Search

Objective: Evidence suggests that the neuropathology of Huntington's disease, a neuropsychiatric disorder due to a mutation on chromosome 4, results from excessive activation of glutamate-gated ion channels, which kills neurons by oxidative stress. Therefore, the authors hypothesized that alpha-tocopherol, which reduces oxyradical damage to cell membranes, might slow the course of Huntington's disease., Method: A prospective, double-blind; placebo-controlled study of high-dose d-alpha-tocopherol treatment was carried out with a cohort of 73 patients with Huntington's disease who were randomly assigned to either d-alpha-tocopherol or placebo. Patients were monitored for changes in neurologic and neuropsychologic symptoms., Results: Treatment with d-alpha-tocopherol had no effect on neurologic and neuropsychiatric symptoms in the treatment group overall. However, post hoc analysis revealed a significant selective therapeutic effect on neurologic symptoms for patients early in the course of the disorder., Conclusions: Antioxidant therapy may slow the rate of motor decline early in the course of Huntington's disease.

The characteristic pathological features of Huntington's disease (HD) are neostriatal atrophy and neuronal loss. Although neuroradiological studies often show caudate atrophy in patients with moderate HD, frequently no caudate atrophy is found early in the illness. There have been no quantitative reports to date on in vivo putamen volume measures in mild HD, although the structure is known to be neuropathologically involved in the illness. We measured volumes of caudate nucleus and putamen and bicaudate ratios (BCR) from magnetic resonance images, blind to diagnosis, in 15 patients with mild HD and 19 age- and sex-matched control subjects using a computerized image analysis system. The region showing greatest atrophy was the putamen, which was reduced 50.1% in mean volume in HD patients compared with control subjects (p less than 0.000001). In contrast, caudate volume was reduced 27.7% (p = 0.004). BCR was increased 28.5% in HD patients (p = 0.0002). Discriminant function analysis was 94% effective in identifying the diagnostic group based on putamen volume alone, whereas caudate measures had considerable overlap. Correction of putamen volume for head size led to 100% separation by group. Putamen measures and BCR correlated with neurological examination scores but caudate volume did not. Volumetric measurement of putamen is a more sensitive indicator of brain abnormalities in mild HD than measures of caudate atrophy.

Two Huntington disease (HD) pedigrees are presented which differ according to mean and distribution of the age at onset, the effect of paternal transmission on the age at onset, presence of manic-depressive symptoms, and type of presenting symptoms. Together with previous reports, the data suggest clinical heterogeneity between HD kindreds which may imply some kind of genetic heterogeneity, most likely subsequent mutation at a single HD locus. The possibility of genetic heterogeneity has important consequences, both in research, and in the counseling and care of families and patients with differing manifestations of the disease.

The rate of occurrence of conduct disorder and affective illness was studied for a sample of 112 offspring of 34 Huntington's Disease (HD) patients. Psychiatric disorder in the offspring was assessed as a function of: (1) age of the parent at the onset of symptoms of HD; (2) family disorganization; and (3) psychiatric disorder in either parent. The findings indicated an increased frequency of conduct disorder in disrupted families, most especially in those where the HD parent had an early onset of symptoms and the non-HD parent showed psychiatric disorder. Affective disorder in the offspring was most strongly associated with the presence of similar symptoms in the HD parent. Affective disorder, but not conduct disorder, may be an early manifestation of the HD gene. The implication of these findings for genetic counselling is discussed.

To test the hypothesis that interfamily variability in Huntington's Disease (HD) is due to mutation at different loci, linkage analysis was undertaken in two large HD kindreds that differed in ethnicity, age-at-onset, and neurologic and psychiatric features. Both families showed linkage of the HD locus to the G8 probe. Several recombinants were documented in each family, and the best estimate of the recombination fraction for the two families was 6 percent with a 95 percent confidence interval of 0 to 12 percent. Although the data support the existence of a single HD locus, use of the G8 probe for presymptomatic testing in these kindreds would have resulted in a 12 percent error rate in genotype assignment at the HD locus.

Major affective disorder clinically similar to the disorder found in conditions other than Huntington's Disease (HD) was found in 41% of patients with HD in a consecutive case series ascertained through multiple sources in a defined geographical area. The association appears to be confined to certain families, and affective disorder may appear as long as 20 years before the onset of chorea and dementia. The association may represent genetic heterogeneity in HD.

The nucleus basalis of Meynert (nbM) provides most of the cholinergic input to the cerebral cortex. The loss of cortical choline acetyltransferase (CAT) activity in Alzheimer's disease (AD) and senile dementia of the Alzheimer's type (SDAT) appears to be related to a severe depopulation of the nbM in this dementia. In Huntington's disease (HD), by contrast, there is no loss of cortical CAT activity. The present quantitative study indicates that (1) there is no significant loss of neurons from the nbM in HD, and (2) that the previously described cytologic changes in the neurons of this nucleus in HD patients do not differ significantly from controls. These findings are consistent with the working hypothesis that the types of dementia associated with reductions of neocortical CAT activity are characterized by dysfunction or death of neurons in the nbM, but dementing disorders with normal neocortical CAT activity manifest no major abnormalities in this cholinergic nucleus of the basal forebrain.

Previous investigators have noted that the type of sampling scheme used to study the natural history of Huntington's disease can affect the observed age of onset distribution. Simulated data are presented to demonstrate that bias is introduced when onset characteristics derived from prevalence samples (i.e., samples of affected individuals alive in the population) are used to evaluate cofactors of disease onset and to compute genetic risk estimates for persons "at risk" of developing the disease. This study demonstrates that prevalence sampling underestimates the proportion of Huntington's disease cases in the population with later onset ages. Using plausible values for onset time, duration, and life expectancy, simulation results suggest that the paternal transmission effect on Huntington's disease onset is overestimated when based on prevalence data.

In a Maryland survey of Huntington disease, the prevalence in blacks was unexpectedly high and equal to that in whites. Age at onset was earlier in blacks, and their clinical features, at all ages at onset, were similar to those seen in juvenile-onset Huntington disease. Blacks had more severe bradykinesia and abnormalities of eye movement and less frequent psychiatric disorder, particularly depression.

From detailed study of a population-based sample of active cases of Huntington's disease it is known that the age of onset of Huntington's disease is strongly affected by whether Huntington's disease was inherited from mother or father. Standard methods for genetic counseling risk computations use age of unaffected consultant as a covariate affecting the quoted risk, but no other covariates are used in these risk computations. We demonstrate the feasibility of using a proportional hazards approach to computation of the penetrance function which in turn enables a risk to be computed incorporating other covariates besides age of consultant. When there is only one significant covariate other than age, direct estimation of age-of-onset distributions corresponding to various values of the covariate also gives useful results. Our analyses show that genetic counseling risks based on covariates are feasible to compute and offer additional accuracy to the recipient of the information.