Manometric investigation of anorectal function in early and late stage Parkinson's disease

Relationship among Parkinson's disease, constipation, microbes, and microbiological therapy

This comprehensive review elucidates the complex interplay between gut microbiota and constipation in Parkinson's disease (PD), a prevalent non-motor symptom contributing significantly to patients' morbidity. A marked alteration in the gut microbiota, predominantly an increase in the abundance of Proteobacteria and Bacteroidetes, is observed in PD-related constipation. Conventional treatments, although safe, have failed to effectively alleviate symptoms, thereby necessitating the development of novel therapeutic strategies. Microbiological interventions such as prebiotics, probiotics, and fecal microbiota transplantation (FMT) hold therapeutic potential. While prebiotics improve bowel movements, probiotics are effective in enhancing stool consistency and alleviating abdominal discomfort. FMT shows potential for significantly alleviating constipation symptoms by restoring gut microbiota balance in patients with PD. Despite promising developments, the causal relationship between changes in gut microbiota and PD-related constipation remains elusive, highlighting the need for further research in this expanding field.

Chronic constipation in Parkinson's disease: clinical features and molecular insights on the intestinal epithelial barrier

Background

Chronic constipation (CC) is a severe symptom in Parkinson's disease (PD), with an unclear pathogenesis. Abnormalities of the enteric nervous system (ENS) and/or intestinal epithelial barrier (IEB) may be pathophysiologically relevant in PD patients with CC. We investigated possible molecular changes of the IEB in PD/CCs compared with CCs and controls.

Methods

Twelve PD/CCs (2 female, age range 51-80 years), 20 CCs (15 female, age range 27-78 years), and 23 controls (11 female, age range 32-74 years) were enrolled. Ten PD/CCs and 10 CCs were functionally characterized by anorectal manometry (AM) and transit time (TT). Colon biopsies were obtained and assessed for gene and protein expression, and localization of IEB tight junction markers claudin-4 (CLDN4), occludin-1 (OCCL-1), and zonula occludens-1 (ZO-1) by RT-qPCR, immunoblot and immunofluorescence labeling.

Results

PD/CCs were clustered in 2 functional categories: patients with delayed TT and altered AM (60%), and a second group showing only modifications in AM pattern (40%). Gene expression of CLDN4, OCCL-1 and ZO-1 was higher in PD/CCs than controls (P<0.05). Conversely, PD/CCs showed a trend to decrease (P>0.05) in CLDN4 and OCCL-1 protein levels than controls, whereas ZO-1 protein was comparable. In PD/CCs compared with controls, decreasing tendency of vasoactive intestinal polypeptide mRNA, protein and immunoreactive fiber density were observed, although the difference was not statistically significant.

Conclusion

Transit and anorectal dysfunctions in PD/CCs are associated with difference in ZO-1, OCCL-1 and CLDN4 expression, thus supporting the role of an altered IEB as a contributory mechanism to possible neuronal abnormalities.

Constipation in Parkinson's Disease

Constipation is one of the most common gastrointestinal features of Parkinson's disease (PD), occurring in over 50% of all PD patients during the course of their disease. Furthermore, constipation is now recognized as an important, prodromal symptom and may predate the onset of the classical motor symptoms by decades. Thereafter, the prevalence and severity of constipation in PD tend to parallel the course of both motor and nonmotor phenomena such as cognitive decline and depression. Difficult defecation (obstructed defecation, dyssynergia) is the primary pathophysiology underlying constipation and likely reflects involvement by the PD process of one or more of the many skeletal muscle groups that are involved in effecting defecation. Management of constipation in PD may be complicated by several patient factors including dysphagia, cognitive impairment, depression, and weak sphincter tone. While the armamentarium available to those who treat constipation, in general, has expanded considerably in recent years, the evidence supporting any therapy in the management of this symptom in PD has remained slim.

Rectal Perforation Secondary to a Self-Administered Water-Hose Enema: A Case Report and Literature Review

Chronic functional constipation is a common condition that can have a significant impact on a patient's quality of life and healthcare costs. Hydrostatic enemas are a commonly observed practice among patients with chronic constipation. Rectal perforation is a rare yet serious complication that can be fatal if not diagnosed and treated promptly. Here, we present the case of an elderly lady with Parkinson's disease who presented with upper rectal perforation after using a hydrostatic enema and was treated with Hartmann's procedure. This case highlights the importance of having a low threshold for suspecting and diagnosing colorectal perforation in patients presenting with abdominal pain after receiving a hydrostatic enema.

Differential Findings on Anorectal Manometry in Patients with Parkinson's Disease and Defecatory Dysfunction

Introduction

Gastrointestinal dysfunction, particularly constipation, is among the most common non-motor manifestations in Parkinson's Disease (PD). We aimed to identify high-resolution anorectal manometry (HR-ARM) abnormalities in patients with PD using the London Classification.

Methods

We conducted a retrospective review of all PD patients at our institution who underwent HR-ARM and balloon expulsion test (BET) for evaluation of constipation between 2015 and 2021. Using age and sex-specific normal values, HR-ARM recordings were re-analyzed and abnormalities were reported using the London Classification. A combination of Wilcoxon rank sum and Fisher's exact test were used.

Results

36 patients (19 women) with median age 71 (interquartile range [IQR]: 69-74) years, were included. Using the London Classification, 7 (19%) patients had anal hypotension, 17 (47%) had anal hypocontractility, and 3 women had combined hypotension and hypocontractility. Anal hypocontractility was significantly more common in women compared to men. Abnormal BET and dyssynergia were noted in 22 (61%) patients, while abnormal BET and poor propulsion were only seen in 2 (5%). Men had significantly more paradoxical anal contraction and higher residual anal pressures during simulated defecation, resulting in more negative recto-anal pressure gradients. Rectal hyposensitivity was seen in nearly one third of PD patients and comparable among men and women.

Conclusion

Our data affirms the high prevalence of anorectal disorders in PD. Using the London Classification, abnormal expulsion and dyssynergia and anal hypocontractility were the most common findings in PD. Whether the high prevalence of anal hypocontractility in females is directly related to PD or other confounding factors will require further research.

Gastrointestinal barriers to levodopa transport and absorption in Parkinson's disease

Levodopa is the gold standard for the symptomatic treatment of Parkinson's disease (PD). There are well documented motor and non-motor fluctuations, however, that occur almost inevitably once levodopa is started after a variable period in people with PD. Whilst brain neurodegenerative processes play a part in the pathogenesis of these fluctuations, a range of barriers across the gastrointestinal (GI) tract can alter levodopa pharmacokinetics, ultimately contributing to non-optimal levodopa response and symptoms fluctuations. GI barriers to levodopa transport and absorption include dysphagia, delayed gastric emptying, constipation, Helicobacter pylori infection, small intestinal bacterial overgrowth and gut dysbiosis. In addition, a protein-rich diet and concomitant medication intake can further alter levodopa pharmacokinetics. This can result in unpredictable or sub-optimal levodopa response, 'delayed on' or 'no on' phenomena. In this narrative review, we provided an overview on the plethora of GI obstacles to levodopa transport and absorption in PD and their implications on levodopa pharmacokinetics and development of motor fluctuations. In addition, management strategies to address GI dysfunction in PD are highlighted, including use of non-oral therapies to bypass the GI tract.

A Critical Analysis of Intestinal Enteric Neuron Loss and Constipation in Parkinson's Disease

Constipation afflicts many patients with Parkinson's disease (PD) and significantly impacts on patient quality of life. PD-related constipation is caused by intestinal dysfunction, but the etiology of this dysfunction in patients is unknown. One possible cause is neuron loss within the enteric nervous system (ENS) of the intestine. This review aims to 1) Critically evaluate the evidence for and against intestinal enteric neuron loss in PD patients, 2) Justify why PD-related constipation must be objectively measured, 3) Explore the potential link between loss of enteric neurons in the intestine and constipation in PD, 4) Provide potential explanations for disparities in the literature, and 5) Outline data and study design considerations to improve future research. Before the connection between intestinal enteric neuron loss and PD-related constipation can be confidently described, future research must use sufficiently large samples representative of the patient population (majority diagnosed with idiopathic PD for at least 5 years), implement a consistent neuronal quantification method and study design, including standardized patient recruitment criteria, objectively quantify intestinal dysfunctions, publish with a high degree of data transparency and account for potential PD heterogeneity. Further investigation into other potential influencers of PD-related constipation is also required, including changes in the function, connectivity, mitochondria and/or α-synuclein proteins of enteric neurons and their extrinsic innervation. The connection between enteric neuron loss and other PD-related gastrointestinal (GI) issues, including gastroparesis and dysphagia, as well as changes in nutrient absorption and the microbiome, should be explored in future research.

Long-Term Risks of Parkinson's Disease, Surgery, and Colorectal Cancer in Patients With Slow-Transit Constipation

BACKGROUND & AIMS

Long-term outcomes of constipation have not been evaluated fully. We investigated the incidence of Parkinson's disease, constipation-related surgery, and colorectal cancer (CRC) in patients with constipation and slow-transit constipation (STC), followed up for up to 20 years.

METHODS

We collected data from 2165 patients (33.1% men; median patient age, 54 y; median symptom duration, 5.0 y) with a diagnosis of constipation (based on Rome II criteria) who underwent an anorectal function test and a colonic transit time study, from 2000 through 2010, at a tertiary university hospital in Seoul, South Korea. The presence of STC was determined from colonic transit time. We used the Kaplan-Meier method to analyze and compare cumulative probabilities of a new diagnosis of Parkinson's disease or CRC according to the presence of STC. The patients were followed up until the end of 2019.

RESULTS

During a median follow-up period of 4.7 years (interquartile range, 0.7-8.3 y), 10 patients underwent constipation-related surgery. The cumulative probabilities of constipation-related surgery were 0.7% at 5 years and 0.8% at 10 years after a diagnosis of constipation. Twenty-nine patients (1.3%) developed Parkinson's disease; the cumulative probabilities were 0.4% at 1 year, 1.0% at 5 years, and 2.6% at 10 years after a diagnosis of constipation. At 10 years, 1.3% of patients with STC required constipation-related surgery and 3.5% of patients with STC developed Parkinson's disease; in contrast, none of the patients without STC required constipation-related surgery (P = .003), and 1.5% developed Parkinson's disease (P = .019). In multivariate analysis, patient age of 65 years or older at the diagnosis of constipation (hazard ratio, 4.834; 95% CI, 2.088-11.190) and the presence of STC (hazard ratio, 2.477; 95% CI, 1.046-5.866) were associated independently with the development of Parkinson's disease. Only 5 patients had a new diagnosis of CRC during the follow-up period. The risk of CRC did not differ significantly between patients with vs without STC (P = .575).

CONCLUSIONS

In a long-term follow-up study of patients with constipation in Korea, most patients had no severe complications. However, patients older than age 65 years with a new diagnosis of STC might be considered for Parkinson's disease screening.

Gastro-intestinal dysfunctions in Parkinson's disease (Review)

In patients with Parkinson's disease (PD), gastrointestinal dysfunction occurs from the early stages of the disease and even in the pre-motor phase. This condition can include the entire digestive tract, with symptoms ranging from delays in gastric emptying to dysphagia, constipation and even malnutrition. Excess saliva accumulates in the mouth due to the low frequency of swallowing. Dysphagia develops in about 50% of patients and may be a reflection of both central nervous system and enteric nervous system disorder. Gastroparesis can cause a variety of symptoms, including nausea, and also may be responsible for some of the motor fluctuations observed with levodopa therapy. Intestinal dysfunction in PD may be the result of both delayed colon transit and impaired anorectal muscle coordination. In addition, recent studies have demonstrated the role of Helicobacter pylori infection in the pathogenesis of diseases but also the occurrence of motor fluctuations by affecting the absorption of anti-parkinsonian medication. In this review, the main gastrointestinal dysfunctions associated with PD are presented.

Gastrointestinal Dysfunction in Parkinson's Disease

Parkinson’s disease (PD) is the second most common neurodegenerative disease. Patients show deposits of pathological, aggregated α-synuclein not only in the brain but throughout almost the entire length of the digestive tract. This gives rise to non-motor symptoms particularly within the gastrointestinal tract and patients experience a wide range of frequent and burdensome symptoms such as dysphagia, bloating, and constipation. Recent evidence suggests that progressive accumulation of gastrointestinal pathology is underway several years before a clinical diagnosis of PD. Notably, constipation has been shown to increase the risk of developing PD and in contrast, truncal vagotomy seems to decrease the risk of PD. Animal models have demonstrated gut-to-brain spreading of pathological α-synuclein and it is currently being intensely studied whether PD begins in the gut of some patients. Gastrointestinal symptoms in PD have been investigated by the use of several different questionnaires. However, there is limited correspondence between subjective gastrointestinal symptoms and objective dysfunction along the gastrointestinal tract, and often the magnitude of dysfunction is underestimated by the use of questionnaires. Therefore, objective measures are important tools to clarify the degree of dysfunction in future studies of PD. Here, we summarize the types and prevalence of subjective gastrointestinal symptoms and objective dysfunction in PD. The potential importance of the gastrointestinal tract in the etiopathogenesis of PD is briefly discussed.

Autonomic Dysfunctions in Parkinson's Disease: Prevalence, Clinical Characteristics, Potential Diagnostic Markers, and Treatment

Parkinson's disease (PD) is a common neurodegenerative disease in the middle-aged and the elderly. Symptoms of autonomic dysfunctions are frequently seen in PD patients, severely affecting the quality of life. This review summarizes the epidemiology, clinical manifestations, and treatment options of autonomic dysfunctions. The clinical significance of autonomic dysfunctions in PD early diagnosis and differential diagnosis is also discussed.

On the Emergence of Tremor in Prodromal Parkinson's Disease

Clinical, neuropathological and neuroimaging research suggests that pathological changes in Parkinson's disease (PD) start many years before the emergence of motor signs. Since disease-modifying treatments are likely to be most effective when initiated early in the disease process, there has been significant interest in characterizing prodromal PD. Some people with PD describe autonomic symptoms at the time of diagnosis suggesting that autonomic dysfunction is a common feature of prodromal PD. Furthermore, subtle motor signs may be present and emerge prior to the time of diagnosis. We present a series of patients who, in the prodromal phase of PD, experienced the emergence of tremor initially only while yawning or straining at stool and discuss how early involvement of autonomic brainstem nuclei could lead to these previously unreported phenomena. The hypothalamic paraventricular nucleus (PVN) plays a central role in autonomic control including bowel/bladder function, cardiovascular homeostasis and yawning and innervates multiple brainstem nuclei involved in autonomic functions (including brainstem reticular formation, locus ceruleus, dorsal raphe nucleus and motor nucleus of the vagus). The PVN is affected in PD and evidence from related phenomena suggest that the PVN could increase tremor either by increasing downstream cholinergic activity on brainstem nuclei such as the reticular formation or by stimulating the locus ceruleus to activate the cerebellothalamocortical network via the ventrolateral nucleus of the thalamus. Aberrant cholinergic/noradrenergic transmission between these brainstem nuclei early in PD couldlead to tremor before the emergence of other parkinsonian signs, representing an early clinical clue to prodromal PD.

Gastrointestinal dysfunction in the synucleinopathies

Interest in gastrointestinal dysfunction in Parkinson's disease has blossomed over the past 30 years and has generated a wealth of investigation into this non-motor aspect of the disorder, research that has encompassed its pathophysiology, its clinical features, and its impact on quality of life. The question of gastrointestinal dysfunction in the other synucleinopathies has not received nearly as much attention, but information and knowledge are growing. In this review, the current knowledge, controversies, and gaps in our understanding of the pathophysiology of gastrointestinal dysfunction in Parkinson's disease and the other synucleinopathies will be addressed, and extended focus will be directed toward the clinical problems involving saliva management, swallowing, gastric emptying, small intestinal function, and bowel function that are so problematic in these disorders.

Autonomic Dysfunction in Parkinson's Disease

Recognition of the importance of nonmotor dysfunction as a component of Parkinson's disease has exploded over the past three decades. Autonomic dysfunction is a frequent and particularly important nonmotor feature because of the broad clinical spectrum it covers. Cardiovascular, gastrointestinal, urinary, sexual, and thermoregulatory abnormalities all can appear in the setting of Parkinson's disease. Cardiovascular dysfunction is characterized most prominently by orthostatic hypotension. Gastrointestinal dysfunction can involve virtually all levels of the gastrointestinal tract. Urinary dysfunction can entail either too frequent voiding or difficulty voiding. Sexual dysfunction is frequent and frustrating for both patient and partner. Alterations in sweating and body temperature are not widely recognized but often are present. Autonomic dysfunction can significantly and deleteriously impact quality of life for individuals with Parkinson's disease. Because effective treatment for many aspects of autonomic dysfunction is available, it is vitally important that assessment of autonomic dysfunction be a regular component of the neurologic history and exam and that appropriate treatment be initiated and maintained.

Enriched Environmental Conditions Modify the Gut Microbiome Composition and Fecal Markers of Inflammation in Parkinson's Disease

Recent findings suggest an implication of the gut microbiome in Parkinson's disease (PD) patients. PD onset and progression has also been linked with various environmental factors such as physical activity, exposure to pesticides, head injury, nicotine, and dietary factors. In this study, we used a mouse model, overexpressing the complete human SNCA gene (SNCA-TG mice) modeling familial and sporadic forms of PD to study whether environmental conditions such as standard vs. enriched environment changes the gut microbiome and influences disease progression. We performed 16S rRNA DNA sequencing on fecal samples for microbiome analysis and studied fecal inflammatory calprotectin from the colon of control and SNCA-TG mice kept under standard environment (SE) and enriched environment (EE) conditions. The overall composition of the gut microbiota was not changed in SNCA-TG mice compared with WT in EE with respect to SE. However, individual gut bacteria at genus level such as Lactobacillus sp. was a significant changed in the SNCA-TG mice. EE significantly reduced colon fecal inflammatory calprotectin protein in WT and SNCA-TG EE compared to SE. Moreover, EE reduces the pro-inflammatory cytokines in the feces and inflammation inducing genes in the colon. Our data suggest that an enriched social environment has a positive effect on the induction of SNCA mediated inflammation in the intestine and by modulating anti-inflammatory gut bacteria.

Gastrointestinal Care of the Parkinson Patient

This article reviews the most common gastrointestinal (GI) problems that occur in patients with Parkinson disease, including weight loss, drooling, dysphagia, delayed gastric emptying, constipation, and defecatory dysfunction. Appropriate workup and treatment options are reviewed in detail in order to provide clinicians with a comprehensive and practical guide to managing these problems in Parkinson disease patients. GI adverse effects of commonly used Parkinson disease motor medications are also reviewed.

Colonic transit, high-resolution anorectal manometry and MRI defecography study of constipation in Parkinson's disease

INTRODUCTION

Despite clinical relevance and potential role on the disease pathogenesis, underlying mechanisms of constipation in Parkinson's disease (PD) remain poorly understood. A systematic assessment using complementary physiological investigations was performed to elucidate constipation pathophysiology in order to improve its symptomatic management.

METHODS

PD patients with constipation were evaluated with clinical questionnaires, colonic transit, high-resolution anorectal manometry and MRI defecography. Results were compared and correlated with clinical features.

RESULTS

A total of 42 patients (69% male; age 68 ± 8 years; disease duration 10.5 ± 6.1 years) were included, of whom 33 (78.6%) had objective constipation defined by < 3 bowel movements per week or straining. Severity of constipation measured by self-administered questionnaires correlated with disease severity, burden of motor and non-motor symptoms but not with age, disease duration or Parkinson's medications. Colonic transit and anorectal function (high-resolution anorectal manometry and/or MRI defecography) was assessed in 15 patients. A combination of both delayed colonic transit and anorectal dysfunction was the pattern most commonly found (60% of patients) and overall anorectal dysfunction was more prevalent than isolated slow transit constipation. Physiological findings were heterogeneous including reduced colonic motility, rectal hyposensitivity, defecatory dyssynergia and poor motor rectal function.

CONCLUSION

Subjective constipation in PD is poorly correlated with commonly used definition, assessment questionnaires and physiological results. Multiple complex overlapping pathophysiological mechanisms are responsible including slow transit and anorectal dysfunction. Complementary investigations to assess colonic transit and anorectal function are required in those with refractory symptoms for a systematic assessment and appropriate symptomatic management.

Does Bilateral Deep Brain Stimulation of the Subthalamic Nucleus Modify Ano-Rectal Motility in Parkinson's Disease? Results of a Randomized Cross-Over Study

BACKGROUND

Ano-rectal motility impairment is often observed during Parkinson's disease (PD), generating symptoms as constipation and/or incontinence with impaired quality of life. Subthalamic nuclei (STN) deep brain stimulation (DBS) improves motor symptoms of PD, but its effects on anorectal motility are unknown. This study aimed to assess the effects of STN-DBS on the anorectal motility in PD patients, in a randomized cross-over study.

METHODS

Sixteen PD patients with bilateral STN-DBS for at least 6 months were included. The anal resting pressure, duration and maximal amplitude of squeeze effort, recto-anal inhibitory reflex, maximal tolerable rectal volume, and anal pressure during defecation effort were measured and compared after STN-DBS was switched OFF and then ON for 2 hours, or vice-versa, in a randomized order.

KEY RESULTS

STN-DBS increased maximal amplitude of anal squeezing pressure (OFF: 85.7 ± 14.5 vs ON: 108.4 ± 21.0 cmH₂ O; P = 0.02), with no significant difference in the duration (P = 0.10). No other significant difference was found between stimulation conditions (OFF vs ON) for anal resting pressure (OFF: 72.5 ± 8.6 cmH₂ O vs ON: 71.7 ± 9.0 cmH₂ O; P = 0.24), recto-anal inhibitory reflex, maximal tolerable rectal volume (OFF: 231 ± 24 mL vs ON: 241 ± 26 mL; P = 0.68), or anal pressure during defecation effort with a similar rate of ano-rectal dyssynergia (7/16 and 8/16 with and without STN-DBS, respectively). No order effect (ON-OFF vs OFF-ON) was observed.

CONCLUSION AND INFERENCES

STN-DBS increased anal squeezing pressure, but did not modify anorectal dyssynergia in PD patients, This study demonstrated the involvement of STN in the voluntary control of anorectal motility in PD patients.

Gastrointestinal Dysfunction in Parkinson's Disease

PURPOSE OF REVIEW

During the past 25 years, there has been an explosion of information regarding the occurrence of gastrointestinal dysfunction in Parkinson's disease. In this review, the clinical features of gastrointestinal dysfunction in Parkinson's disease will be described and information regarding the potential role of the enteric nervous system and the gut microbiome in the genesis of Parkinson's disease will be addressed.

RECENT FINDINGS

Recognition is growing regarding the role that gastroparesis and small intestinal dysfunction may play in Parkinson's disease, especially with regard to erratic responses to anti-Parkinson medication. The presence of enteric nervous system involvement in Parkinson's disease is now well established, but whether the enteric nervous system is the starting point for Parkinson's disease pathology remains a source of debate. The potential role of the gut microbiome also is beginning to emerge. Gastrointestinal dysfunction is a prominent nonmotor feature of Parkinson's disease and dysfunction can be found along the entire length of the gastrointestinal tract. The enteric nervous system is clearly involved in Parkinson's disease. Whether it is the initial source of pathology is still a source of controversy. There also is growing recognition of the role that the gut microbiome may play in Parkinson's disease, but much more research is needed to fully assess this aspect of the disorder.

Early detection of Parkinson's disease through patient questionnaire and predictive modelling

Early detection of Parkinson's disease (PD) is important which can enable early initiation of therapeutic interventions and management strategies. However, methods for early detection still remain an unmet clinical need in PD. In this study, we use the Patient Questionnaire (PQ) portion from the widely used Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) to develop prediction models that can classify early PD from healthy normal using machine learning techniques that are becoming popular in biomedicine: logistic regression, random forests, boosted trees and support vector machine (SVM). We carried out both subject-wise and record-wise validation for evaluating the machine learning techniques. We observe that these techniques perform with high accuracy and high area under the ROC curve (both >95%) in classifying early PD from healthy normal. The logistic model demonstrated statistically significant fit to the data indicating its usefulness as a predictive model. It is inferred that these prediction models have the potential to aid clinicians in the diagnostic process by joining the items of a questionnaire through machine learning.

The Gut and Nonmotor Symptoms in Parkinson's Disease

Gastrointestinal (GI) symptoms are one of the most common nonmotor symptoms (NMS) in patients with Parkinson's disease (PD) involving the whole GI tract (GIT) and being evident throughout the whole course of the disease. Furthermore, constipation serves as a risk factor for PD as well as an early prodromal NMS of PD. The gut as gateway to the environment with its enteric nervous system (ENS) plays a crucial role in the neurodegenerative process that leads to PD. Alpha-synucleinopathy as the pathological hallmark of PD could be found within the whole GIT in a rostrocaudal gradient interacting with the ENS, the gut microbiome, and enteric glial cells. Bidirectional interactions between the ENS and the central nervous system (CNS) via a brain-gut-enteric microbiota axis have been reported. As well as there is evidence out of animal, autopsy, and epidemiological studies that α-synuclein spreads via rostrocranial transmission by transsynaptic cell-to-cell transfer via the sympathetic and parasympathetic nervous system to the CNS causing the typical neuropathological changes of PD. Recognition of GI NMS as prodromal markers of PD as well as a better understanding of the brain-gut connection offers new insights in the pathophysiology of PD and might provide the opportunity of PD diagnosis before CNS involvement. Hereby the opportunity for development of neuroprotective and disease-modifying therapeutics, respectively, seem to be promising. This chapter covers the variety of GI NMS and its consequences in PD as well as the important role of the gut as part of the pathological process in PD.

Gastrointestinal dysfunction in idiopathic Parkinsonism: A narrative review

Currently, gastrointestinal (GI) dysfunctions in Parkinson's disease (PD) are well-recognized problems and are known to be the initial symptoms in the pathological process that eventually results in PD. Many types of PD-associated GI dysfunctions have been identified, including weight loss, nausea, hypersalivation, dysphagia, dyspepsia, abdominal pain, intestinal pseudo-obstruction, constipation, defecatory dysfunction, and small intestinal bacterial overgrowth. These symptoms can influence on other PD symptoms and are the second most significant predictor of the quality of life of these patients. Recognition of GI symptoms requires vigilance on the part of clinicians. Health-care providers should routinely ask direct questions about GI symptoms during office visits so that efforts can be directed at appropriate management of these distressing manifestations. Multiple system atrophy (MSA) and progressive supranuclear palsy are two forms of neurodegenerative Parkinsonism. Symptoms of autonomic dysfunctions such as GI dysfunction are common in patients with parkinsonian disorders. Despite recent progress in the recognition of GI dysfunctions, there are a few reviews on the management of GI dysfunction and GI symptoms in idiopathic Parkinsonism. In this review, the clinical presentation, pathophysiology, and treatment of each GI symptom in PD, MSA, and prostate-specific antigen will be discussed.

Constipation in parkinson's disease: Subjective symptoms, objective markers, and new perspectives

Constipation is among the first nonmotor symptoms to develop in the prodromal phase of PD. Pathological alpha-synuclein deposition is present throughout the gastrointestinal tract up to 20 years preceding diagnosis. Nevertheless, constipation in the context of PD remains ill defined and poorly understood. In this review, we summarize current knowledge of subjective symptoms and objective measures of constipation in PD. More than 10 different definitions of constipation have been used in the PD literature, making generalizations difficult. When pooling results from the most homogeneous studies in PD, a median constipation prevalence of 40% to 50% emerges, but with large variation across individual studies. Also, constipation prevalence tends to increase with disease progression. A similar prevalence is observed among patients with idiopathic rapid eye movement sleep behavior disorder. Interestingly, we detected a correlation between constipation prevalence in PD patients and healthy control groups in individual studies, raising concerns about how various constipation questionnaires are implemented across study populations. More than 80% of PD patients exhibit prolonged colonic transit time, and the same is probably true for de novo PD patients. Thus, the prevalence of objective colonic dysfunction exceeds the prevalence of subjective constipation. Colonic transit time measures are simple, widely available, and hold promise as a useful biomarker in manifest PD. More research is needed to elucidate the role of gastrointestinal dysfunction in disease progression of PD. Moreover, colonic transit measures may have utility as a more accurate risk factor for predicting PD in the prodromal phase. © 2016 International Parkinson and Movement Disorder Society.

Utility of high-resolution anorectal manometry and wireless motility capsule in the evaluation of patients with Parkinson's disease and chronic constipation

BACKGROUND

The aetiology of constipation in Parkinson's disease remains poorly understood. Defaecatory dyssynergia, anal sphincter spasticity and slow transit constipation may, individually or collectively, play a role.

AIMS

In this retrospective cohort analysis of patients with Parkinson's disease and chronic constipation, we determined the utility of high-resolution anorectal manometry, balloon expulsion and wireless motility capsule testing in defining the underlying aetiology for constipation.

METHODS

In this retrospective cohort study, consecutive patients with Parkinson's disease and chronic constipation underwent clinical assessment, manometry with balloon expulsion and wireless motility capsule testing using standard protocols.

RESULTS

We studied 66 patients fulfilling Rome IV criteria for functional constipation. Most patients (89%) had abnormal manometry, exhibiting various types of defaecatory dyssynergia (mostly types II and IV), abnormal balloon expulsion, diminished rectal sensation and, in some, lacking rectoanal inhibitory reflex. 62% exhibited colonic transit delay by wireless motility capsule study, while 57% had combined manometric and transit abnormalities, suggesting of overlap constipation. Symptoms of infrequent defaecation, straining and incomplete evacuation were not discriminatory. There was a relationship between constipation scores and colonic transit times (p=0.01); Parkinson's disease scores and duration were not correlated with either the manometric or transit findings. Faecal incontinence was seen in 26% of the patients.

CONCLUSIONS

Chronic constipation in patients with Parkinson's disease may reflect pelvic floor dyssynergia, slow transit constipation or both, and may be associated with faecal incontinence, suggesting both motor and autonomic dysfunction. Anorectal manometry and wireless motility capsule testing are useful in the assessment of these patients.

High-resolution Anorectal Manometry in Parkinson Disease With Defecation Disorder: A Comparison With Functional Defecation Disorder

GOAL

To investigate the characteristics of high-resolution anorectal manometry (HR-ARM) in Parkinson disease (PD) patients with defecation disorder (DD) compared with patients with functional defecation disorder (FDD).

BACKGROUND

DD is a common gastrointestinal symptom in PD. HR-ARM is a relatively new and reliable method for detecting DD.

STUDY

A cohort of PD patients with DD was matched with FDD patients. Defecatory symptoms were investigated by questionnaire. Anorectal motility and sensation were evaluated by HR-ARM. Differences in defecatory symptoms, sensorimotor parameters, and DD type were analyzed. Defecatory symptoms and manometric variables obtained in early-stage PD were compared with advanced stage, and relationships between manometric parameters and evacuatory symptoms explored.

RESULTS

Straining and sensation of blockage was experienced significantly more in PD than FDD, and stool consistency more severely affected. Maximum squeeze and intrarectal pressure during defecation in PD was lower than in FDD. Anal resting and residual pressures, duration of sustained squeeze, threshold volumes for first sensation, urgency, and maximum discomfort were similar between groups. PD patients presented predominantly with inadequate propulsive forces, whereas FDD patients showed dyssynergic defecation. Defecatory symptoms and manometric parameters did not differ between stages of PD.

CONCLUSIONS

PD patients with DD experienced more straining and sensation of blockage than FDD patients, possibly related to inadequate anorectal motility and paradoxical anal contraction of pelvic floor. Impaired squeeze response and inadequate propulsive forces are specific to anorectal function of PD patients with DD, compared with FDD, with abnormalities unchanged between early and advanced PD.

Constipation: an emerging risk factor for Parkinson's disease?

Constipation is the most prominent and disabling manifestation of lower gastrointestinal (GI) dysfunction in Parkinson's disease (PD). The prevalence of constipation in PD patients ranges from 24.6% to 63%; this variability is due to the different criteria used to define constipation and to the type of population enrolled in the studies. In addition, constipation may play an active role in the pathophysiological changes that underlie motor fluctuations in advanced PD through its negative effects on absorption of levodopa. Several clinical studies now consistently suggest that constipation may precede the first occurrence of classical motor features in PD. Studies in vivo, using biopsies of the GI tract and more recently functional imaging investigations, showed the presence of α-synuclein (α-SYN) aggregates and neurotransmitter alterations in enteric tissues. All these findings support the Braak proposed model for the pathophysiology of α-SYN aggregates in PD, with early pathological involvement of the enteric nervous system and dorsal motor nucleus of the vagus. Therefore, constipation could have the potential sensitivity to be used as a clinical biomarker of the prodromal phase of the disease. The use of colonic biopsies to look at α-SYN pathology, once confirmed by larger prospective studies, might eventually represent a feasible, albeit partially invasive, new diagnostic biomarker for PD.

Gut dysfunction in Parkinson's disease

Early involvement of gut is observed in Parkinson’s disease (PD) and symptoms such as constipation may precede motor symptoms. α-Synuclein pathology is extensively evident in the gut and appears to follow a rostrocaudal gradient. The gut may act as the starting point of PD pathology with spread toward the central nervous system. This spread of the synuclein pathology raises the possibility of prion-like propagation in PD pathogenesis. Recently, the role of gut microbiota in PD pathogenesis has received attention and some phenotypic correlation has also been shown. The extensive involvement of the gut in PD even in its early stages has led to the evaluation of enteric α-synuclein as a possible biomarker of early PD. The clinical manifestations of gastrointestinal dysfunction in PD include malnutrition, oral and dental disorders, sialorrhea, dysphagia, gastroparesis, constipation, and defecatory dysfunction. These conditions are quite distressing for the patients and require relevant investigations and adequate management. Treatment usually involves both pharmacological and non-pharmacological measures. One important aspect of gut dysfunction is its contribution to the clinical fluctuations in PD. Dysphagia and gastroparesis lead to inadequate absorption of oral anti-PD medications. These lead to response fluctuations, particularly delayed-on and no-on, and there is significant relationship between levodopa pharmacokinetics and gastric emptying in patients with PD. Therefore, in such cases, alternative routes of administration or drug delivery systems may be required.

Parkinson Disease-Mediated Gastrointestinal Disorders and Rational for Combinatorial Therapies

A gradual loss of dopamine-producing nerve cells gives rise to a common neurodegenerative Parkinson’s disease (PD). This disease causes a neurotransmitter imbalance in the brain and initiates a cascade of complications in the rest of the body that appears as distressing symptoms which include gait problems, tremor, gastrointestinal (GI) disorders and cognitive decline. To aid dopamine deficiency, treatment in PD patients includes oral medications, in addition to other methods such as deep brain stimulation and surgical lesioning. Scientists are extensively studying molecular and signaling mechanisms, particularly those involving phenotypic transcription factors and their co-regulatory proteins that are associated with neuronal stem cell (SC) fate determination, maintenance and disease state, and their role in the pathogenesis of PD. Advancement in scientific research and “personalized medicine” to augment current therapeutic intervention and minimize the side effects of chemotherapy may lead to the development of more effective therapeutic strategies in the near future. This review focuses on PD and associated GI complications and summarizes the current therapeutic modalities that include stem cell studies and combinatorial drug treatment.

Chronic constipation in the elderly: a primer for the gastroenterologist

Constipation is a frequently reported bowel symptom in the elderly with considerable impact on quality of life and health expenses. Disease-related morbidity and even mortality have been reported in the affected frail elderly. Although constipation is not a physiologic consequence of normal aging, decreased mobility, medications, underlying diseases, and rectal sensory-motor dysfunction may all contribute to its increased prevalence in older adults. In the elderly there is usually more than one etiologic mechanism, requiring a multifactorial treatment approach. The majority of patients would respond to diet and lifestyle modifications reinforced by bowel training measures. In those not responding to conservative treatment, the approach needs to be tailored addressing all comorbid conditions. In the adult population, the management of constipation continues to evolve as well as the understanding of its complex etiology. However, the constipated elderly have been left behind while gastroenterology consultations for this common conditions are at a rise for the worldwide age increment. Aim of this review is to provide an update on epidemiology, quality of life burden, etiology, diagnosis, current approaches and limitations in the management of constipation in the older ones to ease the gastroenterologists’ clinic workload.

Gastrointestinal Autonomic Dysfunction in Patients with Parkinson's Disease

Currently, gastrointestinal dysfunctions in Parkinson’s disease (PD) are well-recognized problems and are known to be an initial symptom in the pathological process that eventually results in PD. Gastrointestinal symptoms may result from the involvement of either the central or enteric nervous systems, or these symptoms may be side effects of antiparkinsonian medications. Weight loss, excessive salivation, dysphagia, nausea/gastroparesis, constipation, and defecation dysfunction all may occur. Increased identification and early detection of these symptoms can result in a significant improvement in the quality of life for PD patients.

Management of constipation in Parkinson's disease

INTRODUCTION

Constipation is a frequent non-motor feature of Parkinson's disease (PD). It is the most common gastrointestinal symptom of the disease and it can precede motor symptoms by as much as 20 years. Constipation can produce discomfort and affect activities of daily living, productivity and quality of life, thus warranting early diagnosis and treatment.

AREAS COVERED

In this review, the safety and efficacy of traditional and novel strategies for constipation management will be discussed. A treatment algorithm for constipation in PD will be presented.

EXPERT OPINION

Polyethylene glycol and lubiprostone are first-line compounds recommended by evidence-based medicine guidelines for the treatment of constipation due to slow colonic transit in PD. Management of constipation secondary to defecatory dysfunction due to pelvic floor dyssynergia can be done by levodopa or apomorphine injections, botulinum toxin type A injection into the puborectalis muscle, and nonpharmacological interventions, like biofeedback therapy or functional magnetic stimulation, which showed some benefit in PD patients with constipation, but in general more extensive studies are warranted.

Dual destructive and protective roles of adaptive immunity in neurodegenerative disorders

Inappropriate T cell responses in the central nervous system (CNS) affect the pathogenesis of a broad range of neuroinflammatory and neurodegenerative disorders that include, but are not limited to, multiple sclerosis, amyotrophic lateral sclerosis, Alzheimer’s disease and Parkinson’s disease. On the one hand immune responses can exacerbate neurotoxic responses; while on the other hand, they can lead to neuroprotective outcomes. The temporal and spatial mechanisms by which these immune responses occur and are regulated in the setting of active disease have gained significant recent attention. Spatially, immune responses that affect neurodegeneration may occur within or outside the CNS. Migration of antigen-specific CD4+ T cells from the periphery to the CNS and consequent immune cell interactions with resident glial cells affect neuroinflammation and neuronal survival. The destructive or protective mechanisms of these interactions are linked to the relative numerical and functional dominance of effector or regulatory T cells. Temporally, immune responses at disease onset or during progression may exhibit a differential balance of immune responses in the periphery and within the CNS. Immune responses with predominate T cell subtypes may differentially manifest migratory, regulatory and effector functions when triggered by endogenous misfolded and aggregated proteins and cell-specific stimuli. The final result is altered glial and neuronal behaviors that influence the disease course. Thus, discovery of neurodestructive and neuroprotective immune mechanisms will permit potential new therapeutic pathways that affect neuronal survival and slow disease progression.

A randomised clinical trial to evaluate the effects of Plantago ovata husk in Parkinson patients: changes in levodopa pharmacokinetics and biochemical parameters

Background

Plantago ovata husk therapy could be used in patients with Parkinson disease to reduce the symptoms of gastrointestinal disorders, but it is important to know whether this compound modifies levodopa pharmacokinetics. The maintenance of constant plasma concentrations of levodopa abolishes the clinical fluctuations in parkinsonian patients. The aim of this randomised clinical trial was to establish the influence of the fiber Plantago ovata husk in the pharmacokinetics of levodopa when administered to Parkinson patients well controlled by their oral medication.

Methods

To evaluate the effects of this fiber on several biochemical parameters. 18 volunteers participated in the study and received alternatively two treatments (Plantago ovata husk or placebo) with their usual levodopa/carbidopa oral dose. On days 0 (initial situation), 14 and 35 of the study, blood samples were taken to assess levodopa pharmacokinetics and to determine biochemical parameters.

Results

Levodopa C_max was very similar in the initial situation (603.2 ng/ml) and after placebo administration (612.0 ng/ml), being slightly lower (547.8 ng/ml) when Plantago ovata husk was given. AUC was very similar in the three groups: initial situation.- 62.87 μg.min/ml, fiber treatment.- 64.47 μg.min/ml and placebo treatment.- 65.10 μg.min/ml. Fiber reduced significantly the number of peaks observed in the levodopa concentrations, maintaining concentrations more stable. No significant differences were found in total cholesterol, LDL-cholesterol and triglycerides with the administration of Plantago ovata husk.

Conclusions

Plantago ovata husk administration caused a smoothing and homogenization of levodopa absorption, providing more stable concentrations and final higher levels, resulting in a great benefit for patients.

Trial registration

EudraCT2006-000491-33

Understanding and treating refractory constipation

Chronic constipation is a frequently encountered disorder in clinical practice. Most constipated patients benefit from standard medical approaches. However, current therapies may fail in a proportion of patients. These patients deserve better evaluation and thorough investigations before their labeling as refractory to treatment. Indeed, several cases of apparent refractoriness are actually due to misconceptions about constipation, poor basal evaluation (inability to recognize secondary causes of constipation, use of constipating drugs) or inadequate therapeutic regimens. After a careful re-evaluation that takes into account the above factors, a certain percentage of patients can be defined as being actually resistant to first-line medical treatments. These subjects should firstly undergo specific diagnostic examination to ascertain the subtype of constipation. The subsequent therapeutic approach should be then tailored according to their underlying dysfunction. Slow transit patients could benefit from a more robust medical treatment, based on stimulant laxatives (or their combination with osmotic laxatives, particularly over the short-term), enterokinetics (such as prucalopride) or secretagogues (such as lubiprostone or linaclotide). Patients complaining of obstructed defecation are less likely to show a response to medical treatment and might benefit from biofeedback, when available. When all medical treatments prove to be unsatisfactory, other approaches may be attempted in selected patients (sacral neuromodulation, local injection of botulinum toxin, anterograde continence enemas), although with largely unpredictable outcomes. A further although irreversible step is surgery (subtotal colectomy with ileorectal anastomosis or stapled transanal rectal resection), which may confer some benefit to a few patients with refractoriness to medical treatments.

Cellular and molecular basis of chronic constipation: Taking the functional/idiopathic label out

In recent years, the improvement of technology and the increase in knowledge have shifted several strongly held paradigms. This is particularly true in gastroenterology, and specifically in the field of the so-called “functional” or “idiopathic” disease, where conditions thought for decades to be based mainly on alterations of visceral perception or aberrant psychosomatic mechanisms have, in fact, be reconducted to an organic basis (or, at the very least, have shown one or more demonstrable abnormalities). This is particularly true, for instance, for irritable bowel syndrome, the prototype entity of “functional” gastrointestinal disorders, where low-grade inflammation of both mucosa and myenteric plexus has been repeatedly demonstrated. Thus, researchers have also investigated other functional/idiopathic gastrointestinal disorders, and found that some organic ground is present, such as abnormal neurotransmission and myenteric plexitis in esophageal achalasia and mucosal immune activation and mild eosinophilia in functional dyspepsia. Here we show evidence, based on our own and other authors’ work, that chronic constipation has several abnormalities reconductable to alterations in the enteric nervous system, abnormalities mainly characterized by a constant decrease of enteric glial cells and interstitial cells of Cajal (and, sometimes, of enteric neurons). Thus, we feel that (at least some forms of) chronic constipation should no more be considered as a functional/idiopathic gastrointestinal disorder, but instead as a true enteric neuropathic abnormality.

Autonomic dysfunction in Parkinson's disease

Growing recognition of the non-motor features of Parkinson's disease (PD) has led to increased awareness of autonomic dysfunction as part of the disease process, not only in advanced disease but also early in its course, sometimes even preceding the development of the classic motor features of PD. Virtually all aspects of autonomic function can become impaired in PD, including cardiovascular, gastrointestinal, urological, sexual and thermoregulatory function. Recognition of the various autonomic abnormalities of PD is important because effective treatment may be available and may measurably improve quality of life for individuals with PD.

A critical appraisal of lubiprostone in the treatment of chronic constipation in the elderly

Chronic constipation is a common disorder in the general population, with higher prevalence in the elderly, and is associated with worse quality of life and with greater health care utilization. Lubiprostone is an intestinal type-2 chloride channel activator that increases intestinal fluid secretion, small intestinal transit, and stool passage. Lubiprostone is currently approved by the US Food and Drug Administration for the treatment of chronic idiopathic constipation and of irritable bowel syndrome with predominant constipation. This review outlines current approaches and limitations in the treatment of chronic constipation in the elderly and discusses the results, limitations, and applicability of randomized, controlled trials of lubiprostone that have been conducted in the general and elderly population, with additional focus on the use of lubiprostone in constipation in Parkinson's disease and in opioid-induced constipation, two clinical entities that can be comorbid in elderly patients.

Anorectal manometric dysfunctions in newly diagnosed, early-stage Parkinson's disease

BACKGROUND AND PURPOSE

Anorectal dysmotility is common in advanced Parkinson's disease (PD), but there have been few evaluations in newly diagnosed PD patients.

METHODS

We conducted anorectal manometric evaluations in 19 newly diagnosed, drug-naïve, early-stage PD patients. All of the PD patients were questioned regarding the presence of anorectal symptoms.

RESULTS

Anorectal manometry was abnormal in 12 of the 19 patients. These abnormalities were more common in patients with more severe anorectal symptoms, as measured using a self-reported scale. However, more than 40% of patients with no or minimal symptoms also exhibited manometric abnormalities.

CONCLUSIONS

These results suggest that anorectal dysmotility manifests in many early-stage PD patients, which this represent evidence for the involvement of neuronal structures in such nonmotor manifestations in PD.

Bladder, bowel, and sexual dysfunction in Parkinson's disease

Bladder dysfunction (urinary urgency/frequency), bowel dysfunction (constipation), and sexual dysfunction (erectile dysfunction) (also called “pelvic organ” dysfunctions) are common nonmotor disorders in Parkinson's disease (PD). In contrast to motor disorders, pelvic organ autonomic dysfunctions are often nonresponsive to levodopa treatment. The brain pathology causing the bladder dysfunction (appearance of overactivity) involves an altered dopamine-basal ganglia circuit, which normally suppresses the micturition reflex. By contrast, peripheral myenteric pathology causing slowed colonic transit (loss of rectal contractions) and central pathology causing weak strain and paradoxical anal sphincter contraction on defecation (PSD, also called as anismus) are responsible for the bowel dysfunction. In addition, hypothalamic dysfunction is mostly responsible for the sexual dysfunction (decrease in libido and erection) in PD, via altered dopamine-oxytocin pathways, which normally promote libido and erection. The pathophysiology of the pelvic organ dysfunction in PD differs from that in multiple system atrophy; therefore, it might aid in differential diagnosis. Anticholinergic agents are used to treat bladder dysfunction in PD, although these drugs should be used with caution particularly in elderly patients who have cognitive decline. Dietary fibers, laxatives, and “prokinetic” drugs such as serotonergic agonists are used to treat bowel dysfunction in PD. Phosphodiesterase inhibitors are used to treat sexual dysfunction in PD. These treatments might be beneficial in maximizing the patients' quality of life.

Anorectal dysfunctions in Parkinson's disease

Anorectal symptoms are frequently found in patients with Parkinson's disease (PD), mainly manifested as diffuse lower abdominal discomfort, constipation, and fecal incontinence. Among these symptoms, constipation may precede by years the motor manifestations of PD. Research has focused for decades on selection of a measurement method for detection of abnormalities and support of clinometric instruments for anorectal symptoms. We review those manifestations and their contribution to evaluation of the anorectal symptoms in patients with PD.

Correlates of constipation in people with Parkinson's

PURPOSE

To investigate clinical, demographic and dietary factors associated with constipation in a sample of community dwelling people with Parkinson's disease, recruited through a specialist outpatient clinic. Partners/carers provided a convenience control group.

SCOPE

Participants completed a baseline questionnaire (background information, diet and exercise, activities of daily living: mobility and manual dexterity, health-related quality of life (SF-12), stool frequency and characteristics, extent of concern due to constipation, laxative taking), and a four-week stool diary. The Rome criterion was used to determine constipation status. Multiple regression methods were used to explore the correlates of constipation. Baseline data were provided by 121 people with Parkinson's, (54 controls), of whom 73% (25%) met the Rome criterion. Prospective diary data from 106 people with Parkinson's (43 controls) showed lower proportions: 35% (7%) meeting the Rome criterion. Among all study subjects, i.e. Parkinson's patients and controls taken together, the presence of constipation is predicted by having Parkinson's disease (p = .003; odds ratio 4.80, 95% CI 1.64-14.04) and mobility score (p = .04; odds ratio 1.15, 95% CI 1.01-1.31), but not by dietary factors. Amongst people with Parkinson's constipation is predicted by number of medications (p = .027). Laxative taking masks constipation, and is significantly associated with wearing protection against bowel incontinence (p = .009; odds ratio 4.80, 95% CI: 1.48-15.52).

CONCLUSIONS

Constipation is disease-related, not a lifestyle factor. More research is needed on optimal management and laxative use.

Gastrointestinal dysfunction in Parkinson's disease

In recent years, an increasingly detailed picture of gastrointestinal dysfunction in the setting of Parkinson's disease has emerged. Abnormalities of function may occur at virtually all levels of the gastrointestinal tract. Weight loss, dental deterioration, salivary excess, dysphagia, gastroparesis, decreased bowel movement frequency, and anorectal dysfunction all may occur. The pathophysiologic basis for this dysfunction entails both central and enteric nervous system involvement.

Behavioral phenotyping of mouse models of Parkinson's disease

Parkinson's disease (PD) is a common neurodegenerative movement disorder afflicting millions of people in the United States. The advent of transgenic technologies has contributed to the development of several new mouse models, many of which recapitulate some aspects of the disease; however, no model has been demonstrated to faithfully reproduce the full constellation of symptoms seen in human PD. This may be due in part to the narrow focus on the dopamine-mediated motor deficits. As current research continues to unmask PD as a multi-system disorder, animal models should similarly evolve to include the non-motor features of the disease. This requires that typically cited behavioral test batteries be expanded. The major non-motor symptoms observed in PD patients include hyposmia, sleep disturbances, gastrointestinal dysfunction, autonomic dysfunction, anxiety, depression, and cognitive decline. Mouse behavioral tests exist for all of these symptoms and while some models have begun to be reassessed for the prevalence of this broader behavioral phenotype, the majority has not. Moreover, all behavioral paradigms should be tested for their responsiveness to L-DOPA so these data can be compared to patient response and help elucidate which symptoms are likely not dopamine-mediated. Here, we suggest an extensive, yet feasible, battery of behavioral tests for mouse models of PD aimed to better assess both non-motor and motor deficits associated with the disease.