Autonomic nervous function in Huntington's disease

Clinical Review of Juvenile Huntington's Disease

 Juvenile Huntington's disease (JHD) is rare. In the first decade of life speech difficulties, rigidity, and dystonia are common clinical motor symptoms, whereas onset in the second decade motor symptoms may sometimes resemble adult-onset Huntington's disease (AOHD). Cognitive decline is mostly detected by declining school performances. Behavioral symptoms in general do not differ from AOHD but may be confused with autism spectrum disorder or attention deficit hyperactivity disorder and lead to misdiagnosis and/or diagnostic delay. JHD specific features are epilepsy, ataxia, spasticity, pain, itching, and possibly liver steatosis. Disease progression of JHD is faster compared to AOHD and the disease duration is shorter, particularly in case of higher CAG repeat lengths. The diagnosis is based on clinical judgement in combination with a positive family history and/or DNA analysis after careful consideration. Repeat length in JHD is usually >  55 and caused by anticipation, usually via paternal transmission. There are no pharmacological and multidisciplinary guidelines for JHD treatment. Future perspectives for earlier diagnosis are better diagnostic markers such as qualitative MRI and neurofilament light in serum.

Autonomic disorders and myocardial 123I-metaiodobenzylguanidine scintigraphy in Huntington's disease

BACKGROUND

Huntington's disease (HD) patients often present with abnormal modulation of blood pressure and heart rate. We investigated whether cardiac autonomic innervation assessed by 123I-metaiodobenzylguanidine (MIBG) imaging is impaired in HD patients, in comparison with controls (Ctrl).

METHODS

Fifteen patients (6 F and 9 M) were assessed by the motor section of the Unified HD Rating Scale, the Total Function Capacity, and the scale for outcomes in Parkinson's disease-autonomic (SCOPA-AUT) questionnaire. All patients and 10 Ctrl (5 F and 5 M) underwent 123I-MIBG imaging. From planar images, the early and late heart-to-mediastinum (H/M) ratios and myocardial washout rates (WR) were calculated.

RESULTS

We did not find significant differences in early and late H/M ratios and WR between the two groups. At individual level, three patients showed reduced early and/or late H/M ratios. The most common autonomic complaints were gastrointestinal and genitourinary disorders. SCOPA-AUT questionnaire score results positively correlated with the disease duration and WR.

CONCLUSIONS

Our study indicates that myocardial postganglionic sympathetic innervation is essentially preserved or only minimally involved in HD. These findings suggest that the cardiovascular dysfunction might be mainly due to the impairment of brain areas associated with the regulation and modulation of the heart function.

Autonomic changes in Huntington's disease correlate with altered central autonomic network connectivity

Autonomic dysfunction has been described in patients with Huntington's disease, but it is unclear if these changes in autonomic tone are related to the central autonomic network. We performed a pilot study to investigate the relationship between the integrity of the central autonomic network and peripheral manifestiations of autonomic dysfunction in premanifest Huntington's disease. We recruited male participants with pre-motor-manifest Huntington's disease and a comparison group consisting of healthy, male participants of approximately the same age. As this was a pilot study, only males were included to reduce confounding. Participants underwent a resting-state functional magnetic resonance imaging study to quantify functional connectivity within the central autonomic network, as well as a resting 3-lead ECG to measure heart rate variability with a particular focus on the parasympathetic time-domain measures of root mean square of successive differences between normal heartbeats. The pre-motor-manifest Huntington's disease participants had significantly decreased root mean square of successive differences between normal heartbeats values compared with the healthy comparison group. The pre-motor-manifest Huntington's disease group had significantly lower functional connectivity within the central autonomic network, which was positively correlated with root mean square of successive differences between normal heartbeats. Patients with pre-motor-manifest Huntington's disease have reduced functional connectivity within the central autonomic network, which is significantly associated with observed changes in autonomic function.

Progressive cardiac arrhythmias and ECG abnormalities in the Huntington's disease BACHD mouse model

Huntington's disease (HD) is a dominantly inherited neurodegenerative disease. There is accumulating evidence that HD patients have increased prevalence of conduction abnormalities and compromised sinoatrial node function which could lead to increased risk for arrhythmia. We used mutant Huntingtin (mHTT) expressing bacterial artificial chromosome Huntington's disease mice to determine if they exhibit electrocardiogram (ECG) abnormalities involving cardiac conduction that are known to increase risk of sudden arrhythmic death in humans. We obtained surface ECGs and analyzed arrhythmia susceptibility; we observed prolonged QRS duration, increases in PVCs as well as PACs. Abnormal histological and structural changes that could lead to cardiac conduction system dysfunction were seen. Finally, we observed decreases in desmosomal proteins, plakophilin-2 and desmoglein-2, which have been reported to cause cardiac arrhythmias and reduced conduction. Our study indicates that mHTT could cause progressive cardiac conduction system pathology that could increase the susceptibility to arrhythmias and sudden cardiac death in HD patients.

Autonomic dysregulation as an early pathologic feature of Huntington Disease

OBJECTIVE

Autonomic nervous system (ANS) dysfunction has been described in adults with motor-manifest Huntington's Disease (HD) or those who are near their predicted motor onset. It is unclear if ANS dysfunction is present years prior to the onset of motor symptoms of HD. To bridge this gap in knowledge, we compared crude markers of ANS function between children with the gene-expansion that causes HD (GE group) who were decades from their predicted motor onset and gene-non-expanded children (GNE group).

METHODS

We included participants from the Kids-HD study who were <18 years old. Linear mixed effects regression models were constructed that controlled for sex, age, and BMI, and included a random effect per participant and per family. We compared resting heart rate (rHR), core body temperature (CBT), systolic blood pressure (SBP), and diastolic blood pressure (DBP) between the GE (n = 84) and GNE (n = 238) groups. We then grouped participants from the GE group based on their predicted years to onset (YTO) and compared their vital signs to the GNE group.

RESULTS

The GE group had higher rHR (∆ = 3.83, p = 0.0064), SBP (∆ = 2.38, p = 0.032), and CBT (∆ = 0.16, t = 2.92, p = 0.007). The mean rHR and CBT became significantly elevated compared to the GNE group in participants who had 15-25 YTO and those who had <15 YTO. The mean SBP of participants who had 25-35 YTO was significantly elevated compared to the GNE group.

CONCLUSION

ANS dysfunction in HD seems to occur approximately 20 years prior to the predicted onset of motor symptoms of HD.

Role of defective calcium regulation in cardiorespiratory dysfunction in Huntington's disease

Huntington’s disease (HD) is a progressive, autosomal dominant neurodegenerative disorder affecting striatal neurons beginning in young adults with loss of muscle coordination and cognitive decline. Less appreciated is the fact that patients with HD also exhibit cardiac and respiratory dysfunction, including pulmonary insufficiency and cardiac arrhythmias. The underlying mechanism for these symptoms is poorly understood. In the present study we provide insight into the cause of cardiorespiratory dysfunction in HD and identify a potentially novel therapeutic target. We now show that intracellular calcium (Ca²⁺) leak via posttranslationally modified ryanodine receptor/intracellular calcium release (RyR) channels plays an important role in HD pathology. RyR channels were oxidized, PKA phosphorylated, and leaky in brain, heart, and diaphragm both in patients with HD and in a murine model of HD (Q175). HD mice (Q175) with endoplasmic reticulum Ca²⁺ leak exhibited cognitive dysfunction, decreased parasympathetic tone associated with cardiac arrhythmias, and reduced diaphragmatic contractile function resulting in impaired respiratory function. Defects in cognitive, motor, and respiratory functions were ameliorated by treatment with a novel Rycal small-molecule drug (S107) that fixes leaky RyR. Thus, leaky RyRs likely play a role in neuronal, cardiac, and diaphragmatic pathophysiology in HD, and RyRs are a potential novel therapeutic target.

This study explores the role of ryanodine receptor calcium channels in the brain, the heart, and the diaphragm and central versus peripheral pathophysiological mechanisms in Huntington’s disease.

Autonomic Changes in Juvenile-Onset Huntington's Disease

Patients with adult-onset Huntington’s Disease (AOHD) have been found to have dysfunction of the autonomic nervous system that is thought to be secondary to neurodegeneration causing dysfunction of the brain–heart axis. However, this relationship has not been investigated in patients with juvenile-onset HD (JOHD). The aim of this study was to compare simple physiologic measures between patients with JOHD (n = 27 participants with 64 visits) and participants without the gene expansion that causes HD (GNE group; n = 259 participants with 395 visits). Using data from the Kids-JOHD study, we compared mean resting heart rate (rHR), systolic blood pressure (SBP), and diastolic blood pressure (DBP) between the JOHD and GNE groups. We also divided the JOHD group into those with childhood-onset JOHD (motor diagnosis received before the age of 13, [n = 16]) and those with adolescent-onset JOHD (motor diagnosis received at or after the age of 13 [n = 11]). We used linear mixed-effects models to compare the group means while controlling for age, sex, and parental socioeconomic status and including a random effect per participant and family. For the primary analysis, we found that the JOHD group had significant increases in their rHR compared to the GNE group. Conversely, the JOHD group had significantly lower SBP compared to the GNE group. The JOHD group also had lower DBP compared to the GNE group, but the results did not reach significance. SBP and DBP decreased as disease duration of JOHD increased, but rHR did not continue to increase. Resting heart rate is more sensitive to changes in autonomic function as compared to SBP. Therefore, these results seem to indicate that early neurodegenerative changes of the central autonomic network likely lead to an increase in rHR while later progression of JOHD leads to changes in blood pressure. We hypothesize that these later changes in blood pressure are secondary to neurodegeneration in brainstem regions such as the medulla.

Circadian dysfunction in the Q175 model of Huntington's disease: Network analysis

Disturbances in sleep/wake cycle are a common complaint of individuals with Huntington's disease (HD) and are displayed by HD mouse models. The underlying mechanisms, including the possible role of the circadian timing system, have been the topic of a number of recent studies. The (z)Q175 mouse is a knock-in model in which the human exon 1 sequence of the huntingtin gene is inserted into the mouse DNA with approximately 190 CAG repeats. Among the numerous models available, the heterozygous Q175 offers strong construct validity with a single copy of the mutation, genetic precision of the insertion and control of mutation copy number. In this review, we will summarize the evidence that this model exhibits disrupted diurnal and circadian rhythms in locomotor activity. We found overwhelming evidence for autonomic dysfunction including blunted daily rhythms in heart rate and core body temperature (CBT), reduced heart rate variability, and almost a complete failure of the sympathetic arm of the autonomic nervous system to function during the baroreceptor reflex. Mechanistically, the Q175 mouse model exhibits deficits in the neural output of the central circadian clock, the suprachiasmatic nucleus along with an enhancement of at least one type of potassium current in these neurons. Finally, we report a novel network analysis examining the phase coherence between activity, CBT, and cardiovascular measures. Such analyses found that even young Q175 mutants (heterozygous or homozygous) show coherence degradation, and suggests that loss of phase coherence is a variable that should be considered as a possible biomarker for HD.

Aortic valve approaches in the era of minimally invasive cardiac surgery

The concept of minimally invasive cardiac surgery has been gradually adopted world-wide since its inception more than 2 decades ago. Recently, catheter intervention has been used in the treatment of structural heart disease. Most notably, minimally invasive transcatheter aortic valve implantation is now an established treatment option for aortic valve stenosis. There are three major approaches for minimally invasive aortic valve surgery: via median sternotomy, via the parasternal approach, and via the thoracotomy approach. All these approaches allow for a small skin incision and/or avoid full sternotomy. Moreover, several advanced variations with additional aortic procedures or totally endoscopic management have been developed. When considering each approach, low invasiveness must be balanced with safety, as surgeons broaden their insight of advanced medicine. Physical invasiveness is largely related to the surgical approach in minimally invasive surgery. We review the history and evolution of the different surgical approaches for minimally invasive aortic valve replacement.

Neurocardiovascular deficits in the Q175 mouse model of Huntington's disease

Cardiovascular dysautonomia as well as the deterioration of circadian rhythms are among the earliest detectable pathophysiological changes in individuals with Huntington's disease (HD). Preclinical research requires mouse models that recapitulate disease symptoms and the Q175 knock-in model offers a number of advantages but potential autonomic dysfunction has not been explored. In this study, we sought to test the dual hypotheses that cardiovascular dysautonomia can be detected early in disease progression in the Q175 model and that this dysfunction varies with the daily cycle. Using radiotelemetry implants, we observed a significant reduction in the diurnal and circadian activity rhythms in the Q175 mutants at the youngest ages. By middle age, the autonomically driven rhythms in core body temperature were highly compromised, and the Q175 mutants exhibited striking episodes of hypothermia that increased in frequency with mutant huntingtin gene dosage. In addition, Q175 mutants showed higher resting heart rate (HR) during sleep and greatly reduced correlation between activity and HR HR variability was reduced in the mutants in both time and frequency domains, providing more evidence of autonomic dysfunction. Measurement of the baroreceptor reflex revealed that the Q175 mutant could not appropriately increase HR in response to a pharmacologically induced decrease in blood pressure. Echocardiograms showed reduced ventricular mass and ejection fraction in mutant hearts. Finally, cardiac histopathology revealed localized points of fibrosis resembling those caused by myocardial infarction. Thus, the Q175 mouse model of HD exhibits cardiovascular dysautonomia similar to that seen in HD patients with prominent sympathetic dysfunction during the resting phase of the activity rhythm.

Neurocardiac dysregulation and neurogenic arrhythmias in a transgenic mouse model of Huntington's disease

Huntington's disease (HD) is a heritable neurodegenerative disorder, with heart disease implicated as one major cause of death. While the responsible mechanism remains unknown, autonomic nervous system (ANS) dysfunction may play a role. We studied the cardiac phenotype in R6/1 transgenic mice at early (3 months old) and advanced (7 months old) stages of HD. While exhibiting a modest reduction in cardiomyocyte diameter, R6/1 mice had preserved baseline cardiac function. Conscious ECG telemetry revealed the absence of 24-h variation of heart rate (HR), and higher HR levels than wild-type littermates in young but not older R6/1 mice. Older R6/1 mice had increased plasma level of noradrenaline (NA), which was associated with reduced cardiac NA content. R6/1 mice also had unstable R-R intervals that were reversed following atropine treatment, suggesting parasympathetic nervous activation, and developed brady- and tachyarrhythmias, including paroxysmal atrial fibrillation and sudden death. c-Fos immunohistochemistry revealed greater numbers of active neurons in ANS-regulatory regions of R6/1 brains. Collectively, R6/1 mice exhibit profound ANS-cardiac dysfunction involving both sympathetic and parasympathetic limbs, that may be related to altered central autonomic pathways and lead to cardiac arrhythmias and sudden death.

Paraventricular nucleus neuropeptide expression in Huntington's disease patients

Neuroendocrine, metabolic and autonomic nervous system dysfunctions are prevalent among patients with Huntington's disease (HD) and may underlie symptoms such as depression, weight loss and autonomic failure. Using post-mortem paraffin-embedded tissue, we assessed the integrity of the major neuropeptide populations in the paraventricular nucleus (PVN)-the hypothalamic neuroendocrine and autonomic integration center-in HD patients. The number corticotropin-releasing hormone, cocaine- and amphetamine-regulated transcript, arginine vasopressin and oxytocin immunoreactive (ir) neurons did not differ between HD patients and control subjects. However, the significant positive correlation between arginine vasopressin and oxytocin ir neurons in control subjects (P = 0.036) was absent in patients. Corticotropin-releasing hormone mRNA levels were 68% higher in HD patients (P = 0.046). Thyrotropin-releasing hormone mRNA levels did not differ between HD patients and control subjects, although a negative correlation with disease duration was present in the former (P = 0.036). These findings indicate that the PVN is largely unaffected in HD patients. However, our findings suggest that hypothalamic-pituitary-thyroid axis activity may alter during the course of the disease and that autonomic nervous system dysfunction might partly arise from an imbalance between arginine vasopressin and oxytocin neurons in the PVN.

Baroreceptor reflex dysfunction in the BACHD mouse model of Huntington's disease

Huntington’s disease is a progressive, neurodegenerative disorder that presents with a triad of clinical symptoms, which include movement abnormalities, emotional disturbance and cognitive impairment. Recent studies reported dysfunction of the autonomic nervous system in Huntington’s disease patients, which may contribute to the increased incidence of cardiovascular events in this patient population that often leads to death. We measured the baroreceptor reflex, a process dependent on proper autonomic function, in the BACHD mouse model of Huntington’s disease. We found a blunted response of the baroreceptor reflex as well as significantly higher daytime blood pressure in BACHD mice compared to WT controls, which are both indications of autonomic dysfunction. BACHD mice had increased heart weight to tibia length ratios at 7 and 12 mo of age suggesting hypertrophic changes of the heart, which we speculate is a response to the increased blood pressure and aberrant baroreceptor reflex. Despite these structural changes, the hearts of BACHD mice continue to function normally as assessed by echocardiographic analysis. Studies of autonomic and cardiovascular function in BACHD mice may help elucidate the pathophysiology of Huntington’s disease and aid in the development of clinical strategies to offset the incidence of fatal cardiovascular events in the Huntington’s disease patient population.

Microcirculation response to local cooling in patients with Huntington's disease

Altered autonomic nervous system (ANS) functioning in early stages of Huntington's disease (HD) has been suggested, presumably due to distorted high-order autonomic control. ANS functioning in the early stages of HD was further investigated. Laser-Doppler (LD) flux in the skin of the fingertips, heart rate (HR), HR variability, systolic and diastolic blood pressure were measured during rest and during a 6 min cooling of one hand at 15°C. Data of 15 presymptomatic gene mutation carriers (PHD), 15 early symptomatic HD patients (EHD), and two groups of 15 age- and sex-matched controls were compared. The area under the low frequency (LF) and high frequency (HF) bands of the HR variability spectrum were calculated. An augmented reduction of cutaneous LD flux was found in response to the direct cooling in the PHD group (37.5 ± 8.5% of resting value) compared to the PHD controls (67.27 ± 8.4%) (p < 0.05). In addition, the PHD group had higher (LF/(LF + HF) index of primary sympathetic modulation of the HR at rest (53.6 ± 3.3) compared to the EHD patients (39.7 ± 4.2) (p < 0.05). In the EHD group, a significantly smaller change of HR during cooling (100.26 ± 1.2%) was found compared to the EHD controls (95.9 ± 1.0%) (p < 0.05). The results are in line with the hypothesis that ANS dysfunction occurs even in PHD subjects. Further, they support the hypothesis that dysfunction of the high-order autonomic centres are involved in HD.

Autonomic dysfunction in presymptomatic and early symptomatic Huntington's disease

OBJECTIVES

Although autonomic dysfunction was found in advanced Huntington's disease (HD) patients it is not clear whether there is autonomic dysfunction in presymptomatic and early symptomatic HD.

MATERIAL & METHODS

Different cardiovascular autonomic tests were performed in 14 presymptomatic HD mutation carriers (PHD), 11 early symptomatic HD patients (EHD) and in 25 sex and age matched controls.

RESULTS

We found attenuated response to simple mental arithmetic test (relative heart rate in PHD and EHD was 10% lower than in controls; diastolic pressure was 10.6% lower in EHD than in controls; P < 0.05) and exaggerated response to the late phase of cold pressor test (relative heart rate was 10% higher in PHD and 7% higher in EHD than in controls; P < 0.05). The rest of the cardiovascular autonomic tests did not reveal significant differences between patients and controls.

CONCLUSIONS

Our results suggest that subtle autonomic dysfunction occurs even in PHD and EHD.

Autonomic symptoms in patients and pre-manifest mutation carriers of Huntington's disease

BACKGROUND AND PURPOSE

Although autonomic function tests have revealed abnormalities of the autonomic nervous system in Huntington's disease (HD), autonomic symptoms and their association with other symptoms and signs of HD have not yet been assessed in large groups of patients or pre-manifest mutation carriers. Therefore, we aimed at delineating the characteristics and correlates of autonomic symptoms in HD.

METHODS

Using the scales for outcomes in Parkinson's disease-autonomic symptoms (SCOPA-AUT) and Beck Depression Inventory questionnaires, autonomic symptoms and depressed mood were assessed in 63 patients with HD, 21 pre-manifest mutation carriers, and 85 controls. The Unified Huntington's Disease Rating Scale was used to assess other HD symptoms and signs.

RESULTS

Relative to controls, patients with HD experienced significantly more gastrointestinal, urinary, cardiovascular and, in men, sexual problems. The most prevalent symptoms were swallowing difficulties, erection and ejaculation problems, dysphagia, sialorrhea, early abdominal fullness, straining for defecation, fecal and urinary incontinence, urgency, incomplete bladder emptying, and light-headedness whilst standing. Pre-manifest mutation carriers experienced significantly more swallowing difficulties and light-headedness on standing up compared with controls. In patients with HD, autonomic symptoms were associated with a greater degree of functional disability, more severe depression, and antidepressant drugs use. However, depression was the only independent predictor of autonomic dysfunction.

CONCLUSIONS

Autonomic symptoms are highly prevalent in patients with HD and may even precede the onset of motor signs. Moreover, autonomic dysfunction is related to functional disability and depression in HD.

The current clinical management of Huntington's disease

Huntington's disease is a neurodegenerative condition, characterized by movement disorders, cognitive decline, and psychiatric disturbance. We review the pharmacological management of the various movement disorders associated with the disease, the cognitive decline and the commonly encountered behavioral disturbances. We discuss the nonclassical features of the disease, important in the management of these patients. Nonpharmacological support including genetic counseling and therapy and the importance of palliative care are also addressed. Finally, experimental approaches that may soon impact upon clinical practice are discussed.

Cardiovagal modulation upon postural change is altered in Huntington's disease

BACKGROUND

Cardiac autonomic nervous system (ANS) dysfunction in Huntington's disease (HD) might affect both the sympathetic and parasympathetic branch of the ANS.

RESULTS AND CONCLUSIONS

The pattern of linear heart rate variability we found in mid stage HD patients points towards a predominately reduced cardiovagal modulation compared with healthy subjects, which might influence HD patients' susceptibility for cardiovascular complications such as syncopes and cardiac arrhythmias.

Hypothalamic dysfunction and neuroendocrine and metabolic alterations in Huntington's disease: clinical consequences and therapeutic implications

Huntington's disease (HD) is a hereditary neurodegenerative disorder characterized by cognitive, psychiatric, behavioural and motor disturbances. Although the course of HD is also frequently complicated by unintended weight loss, sleep disturbances and autonomic nervous system dysfunction, the aetiology of these signs and symptoms remains largely unknown. In recent years, many novel findings from both animal and human studies have emerged that indicate considerable hypothalamic, endocrine and metabolic alterations in HD. However, a comprehensive overview of these findings is lacking and their precise clinical significance is far from clear. Therefore, in this review we attempt to put these recent developments in the field into perspective by integrating them with previous findings in a comprehensible manner, and by discussing their clinical relevance, with a special focus on body weight, sleep and autonomic functions in HD, which will also allow for the identification of future lines of research in this area.

Early sympathetic hyperactivity in Huntington's disease

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.

Tropicamide effects on pupil size and pupillary light reflexes in Alzheimer's and Parkinson's disease

Diagnostic tests for Alzheimer's disease (AD) involving tropicamide blockade of cholinergic oculomotor functions were examined in AD patients (n=15), Parkinson's disease (PD) patients (n=15), and non-clinical control (NC) participants (n=15). Pupillographic methods were used to measure pupil diameter and pupillary light reflexes after double-blind ocular administration of dilute tropicamide (0.01%) in one eye and saline in the other eye. Changes in pupil size were measured in bright background light and near-darkness. Tropicamide increased pupil diameter to a similar extent in all three groups in light and darkness. Tropicamide also reduced the amplitude and latency of the pupillary light reflex to a similar extent for all three groups. Tropicamide pupillary response tests, therefore, were not sensitive or specific diagnostic tests for AD. Peak constriction amplitude of the pupillary light reflex was significantly reduced in both eyes in AD and PD groups relative to non-clinical controls, but AD and PD groups did not differ significantly. The pupillary light reflex test, therefore, was sensitive to AD, but lacked adequate specificity. Finally, peak constriction amplitude correlated significantly with dementia severity and donepezil treatment may have partially normalized pupillary light reflex abnormalities in AD patients. The pupillary light reflex test, therefore, may index central cholinergic dysfunction associated with disease progression and improvement in cholinergic function associated with pharmacologic treatment response in AD.

Autonomic nervous system function in Huntington's disease

OBJECTIVE

To investigate whether Huntington's disease (HD) affects autonomic nervous system (ANS) functioning.

METHODS

Twenty patients with HD who had positive genetic test results underwent standardised ANS function tests including sympathetic skin responses (SSRs) of the hands and feet, measurements of heart rate variability (HRV), both during five minutes of resting and deep respiration, and an orthostatic blood pressure test. Patients were classified according to the motor subscale of the unified Huntington's disease rating scale (UHDRS; mean (SD) score 26.4 (13.6)) and divided into two subgroups: UHDRS <25 points (early stages, E-HD) and UHDRS > or =25 points (mid stages, M-HD). Autonomic indices were compared with those obtained for a group of well matched healthy controls (n=60).

RESULTS

Overall, patients showed lower HRV indices than controls. Multivariate analysis with the independent factor of "group" (controls, E-HD, M-HD) showed a significant group effect on both the high frequency power (F=4.32, p=0.017) and the coefficient of variation (F=4.23, p=0.018), indicating a significant reduction in vagal modulation in the M-HD group. There was a shift in autonomic neurocardiac balance towards sympathetic predominance in the M-HD group compared with controls (F=2.89, p=0.062). Moreover, we found an inverse correlation between the severity of clinical HD symptoms (assessed by the UHDRS) and the modulation of cardiovagal activity (p=0.028). Vagal dysregulation was present in two patients; one of them also showed a pathological blood pressure test and a latency prolongation in the SSRs of the hands. Two other patients had pathologically reduced SSR amplitudes. Only patients of the M-HD group were affected.

CONCLUSION

Autonomic dysfunction is present even in the middle stages of HD and affects both the sympathetic and parasympathetic branch of the ANS.

Anaesthesia and juvenile Huntington's disease

Juvenile Huntington's Disease (JHD) is an involuntary movement disorder that comprises both neurological and psychiatric symptoms. Whilst it has many similarities to Huntington's Disease, it is regarded as a separate clinical entity. The anaesthetic plan should be based on careful assessment of the important issues, including the risk of regurgitation and pulmonary aspiration, possible associated autonomic neuropathy, poor respiratory function and the avoidance of precipitating convulsions and clonic spasms. We describe the management of a 12-year-old girl with JHD scheduled for gastroscopy under general anaesthesia necessitating the use of suxamethonium. We suggest an alternative mechanism for the delayed recovery seen in our patient and in other adult case reports.

Huntington's disease

Huntington's disease is a genetically inherited degenerative neuropsychiatric disorder, characterized by motor alterations, including involuntary movements such as chorea, dementia and psychiatric disturbances. In this article, the authors review the clinical features of the disease. They also analyze some genetic and pathophysiologic aspects, that can help to improve our understanding of this disorder involving the basal ganglia.

Autonomic dysfunction in Alzheimer's disease

Twenty-nine patients fitting the NINCDS-ADRDA criteria of Alzheimer's disease participated in a study of autonomic functions. A number of tests on parasympathetic and sympathetic functions were made. Eighteen of the patients were tested a second time one year later. Fifteen healthy subjects with no family history of dementia disorders served as controls. Compared to the controls, the patients showed signs suggesting autonomic dysfunction affecting parasympathetic, as well as vasomotor sympathetic, functions.

Cardiovascular autonomic reflexes in brain infarction

BACKGROUND AND PURPOSE

Increased sympathetic activity is associated with cardiovascular complications in stroke, but the role of the parasympathetic nervous system has not been carefully outlined. In the present study our purpose was to assess quantitatively autonomic cardiovascular disturbances in brain infarction by measuring cardiovascular autonomic reflexes.

METHODS

We studied the autonomic regulation of cardiovascular functions prospectively in 40 patients with brain infarction (acute phase, 1 month, and 6 months) and in 55 healthy control subjects by recording heart rate and blood pressure responses to normal and deep breathing, the Valsalva maneuver, tilting, and isometric work.

RESULTS

In the acute phase, heart rate responses to normal breathing, deep breathing, the Valsalva maneuver, and tilting were significantly (P < .05) impaired in both hemispheric and brain stem infarctions, thus indicating hypofunction of the parasympathetic nervous system. At 1 month heart rate responses to normal breathing (brain stem, P < .05), the Valsalva maneuver (brain stem, P < .01), and tilting (hemispheric, P < .05) were still significantly lower than those of the control subjects, but at 6 months significant suppression of the response was found only in tilting (hemispheric, P < .05).

CONCLUSIONS

These findings suggest that in addition to the previously well-established sympathetic hyperfunction, brain infarction also seems to cause parasympathetic hypofunction, brain which may be involved in cardiovascular and other known manifestations of autonomic failure associated with stroke.

Autonomic nervous system dysfunction in Parkinson's disease: relationships with age, medication, duration, and severity

Heart rate variability at rest, during deep breathing, or standing up and with the Valsalva manoeuvre did not differ significantly between 67 patients with idiopathic Parkinson's disease (PD) and 31 healthy age matched controls. Blood pressure (BP) responses to standing up and sustained handgrip revealed diminished autonomic function in the PD group. In a preliminary analysis of the PD group older age, anti-Parkinson medication and higher Hoehn and Yahr (HY) stages were each associated with poor autonomic responsiveness. Disease duration was only related to the systolic BP fall on standing up. Multiple stepwise regression analysis showed that older age explained most of the variance of heart rate variability (up to 36%), and the only significant PD related factor was the use of medication, which explained less than 7%. The HY stage accounted for 12.7% of the variance in the standing up BP test, and the use of medication explained 10.6% of the variance of the systolic BP change in the sustained hand grip test. The unmedicated PD subgroup (n = 33), who had mild disease of short duration, showed no evidence of autonomic dysfunction. Cardiovascular autonomic dysfunction in PD is mild, mainly affects blood pressure responses, and occurs only in advanced cases.

Cardiovascular reflexes in Parkinson disease

We have investigated the autonomic function of 95 patients with Parkinson disease (PD) by testing their cardiovascular reflexes and compared the results with those of 53 healthy volunteers. 51.1% of the patients were on antiparkinsonian therapy. The patients showed a smaller heart rate response to deep breathing with a mean exhalation-inspiration difference of 87.73 +/- 7 (p: 0.0005), a smaller heart rate response to standing with a mean 30: 15 index of 1.18 +/- 0.25 (p: 0.01), and a smaller blood pressure rise to handgrip with a mean rise of 9.53 +/- 8.76 mmHg (p: 0.005). We found a higher percentage of patients with established sympathetic lesion (41% vs 34%) or atypical patterns of global autonomic function involvement (33% vs 26%), but the percentage of subjects with parasympathetic lesion was similar in both, patients and controls (16% vs 15%). We found no significant difference on cardiovascular performance between treated and untreated patients. The patients with autonomic impairment were older than the patients with normal autonomic function. Our findings suggest that patients with PD have a true autonomic dysfunction.

Non-invasive assessment of autonomic nervous function in Gilles de la Tourette syndrome

Autonomic nervous function was investigated in 18 Gilles de la Tourette (GTS) patients and in 23 controls, who matched the patients in age, sex, baseline blood pressure and baseline heart rate. Four heart rate tests were used (variation at rest, during deep breathing, following standing up and during a Valsalva manoeuvre), and two blood pressure tests (standing up and sustained handgrip). The only significant difference between the groups was found in the Valsalva test. This was due to the initial heart rate increase which was higher in the GTS group; the subsequent decrease did not differ between the groups. Increased sympathetic activity is a possible explanation for this finding, but no additional evidence in its favour was found. No signs of autonomic failure were found.

Autonomic nervous system tests depend on resting heart rate and blood pressure

In order to study the effects of baseline blood pressure and heart frequency on autonomic function tests, 75 normal subjects (aged 8-96 years) were investigated. Heart rate variability was studied at rest, during deep breathing, following standing up and during a Valsalva manoeuvre. Blood pressure changes were recorded during standing up and during sustained handgrip. Responses were described as ratios and as differences to study the efficacy of both methods. Multiple regression analysis showed that significant relationships with the resting heart rate existed for ratios but not for differences. The blood pressure rise in the sustained handgrip test showed a significant relationship with resting blood pressure regardless of the description method. As expected, relationships with age existed for all four heart rate tests regardless of the description method. The blood pressure responses were not significantly related to age. We advise that heart rate test results should be presented as differences, as this avoids the need for correction for the resting heart rate. Correction for the resting blood pressure improves the accuracy of the standing up blood pressure test. Correction for age remains necessary for heart rate tests but not for blood pressure tests.