Autonomic Dysfunction in Parkinson’s Disease

Gastrointestinal Dysfunction in Parkinson’s Disease: Current and Potential Therapeutics

Abnormalities in the gastrointestinal (GI) tract of Parkinson’s disease (PD) sufferers were first reported over 200 years ago; however, the extent and role of GI dysfunction in PD disease progression is still unknown. GI dysfunctions, including dysphagia, gastroparesis, and constipation, are amongst the most prevalent non-motor symptoms in PD. These symptoms not only impact patient quality of life, but also complicate disease management. Conventional treatment pathways for GI dysfunctions (i.e., constipation), such as increasing fibre and fluid intake, and the use of over-the-counter laxatives, are generally ineffective in PD patients, and approved compounds such as guanylate cyclase C agonists and selective 5-hyroxytryptamine 4 receptor agonists have demonstrated limited efficacy. Thus, identification of potential targets for novel therapies to alleviate PD-induced GI dysfunctions are essential to improve clinical outcomes and quality of life in people with PD. Unlike the central nervous system (CNS), where PD pathology and the mechanisms involved in CNS damage are relatively well characterised, the effect of PD at the cellular and tissue level in the enteric nervous system (ENS) remains unclear, making it difficult to alleviate or reverse GI symptoms. However, the resurgence of interest in understanding how the GI tract is involved in various disease states, such as PD, has resulted in the identification of novel therapeutic avenues. This review focuses on common PD-related GI symptoms, and summarizes the current treatments available and their limitations. We propose that by targeting the intestinal barrier, ENS, and/or the gut microbiome, may prove successful in alleviating PD-related GI symptoms, and discuss emerging therapies and potential drugs that could be repurposed to target these areas.

Parkinson's Disease: Personalized Pathway of Care for Device-Aided Therapies (DAT) and the Role of Continuous Objective Monitoring (COM) Using Wearable Sensors

Parkinson’s disease (PD) is a chronic, progressive neurological disorder and the second most common neurodegenerative condition. Advanced PD is complicated by erratic gastric absorption, delayed gastric emptying in turn causing medication overload, and hence the emergence of motor and non-motor fluctuations and dyskinesia, which is initially predictable and then becomes unpredictable. As the patient progresses to the advanced stage, advanced Parkinson’s disease (APD) is characterized by refractory motor and non motor fluctuations, unpredictable OFF periods, and troublesome dyskinesias. The management of APD is a complex affair. There is growing recognition that GI dysfunction is common in PD, with virtually the entire GI system (the upper and lower GI tracts) causing problems from dribbling to defecation. The management of PD should focus on personalized care addressing both motor and non-motor symptoms, ideally including not only dopamine replacement but also associated non-dopaminergic circuits, particularly focusing on noradrenergic, serotonergic, and cholinergic therapies bypassing the gastrointestinal tract (GIT) by infusion or device-aided therapies (DAT), including levodopa–carbidopa intestinal gel infusion, apomorphine subcutaneous infusion, and deep brain stimulation, which are available in many countries for the management of the advanced stage of Parkinson’s disease (APD). The PKG (KinetiGrap) can be used as a continuous objective monitoring (COM) aid, as a screening tool to help to identify advanced PD (APD) patients suitable for DAT, and can thus improve clinical outcomes.

T-Cell-Driven Inflammation as a Mediator of the Gut-Brain Axis Involved in Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative disorder affecting mainly the dopaminergic neurons of the nigrostriatal pathway, a neuronal circuit involved in the control of movements, thereby the main manifestations correspond to motor impairments. The major molecular hallmark of this disease corresponds to the presence of pathological protein inclusions called Lewy bodies in the midbrain of patients, which have been extensively associated with neurotoxic effects. Importantly, different research groups have demonstrated that CD4⁺ T-cells infiltrate into the substantia nigra of PD patients and animal models. Moreover, several studies have consistently demonstrated that T-cell deficiency results in a strong attenuation of dopaminergic neurodegeneration in animal models of PD, thus indicating a key role of adaptive immunity in the neurodegenerative process. Recent evidence has shown that CD4⁺ T-cell response involved in PD patients is directed to oxidised forms of α-synuclein, one of the main constituents of Lewy bodies. On the other hand, most PD patients present a number of non-motor manifestations. Among non-motor manifestations, gastrointestinal dysfunctions result especially important as potential early biomarkers of PD, since they are ubiquitously found among confirmed patients and occur much earlier than motor symptoms. These gastrointestinal dysfunctions include constipation and inflammation of the gut mucosa and the most distinctive pathologic features associated are the loss of neurons of the enteric nervous system and the generation of Lewy bodies in the gut. Moreover, emerging evidence has recently shown a pivotal role of gut microbiota in triggering the development of PD in genetically predisposed individuals. Of note, PD has been positively correlated with inflammatory bowel diseases, a group of disorders involving a T-cell driven inflammation of gut mucosa, which is strongly dependent in the composition of gut microbiota. Here we raised the hypothesis that T-cell driven inflammation, which mediates dopaminergic neurodegeneration in PD, is triggered in the gut mucosa. Accordingly, we discuss how structural components of commensal bacteria or how different mediators produced by gut-microbiota, including short-chain fatty acids and dopamine, may affect the behaviour of T-cells, triggering the development of T-cell responses against Lewy bodies, initially confined to the gut mucosa but later extended to the brain.

Parkinsonian GM2 synthase knockout mice lacking mature gangliosides develop urinary dysfunction and neurogenic bladder

Parkinson's disease is a neurodegenerative disorder that reduces a patients' quality of life by the relentless progression of motor and non-motor symptoms. Among the non-motor symptoms is a condition called neurogenic bladder that is associated with detrusor muscle underactivity or overactivity occurring from neurologic damage. In Parkinson's disease, Lewy-body-like protein aggregation inside neurons typically contributes to pathology. This is associated with dopaminergic neuron loss in substantia nigra pars compacta (SNc) and in ventral tegmental area (VTA), both of which play a role in micturition. GM1 gangliosides are mature glycosphingolipids that enhance normal myelination and are reduced in Parkinson's brain. To explore the role of mature gangliosides in vivo, we obtained GM2 Synthase knockout (KO) mice, which develop parkinsonian pathology including a loss of SNc dopaminergic neurons, which we reconfirmed. However, bladder function and innervation have never been assessed in this model. We compared GM2 Synthase KO and wild type (WT) littermates' urination patterns from 9 to 19 months of age by counting small and large void spots produced during 1 h tests. Because male and female mice had different patterns, we evaluated data by sex and genotype. Small void spots were significantly increased in 12-16 month GM2 Synthase KO females, consistent with overactive bladder. Similarly, at 9-12 month GM2 KO males tended to have more small void spots than WT males. As GM2 Synthase KO mice aged, both females and males had fewer small and large void spots, consistent with detrusor muscle underactivity. Ultrasounds confirmed bladder enlargement in GM2 Synthase KO mice compared to WT mice. Tyrosine hydroxylase (TH) immunohistochemistry revealed significant dopaminergic loss in GM2 Synthase KO VTA and SNc, and a trend toward TH loss in the GM2 KO periaqueductal gray (PAG) micturition centers. Levels of the nerve growth factor precursor, proNGF, were significantly increased in GM2 Synthase KO bladders and transmission electron micrographs showed atypical myelination of pelvic ganglion innervation in GM2 Synthase KO bladders. Cumulatively, our findings provide the first evidence that mature ganglioside loss affects micturition center TH neurons as well as proNGF dysregulation and abnormal innervation of the bladder. Thus, identifying therapies that will counteract these effects should be beneficial for those suffering from Parkinson's disease and related disorders.

Asiaticoside: Attenuation of rotenone induced oxidative burden in a rat model of hemiparkinsonism by maintaining the phosphoinositide-mediated synaptic integrity

Asiaticoside (AS), a triterpenoid saponin isolated from the Indian medicinal herb Centella asiatica is known to exert a neuroprotective effect by attenuating the neurobehavioral, neurochemical and pathological changes in animal models. However, its potential neuroprotection in rotenone-induced hemiparkinsonism which implicates phospholipid-mediated neurotransmission remains unclear. Therefore, we have investigated the neuroprotective effects of AS in rat model of ROT-infused hemiparkinsonism with respect to phosphoinositides-assisted cytodynamics and synaptic function. Adult male Sprague-Dawley rats (250-300g) were distributed randomly into 6 groups, with 6 rats in each group: Sham control, Vehicle control (DMSO-0.1%), ROT-infused group (6μg/μl/kg), AS-treated group (50mg/kg/day), Drug (AS) control and Levodopa (l-DOPA)-treated group (6mg/kg/day). At the end of the experimental period, the rats were sacrificed after performing behavioral analyses and the striatum regions were dissected out. Phosphoinositides (PI) are involved in intrinsic membrane signals that regulate intracellular membrane trafficking vesicle and endocytosis. We have assessed mRNA and protein expressions of genes involved in PI-mediated signaling and also in synaptic function (PI3K, PDK 1, PEBP, Stx 1A and TH) in addition to the levels of neurotransmitters and the enzymatic antioxidant profile. AS caused an improved working memory and motor co-ordination in the ROT group. It alters the levels of neurotransmitters (p<0.01), the expression of mRNA and protein assessed which were significantly affected (P<0.001) by rotenone, thus exhibiting its intervention in the progression of neurodegeneration. We demonstrate that AS can mediate distinct function in PI-assisted vesicle endocytosis, cytoprotective signaling and in the synaptic function thereby mitigating the ROT-infused hemiparkinsonism, however, its specific regulatory role remains to be unraveled.

Gastrointestinal Dysfunctions in Parkinson's Disease: Symptoms and Treatments

A diagnosis of Parkinson's disease is classically established after the manifestation of motor symptoms such as rigidity, bradykinesia, and tremor. However, a growing body of evidence supports the hypothesis that nonmotor symptoms, especially gastrointestinal dysfunctions, could be considered as early biomarkers since they are ubiquitously found among confirmed patients and occur much earlier than their motor manifestations. According to Braak's hypothesis, the disease is postulated to originate in the intestine and then spread to the brain via the vagus nerve, a phenomenon that would involve other neuronal types than the well-established dopaminergic population. It has therefore been proposed that peripheral nondopaminergic impairments might precede the alteration of dopaminergic neurons in the central nervous system and, ultimately, the emergence of motor symptoms. Considering the growing interest in the gut-brain axis in Parkinson's disease, this review aims at providing a comprehensive picture of the multiple gastrointestinal features of the disease, along with the therapeutic approaches used to reduce their burden. Moreover, we highlight the importance of gastrointestinal symptoms with respect to the patients' responses towards medical treatments and discuss the various possible adverse interactions that can potentially occur, which are still poorly understood.

The Effects of Parkinson's Disease on Caregivers and People with Parkinson's Disease: A Literature Review

Parkinson's disease (PD) is a complex, slowly progressive, neurodegenerative, neurological condition characterised by a wide range of motor problems such as movement disorders, issues with gait and balance, and difficulty with swallowing and speech. In addition, sufferers also experience non-motor symptoms such as disorder of sleep, postural hypotension, mood alterations, lethargy, and cognitive dysfunction. As PD progresses to an advanced stage, people experience periods of debilitating physical and neurological problems and their caregivers face increasing complexity of care. Many people with PD require the support of a caregiver to attend to activities of daily living. This paper will review the literature on the effects of Parkinson's disease on both the patient and caregiver. Findings highlight the progressive nature of the disease affecting both functional and affective domains, and the need for caregiver support to enable the delivery of quality of care to this group throughout the disease trajectory.

Autonomic involvement in Parkinson's disease: pathology, pathophysiology, clinical features and possible peripheral biomarkers

Autonomic nervous system involvement occurs at early stages in both Parkinson's disease (PD) and incidental Lewy body disease (ILBD), and affects the sympathetic, parasympathetic, and enteric nervous systems (ENS). It has been proposed that alpha-synuclein (α-SYN) pathology in PD has a distal to proximal progression along autonomic pathways. The ENS is affected before the dorsal motor nucleus of the vagus (DMV), and distal axons of cardiac sympathetic nerves degenerate before there is loss of paravertebral sympathetic ganglion neurons. Consistent with neuropathological findings, some autonomic manifestations such as constipation or impaired cardiac uptake of norepinephrine precursors, occur at early stages of the disease even before the onset of motor symptoms. Biopsy of peripheral tissues may constitute a promising approach to detect α-SYN neuropathology in autonomic nerves and a useful early biomarker of PD.

Potential of cystamine and cysteamine in the treatment of neurodegenerative diseases

Neurodegenerative disorders are a subset of disabling pathologies characterized, in part, by a progressive and specific loss of certain brain cell populations. Current therapeutic approaches for the treatment of these disorders are mainly designed towards symptom management and do not manifestly block their typified neuronal loss. However, research conducted over the past decade has reflected the increasing interest and need to find disease-modifying molecules. Among the several neuroprotective agents emerging from experimental animal work, cystamine, as well as its reduced form cysteamine, have been identified as potential candidate drugs. Given the significant benefits observed in a Huntington's disease (HD) model, cysteamine has recently leaped to clinical trial. Here, we review the beneficial properties of these compounds as reported in animal studies, their mechanistic underpinnings, and their potential implications for the future treatment of patients suffering from neurodegenerative diseases, and more specifically for HD and Parkinson's disease (PD).

Clinical review of treatment options for select nonmotor symptoms of Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is associated with a host of nonmotor symptoms, including psychosis, cognitive impairment, depression, sleep disturbance, swallowing disorders, gastrointestinal symptoms, and autonomic dysfunction. The nonmotor symptoms of PD have the potential to be more debilitating than the motor features of the disorder.

OBJECTIVE

The aim of this article was to review treatment options for the nonmotor manifestations of PD, including pharmacologic and nonpharmacologic interventions.

METHODS

The PubMed and MEDLINE databases were searched for articles published in English between January 1966 and April 2010, using the terms Parkinson's disease, nonmotor, psychosis, hallucination, antipsychotic, cognitive impairment, dementia, depression, sleep disturbance, sleepiness, REM (rapid eye movement) sleep behavior disorder, dysphagia, swallowing disorder, sialorrhea, gastrointestinal, constipation, autonomic dysfunction, orthostatic hypotension, gastroparesis, erectile dysfunction, sexual dysfunction, and urinary dysfunction. Articles were selected for review if they were randomized controlled trials (RCTs), meta-analyses, or evidence-based reviews of treatment of patients with PD, and/or expert opinion regarding the treatment of nonmotor symptoms of PD.

RESULTS

A total of 148 articles, including RCTs, meta-analyses, and evidence-based reviews, were included in this review. The treatment of hallucinations or psychosis in PD should include a stepwise reduction in medications for motor symptoms, followed by the use of quetiapine or clozapine. Dementia may be treated with acetylcholinesterase inhibitors. Evidence is lacking concerning the optimal pharmacologic treatment for depression in PD, with expert opinions indicating selective serotonin reuptake inhibitors as the antidepressants of choice. However, the largest study to date found nortriptyline therapy to be efficacious compared with placebo, whereas paroxetine controlled release was not. A variety of sleep disturbances may plague a person with PD, and treatment must be individualized to the patient's specific sleep disturbance pattern and contributing factors. Swallowing disorders may lead to aspiration and pneumonia, and patients with dysphagia should be referred to a speech therapist for further evaluation and treatment. Orthostasis may be treated with nonpharmacologic interventions as well as pharmacologic treatments (eg, fludrocortisone, midodrine, indomethacin). Other autonomic symptoms are managed in a manner similar to that in patients without PD, although careful attention must be aimed at avoiding dopamine-blocking therapies in the treatment of gastrointestinal dysfunction and gastroparesis.

CONCLUSIONS

Various pharmacologic and nonpharmacologic strategies are available for the management of the nonmotor symptoms of PD. The challenges associated with nonmotor symptoms must not be forgotten in light of the motor symptoms of PD, and treatment of nonmotor symptoms should be encouraged.

Future directions for immune modulation in neurodegenerative disorders: focus on Parkinson's disease

One common feature of neurodegenerative diseases is neuroinflammation. In the case of Parkinson's disease (PD), neuroinflammation appears early and persists throughout the disease course. The principal cellular mediator of brain inflammation is the resident microglia which share many features with related hematopoietically derived macrophages. Microglia can become activated by misfolded proteins including the PD relevant example, alpha-synuclein, a presynaptic protein. When activated, microglia release pro-inflammatory diffusible mediators that promote dysfunction and contribute to the death of the PD vulnerable dopaminergic neurons in the midbrain. Recently, the orphan nuclear receptor Nurr1, well known as a critical determinant in dopaminergic neuron maturation, has been ascribed two new properties. First, it promotes the production and release of the neuropeptide vasoactive intestinal peptide that functions both to stimulate dopaminergic neuron survival and inhibit neuroinflammation. Second, Nurr1 suppresses the expression and release of pro-inflammatory cytokines in glial cells. Herein, we discuss these new findings in context of strategies to attenuate neuroinflammation in PD.

Sleep dysfunction and role of dysautonomia in Parkinson's disease

Altered sleep is a common non motor symptom in Parkinson's disease. Sleep dysfunction has been reported to occur in 60-90% of all PD patients, having a detrimental impact on quality of life and increasing disability. alpha-Synuclein deposits in the lower brainstem affecting autonomic and sleep regions have been identified in the pathophysiology. The resultant non motor symptoms such as REM sleep behaviour disorder (RBD) can precede the motor symptoms by years. RBD is violent, enacted dreams that expose the patient or their sleeping partner to night-time injuries. Excessive daytime sleepiness, sometimes with a narcolepsy-like phenotype, is a common occurrence in PD, owing to lesions in the arousal systems of the brain. Restless legs syndrome and sleep disordered breathing can all affect daytime alertness of PD patients. Autonomic deregulation can also negatively affect sleep patterns, by adding to night-time wakening and disrupting sleep.

Gene therapy in Parkinson's disease: rationale and current status

Parkinson's disease is the second most common age-related neurodegenerative disorder, typified by the progressive loss of substantia nigra pars compacta dopamine neurons and the consequent decrease in the neurotransmitter dopamine. Patients exhibit a range of clinical symptoms, with the most common affecting motor function and including resting tremor, rigidity, akinesia, bradykinesia and postural instability. Current pharmacological interventions are palliative and largely aimed at increasing dopamine levels through increased production and/or inhibition of metabolism of this key neurotransmitter. The gold standard for treatment of both familial and sporadic Parkinson's disease is the peripheral administration of the dopamine precursor, levodopa. However, many patients gradually develop levodopa-induced dyskinesias and motor fluctuations. In addition, dopamine enhancement therapies are most useful when a portion of the nigrostriatal pathway is intact. Consequently, as the number of substantia nigra dopamine neurons and striatal projections decrease, these treatments become less efficacious. Current translational research is focused on the development of novel disease-modifying therapies, including those utilizing gene therapeutic approaches. Herein we present an overview of current gene therapy clinical trials for Parkinson's disease. Employing either recombinant adeno-associated virus type 2 (rAAV2) or lentivirus vectors, these clinical trials are focused on three overarching approaches: augmentation of dopamine levels via increased neurotransmitter production; modulation of the neuronal phenotype; and neuroprotection. The first two therapies discussed in this article focus on increasing dopamine production via direct delivery of genes involved in neurotransmitter synthesis (amino acid decarboxylase, tyrosine hydroxylase and GTP [guanosine triphosphate] cyclohydrolase 1). In an attempt to bypass the degenerating nigrostriatal pathway, a third clinical trial utilizes rAAV2 to deliver glutamic acid decarboxylase to the subthalamic nucleus, converting a subset of excitatory neurons to GABA-producing cells. In contrast, the final clinical trial is aimed at protecting the degenerating nigrostriatum by striatal delivery of rAAV2 harbouring the neuroprotective gene, neurturin. Based on preclinical studies, this gene therapeutic approach is posited to slow disease progression by enhancing neuronal survival. In addition, we discuss the outcome of each clinical trial and discuss the potential rationale for the marginal yet incremental clinical advancements that have thus far been realized for Parkinson's disease gene therapy.

The relation of ventromedial prefrontal cortex activity and heart rate fluctuations at rest

Recent studies applying functional magnetic resonance imaging have focused on the description of cerebral substrates of changes in cardiac function during diverse autonomic maneuvers or stressful cognitive tasks. These studies might be limited by the indistinguishable neuronal activity due to cognitive processes, which are known to influence autonomic function, and the 'baseline' activity in the central autonomic network. We therefore investigated 26 healthy volunteers in the magnetic resonance scanner to simultaneously obtain functional brain images and RR intervals (intervals between ventricular depolarizations) of the high-resolution electrocardiogram. The mean RR interval length within each functional scan was computed, which was finally convolved with the canonical hemodynamic response function to obtain a regressor for the functional time series. The resulting individual contrast image indicated a positive covariation of the blood oxygen level-dependent signal and RR interval length in the ventromedial prefrontal cortex (vmPFC). Furthermore, a reduced mean cross-approximate entropy value was shown for the interaction between the vmPFC and individual RR intervals. This suggests reduced asynchrony between the heart rate and vmPFC activity in contrast to other brain areas. Our findings confirm data obtained in animals describing the vmPFC as an important forebrain structure of the central autonomic network and an influence of the vmPFC in the cortical generation of efferent vagal activity. This finding needs to be investigated in diseases with known suppression of efferent vagal modulation.

Neurodegenerative disorders and nanoformulated drug development

Degenerative and inflammatory diseases of the CNS include, but are not limited to, Alzheimer's and Parkinson's disease, amyotrophic lateral sclerosis, stroke, multiple sclerosis and HIV-1-associated neurocognitive disorders. These are common, debilitating and, unfortunately, hold few therapeutic options. In recent years, the application of nanotechnologies as commonly used or developing medicines has served to improve pharmacokinetics and drug delivery specifically to CNS-diseased areas. In addition, nanomedical advances are leading to therapies that target CNS pathobiology and as such, can interrupt disordered protein aggregation, deliver functional neuroprotective proteins and alter the oxidant state of affected neural tissues. This article focuses on the pathobiology of common neurodegenerative disorders with a view towards how nanomedicine may be used to improve the clinical course of neurodegenerative disorders.

A cross-study transcriptional analysis of Parkinson's disease

The study of Parkinson's disease (PD), like other complex neurodegenerative disorders, is limited by access to brain tissue from patients with a confirmed diagnosis. Alternatively the study of peripheral tissues may offer some insight into the molecular basis of disease susceptibility and progression, but this approach still relies on brain tissue to benchmark relevant molecular changes against. Several studies have reported whole-genome expression profiling in post-mortem brain but reported concordance between these analyses is lacking. Here we apply a standardised pathway analysis to seven independent case-control studies, and demonstrate increased concordance between data sets. Moreover data convergence increased when the analysis was limited to the five substantia nigra (SN) data sets; this highlighted the down regulation of dopamine receptor signaling and insulin-like growth factor 1 (IGF1) signaling pathways. We also show that case-control comparisons of affected post mortem brain tissue are more likely to reflect terminal cytoarchitectural differences rather than primary pathogenic mechanisms. The implementation of a correction factor for dopaminergic neuronal loss predictably resulted in the loss of significance of the dopamine signaling pathway while axon guidance pathways increased in significance. Interestingly the IGF1 signaling pathway was also over-represented when data from non-SN areas, unaffected or only terminally affected in PD, were considered. Our findings suggest that there is greater concordance in PD whole-genome expression profiling when standardised pathway membership rather than ranked gene list is used for comparison.

The search for biomarkers in Parkinson's disease: a critical review

Parkinson's disease (PD) is a progressive neurodegenerative disorder that primarily presents with features of bradykinesia, rigidity and tremor, and has, as part of its core pathology, the degeneration of dopaminergic neurons in the substantia nigra pars compacta. There is a great need for the development of a reliable diagnostic tool to improve promptness of diagnosis, definition of disease subtypes, and to monitor disease progression and demonstrate treatment efficacy in the case of disease modifying therapies. Current biomarkers range from objective clinical tools, to neuroimaging, to 'wet' markers involving blood and cerebrospinal fluid. To date, all candidate biomarkers for PD have failed to be developed into a clinically useful tool. Ideally, a combination of sensitive markers will be needed, not only to predict the onset of PD, but also to help in subtype classification and to follow progression. Here, we critically review various PD biomarker studies.

Neural control of the gastrointestinal tract: implications for Parkinson disease

Disorders of swallowing and gastrointestinal motility are prominent nonmotor manifestations of Parkinson disease (PD). Motility of the gut is controlled both by extrinsic inputs from the dorsal motor nucleus of the vagus (DMV) and paravertebral sympathetic ganglia and by local reflexes mediated by intrinsic neurons of the enteric nervous system (ENS). Both the ENS and the DMV are affected by Lewy body pathology at early stages of PD. This early involvement provides insights into the pathophysiology of gastrointestinal dysmotility in this disorder and may constitute an important step in the etiopathogenesis of Lewy body disease.

Sexual dysfunction in Parkinson's disease

Sexual dysfunction is one of the more disabling and poorly investigated aspects of PD. Several variables should be considered when evaluating sexual dysfunction in a disease in which physical, psychological, neurobiological and pharmacological features merge and are not easily distinguishable. Although sexual dysfunction is common in Parkinson's disease, the development of hypersexuality and aberrant sexual behaviour, probably due to dopamine replacement therapy, calls into question the role of dopamine in sexual behaviour. This paper reviews studies that have investigated sexual behaviour and dysfunction in PD patients, paying particular attention to the effect of dopamine replacement therapy.