deficits were found for the premanifest HD group.

Seven-year clinical follow-up of premanifest carriers of Huntington's disease

Detecting subtle clinical abnormalities in the 'premanifest' phase of Huntington's disease (HD) is of importance in the development of instruments to monitor early therapeutic intervention trials. The current study examined changes in motor function, cognition and behaviour over a period of seven years in premanifest carriers of the HD gene mutation. Twenty-nine carriers without unequivocal motor signs of HD and 43 non-carrier controls were prospectively examined four times. The assessments consisted of the Unified Huntington's Disease Rating Scale (UHDRS) and an extensive neuropsychological test battery addressing global cognitive function, memory, language and executive function. Rate of Change (RoC) analysis was performed to measure longitudinal differences between carriers and non-carriers. Carriers performed consistently worse on executive function (Symbol Digit Modalities Test (SDMT), Stroop, Trail Making Test (TMT) and WAIS-R arithmetic). Over the years, carriers showed a decline in memory and concentration function (Wechsler Memory Scale (WMS)) and in motor function (UHDRS motor scale). Changes over time could be particularly ascribed to carriers converting to manifest HD. These results demonstrate that standardized motor assessments and objective memory and concentration tasks are sensitive to change over a period of 7 years, specifically in carriers converting to manifest HD. Executive tasks also showed subtle cognitive abnormalities in premanifest HD, but a decline over time could not be demonstrated.

Abnormal error-related antisaccade activation in premanifest and early manifest Huntington disease

OBJECTIVE

Individuals with the trinucleotide CAG expansion (CAG+) that causes Huntington's disease (HD) have impaired performance on antisaccade (AS) tasks that require directing gaze in the mirror opposite direction of visual targets. This study aimed to identify the neural substrates underlying altered antisaccadic performance.

METHOD

Three groups of participants were recruited: (1) Imminent and early manifest HD (early HD, n = 8); (2) premanifest (presymptomatic) CAG+ (preHD, n = 10); and (3) CAG unexpanded (CAG-) controls (n = 12). All participants completed a uniform study visit that included a neurological evaluation, neuropsychological battery, molecular testing, and functional MRI during an AS task. The blood oxygenation level dependent (BOLD) response was obtained during saccade preparation and saccade execution for both correct and incorrect responses using regression analysis.

RESULTS

Significant group differences in BOLD response were observed when comparing incorrect AS to correct AS execution. Specifically, as the percentage of incorrect AS increased, BOLD responses in the CAG- group decreased progressively in a well-documented reward detection network that includes the presupplementary motor area and dorsal anterior cingulate cortex. In contrast, AS errors in the preHD and early HD groups lacked this relationship with BOLD signal in the error detection network, and BOLD responses to AS errors were smaller in the two CAG+ groups as compared with the CAG- group.

CONCLUSIONS

These results are the first to suggest that abnormalities in an error-related response network may underlie early changes in AS eye movements in premanifest and early manifest HD. (PsycINFO Database Record (c) 2011 APA, all rights reserved).

Comparison of vertical and horizontal saccade measures and their relation to gray matter changes in premanifest and manifest Huntington disease

Saccades are a potentially important biomarker of Huntington disease (HD) progression, as saccadic abnormalities can be detected both cross-sectionally and longitudinally. Although vertical saccadic impairment was reported decades ago, recent studies have focused on horizontal saccades. This study investigated antisaccade (AS) and memory guided saccade (MG) impairment in both the horizontal and vertical directions in individuals with the disease-causing CAG expansion (CAG+; n = 74), using those without the expansion (CAG-; n = 47) as controls. Percentage of errors, latency, and variability of latency were used to measure saccadic performance. We evaluated the benefits of measuring saccades in both directions by comparing effect sizes of horizontal and vertical measures, and by investigating the correlation of saccadic measures with underlying gray matter loss. Consistent with previous studies, AS and MG impairments were detected prior to the onset of manifest disease. Furthermore, the largest effect sizes were found for vertical saccades. A subset of participants (12 CAG-, 12 premanifest CAG+, 7 manifest HD) underwent magnetic resonance imaging, and an automated parcellation and segmentation procedure was used to extract thickness and volume measures in saccade-generating and inhibiting regions. These measures were then tested for associations with saccadic impairment. Latency of vertical AS was significantly associated with atrophy in the left superior frontal gyrus, left inferior parietal lobule, and bilateral caudate nuclei. This study suggests an important role for measuring vertical saccades. Vertical saccades may possess more statistical power than horizontal saccades, and the latency of vertical AS is associated with gray matter loss in both cortical and subcortical regions important in saccade function.

Perceived stress in prodromal Huntington disease

This study examines perceived stress and its relationship to depressive symptoms, life changes and functional capacity in a large sample of individuals who are positive for the Huntington disease (HD) gene expansion but not yet diagnosed. Participants were classified by estimated proximity to HD diagnosis (far, mid, near) and compared with a non-gene-expanded comparison group. Persons in the mid group had the highest stress scores. A significant interaction between age and time since HD genetic testing was also found. Secondary analyses using data from a different data collection point and including a diagnosed group showed the highest stress scores in the diagnosed group. Possible explanations and implications are discussed.

Early changes in white matter pathways of the sensorimotor cortex in premanifest Huntington's disease

OBJECTIVES

To investigate the function-structure relationship of white matter within different stages of Huntington's disease (HD) using diffusion tensor imaging (DTI).

EXPERIMENTAL DESIGN

From the TRACK-HD study, an early stage HD group and a premanifest gene carrier group (PMGC) were age-matched to two healthy control groups; all underwent 3-T MRI scanning of the brain. Region of interest (ROI) segmentation of the corpus callosum, caudate nucleus, thalamus, prefrontal cortex, and sensorimotor cortex was applied, and the apparent fiber pathways of these regions were analyzed. Functional measures of motor, oculomotor, cognition, and behavior were correlated to DTI measures. PRINCIPLE OBSERVATIONS: In PMGC versus controls, higher apparent diffusion coefficient (ADC) was seen in white matter pathways of the sensorimotor cortex (P < 0.01) and in the ROI of corpus callosum (P < 0.017). In early HD, fiber tract analysis showed higher ADC in pathways of the corpus callosum, thalamus, sensorimotor, and prefrontal region (P < 0.01). ROI analysis showed higher diffusivity in the corpus callosum and caudate nucleus (P < 0.017). Motor, oculomotor, cognition, and probability of onset within 2 and 5 years, correlated well with ADC measures of the corpus callosum (P < 0.01 - P < 0.005), sensorimotor (P < 0.01 - P < 0.005), and prefrontal region (P < 0.01).

CONCLUSIONS

Disturbances in the white matter connections of the sensorimotor cortex can be demonstrated not only in manifest HD but also in premanifest gene carriers. Connectivity measures are well related to clinical functioning. DTI measures can be regarded as a potential biomarker for HD, due to their ability to objectify changes in brain structures and their role within brain networks.

Neurocognitive signs in prodromal Huntington disease

OBJECTIVE

PREDICT-HD is a large-scale international study of people with the Huntington disease (HD) CAG-repeat expansion who are not yet diagnosed with HD. The objective of this study was to determine the stage in the HD prodrome at which cognitive differences from CAG-normal controls can be reliably detected.

METHOD

For each of 738 HD CAG-expanded participants, we computed estimated years to clinical diagnosis and probability of diagnosis in 5 years based on age and CAG-repeat expansion number (Langbehn, Brinkman, Falush, Paulsen, & Hayden, 2004). We then stratified the sample into groups: NEAR, estimated to be ≤9 years; MID, between 9 and 15 years; and FAR, ≥15 years. The control sample included 168 CAG-normal participants. Nineteen cognitive tasks were used to assess attention, working memory, psychomotor functions, episodic memory, language, recognition of facial emotion, sensory-perceptual functions, and executive functions.

RESULTS

Compared with the controls, the NEAR group showed significantly poorer performance on nearly all of the cognitive tests and the MID group on about half of the cognitive tests (p = .05, Cohen's d NEAR as large as -1.17, MID as large as -0.61). One test even revealed significantly poorer performance in the FAR group (Cohen's d = -0.26). Individual tasks accounted for 0.2% to 9.7% of the variance in estimated proximity to diagnosis. Overall, the cognitive battery accounted for 34% of the variance; in comparison, the Unified Huntington's Disease Rating Scale motor score accounted for 11.7%.

CONCLUSIONS

Neurocognitive tests are robust clinical indicators of the disease process prior to reaching criteria for motor diagnosis of HD.

A double blind evaluation of cognitive decline in a Norwegian cohort of asymptomatic carriers of Huntington's disease

Previous studies investigating subclinical signs of cognitive decline in presymptomatic carriers of Huntington's disease (HD) have shown conflicting results. The current study examines cognition in 105 at-risk individuals, using a broad neuropsychological test battery and adopting strict inclusion criteria for attaining a homogeneous sample. Results obtained by analyses of variance and effect size calculations indicate no clinical evidence of significant cognitive decline in asymptomatic HD carriers very far from onset of illness compared to noncarriers. Closeness to disease onset amongst gene carriers influenced cognition negatively whereas cytosine-adenine-guanine (CAG) repeat size did not. The findings call for longitudinal follow-up studies using a combination of clinical instruments and experimental paradigms to pinpoint when subtle cognitive deficits occur and within which of the cognitive domains.