Exploring bradyphrenia in Huntington's disease using the computerized test of information processing (CTiP).

Background: Bradyphrenia, best thought of as the mental equivalent of bradykinesia, has been described in several disorders of the brain including Parkinson's disease and schizophrenia; however, little is known about this phenomenon in Huntington's Disease (HD). Objective: The aim of this study was to investigate the presence of bradyphrenia in HD using the Computerized Test of Information Processing (CTiP), an easy to administer and objective task that assesses cognitive processing speed with increasing task complexity. Methods: This study included 211 participants: Huntington's Disease Integrated Staging System (HD-ISS) Stage 0 [n = 28], Stage 1 [n = 30], Stage 2 [n = 48] and Stage 3 [n = 48], and healthy controls (HC) [n = 57]. The CTiP incorporates three subtests: Simple Reaction Time (SRT), which assesses baseline motor function; Choice Reaction Time (CRT), with an added decisional component; and Semantic Search Reaction Time (SSRT), with an added conceptual component. SRT scores were subtracted from CRT and SSRT scores to establish a motor-corrected measure of central conduction time, which was used to operationalize bradyphrenia. Results: HD-ISS and HC within-group reaction times differed significantly when comparing motor-corrected CRT vs SSRT (all ps < 0.0001). Furthermore, the magnitude of these differences increased with HD disease stage (p < 0.0001). An ROC analysis determined that motor-corrected within-subject differences significantly distinguished Stage 2 + 3 from Stage 0 + 1 (AUC = 0.72, p < 0.0001). Conclusions: We report evidence of bradyphrenia in HD that increases with disease progression. This processing deficit, which can be quantified using the CTiP, has the potential to greatly impact HD daily life and warrants additional research.

Graphomotor Dysfluency as a Predictor of Disease Progression in Premanifest Huntington's Disease.

BACKGROUND: Prior studies have relied on conventional observer-based severity ratings such as the Unified Huntington's Disease Rating Scale (UHDRS) to identify early motor markers of decline in Huntington's disease (HD). OBJECTIVE: The present study examined the predictive utility of graphomotor measures handwriting and drawing movements. METHODS: Seventeen gene-positive premanifest HD subjects underwent comprehensive clinical, cognitive, motor, and graphomotor assessments at baseline and at follow-up intervals ranging from 9-36 months. Baseline graphomotor assessments were subjected to linear multiple regression procedures to identify factors associated with change on the comprehensive UHDRS index. RESULTS: Subjects were followed for an average of 21.2 months. Three multivariate regression models based on graphomotor variables derived from a complex loop task, a maximum speed circle drawing task and a combined task returned adjusted R2 coefficients of 0.76, 0.71, and 0.80 respectively accounting for a significant portion of the variability in cUHDRS change score. The best-fit model based on the combined tasks indicated that greater decline on the cUHDRS was associated with increased pen movement dysfluency and stroke-stroke variability at baseline. CONCLUSION: Performance on multiple measures of graphomotor dysfluency assessed during the premanifest or prodromal stage in at-risk HD individuals was associated with decline on a multidimensional index of HD morbidity preceding an HD diagnosis.

Development and Psychometric Properties of a New Brief, Yet Comprehensive, Behavioral Questionnaire for Huntington's Disease.

Background: Individuals with Huntington's disease (HD) experience motoric, cognitive, and psychiatric dysfunction. These difficulties can cause maladaptive behaviors that can be very distressing to family and caregivers. Capturing these behaviors in clinical and research settings is crucial. Objectives: To develop and evaluate the psychometric properties of an instrument that is brief, yet comprehensive, in assessing a broad range of behaviors in HD. Methods: A pool of 30 items encompassing common behaviors in HD was generated. Items were scored on a 4-point Likert scale ranging from completely disagree to completely agree, with higher scores indicating greater dysfunction. The self-report measure was piloted on a small sample of individuals with HD. Reliability (test-retest, internal consistency) and validity (convergent, discriminant, criterion) were evaluated. Results: The HD-Behavioral Questionnaire (HD-BQ) demonstrated evidence for reliability with a test-retest correlation coefficient of r = 0.81 and an internal consistency of 0.96. Validity was established with evidence for good convergent, divergent, and criterion validity. A receiver operating characteristic curve showed that the HD-BQ outperformed a similar commonly used measure in diagnostic capability of behaviors in HD. Conclusions: The HD-BQ, a patient self-report measure, was created to more fully explore behavioral issues that people with HD experience in response to limitations of commonly used instruments in the field. Psychometric evidence supports that the HD-BQ is a valid and reliable instrument for the brief, yet comprehensive, assessment of problematic behaviors in HD.

Anosognosia in HD: Comparison of self-report and caregiver ratings with objective performance measures.

INTRODUCTION: Individuals with Huntington's disease (HD) commonly experience anosognosia, a lack of awareness of deficits. Thus, it is important to examine the accuracy of patient vs caregiver ratings on the basis of objective performance-based measures. METHODS: The Anosognosia Scale (AS) was given to 33 patients with manifest HD and their caregivers. The AS consists of 8 items in which individuals rate their global abilities relative to same-aged peers. Scores range from very impaired to excellent. Caregiver and patient ratings were then correlated with objective measures. RESULTS: Caregivers' evaluations of patients' cognitive and motoric abilities were more highly correlated with objective measures than patients' ratings. Specifically, caregivers' AS item scores were highly correlated with objective measures of walking (Unified Huntington Disease Rating Scale (UHDRS) tandem walking score [r = 0.57, p = .001] vs. patient [r = 0.39, p = .031]); dexterity (UHDRS pronation supination score [r = 0.55, p = .011] vs. patient [r = 0.18, p = .393]); speech (UHDRS dysarthria score [r = 0.55, p = .004] vs. patient [r = 0.03, p = .854]); memory (MoCA score [r = -.45, p = .048] vs. patient [r = -.11, p = .963]); attention (Trails Making Test A score [r = 0.58, p = .004] vs. patient [r = 0.08, p = .686]); and word retrieval (category fluency ([r = -.58, p = .004] vs. patient [r = -.02, p = 1.00]). Moreover, both the UHDRS total motor score (TMS) (F(1,29) = 7.50, p = .010) and the Mini Mental Status Exam (MMSE) (F(1,31) = 5.40, p = .027) were significant predictors of patient levels of anosognosia. CONCLUSIONS: Our findings indicate that caregivers may be better able to rate HD patients' cognitive and motor abilities than patients themselves. Both cognitive and motor severity are significant predictors of levels of anosognosia in HD.

Source recognition discriminability impairment in Huntington's versus Alzheimer's disease: Evidence from the CVLT-3.

Research suggests that individuals with Huntington's disease (HD) perform better than individuals with Alzheimer's disease (AD) on the California Verbal Learning Test (CVLT) Yes/No Recognition trial. However, those with HD have been shown to have deficits comparable to those with AD on the Source Recognition Discriminability (RD) index (which assesses the ability to distinguish between List A targets and List B distractors), suggesting that HD may involve selective impairment in aspects of yes/no recognition that rely on source memory. However, whether individuals with HD and AD show comparable deficits on Source RD across stages of dementia severity has not been adequately investigated. We examined performance on the CVLT-3 List A vs. List B RD index in individuals with HD or AD and mild or moderate dementia. Among individuals with mild dementia, scores were higher in the HD versus AD group, whereas among individuals with moderate dementia, scores were comparable between the HD and AD groups; this corresponded to differential performance across dementia stages among individuals with HD, but not AD. The present findings suggest that, relative to AD, HD may be associated with disproportionate decline in aspects of yes/no recognition that rely on source memory.