Disorders of gastrointestinal motility in neurologic diseases

The Role of the Vagus Nerve in the Microbiome and Digestive System in Relation to Epilepsy

The Enteric Nervous System (ENS) is described as a division of the Peripheral Nervous System (PNS), located within the gut wall and it is formed by two main plexuses: the myenteric plexus (Auerbach's) and the submucosal plexus (Meissner's). The contribution of the ENS to the pathophysiology of various neurological diseases such as Parkinson's or Alzheimer's disease has been described in the literature, while some other studies have found a connection between epilepsy and the gastrointestinal tract. The above could be explained by cholinergic neurons and neurotransmission systems in the myenteric and submucosal plexuses, regulating the vagal excitability effect. It is also understandable, as the discharges arising in the amygdala are transmitted to the intestine through projections the dorsal motor nucleus of the vagus, giving rise to efferent fibers that stimulate the gastrointestinal tract and consequently the symptoms at this level. Therefore, this review's main objective is to argue in favor of the existing relationship of the ENS with the Central Nervous System (CNS) as a facilitator of epileptogenic or ictogenic mechanisms. The gut microbiota also participates in this interaction; however, it depends on many individual factors of each human being. The link between the ENS and the CNS is a poorly studied epileptogenic site with a big impact on one of the most prevalent neurological conditions such as epilepsy.

Diabetic Gastroparesis and its Emerging Therapeutic Options: A Narrative Review of the Literature

Diabetic gastroparesis (DG) is one of the many complications of diabetes mellitus (DM). Even though this condition surfaces years after uncontrolled disease, it affects the quality of life in several ways and causes significant morbidity. Common symptoms experienced by the patients include postprandial nausea, vomiting, abdominal fullness, and pain. Strict glycemic control is essential to evade the effects of DG. The purpose of this review article is to briefly study the pathophysiology, clinical features, diagnostic modalities, and the effects of DG on different aspects of life. Furthermore, it also focuses on the emerging treatment modalities for DG. Tradipitant and relamorelin are two such treatment options that are gaining noteworthy recognition and are discussed in detail in this review article. As observed through various clinical trials, these drugs help alleviate symptoms like nausea, vomiting, abdominal pain, and bloating in patients suffering from DG, thereby targeting the most common and bothersome symptoms of the disease. This leads to an improvement in the quality of life, making it a reliable treatment option for this disease. But while pharmacological intervention is vital, psychological support and lifestyle changes are equally important and are the reason why a multidisciplinary approach is required for the treatment of DG.

Dystrophin in the Neonatal and Adult Rat Intestine

Background: Gastrointestinal (GI) complaints are frequently noted in aging dystrophinopathy patients, yet their underlying molecular mechanisms are largely unknown. As dystrophin protein isoform 71 (Dp71) is particularly implicated in the development of smooth muscle cells, we evaluated its distribution in the neonatal and adult rat intestine in this study. Methods: Dp71 expression levels were assessed in the proximal (duodenum, jejunum and ileum) and distal (caecum, colon and rectum) intestine by Western blotting and qPCR. In addition, the cellular distribution of total Dp was evaluated in the duodenum and colon by immunohistochemical colocalization studies with alpha-smooth muscle actin (aSMA), Hu RNA binding proteins C and D (HuC/HuD) for neurons and vimentin (VIM) for interstitial cells. Results: In neonatal and adult rats, the distal intestine expressed 2.5 times more Dp71 protein than the proximal part (p < 0.01). This regional difference was not observed in Dp71 mRNA. During both stages, Dp-immunoreactivity was predominant in the muscularis propria, where it co-localized with aSMA and HuC/HuD. Conclusions: In neonatal and adult rats, Dp71 was expressed highest in the distal intestine. Together with the observation that Dp may be expressed by myenteric neurons, this warrants a paradigm shift in the treatment of GI comorbidities.

Intussusception Caused by Percutaneous Endoscopic Gastrostomy With Jejunal Extension in Patients With Severe Motor and Intellectual Disabilities

The risk of intussusception related to percutaneous endoscopic gastrostomy with jejunal extension (PEG-J) in patients with severe motor and intellectual disabilities (SMID) remains unknown. In a cross-sectional study, a review of 26 patients (mean age, 11.6 ± 6.4 years) with SMID who underwent PEG-J was performed. During the follow-up period, 6 of 26 (23%) patients developed intussusception. The median period from PEG-J to the onset of intussusception was 364 (range, 8-1344) days. No significant difference was observed in the Cobb angle between the intussusception and nonintussusception groups; however, body mass index at the time of PEG-J was significantly lower in the intussusception group. Intussusception related to PEG-J occurs relatively frequently in patients, and it is possibly attributable to factors such as deformity caused by undernutrition and weight loss. If enteral nutrition via PEG-J has been established, earlier enterostomy can be recommended because of the high risk of intussusception in patients with SMID.

Peripheral Neuronopathy Associated With Ebola Virus Infection in Rhesus Macaques: A Possible Cause of Neurological Signs and Symptoms in Human Ebola Patients

Neurological signs and symptoms are the most common complications of Ebola virus disease. However, the mechanisms underlying the neurologic manifestations in Ebola patients are not known. In this study, peripheral ganglia were collected from 12 rhesus macaques that succumbed to Ebola virus (EBOV) disease from 5 to 8 days post exposure. Ganglionitis, characterized by neuronal degeneration, necrosis, and mononuclear leukocyte infiltrates, was observed in the dorsal root, autonomic, and enteric ganglia. By immunohistochemistry, RNAscope in situ hybridization, transmission electron microscopy, and confocal microscopy, we confirmed that CD68+ macrophages are the target cells for EBOV in affected ganglia. Further, we demonstrated that EBOV can induce satellite cell and neuronal apoptosis and microglial activation in infected ganglia. Our results demonstrate that EBOV can infect peripheral ganglia and results in ganglionopathy in rhesus macaques, which may contribute to the neurological signs and symptoms observed in acute and convalescent Ebola virus disease in human patients.

Gastrointestinal motility disorders in neurologic disease

The extrinsic and autonomic nervous system intricately controls the major functions of the gastrointestinal tract through the enteric nervous system; these include motor, secretory, sensory, storage, and excretory functions. Disorders of the nervous system affecting gastrointestinal tract function manifest primarily as abnormalities in motor (rather than secretory) functions. Common gastrointestinal symptoms in neurologic disorders include sialorrhea, dysphagia, gastroparesis, intestinal pseudo-obstruction, constipation, diarrhea, and fecal incontinence. Diseases of the entire neural axis ranging from the cerebral hemispheres to the peripheral autonomic nerves can result in gastrointestinal motility disorders. The most common neurologic diseases affecting gastrointestinal function are stroke, parkinsonism, multiple sclerosis, and diabetic neuropathy. Diagnosis involves identification of the neurologic disease and its distribution, and documentation of segmental gut dysfunction, typically using noninvasive imaging, transit measurements, or intraluminal measurements of pressure activity and coordination of motility. Apart from treatment of the underlying neurologic disease, management focuses on restoration of normal hydration and nutrition and pharmacologic treatment of the gut neuromuscular disorder.

Esophageal and Gastric Motility Disorders in the Elderly

The elderly are particularly prone to developing upper gastrointestinal disturbances. Changes are due to the aging process, diabetes, cardiovascular risk factors, and neurologic issues. Medications used to treat these underlying conditions can cause gastrointestinal symptoms. Dysphagia is common and can be oropharyngeal and/or esophageal. Gastroparesis is due to either medications such opiates, or due to neurologic sequala of diabetes, cerebrovascular accidents, or neurologic diseases such as Parkinson's disease. Given limitations in many commonly used prokinetics with a wide range of side effect profiles including neurologic and cardiac, the focus of treatment should be on symptom management with dietary changes.

Basics of autonomic nervous system function

The autonomic nervous system has widespread innervation to nearly every organ system in the body. In order to understand the basics of autonomic function, knowledge of the neuroanatomy of the autonomic nervous system is necessary. Frequently considered to control the "fight or flight" and "rest and digest" functions, the autonomic nervous system has an intricate network of connections to finely tune the systemic response to nearly any situation. Although traditionally considered two discrete systems (sympathetic and parasympathetic), the enteric nervous system is now considered a third component of the autonomic nervous system. This chapter reviews the background of the neuroanatomical distribution of the autonomic nervous system in order to facilitate understanding the basics of autonomic function.

Clinical nutrition and gastrointestinal dysfunction in critically ill stroke patients

Background Data on the epidemiology and risk factors of altered gastrointestinal motility (AGIM) is virtually lacking for patients suffering from non-traumatic neurologic diseases and stroke. This study investigated whether patterns of AGIM differ between patients with stroke and other severe acute brain diseases. Methods Clinical records of stroke and non-stroke patients treated at a neurological intensive care unit (ICU) were reviewed at day 1-5 and at day 10 after admission. The data was analyzed for the course of enteral/parenteral nutrition and for and for signs and symptoms of gastrointestinal dysfunction. The study included data of 76 patients, 57 with stroke (stroke group, SG) and 19 with other neurological diseases (non-stroke group, NSG). Results Basic demographic as well as clinical baseline characteristics and alimentation regime were similar in both groups. At least one sign of AGIM was seen in 33/57 (58%) SG and in 15/19 (79%) NSG patients (P = 0.099). Regurgitation was significantly more frequent among patients from the NSG (P < 0.05). Subjects from the NSG also spent a higher proportion of time with at least one symptom of AGIM present (P < 0.05). Conclusions For the first time, this study investigated the prevalence of AGIM in patients suffering from severe stroke. The prevalence of disturbed gastrointestinal function was found to be high in stroke patients, but was lower than in a group of non-stroke patients with similar general disease severity and baseline characteristics.

Autonomic nervous system dysregulation in irritable bowel syndrome

BACKGROUND

Autonomic nervous system (ANS) regulation may be altered in functional diseases, including irritable bowel syndrome (IBS), but published data are not clear to date. The aim of the study was to analyze ANS function in IBS subjects classified by Rome III criteria and healthy controls using standardized technique.

METHODS

ANS activity was evaluated by autoregressive spectral analysis of RR interval and systolic arterial pressure variabilities, to obtain indices of sympatho-vagal modulation of the heart and of spontaneous cardiac baroreflex (α index). A symptom list was used to score 18 somatic complaints (score 0-180) (4SQ). Fatigue and stress were assessed through the use of a global scoring index (0-10).

KEY RESULTS

We enrolled 41 IBS subjects (29 F, age 40 ± 2 years) and 42 healthy matched controls. Heart rate was higher in IBS than control subjects (69 ± 2 vs 61 ± 1; p < 0.001). The total variance of RR interval variability, and α index, were significantly lower in IBS compared to controls (1983.12 ± 384.64 ms(2) vs 4184.55 ± 649.59 ms(2) ; 18.1 ± 2 ms/mmHg vs 29 ± 3 ms/mmHg; p < 0.01). The α index results showed an inverse correlation with stress scores and somatic symptoms.

CONCLUSIONS & INFERENCES

IBS subjects display a significant reduction in α index, an established marker of cardiac baroreflex. ANS dysfunction appears to be involved in the pathophysiology of IBS and its assessment may open new perspectives for clinical management of patients suffering from IBS.

A wireless capsule system with ASIC for monitoring the physiological signals of the human gastrointestinal tract

This paper presents the design of a wireless capsule system for monitoring the physiological signals of the human gastrointestinal (GI) tract. The primary components of the system include a wireless capsule, a portable data recorder, and a workstation. Temperature, pH, and pressure sensors; an RF transceiver; a controlling and processing application specific integrated circuit (ASIC); and batteries were applied in a wireless capsule. Decreasing capsule size, improving sensor precision, and reducing power needs were the primary challenges; these were resolved by employing micro sensors, optimized architecture, and an ASIC design that include power management, clock management, a programmable gain amplifier (PGA), an A/D converter (ADC), and a serial peripheral interface (SPI) communication unit. The ASIC has been fabricated in 0.18- μm CMOS technology with a die area of 5.0 mm × 5.0 mm. The wireless capsule integrating the ASIC controller measures Φ 11 mm × 26 mm. A data recorder and a workstation were developed, and 20 cases of human experiments were conducted in hospitals. Preprocessing in the workstation can significantly improve the quality of the data, and 76 original features were determined by mathematical statistics. Based on the 13 optimal features achieved in the evaluation of the features, the clustering algorithm can identify the patients who lack GI motility with a recognition rate reaching 83.3%.

Nicotine enhances inhibition of mouse vagal motor neurons by modulating excitability of premotor GABAergic neurons in the nucleus tractus solitarii

The caudal nucleus of the solitary tract (NTS) serves as the site of the first synapse for visceral sensory inputs to the central nervous system. The NTS sends functional projections to multiple brain nuclei, with gastric-related projections primarily targeting the dorsal motor nucleus of the vagus (DMV). Previous studies have demonstrated that the majority of caudal NTS neurons that project to the DMV respond robustly to nicotine and express nicotinic acetylcholine receptors (nAChRs). However, the cytochemical identity and relationship with specific viscera of DMV-projecting, nicotine-responsive caudal NTS neurons have not been determined. The present study used transgenic mice that express enhanced green fluorescent protein (EGFP) under a GAD67 promoter in a subset of GABAergic neurons, in vivo retrograde pseudorabies viral labeling to identify gastric-related vagal complex neurons, and patch-clamp electrophysiology in acute brain stem slices to test the hypothesis that gastric-related and GABAergic inhibitory synaptic input to the DMV from the caudal NTS is under a robust modulatory control by nAChRs. Our results suggest that activation of nAChRs in the caudal NTS, but not DMV, potentiates GABAergic, but not glutamatergic, input to the DMV. Gastric-related caudal NTS and DMV neurons are directly involved in this nicotine-sensitive circuitry. Understanding the central patterns of nicotinic modulation of visceral sensory-motor circuitry may help develop therapeutic interventions to restore autonomic homeostasis in patients with autonomic impairments.

Responsiveness to nicotine of neurons of the caudal nucleus of the solitary tract correlates with the neuronal projection target

The caudal nucleus of the solitary tract (NTS) is the key integrating center of visceral sensory-motor signaling supporting autonomic homeostasis. Two key projections of this nucleus are the parabrachial nucleus (PbN) and the dorsal motor nucleus of the vagus (DMV). The PbN integrates and relays viscerosensory information primarily to the forebrain, supporting behavioral, emotional, and endocrine responses to visceral events, while the DMV contains parasympathetic preganglionic cholinergic motoneurons that support primarily gastrointestinal reflexes. Subsets of caudal NTS neurons express presynaptic and somatodendritic nicotinic acetylcholine receptors (nAChRs). However, the anatomical identification of nicotine-responsive caudal NTS neurons has not been determined. This study used in vivo and ex vivo fluorescent tracing and slice patch-clamp electrophysiological recordings from anatomically identified caudal NTS neurons to test the hypothesis that the responsiveness of these cells to nicotine correlates with the target of their axonal projections. The results demonstrate that the majority of glutamatergic terminals that synapse on PbN-projecting caudal NTS neurons are unaffected by nicotine. Moreover, only a fraction of these cells express somatodendritic nAChRs. In contrast, the majority of DMV-projecting caudal NTS neurons exhibit robust presynaptic and somatodendritic responsiveness to nicotine. However, PbN-projecting neurons also exhibit significantly lower background frequencies of glutamatergic miniature postsynaptic currents than DMV-projecting neurons. Therefore, presynaptic unresponsiveness to nicotine may result from deficient glutamatergic innervation of PbN-projecting neurons. Nevertheless, the caudal NTS contains function-specific subsets of cells with target-specific responsiveness to nicotine. These results may support development of therapeutic strategies for selective targeting of specific autonomic pathways and impaired autonomic homeostasis.

Autonomic function at rest and in response to emotional and rectal stimuli in women with irritable bowel syndrome

Our aim was to study autonomic function in patients with Irritable bowel syndrome (IBS) without constipation and psychiatric comorbidity. Respiratory sinus arrhythmia (RSA) (representing cardiac vagal activity), skin conductance (representing sympathetic activity) and heart rate were measured at baseline and as a response to emotional stress and rectal discomfort in 33 women with IBS and 21 healthy women. Baseline heart rate was higher in the patients than in the healthy volunteers. Both groups had decreased RSA and increased heart rate and skin conductance level when exposed to emotional stress, but the autonomic responses did not differ significantly between the groups. At discomfort threshold the patients had increased heart rate response and skin conductance amplitude when compared to the healthy volunteers. Correlations between autonomic responses and the depression subscale of the Hospital Anxiety and Depression (HAD) score differed markedly between the diarrhea-predominant IBS patients and the IBS patients with alternating stool habits.

Gastrointestinal symptoms related to autonomic dysfunction following spinal cord injury

The impact of spinal cord injury on an individual's gastrointestinal tract function is often poorly understood by the general public and also by those involved with persons with spinal cord injury. This chapter reviews the anatomy, physiology and function of the gastrointestinal tract, with particular emphasis on neurological control mechanisms. In turn, it relates the effect that spinal cord injury has on the neurological control of the gastrointestinal tract. The symptoms that are encountered by patients in the acute phase following injury, and by individuals in the months/years after injury, with particular reference to the effect of altered autonomic nervous system control of the gastrointestinal tract, are discussed. Together with a following summary of current bowel management regimens and techniques, this chapter aims to provide an overall view of the effect that autonomic dysfunction due to spinal cord injury has on gastrointestinal function.

Thymoma-associated neuromyotonia with antibodies against voltage-gated potassium channels presenting as chronic intestinal pseudo-obstruction

Chronic intestinal pseudo-obstruction can occur as a paraneoplastic disorder, and several cases have been reported in association with thymoma or small-cell lung cancer. Autoantibodies against voltage-gated potassium channels (VGKCs) are found in acquired neuromyotonia (Isaac's syndrome), and have been reported in one case of slow transit constipation without apparent neurological disease. We describe a patient with VGKC antibodies, acquired neuromyotonia and thymoma, who first presented with a severe slow-transit constipation and in whom the gastrointestinal symptoms responded well to plasmapheresis. We suggest that VGKC antibodies might be helpful in patients with possible paraneoplastic chronic intestinal pseudo-obstruction, and a positive result should stimulate the search for a thymoma or other tumour and raise the possibility of immunotherapy.

A non-invasive method for gastrointestinal parameter monitoring

AIM: To propose a new, non-invasive method for monitoring 24-h pressure, temperature and pH value in gastrointestinal tract.

METHODS: The authors developed a miniature, multi-functional gastrointestinal monitoring system, which comprises a set of indigestible biotelemetry capsules and a data recorder. The capsule, after ingested by patients, could measure pressure, temperature and pH value in the gastrointestinal tract and transmit the data to the data recorder outside the body through a 434 MHz radio frequency data link. After the capsule passed out from the body, the data saved in the recorder were downloaded to a workstation via a special software for further analysis and comparison.

RESULTS: Clinical experiments showed that the biotelemetry capsules could be swallowed by volunteers without any difficulties. The data recorder could receive the radio frequency signals transmitted by the biotelemetry in the body. The biotelemetry capsule could pass out from the body without difficulties. No discomfort was reported by any volunteer during the experiment. In vivo pressure and temperature data were acquired.

CONCLUSION: A non-invasive method for monitoring 24-h gastrointestinal parameters was proposed and tested by the authors. The feasibility and functionality of this method are verified by laboratory tests and clinical experiments.

Diagnosis and treatment of neuromuscular disorders of the stomach

Gastric neuromuscular disorders encompass a spectrum of dysfunction in nerve and smooth muscle that includes gastric visceral hypersensitivity, gastric dysrhythmias, fundic dysfunction, antral hypomotility, and gastroparesis. Patients with each disorder may present with such vague dyspepsia symptoms as early satiety, upper abdominal discomfort, bloating, or nausea with or without vomiting. A careful history and physical examination may suggest a gastric neuromuscular disorder, but symptoms are nonspecific. Gastroparesis is the most severe form of neuromuscular dysfunction. Such reversible causes of gastroparesis as mechanical obstruction of the stomach and chronic mesenteric ischemia must be excluded. Gastroparesis, gastric dysrhythmias, and hypersensitivity may follow viral infection or be due to degenerative processes that affect the gastric enteric neurons, smooth muscle, or interstitial cells of Cajal. Commonly, the cause of these gastric neuromuscular disorders is unknown. An approach to the diagnosis and treatment of gastric neuromuscular disorders is reviewed, including dietary counseling, drugs, and medical devices.

Motility disorders of the small intestine: new insights into old problems

Motility of the gastrointestinal tract is responsible for the orderly movement of food, in an oral-to-aboral direction, and allows for the digestion and absorption of nutrients and water, and the elimination of indigestible material. This complex series of events results from the integrated activity of enteric nerves, extrinsic nerves, the intrinsic properties of smooth muscle, and gastrointestinal hormones. Abnormalities in any of these components or in their integration can result in dysmotility: increased transit, decreased transit, or nonpropulsive activity. This review outlines the current understanding of the causes, pathophysiology, diagnostic evaluation, and treatment of motility disorders of the small intestine.

Inhibitory effects of NPY on ganglionic transmission in myenteric neurones of the guinea-pig descending colon

Intracellular recordings were made from myenteric neurones of the guinea-pig descending colon. Neuropeptide Y (NPY) and related pancreatic polypeptides were applied by superfusion and the effects upon the amplitude of fast excitatory synaptic potentials (ESPs) and the ratio of paired fast ESPs evoked by stimulation of internodal fibre tracts were noted. NPY produced a concentration-dependent inhibition in fast ESP amplitude in the majority of neurones (17/21) with a calculated IC50 value of 7 nM; in some neurones this inhibition was mediated via the local release of noradrenaline. Peptide YY (PYY) (eight out of 11 neurones; IC50 = 1 nM), NPY(3-36) (three out of three neurones) and [Leu31, Pro34]NPY (four out of five neurones) also decreased the amplitude of fast ESPs. The effects of two or more pancreatic polypeptides or analogues on fast synaptic transmission were compared directly in six neurones; the apparent relative potency of agonists suggested the involvement of Y2-receptors and at least one other Y-receptor type. In the absence of any direct postsynaptic effects of pancreatic polypeptides on the active or passive properties of myenteric neurones, or on their sensitivity to ionophoretically applied acetylcholine, inhibition of fast ganglionic transmission was presumed to be presynaptic in origin. It is concluded that, in addition to their previously described depressant actions on neuro-effector transmission to colonic smooth muscle, pancreatic polypeptides can exert powerful inhibitory effects on myenteric neurones of the descending colon.

Myasthenia gravis, thymoma, intestinal pseudo-obstruction, and neuronal nicotinic acetylcholine receptor antibody

Intestinal pseudo-obstruction occurs rarely in patients with myasthenia gravis (MG) and thymoma. The etiology of the intestinal pseudo-obstruction remains to be elucidated, although an autoimmune mechanism is postulated. We present the first report of neuronal nicotinic acetylcholine receptor (AChR)-specific antibody in a patient with seropositive MG, malignant thymoma, and intestinal pseudo-obstruction. This finding provides evidence that intestinal pseudo-obstruction associated with thymoma and possibly other neoplasms may be related to antibodies against the neuronal nicotinic receptors at autonomic ganglia.

Gastrointestinal manifestations in children with cerebral palsy

We describe the prevalence and nature of gastrointestinal (GI) symptoms in 58 children affected by cerebral palsy (range: from 6 months to 12 years of age) referred to a pediatric neurology outpatient clinic. In each patient we assessed (GI) symptoms and defined the associated GI functional or structural abnormalities. Furthermore, we tried to correlate the type of GI dysfunction with findings on computed tomography (CT) or magnetic resonance imaging (MRI) of the brain. Our results showed that 92% of children with cerebral palsy had clinically significant gastrointestinal symptoms. Swallowing disorders were present in 60% of patients, regurgitation and/or vomiting in 32%, abdominal pain in 32%, episodes of chronic pulmonary aspiration in 41% and chronic constipation in 74%. Dysfunction of the oral and/or pharyngeal phase of swallowing was found in 28 of 30 (93%) patients with swallowing disorders. Of the 45 patients with symptoms suggesting gastroesophageal reflux, 41 (91%) had an abnormal pH-monitoring and/or esophagitis. Furthermore, a significant delay in the scintigraphic gastric emptying of liquids was found in 12 of 18 patients (67%) and an abnormal esophageal motility in 11 of the 18 (61%) investigated patients. In 25 patients with chronic constipation evaluation of colonic transit showed a delay at level of the proximal segments of the colon in 13 (52%), at level of the left colon and rectum in 9 (36%) and in 3 (12%) at level of the rectum only. Computed tomography and/or magnetic resonance imaging were normal in 5 (9%) and abnormal in 53 (91%) of the 58 children with cerebral palsy. No GI symptom was significantly associated with any kind of abnormal neuroimaging. In conclusion, children with cerebral palsy exhibited diffuse GI clinical manifestations, mostly due to disorders of GI motility. The GI symptoms seemed not to be related to any specific finding on CT or MRI of the brain.

Chronic Intestinal Pseudo-obstruction

For many patients, nutritional support and relief of symptoms remain the primary management goal of pseudo-obstruction. Specific pharmacological agents for this disorder are, in general, lacking. Given that the efficacy of many of the individual available agents is far from excellent, several centers have turned to combination therapy. Though there is at present no evidence from controlled studies to support this strategy, it is, at the very least, theoretically attractive as these agents act through a number of separate mechanisms. The combination of a prokinetic and an emetic may prove especially useful. As the pseudo-obstruction syndromes are, individually, rare, and experience with any given prokinetic agent in these disorders limited, it is difficult to develop strict guidelines for their use in this context. It stands to reason that a response to a prokinetic agent would seem unlikely in a patient with an advanced myopathic process; anecdotal evidence suggests, however, that some patients with severe scleroderma may derive some symptomatic improvement. Where oral therapy is tolerated, cisapride would appear the best choice among available agents. When this fails, subcutaneous octreotide may be added or substituted. In the acute situation, intravenous erythromycin may alleviate gastroparesis, but probably exerts little beneficial effect beyond the pylorus; parenteral metoclopramide may be tried, but, here again, convincing evidence of efficacy is lacking. The roles of endoscopy and surgery are largely confined to facilitating nutrition and providing decompression.

Autonomic dysfunction and the gastrointestinal tract

Autonomic neuropathy of the gastrointestinal tract may represent a primary disorder, but much more often it is secondary due to systemic disorders like diabetes mellitus. This review gives an overview about the common clinical manifestations and the principles and limitations in diagnostic work-up of autonomic dysfunction of the gastrointestinal tract. Diagnostic evaluation usually includes a combination of screening tests for autonomic neuropathy and specialized diagnostic procedures for the detection of sequela of autonomic neuropathy in gastrointestinal motility.

Intestinal pseudo-obstruction

Pseudo-obstruction syndromes are increasingly recognized in clinical practice. They result from impairment of intrinsic neuromuscular or extrinsic control of gut motility. Typically, pseudo-obstruction syndromes result in features suggestive of mechanical obstruction and bowel dilatation in the absence of any demonstrable obstruction or mucosal disease. The syndrome may affect any region of the gut. Less severe variants without bowel dilatation are diagnosed by measurement of gastrointestinal transit and pressure profiles. The aims of treatment are restoration of nutrition and hydration, symptom relief, normalization of intestinal propulsion with prokinetics, and suppression of bacterial overgrowth. Surgery plays a limited role, adjunctive to medical treatment, facilitating enteral nutrition and decompression by means of jejunostomy. Infrequently, resection of localized disease or intestinal transplantation are indicated. The roles of intestinal pacemakers (interstitial cells of Cajal) and genetic mutations in the etiology of pseudo-obstruction, as well as the cost-benefit ratio of transplantation for pseudo-obstruction, will be clarified in the future.

Spectral analysis of heart rate variability in patients with irritable bowel syndrome

BACKGROUND

Autonomic dysfunction, both adrenergic and cholinergic, has been associated with the irritable bowel syndrome (IBS). The accuracy of the methods in use, however, has been limited by the need for active co-operation by the patients, with consequent difficulties in standardization. The aim of this study was to investigate the function of the autonomic nervous system in patients with IBS by using spectral analysis of the heart rate variability, an accurate method depending very little on patient cooperation.

METHODS

Eighteen patients with IBS were compared with 36 sex- and age-matched controls. Spectral analysis of heart rate variability was performed to quantify sympathetic and parasympathetic nerve activity.

RESULTS

The patients with IBS had significantly higher sympathetic activity than controls (P = 0.005). There was no significant (P = 0.308) increase in parasympathetic activity. There were no significant differences in heart rate or blood pressure between the patients and controls.

CONCLUSION

Spectral analysis of heart rate variability has been used to assess the function of the autonomic nervous system in patients with IBS. IBS patients have significantly increased symphathetic activity, whereas parasympathetic activity does not differ from that of controls.

Effect of perturbations and a meal on superior mesenteric artery flow in patients with orthostatic hypotension

Our aims were to evaluate to role of superior mesenteric blood flow in the pathophysiology of orthostatic hypotension in patients with generalized autonomic failure.

METHODS

Twelve patients with symptomatic neurogenic orthostatic hypotension and 12 healthy controls underwent superior mesenteric artery flow measurements using Doppler ultrasonography during head-up tilt and tilt plus meal ingestion. Autonomic failure was assessed using standard tests of the function of the sympathetic adrenergic, cardiovagal and postganglionic sympathetic sudomotor function.

RESULTS

Superior mesenteric flow volume and time-averaged velocity were similar in patients and controls at supine rest; however, responses to cold pressor test and upright tilt were attenuated (p < 0.05) in patients compared to controls. Head-up tilt after the meal evoked a profound fall of blood pressure and mesenteric blood flow in the patients; the reduction of mesenteric blood flow correlated (r = 0.89) with the fall of blood pressure in these patients, providing another manifestation of failed baroreflexes. We make the novel finding that the severity of postprandial orthostatic hypotension regressed negatively with the postprandial increase in mesenteric flow in patients with orthostatic hypotension.

CONCLUSION

Mesenteric flow is under baroreflex control, which when defective, results in, or worsens orthostatic hypotension. Its large size and baroreflexivity renders it quantitatively important in the maintenance of postural normotension. The effects of orthostatic stress can be significantly attenuated by reducing the splanchnic-mesenteric volume increase in response to food. Evaluation of mesenteric flow in response to eating and head-up tilt provide important information on intra-abdominal sympathetic adrenergic function, and the ability of the patient to cope with orthostatic stress.

AAEM minimonograph #48: autonomic nervous system testing

The autonomic nervous system maintains internal homeostasis by regulating cardiovascular, thermoregulatory, gastrointestinal, genitourinary, exocrine, and pupillary function. Testing and quantifying autonomic nervous system function is an important but difficult area of clinical neurophysiology. Tests of parasympathetic cardiovagal regulation include heart rate analysis during standing (the 30:15 ratio), heart rate variation with deep breathing, and the Valsalva ratio. Tests of sympathetic adrenergic vascular regulation include blood pressure analysis while standing, the Valsalva maneuver, sustained handgrip, mental stress, and cold water immersion. Tests of sympathetic cholinergic sudomotor function include the sympathetic skin response, quantitative sudomotor axon reflex test, sweat box testing, and quantification of sweat imprints. Pupil function is tested pharmacologically and with pupiilographic techniques. Tests of gastrointestinal and genitourinary function do not satisfactorily isolate autonomic regulation from their other functions. The available tests have various sensitivities and ease of administration. They are typically administered in a battery of multiple tests, which improves sensitivity and reliability, and allows probing of various autonomic functions.

Recurrence of acute colonic pseudo-obstruction in selective adrenergic dysautonomia associated with infectious toxoplasmosis

BACKGROUND

Acute colonic pseudo-obstruction is a life-threatening condition associated with several pathologic conditions, whose pathophysiology is still uncertain.

CASE

Autonomic function in a young patient operated on for acute colonic pseudo-obstruction was carefully evaluated; none of the common clinical conditions described in the literature was found to have caused the syndrome. Selective adrenergic failure was suggested by the presence of severe orthostatic hypotension, low basal plasma catecholamine level, and absence of the expected increase on standing and by the findings of provocation tests, cardiovascular tests, and acetylcholine sweat spot test. Biopsy specimens from the colon and small-bowel wall did not show any morphologic or immunohistochemical alteration either in muscle layers or in the autonomic plexus, testifying to the possible occurrence of extrinsic denervation in the presence of an intact plexus. Infectious toxoplasmosis was proved through indirect and direct hemagglutination assays, enzyme-linked immunosorbent assay IgG, IgM, and IgA, immunosorbent agglutination IgM assay, and the protozoa were demonstrated in a biopsy specimen from the rectus abdominis muscle.

CONCLUSIONS

Selective adrenergic denervation of the gut resulted in recurrent episodes of colonic pseudo-obstruction, probably by direct toxicity or a cross-reaction between the immune process and a toxoplasmic antigen, stressing the importance of sympathetic inhibitory modulation on colon motor activity.

Gastric and small intestinal motility in health and disease

Although symptoms possibly related to motor dysfunction appear to be common, primary disorders of the foregut motor apparatus, defined on the basis of a discrete myoneural pathology, are notably rare. This phenomenon may as much reflect the relatively primitive nature of diagnostic methods as the true rarity of such disorders. Although diagnostic methodologies increase in sophistication and availability, their clinical impact has been limited by an imperfect relationship between symptoms and dysfunction and by a relatively poor ability of such tests to predict response to available therapeutic strategies. An ever-increasing understanding of the complex, often interrelated motor and sensory phenomena that contribute to symptoms, together with the development of consensus on the use and interpretation of motility tests and the more widespread application of sophisticated histologic, immunologic, biochemical, and molecular biologic methodologies to the study of these disorders, should lead, in the years to come, to much needed progress in this area.

Reduced accuracy of 14C-D-xylose breath test for detecting bacterial overgrowth in gastrointestinal motility disorders

The accuracy of the 14C-D-xylose breath test in the diagnosis of small-bowel bacterial overgrowth was prospectively evaluated in 10 patients with motility disorders: 6 myopathic, 3 neuropathic, and 1 mechanical obstruction. Six of the 10 patients had small-bowel bacterial overgrowth (> or = 10(5) colony-forming units/ml) on culture of small-bowel aspirate. Increased breath 14CO2 levels were documented in three of six patients with positive cultures and in two of four with negative cultures. Two patients with positive results by both methods and one of two patients with positive breath 14CO2 but negative cultures had previously undergone gastric surgery. Three patients with myopathic dysmotility had positive cultures but negative breath tests. Cultures of duodenal aspirates and the D-xylose test had sensitivities of 80% and 40%, respectively, for the finding of hypoalbuminemia. Compared with cultures, the sensitivity and specificity of the breath test were 60% and 40%, respectively. Impaired delivery of 14C-D-xylose for bacterial metabolism may result from postprandial antral hypomotility (n = 4) or low-amplitude (n = 6) small-bowel motility, contributing to the false-negative breath tests. Thus, culture is the optimal method to detect small-bowel bacterial overgrowth in patients with motility disorders.

Chronic diarrhea in diabetes mellitus: mechanisms and an approach to diagnosis and treatment

In this study, our aim was to develop a practical strategy to facilitate the management of patients with diabetes mellitus and chronic diarrhea in a tertiary referral practice. We reviewed the pertinent English-language literature of the past 30 years that described the pathophysiologic mechanisms and treatment of patients with diabetic diarrhea and retrospectively reviewed the medical records of all patients with diabetic diarrhea examined at the Mayo Clinic during 1990. Three typical case studies are described to illustrate the diverse mechanisms that lead to chronic diarrhea in patients with diabetes. No report in the literature has systematically evaluated all the putative mechanisms of chronic diarrhea in any group of patients with diabetes. In our tertiary referral practice, diabetic diarrhea was frequently due to celiac sprue, bacterial overgrowth in the small bowel, or fecal incontinence in conjunction with anorectal dysfunction; however, in almost 50% of the patients, these causes were excluded, and abnormal intestinal motility or secretion was postulated to be one of the likely causes of the diarrhea. These data suggest a practical algorithm based on three sequential assessments: first, tests of blood and stool specimens and flexible sigmoidoscopy to detect evidence of malabsorption or disease in the distal colon; second, small bowel aspirate and biopsy if the results of initial blood or stool tests are abnormal or anorectal function tests if those test results are normal; and, finally, measurement of gastrointestinal transit or therapeutic trials with opioids, clonidine hydrochloride, and, rarely, cholestyramine resin or octreotide acetate (or both methods). The mechanisms whereby abnormal neural function due to diabetes results in altered digestive, secretory, absorptive, or motor function necessitate further elucidation. The management of chronic diarrhea in patients in a tertiary referral practice, however, can be based on a practical algorithm to determine the cause and to adopt specific treatment to correct it.

Autonomic dysfunction in patients with chronic intestinal pseudo-obstruction

We prospectively evaluated autonomic function in 50 patients with clinical and manometric features of a neuropathic form of chronic intestinal pseudo-obstruction (CIP). In 26 patients, there were underlying disease processes that may have affected extrinsic neural control to viscera: diabetes mellitus (n = 16), previous gastric surgery (n = 5), and other neurologic disorders (n = 5). Our aim was to characterize autonomic function in these patients, and those 24 with CIP unassociated with a known underlying neurologic disorder (idiopathic group). We assessed vagal function and sympathetic cholinergic and adrenergic function by means of standardized autonomic tests and quantitated postprandial antral pressure activity. We also measured postprandial levels of pancreatic polypeptide and neurotensin as indicators of vagal function and of the delivery of nutrients to the distal small bowel. Among the idiopathic group (n = 24), two had evidence of a generalized sympathetic neuropathy and five abdominal vagal dysfunction (one had both). Among diabetic patients, three had sympathetic adrenergic failure, six had orthostasis with normal plasma noradrenaline, ten had signs of generalized sympathetic neuropathy and eight had abdominal vagal dysfunction. Vagal dysfunction was identified in all three patients who underwent vagotomy as part of their previous gastric surgery. In the other neurologic syndromes, vagal function was abnormal in three of the five patients. Thus, autonomic and, particularly, vagal dysfunction are confirmed in a majority of patients with CIP associated with known diabetes or neurologic disorders; however, a previously unrecognized autonomic (chiefly vagal) neuropathy of undetermined cause has been identified in five of the 24 'idiopathic' CIP patients.

Familial enteric neuropathy with pseudoobstruction

We report a case of autosomal dominant chronic intestinal pseudoobstruction secondary to a familial enteric neuropathy. Esophagogastrointestinal manometry studies in the index case showed decreased postprandial contractile frequency with normal amplitude of pressure activity in the stomach and small bowel. Pupillary function and autonomic reflexes were all normal, excluding an extrinsic autonomic neuropathy of the viscera. Histologic examination of the small intestine by hematoxylin and eosin stains revealed normal smooth muscles but a reduced number of neurons in the myenteric plexus without inflammatory cells or neuroNal intranuclear inclusions. Histologic examination of the myenteric plexus using the sections taken along the longitudinal axis of the intestine, stained with silver by the Smith technique, disclosed decreased numbers of argyrophilic neurons and degeneration of neurons and axons; however, there was no reactive increase in the number of glial cell nuclei. The patient's mother had suffered from chronic intestinal pseudoobstruction, which did not abate following extensive small bowel resection. This is the third family reported with an autosomal dominant enteric neuropathy unassociated with evidence of extrinsic autonomic or peripheral neuropathy. Subtotal resection of the small bowel was followed by recurrence of the pseudoobstruction syndrome in both affected members of the family.