Gastric myoelectrical activity in patients with Parkinson's disease: evidence of a primary gastric abnormality

The substantia nigra modulates proximal colon tone and motility in a vagally-dependent manner in the rat

A monosynaptic pathway connects the substantia nigra pars compacta (SNpc) to neurons of the dorsal motor nucleus of the vagus (DMV). This monosynaptic pathway modulates the vagal control of gastric motility. It is not known, however, whether this nigro-vagal pathway also modulates the tone and motility of the proximal colon. In rats, microinjection of retrograde tracers in the proximal colon and of anterograde tracers in SNpc showed that bilaterally labelled colonic-projecting neurons in the DMV received inputs from SNpc neurons. Microinjections of the ionotropic glutamate receptor agonist, NMDA, in the SNpc increased proximal colonic motility and tone, as measured via a strain gauge aligned with the colonic circular smooth muscle; the motility increase was inhibited by acute subdiaphragmatic vagotomy. Upon transfection of SNpc with pAAV-hSyn-hM3D(Gq)-mCherry, chemogenetic activation of nigro-vagal nerve terminals by brainstem application of clozapine-N-oxide increased the firing rate of DMV neurons and proximal colon motility; both responses were abolished by brainstem pretreatment with the dopaminergic D1-like antagonist SCH23390. Chemogenetic inhibition of nigro-vagal nerve terminals following SNpc transfection with pAAV-hSyn-hM4D(Gi)-mCherry decreased the firing rate of DMV neurons and inhibited proximal colon motility. These data suggest that a nigro-vagal pathway modulates activity of the proximal colon motility tonically via a discrete dopaminergic synapse in a manner dependent on vagal efferent nerve activity. Impairment of this nigro-vagal pathway may contribute to the severely reduced colonic transit and prominent constipation observed in both patients and animal models of parkinsonism. KEY POINTS: Substantia nigra pars compacta (SNpc) neurons are connected to the dorsal motor nucleus of the vagus (DMV) neurons via a presumed direct pathway. Brainstem neurons in the lateral DMV innervate the proximal colon. Colonic-projecting DMV neurons receive inputs from neurons of the SNpc. The nigro-vagal pathway modulates tone and motility of the proximal colon via D1-like receptors in the DMV. The present study provides the mechanistic basis for explaining how SNpc alterations may lead to a high rate of constipation in patients with Parkinson's Disease.

Neurophysiology of Brain Networks Underlies Symptoms of Parkinson's Disease: A Basis for Diagnosis and Management

Parkinson's disease (PD) is one of the leading neurodegenerative disorders. It is considered a movement disorder, although it is accepted that many nonmotor symptoms accompany the classic motor symptoms. PD exhibits heterogeneous and overlaying clinical symptoms, and the overlap of motor and nonmotor symptoms complicates the clinical diagnosis and management. Loss of modulation secondary to the absence of dopamine due to degeneration of the substantia nigra compacta produces changes in firing rates and patterns, oscillatory activity, and higher interneuronal synchronization in the basal ganglia-thalamus-cortex and nigrovagal network involvement in motor and nonmotor symptoms. These neurophysiological changes can be monitored by electrophysiological assessment. The purpose of this review was to summarize the results of neurophysiological changes, especially in the network oscillation in the beta-band level associated with parkinsonism, and to discuss the use of these methods to optimize the diagnosis and management of PD.

Dynamic Monitoring of Probiotics Effect in Parkinson's Disease Patients via Swarm Decomposition and Bispectral Analysis of Electrogastrograms

People with Parkinson's Disease (PwP) experience a significant deterioration of their daily life quality due to non-motor symptoms, with gastrointestinal dysfunctions manifesting as a vanguard of the latter. Electrogastrography (EGG) is a noninvasive diagnostic tool that can potentially provide biomarkers for the monitoring of dynamic gastric alterations that are related to daily lifestyle and treatment regimens. In this work, a robust analysis of EGG dynamics is introduced to evaluate the effect of probiotic treatment on PwP. The proposed framework, namely biSEGG, introduces a Swarm Decomposition-based enhancement of the EGG, combined with Bispectral feature engineering to model the underlying Quadratic Phase Coupling interactions between the gastric activity oscillatory components of EGG. The biSEGG features are benchmarked against the conventional Power Spectrum-based ones and evaluated through machine learning classifiers. The experimental results, when biSEGG was applied on data epochs from 11 PwP (probiotic vs placebo, AUROC: 0.67, Sensitivity/Specificity: 75/58%), indicate the superiority of biSEGG over Power Spectrum-based approaches and justify the efficiency of biSEGG in capturing and explaining intervention- and meal consumption-related alterations of the gastric activity in PwP.Clinical relevance- biSEGG holds potential for dynamic monitoring of gastrointestinal dysfunction and health status of PwP across diverse daily life scenarios.

"Janus-Faced" α-Synuclein: Role in Parkinson's Disease

Parkinson's disease (PD) is a pathological condition characterized by the aggregation and the resultant presence of intraneuronal inclusions termed Lewy bodies (LBs) and Lewy neurites which are mainly composed of fibrillar α-synuclein (α-syn) protein. Pathogenic aggregation of α-syn is identified as the major cause of LBs deposition. Several mutations in α-syn showing varied aggregation kinetics in comparison to the wild type (WT) α-syn are reported in PD (A30P, E46K, H 50Q, G51D, A53E, and A53T). Also, the cell-to-cell spread of pathological α-syn plays a significant role in PD development. Interestingly, it has also been suggested that the pathology of PD may begin in the gastrointestinal tract and spread via the vagus nerve (VN) to brain proposing the gut-brain axis of α-syn pathology in PD. Despite multiple efforts, the behavior and functions of this protein in normal and pathological states (specifically in PD) is far from understood. Furthermore, the etiological factors responsible for triggering aggregation of this protein remain elusive. This review is an attempt to collate and present latest information on α-syn in relation to its structure, biochemistry and biophysics of aggregation in PD. Current advances in therapeutic efforts toward clearing the pathogenic α-syn via autophagy/lysosomal flux are also reviewed and reported.

Electrogastrography for diagnosis of early-stage Parkinson's disease

INTRODUCTION

Patients with Parkinson's disease (PD) often present with gastric symptoms. Electrogastrography (EGG) can noninvasively assess gastric electric activity and may be useful for early PD diagnosis. The present study aimed to compare the efficacy of EGG in early PD diagnosis with those of ¹²³I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy and odor stick identification test -Japanese version (OSIT-J).

METHODS

Thirty-seven untreated PD patients (mean age ± SD, 66 ± 8years; disease duration < 3 years) and 20 healthy control subjects (68 ± 6.9 years) were recruited. EGG and OSIT-J were performed in both groups, and MIBG scintigraphy in the PD group. EGG parameters were assessed in the preprandial and early and late postprandial segments using power spectrum analysis.

RESULTS

Irregular EGG waves were observed in PD patients. The preprandial instability coefficient of dominant frequency (ICDF), an index of EGG irregularity, in PD patients (9.5% [6.3%]) was higher than that in controls (3.9% [3.9%], p = 0.00005). The OSIT-J score was also lower in PD patients (4.6 [3.3]) than in controls (7.7 [3.3], p = 0.006). In receiver operating characteristics analyses, the areas under the curves of preprandial ICDF and OSIT-J were 0.83 and 0.72, respectively. The sensitivities of preprandial ICDF and MIBG (delayed-phase) scintigraphy were 73% and 70%, respectively.

CONCLUSIONS

Early and untreated PD patients showed irregular EGG waves and high ICDF. EGG showed better accuracy than the olfactory test for early PD diagnosis and similar sensitivity to MIBG scintigraphy.

Ingestion of subthreshold doses of environmental toxins induces ascending Parkinsonism in the rat

Increasing evidence suggests that environmental neurotoxicants or misfolded α-synuclein generated by such neurotoxicants are transported from the gastrointestinal tract to the central nervous system via the vagus nerve, triggering degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and causing Parkinson's disease (PD). We tested the hypothesis that gastric co-administration of subthreshold doses of lectins and paraquat can recreate the pathology and behavioral manifestations of PD in rats. A solution containing paraquat + lectin was administered daily for 7 days via gastric gavage, followed by testing for Parkinsonian behavior and gastric dysmotility. At the end of the experiment, brainstem and midbrain tissues were analyzed for the presence of misfolded α-synuclein and neuronal loss in the SNpc and in the dorsal motor nucleus of the vagus (DMV). Misfolded α-synuclein was found in DMV and SNpc neurons. A significant decrease in tyrosine hydroxylase positive dopaminergic neurons was noted in the SNpc, conversely there was no apparent loss of cholinergic neurons of the DMV. Nigrovagally-evoked gastric motility was impaired in treated rats prior to the onset of parkinsonism, the motor deficits of which were improved by l-dopa treatment. Vagotomy prevented the development of parkinsonian symptoms and constrained the appearance of misfolded α-synuclein to myenteric neurons. These data demonstrate that co-administration of subthreshold doses of paraquat and lectin induces progressive, l-dopa-responsive parkinsonism that is preceded by gastric dysmotility. This novel preclinical model of environmentally triggered PD provides functional support for Braak's staging hypothesis of idiopathic PD.

A Nigro-Vagal Pathway Controls Gastric Motility and Is Affected in a Rat Model of Parkinsonism

BACKGROUND & AIMS

In most patients with Parkinson's disease, gastrointestinal (GI) dysfunctions, such as gastroparesis and constipation, are prodromal to the cardinal motor symptoms of the disease. Sporadic Parkinson's disease has been proposed to develop after ingestion of neurotoxicants that affect the brain-gut axis via the vagus nerve, and then travel to higher centers, compromising the substantia nigra pars compacta (SNpc) and, later, the cerebral cortex. We aimed to identify the pathway that connects the brainstem vagal nuclei and the SNpc, and to determine whether this pathway is compromised in a rat model of Parkinsonism.

METHODS

To study this neural pathway in rats, we placed tracers in the dorsal vagal complex or SNpc; brainstem and midbrain were examined for tracer distribution and neuronal neurochemical phenotype. Rats were given injections of paraquat once weekly for 3 weeks to induce features of Parkinsonism, or vehicle (control). Gastric tone and motility were recorded after N-methyl-d-aspartate microinjection in the SNpc and/or optogenetic stimulation of nigro-vagal terminals in the dorsal vagal complex.

RESULTS

Stimulation of the SNpc increased gastric tone and motility via activation of dopamine 1 receptors in the dorsal vagal complex. In the paraquat-induced model of Parkinsonism, this nigro-vagal pathway was compromised during the early stages of motor deficit development.

CONCLUSIONS

We identified and characterized a nigro-vagal monosynaptic pathway in rats that controls gastric tone and motility. This pathway might be involved in the prodromal gastric dysmotility observed in patients with early-stage Parkinson's disease.

Association of Helicobacter pylori with Parkinson's Disease

Background and Purpose

Parkinson's disease (PD) is a major neurological disorder that requires lifelong treatment, and the combined presence of Helicobacter pylori (H. pylori) infection can increase the required anti-PD medications. We aim to investigate the effect of H. pylori infection in Indian PD patients.

Methods

We prospectively recruited 36 PD patients from December 2007 to January 2011. All patients underwent a detailed neurological evaluation and serological examination for H. pylori infection. Seropositive and seronegative patients were considered to be the cases and controls, respectively. All patients who were seropositive received triple therapy for 2 weeks. Outcome measures of the mean ‘off’ Unified Parkinson's Disease Rating Scale (UPDRS)-III score, mean ‘on’ UPDRS-III score, mean onset time, mean ‘on’ duration, and mean daily ‘on’ time were measured at baseline and at a 3-week follow-up.

Results

H. pylori-IgG positivity was present in 18 (50%) PD patients. The prevalence of men (72.2% vs. 33.3%), mean duration of disease (13.8 vs. 12.5) and mean levodopa equivalent daily dose (824 mg vs. 707 mg) were significantly higher among H. pylori positive patients than in controls (p<0.0001). Controls had a significantly longer ‘on’ duration and daily ‘on’ time, and better ‘on’ UPDRS-III scores. Seropositive patients took a significantly longer time to turn ‘on’ after a levodopa challenge. At the 3-week follow-up, H. pylori eradication significantly improved the mean ‘on’ UPDRS-III score, onset time, ‘on’ duration, and daily ‘on’ time.

Conclusions

H. pylori infection was present in 50% of Indian PD patients. H. pylori seropositivity was associated with a poor response to levodopa and increased medication usage, while eradication therapy was associated with better patient outcomes.

Gastric dysregulation induced by microinjection of 6-OHDA in the substantia nigra pars compacta of rats is determined by alterations in the brain-gut axis

Idiopathic Parkinson's disease (PD) is a late-onset, chronic, and progressive motor dysfunction attributable to loss of nigrostriatal dopamine neurons. Patients with PD experience significant gastrointestinal (GI) issues, including gastroparesis. We aimed to evaluate whether 6-hydroxy-dopamine (6-OHDA)-induced degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNpc) induces gastric dysmotility via dysfunctions of the brain-gut axis. 6-OHDA microinjection into the SNpc induced a >90% decrease in tyrosine hydroxylase-immunoreactivity (IR) on the injection site. The [13C]-octanoic acid breath test showed a delayed gastric emptying 4 wk after the 6-OHDA treatment. In control rats, microinjection of the indirect sympathomimetic, tyramine, in the dorsal vagal complex (DVC) decreased gastric tone and motility; this inhibition was prevented by the fourth ventricular application of either a combination of α1- and α2- or a combination of D1 and D2 receptor antagonists. Conversely, in 6-OHDA-treated rats, whereas DVC microinjection of tyramine had reduced effects on gastric tone or motility, DVC microinjection of thyrotropin-releasing hormone induced a similar increase in motility as in control rats. In 6-OHDA-treated rats, there was a decreased expression of choline acetyl transferase (ChAT)-IR and neuronal nitric oxide synthase (NOS)-IR in DVC neurons but an increase in dopamine-β-hydroxylase-IR in the A2 area. Within the myenteric plexus of the esophagus, stomach, and duodenum, there were no changes in the total number of neurons; however, the percentage of NOS-IR neurons increased, whereas that of ChAT-IR decreased. Our data suggest that the delayed gastric emptying in a 6-OHDA rat model of PD may be caused by neurochemical and neurophysiological alterations in the brain-gut axis.

Mice overexpressing wild-type human alpha-synuclein display alterations in colonic myenteric ganglia and defecation

BACKGROUND

Prevalent non-motor symptoms of Parkinson's disease (PD) include gastrointestinal motor impairments and advanced stage PD displays pathological aggregates of α-synuclein in colonic enteric neurons. We previously showed that 12 months old mice overexpressing human wild type (WT) α-synuclein under the Thy1 promoter (Thy1-aSyn) displayed colonic motor dysfunction. We investigated functional gut alterations at earlier ages and histological correlates.

METHODS

Defecation, gastric emptying (GE), and immunostaining for α-synuclein, peripheral choline acetyltransferase (pChAT), tyrosine hydroxylase (TH), neuronal nitric oxide synthase (nNOS), and vasoactive intestinal peptide (VIP) in distal colon myenteric plexuses were assessed in male Thy1-aSyn compared to littermate WT mice.

KEY RESULTS

Thy1-aSyn mice aged 2.5-3 or 7-8 months old had 81% and 55% reduction in fecal pellet output, respectively, in the first 15 min of exposure to a novel environment. The reduction remained significant in the older group for 2-h, and subsequent refeeding resulted also in a 60% and 69% reduction of defecation in the first hour, respectively. Thy1-aSyn mice (8-10 months) displayed increased α-synuclein in the myenteric plexuses with abundant varicose terminals surrounding pChAT-immunoreactive (ir) neurons, and only a few, nNOS-ir neurons. There were no conspicuous changes in pChAT- and nNOS-ir neurons, or TH- and VIP-ir nerve fibers. Thy1-aSyn mice aged 4-18 months had normal GE.

CONCLUSIONS & INFERENCES

The occurrence of over-production of pre-synaptic α-synuclein in colonic myenteric ganglia several months before the loss of striatal dopamine may provide an anatomical basis for interference with cholinergic neuronal activation, causing an early impairment in defecation to stimuli.

Is there a difference in gastric emptying between Parkinson's disease patients under long-term L-dopa therapy with and without motor fluctuations? An analysis using the 13C-acetate breath test

The mechanism underlying the motor fluctuations that develop after long-term L-dopa therapy is not fully known. It has been speculated that malabsorption of L-dopa from the small intestine occurs. It was reported that gastric retention in Parkinson's disease (PD) patients with motor fluctuations is increased as compared with that in PD without fluctuations. Because L-dopa therapy may worsen the symptoms of delayed gastric emptying (GE), it was not clear whether the delayed GE of PD patients with motor fluctuation was affected by L-dopa therapy. We assessed GE in PD patients with and without motor fluctuations. We investigated GE in 40 patients with PD under long-term L-dopa therapy, 20 fluctuators with "delayed-on" and "noon" phenomena, 20 nonfluctuators, and 20 healthy volunteers. GE was examined by the 13C-acetate breath test ((13)CABT) [the half emptying time (HET), the peak time of the (13)C-%-dose-excess curve (T(max))], with expirations collected for 4 h after a test meal and analyzed for (13)CO(2) using an infrared (IR) spectrophotometer. The T(max) of GE as assessed using the (13)C-ABT was significantly delayed in all PD patients as compared with controls (P = 0.002). The HET was significantly delayed in all PD patients as compared with controls (P < 0.001). The T(max) and HET were not significantly delayed in PD patients with motor fluctuations as compared with PD patients without motor fluctuations. These results demonstrated that GE is commonly delayed in PD patients with long-term L-dopa therapy. Delayed GE does not differ between PD patients with and without motor fluctuations. This finding demonstrated that the motor fluctuation in PD may not be influenced by GE.

Gastroparesis and Parkinson's disease: a systematic review

Some of the gastrointestinal (GI) symptoms commonly experienced by patients with Parkinson's disease (PD) have been attributed to gastroparesis; however, the precise prevalence and relevance of gastric emptying delay in PD is unclear. The definition of gastroparesis varies; currently the most widely accepted definition (from the National Institute of Diabetes and Digestive and Kidney Diseases Gastroparesis Clinical Research Consortium) is the presence of appropriate symptoms (including nausea, retching, vomiting, stomach fullness, and inability to finish a meal) for ≥ 12 weeks, together with delayed gastric emptying on scintigraphy and the absence of any obstructive lesions on upper GI endoscopy. In PD patients, gastroparesis has the potential to affect nutrition and quality of life, as well as the absorption of PD medications, including L-dopa. This reduced absorption of L-dopa has implications for the control of the PD motor symptoms for which it is administered. We performed a systematic review of the literature on gastroparesis in PD with the aim of developing an evidence-based approach to its management. Based on this review, we conclude that while gastric emptying has been reported to be frequently delayed in PD, the existing data do not permit definitive conclusions concerning its true prevalence, relationship to the underlying disease process, relevance to PD management, or the optimal therapy of related GI symptoms. Further study of these important issues is, therefore, required.

The clinical spectrum of levodopa-induced motor complications

After more than 40 years of clinical use, levodopa (LD) still remains the gold standard for symptomatic efficacy in Parkinson's disease (PD). However, long-term treatment with LD is often complicated by the development of various types of motor response oscillations as well as drug-induced dyskinesias. These treatment-related motor complications evolve in approximately one-third of patients after only 2 years of LD exposure and, once established, they are difficult to treat and significantly contribute to overall disability and disease burden. Although first described soon after the introduction of LD, the pathophysiology of motor complications is still not completely understood. In fact, it is most likely that non-physiological pulsatile stimulation of dopamine receptors, which is followed by various downstream alterations, plays a key role in the development of LD-induced motor response oscillations and dyskinesias. This review outlines the various types of motor complications and will also address underlying mechanisms, treatment options, as well as impact on clinical disability and quality of life (QoL).

Parkinson's disease: lesions in dorsal horn layer I, involvement of parasympathetic and sympathetic pre- and postganglionic neurons

Clinical signs frequently recognized in early phases of sporadic Parkinson's disease (PD) may include autonomic dysfunctions and the experience of pain. Early disease-related lesions that may account for these symptoms are presently unknown or incompletely known. In this study, immunocytochemistry for alpha-synuclein was used to investigate the first relay stations of the pain system as well as parasympathetic and sympathetic pre- and postganglionic nerve cells in the lower brainstem, spinal cord, and coeliac ganglion in 100 microm polyethylene glycol embedded sections from six autopsy individuals, whose brains were staged for PD-associated synucleinopathy. Immunoreactive inclusions were found for the first time in spinal cord lamina I neurons. Lower portions of the spinal cord downwards of the fourth thoracic segment appeared to be predominantly affected, whereas the spinal trigeminal nucleus was virtually intact. Additional involvement was seen in parasympathetic preganglionic projection neurons of the vagal nerve, in sympathetic preganglionic neurons of the spinal cord, and in postganglionic neurons of the coeliac ganglion. The known interconnectivities between all of these components offer a possible explanation for their particular vulnerability. Lamina I neurons (pain system) directly project upon sympathetic relay centers, and these, in turn, exert influence on the parasympathetic regulation of the enteric nervous system. This constellation indicates that physical contacts between vulnerable regions play a key role in the pathogenesis of PD.

Levodopa availability improves with progression of Parkinson’s disease

BACKGROUND

Previous pharmacokinetic trials with standard levodopa formulations showed a different behaviour of levodopa degradation in plasma of patients with Parkinson's disease (PD) in various stages.

OBJECTIVES

To investigate associations between levodopa plasma levels in relation to the scored intensity of PD.

SUBJECTS AND METHODS

We administered water soluble 100 mg levodopa and 25 mg benserazide to 50 PD patients, taken off medication for at least 12 hours, and assessed the levodopa plasma concentrations during an 180 minutes period under standardised conditions.

RESULTS

The computed area under the curve (AUC) values of levodopa plasma levels were significant higher in advanced PD patients. PD rating scores significantly correlated to the AUC outcomes and the maximum levodopa plasma concentration.

CONCLUSIONS

Levodopa availability improves with progression of PD. This may result from deteriorated peripheral activity of levodopa metabolising enzymes or an increasing enteric dysfunction with subsequent better duodenal levodopa absorption or both.

Electrogastrography in patients with Parkinson's disease

BACKGROUND

Impaired gastrointestinal motility in Parkinson's disease may affect absorption of levodopa and contribute to the disabling response fluctuations (RF). In this study gastric myoelectric activity was recorded with electrogastrography in patients with PD and correlated with the duration, severity and the presence of RF.

METHOD

Electrogastrography (EGG) was performed in 36 patients with PD of which 22 were men. The mean age was 67 years (48-81), mean duration of disease was 7.07 years (1-20), and mean duration of treatment with levodopa was 5.07 years (1-20). Gastric dysrhythmia was diagnosed when either preprandial or postprandial dysrhythmia for more than 30% of the recording period was detected.

RESULTS

The EGG was abnormal in 24 of 36 patients. Significant association was found between preprandial dysrhythmia and duration of disease (P=0.002); duration of levodopa treatment (P=0.003), severity of 86RF (P=0.001), but not with age (P=0.076). Out of 18 patients with RF, 17 had at least one pattern of dysrhythmia. In 11 out of the 18 patients without RF, the EGG was normal while the remaining seven had at least one pattern of dysrhythmia.

CONCLUSION

Abnormal EGG was quite common in this group of patients with PD, particularly in those with RF. The most common pattern of abnormality was preprandial dysrhythmia, which was positively associated with disease duration and length of levodopa treatment. Although frequently asymptomatic, preprandial dysrhythmia leading to impaired gastric emptying may contribute to irregular absorption of levodopa from the small intestine and contribute to disabling response fluctuations.

Electrogastrography: basic knowledge, recording, processing and its clinical applications

The slow wave (SW) of the gastrointestinal (GI) tract mainly functions to trigger the onset of spike to elicit smooth muscle contraction, which provides the essential power of motility. Smooth muscle myogenic control activity or SW is believed to originate in the interstitial cells of Cajal (ICC). The electrical coupling promotes interaction between muscle cells, and ICC additionally contribute to SW rhythmicity. Stomach SW originates in the proximal body showing the continuous rhythmic change in the membrane potential and propagates normally to the distal antrum with a regular rhythm of approximately 3 c.p.m. A technique using electrodes positioned on the abdominal skin to pick up stomach rhythmic SW refers to electrogastrography (EGG). The stomach SW amplitude is very weak, while many visceral organs also produce rhythmic electricities, for example heartbeat, respiration, other organs of the GI tract and even body movements. Thus noise other than SW should be filtered out during the recording, while motion artifacts are visually examined and deleted. Finally, the best signal among all recordings is selected to compute EGG parameters based on spectral analysis. The latter is done not only to tranform frequency domain to time domain but also to provide information of time variability in frequency. Obtained EGG parameters include dominant frequency/power, % normal rhythm, % bradygastria, % tachygastria, instability coefficient and power ratio. Clinical experience in EGG has been markedly accumulated since its rapid evolution. In contrast, lack of standardized methodology in terms of electrode positions, recording periods, test meals, analytic software and normal reference values makes the significance of EGG recording controversial. Unlike imaging or manometrical studies, stomach motility disorders are not diagnosed based only on abnormal EGG parameters. Limitations of EGG recording, processing, computation, acceptable normal parameters, technique and reading should be known to conduct subjective assessments when EGG is used to resolve stomach dysfunction. Understanding basic SW physiology, recording methodology and indications may open EGG as a new domain to approach the stomach motor dysfunction.

Impaired gastric emptying of a solid test meal in patients with Parkinson's disease using 13C-sodium octanoate breath test

Up to now gastric emptying in patients with Parkinson's disease was determined by radioscintigraphy. The 13C-sodium octanoate breath test (OBT) has been established for the non-invasive evaluation of gastric emptying with a solid test meal. The aim of the study was to evaluate the OBT in patients with Parkinson's disease and to investigate the prevalence of delayed gastric emptying for solids in PD and the relationship to clinical staging patterns. Twenty-two healthy subjects and 36 patients with different clinical stages of PD classified using Hoehn and Yahr (H&Y) and Unified Parkinson's Disease Rating Scale (UPDRS) were studied. Each fasting control and patient received a solid test meal (241 kcal) labelled with 100 mg of 13C-sodium octanoate. Breath samples were obtained before substrate administration and then in 15-min intervals over 4 h. The 13CO2/12CO2 ratio was determined in each breath sample as delta over baseline. Time to peak (t(peak)), gastric half emptying time (t1/2b), lag phase (t(lagb)) and gastric emptying coefficient (GEC) were calculated. Significant differences in t(peak), t1/2b, t(lagb) and GEC were found between patients and healthy volunteers (p<0.0001), with a 60% delay in gastric half emptying time in the patient group. Gastric half emptying time was different between clinical disease groups (H&Y 0-2 versus H&Y 2.5-5, p=0.001; UPDRS 0-30 versus UPDRS 61-92, p<0.05). The OBT detects a significant delay in gastric emptying of a solid test meal in patients with PD. Delayed gastric emptying for solids is associated with disease severity.

Gastrointestinal dysfunction in Parkinson's disease

There is growing recognition that gastrointestinal dysfunction is common in Parkinson's disease (PD). Virtually all parts of the gastrointestinal tract can be affected, in some cases early in the disease course. Weight loss is common but poorly understood in people with PD. Dysphagia can result from dysfunction at the mouth, pharynx, and oesophagus and may predispose individuals to aspiration (accidental inhalation of food or liquid). Gastroparesis can produce various symptoms in patients with PD and may cause erratic absorption of drugs given to treat the disorder. Bowel dysfunction can consist of both slowed colonic transit with consequent reduced bowel-movement frequency, and difficulty with the act of defecation itself with excessive straining and incomplete emptying. Recognition of these gastrointestinal complications can lead to earlier and potentially more effective therapeutic intervention.

Gastric myoelectrical activity and gut hormone secretion in myotonic dystrophy

BACKGROUND

Myotonic dystrophy (MD) is a systemic disease affecting striated, cardiac and smooth muscles, as well as nerve structures and endocrine glands. Patients with MD may suffer from slow gastric emptying.

OBJECTIVE

To study electrogastrograms (EGG) and postprandial gut hormone profiles in MD in order to evaluate whether disturbances in these regulatory mechanisms could explain, or contribute to, the delayed gastric emptying.

SUBJECTS

Ten patients with MD complaining of symptoms consistent with slow gastric emptying, and ten healthy matched controls.

METHODS

After an overnight fast, the patients and the control subjects were examined with standard EGG using surface electrodes before and during intake of a standard meal. Blood tests were drawn at regular time intervals for hormone analyses.

RESULTS

The EGG in MD showed a reduced amount of normal three cycles per minute activity compared with controls (P < 0.04). The dominant frequency in MD was less stable than in controls (P < 0.03), and the power of the signal showed less increase after a meal. The postprandial increase in plasma motilin (P < 0.05) and glucagon-like peptide-1 (GLP-1) (P < 0.001) was significantly less pronounced in MD compared with controls, whereas the plasma concentrations of cholecystokinin (CCK), neurotensin (NT), peptide YY (PYY) and somatostatin (SOM) did not differ significantly.

CONCLUSION

Disturbed electrophysiological control of the stomach and impaired secretion of gastrointestinal peptide hormones could contribute to slow gastric emptying in MD. Combined impairment of gastric pacing and gastrointestinal hormone responses was found in patients with the most prominent retardation of gastric emptying.

Gastric Dysmotility and Gastroparesis

Nutrition support in gastroparesis begins with encouraging smaller volume, low-fat, low-fiber meals and, if necessary, liquid caloric supplements. There should be a low threshold for placing a jejunal feeding tube either by laparoscopy or mini-laparotomy. Parenteral nutrition should be used only briefly during hospitalization and not encouraged or sustained as an outpatient. Metoclopramide is now the prokinetic of choice for patients who can tolerate this agent; subcutaneous administration is an important method that allows for continued guaranteed absorption. Low-dosage erythromycin also has a prokinetic role alone or in combination with metoclopramide. Domperidone, a centrally acting antiemetic and prokinetic, is only be available to US citizens who can access sources in Canada or Mexico. Antiemetics should be used extensively because nausea is a very severe debilitating symptom, which is under-appreciated and under-treated by physicians. We recommend scopolamine patches to gain maximal absorption, in spite of vomiting and unpredictable oral intakes. The 5-hydroxytryptamine-3 (5-HT3) antagonists ondansetron and granisetron are the most powerful agents. Relief bands using the P6 acupuncture point are useful adjunct. Special vigilance should be paid to situations that can undermine medical therapy or result in breakthrough symptoms, such as hyperglycemic events in patients with diabetes, migraine headaches, cyclic nausea and vomiting, menstrual cycles, rumination syndrome (psychogenic vomiting), and elevated herpes simplex titers. Most excitingly, the era of gastric electrical stimulation has arrived for patients not responding to standard medical therapy. The dramatic improvement in nausea and vomiting, as well as a sustained evidence of improved quality of life, gastric emptying, nutritional status, and decreased hospitalizations by this device are documented by long-term follow-up of more than a year for patients in this country and world-wide.

Gastroduodenal motility

Several major themes emerged over the past year in the area of gastroduodenal motility. Mostly, these themes represented extensions of research areas discussed in prior reviews in this series rather than the emergence of completely new concepts. Thus, for example, considerable emphasis has again been placed on regional gastric motor function in dyspepsia and on the role of fundic relaxation and accommodation, in particular. Not surprisingly, basic physiologic research has also shown a keen interest in the regulation of fundic relaxation. One new and exciting development is the recognition of the stomach's role in satiety. The spectrum of gastric motor dysfunction in diabetes mellitus continues to be explored, and the important role of hyperglycemia in regulating gastric function has been further emphasized. More data have been provided on noninvasive alternatives to gastric motor function testing, and several studies have looked at factors that may influence variability in these various tests. There have been few innovations over the past year in the therapeutic arena; rather, the indications and limitations of current therapies have been further developed.