Verbal episodic memory declines prior to diagnosis in Huntington's disease

Previous studies of verbal episodic memory in pre-diagnostic Huntington's disease (HD) have yielded mixed results; some evidence suggests that memory decline is evident prior to the onset of pronounced neurological signs of HD, whereas other data indicate that memory function remains normal throughout the pre-diagnostic period. This study examines verbal episodic memory in a sample of CAG expanded individuals who have not yet been clinically diagnosed, and who represent a wide range of points along the continuum from health to disease. The Hopkins Verbal Learning Test-Revised (HVLT-R) was administered to 479 participants (428 with the HD CAG expansion and 51 without), and performance was compared to neurobiological indices of disease progression, including a DNA-based estimate of proximity to clinical diagnosis, magnetic resonance imaging (MRI) measures of striatal volume, and neurologist ratings of motor signs. Lower HVLT-R scores were associated with closer proximity to clinical diagnosis and smaller striatal volumes; these relationships were found even in groups with no neurological signs of HD. The CAG expanded groups, including those with only minimal neurological signs, had significantly lower HVLT-R scores than the control group, and performance was worse in sub-groups that had more neurological signs consistent with HD. These findings indicate that verbal episodic memory is affected in early pre-diagnostic HD and may decline as striatal volumes decrease and individuals approach the motor diagnostic threshold.

Predictive Testing for Huntington's Disease: How Does it Impact on Cognitive Performance?

The discovery of a polymorphic DNA marker for Huntington's Disease (HD) in 1983, and the specific gene responsible in 1993, led to predictive testing programmes out of which came research into whether or not cognitive impairment was present presymptomatically in those at risk for HD. The results of these studies have been conflicting and inconclusive. Methodoiogical limitations have probably contributed to the differing findings. The present study attempted to expand upon previous studies by analysing the data in a more comprehensive manner, and with additional control conditions. In this study, 26 individuals, at risk but presymptomatic, for HD were recruited from the Johannesburg Predictive Testing Programme and administered a battery of psychological tests prior to molecular analysis. Of this HD group, 11 were subsequently positive for the gene (the HD+ group) and 15 were negative (HD- group). A carefully chosen control group, (matched for age, sex, and education - Control Group 1) and a group of individuals experiencing a life threatening medical illness (without CNS involvement - Control Group 2) were administered the same battery of psychological tests. Four-way Analysis of Variance between the HD+, HD-, and Control groups was conducted to detect specific differences between the groups. The results indicated that the HD+ group showed mild impairment for declarative memory function. However, it would appear that undergoing the psychological evaluation itself impacted upon the test performance of both the HD+ and HD- groups.

Is verbal recognition memory really different in Huntington's and Alzheimer's disease

Verbal recall and recognition were examined in Huntington's disease (HD) and Alzheimer's disease (AD) patients. Subgroups of HD and AD patients were matched for overall severity of dementia. Subjects were administered the Hopkins Verbal Learning Test, a list-learning task with three free-recall trials followed immediately by one yes/no recognition trial with semantically related and unrelated distractors. The matched AD and HD groups did not differ in the number of words recalled, although the HD patients showed slightly greater improvement over trials. Recognition performance was evaluated with measures of accuracy and response bias that are independent of each other. The matched groups did not differ in overall recognition accuracy, but the AD patients tended to have a more liberal ("yea-saying") response bias than did the HD patients. In addition, only the AD patients were differentially enticed to false-positive responding by semantically related distractors. The results suggest that the rule for making decisions when uncertain, rather than memory strength per se, distinguishes the recognition memory performance of AD and HD patients.

Neuropsychological, neurological, and MRI correlates of dementia in advanced Huntington's disease: a single case study

Affected Huntington's disease patients present with a progressive dementia that can be detected with a variety of neuropsychological procedures. Neuropsychological findings include impaired mental flexibility and concentration, deterioration of verbal and procedural memory, diminished nonverbal memory, and slowing of both fine and gross motor functions. Magnetic resonance imaging (MRI) offers unique advantages in depicting morphologic changes associated with Huntington's disease. Frontotemporal atrophy and, in particular, atrophy of the corpus striatum are characteristically observed. Given the ease of obtaining coronal images and the improved differentiation of gray matter and white matter, MRI can provide better identification of these findings than traditional imaging methods such as computed tomography (CT). Finally, the presence of steadily progressive neuropsychological deterioration in conjunction with characteristic atrophy observed on MRI can be combined with diminished metabolic activity of the corpus striatum as observed on positron emission tomography (PET) for added diagnostic specificity.