To investigate whether Huntington's disease (HD) affects autonomic nervous system (ANS) functioning 33 subjects with positive genetic test results were studied. The subjects were classified according to Shoulson and Fahn (S&F) HD disability scale into three subgroups: subgroup 1 (eight asymptomatic gene carriers), subgroup 2 (13 mildly disabled HD patients) and subgroup 3 (eight moderately and four severely disabled HD patients). A battery of cardiovascular autonomic tests (Valsalva maneuver, deep breathing test, sustained handgrip test, orthostatic test) and the spectral analysis of heart rate variability (HRV) were performed. The results were compared with a group of matched controls. In subgroup 1, there was a higher power of low-frequency band (LFB) (P < 0.05). In subgroup 2 a higher power of LFB was detected, LFB/high-frequency band (HFB) coefficient was increased and the blood pressure response to sustained handgrip was elevated (P < 0.05). Subgroup 3 showed significantly lower blood pressure response to sustained handgrip, lower respiratory (P < 0.05) and orthostatic ratio (P < 0.01). Our results suggest that sympathetic hyperfunction is present in asymptomatic gene carriers and mildly disabled HD patients. Contrary to that, ANS hypofunction was found in advanced HD patients.

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The influence of the type, duration, severity and levodopa treatment of Parkinson's disease on autonomic involvement has been assessed. The Valsalva manoeuvre, deep breathing, handgrip and orthostatic tests were performed in 50 patients with Parkinson's disease and in a control group of 30 healthy subjects. No attempt was made to classify further patients with parkinsonian features into groups such as the Shy-Drager syndrome or multiple system atrophy. All test results were significantly smaller in patients than in healthy subjects. The diastolic pressure increase during handgrip was significantly smaller in akinetic-rigid than in tremor-akinetic-rigid type patients. The Valsalva ratio and orthostatic test results were significantly smaller in patients with longer duration than in those with shorter duration of disease. All test results except those of the orthostatic test were significantly smaller in patients with the more severe form than in those with the less severe form of disease. Comparing test results of levodopa-treated and -untreated patients no significant differences were found. Our studies in parkinsonian patients suggest that (1) sympathetic impairment is more pronounced in akinetic-rigid than in tremor-akinetic-rigid type patients; (2) sympathetic impairment occurs early, whereas parasympathetic impairment develops later; (3) sympathetic and parasympathetic impairment parallels the severity of disease; (4) orthostatic parameters are more duration-sensitive than severity-sensitive; (5) chronic levodopa treatment does not markedly influence cardiovascular autonomic responses.

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