Migraine, Cyclic Vomiting Syndrome, and Other Gastrointestinal Disorders

Amitriptyline-Induced Insomnia in a Young Lady Diagnosed With Cyclic Vomiting Syndrome: A Case Report

The author reports a 19-year-old woman suffering from repeated episodes of non-bloody vomiting for 18 months. All routine and special investigations were normal. She was labeled as a case of cyclic vomiting syndrome (CVS), and she developed insomnia after the initiation of amitriptyline as a prophylactic treatment. The case was reported to increase awareness regarding the importance of monitoring medication side effects among clinicians when using different classes of medications to treat CVS.

Association of Anxiety and Gastrointestinal Comorbidities in Repeat Hospital Admissions in Pediatric Cyclic Vomiting Syndrome

INTRODUCTION

Cyclic vomiting syndrome (CVS) is a functional gastrointestinal disorder with recurrent episodes of intense nausea and vomiting and thus may require frequent hospitalizations. There is paucity of data exploring the association of psychiatric and gastrointestinal comorbidities in repeat hospitalizations among pediatric patients with CVS.

METHODS

We analyzed the Pediatric Health Information System database and included all patients up to 18 years of age with a diagnosis of CVS between 2016 and 2020. We excluded patients with chronic conditions, which mimic CVS. The primary outcome variable was 90-day admission rate, which was defined as a visit to emergency department or admission to observation/inpatient unit with a primary diagnosis of CVS within 90 days after an index CVS hospitalization.

RESULTS

We evaluated a total of 2,604 hospitalizations represented by 1,370 unique individuals. The overall 90-day admission rate was 28.5%, which steadily decreased from 35.7% in 2016 to 23% in 2019 ( P < 0.001). Patients in the repeat hospitalization cohort were slightly older and more often men. Patients with repeat admissions had an increased proportion of anxiety and other gastrointestinal disorders. Multivariable logistic regression showed that anxiety, gastroesophageal reflux disease, functional dyspepsia, and abdominal migraine were associated with increased odds of repeat admissions.

DISCUSSION

Ninety-day admission rates in pediatric CVS are decreasing overall, although still contributing to significant healthcare expenditure. Anxiety and gastrointestinal comorbidities were associated with increased risk of repeat admissions. Further prospective studies are needed to better understand the complex interactions of these comorbidities and their management affecting the natural course of CVS.

Whole exome/genome sequencing in cyclic vomiting syndrome reveals multiple candidate genes, suggesting a model of elevated intracellular cations and mitochondrial dysfunction

Objective

To utilize whole exome or genome sequencing and the scientific literature for identifying candidate genes for cyclic vomiting syndrome (CVS), an idiopathic migraine variant with paroxysmal nausea and vomiting.

Methods

A retrospective chart review of 80 unrelated participants, ascertained by a quaternary care CVS specialist, was conducted. Genes associated with paroxysmal symptoms were identified querying the literature for genes associated with dominant cases of intermittent vomiting or both discomfort and disability; among which the raw genetic sequence was reviewed. "Qualifying" variants were defined as coding, rare, and conserved. Additionally, "Key Qualifying" variants were Pathogenic/Likely Pathogenic, or "Clinical" based upon the presence of a corresponding diagnosis. Candidate association to CVS was based on a point system.

Results

Thirty-five paroxysmal genes were identified per the literature review. Among these, 12 genes were scored as "Highly likely" (SCN4A, CACNA1A, CACNA1S, RYR2, TRAP1, MEFV) or "Likely" (SCN9A, TNFRSF1A, POLG, SCN10A, POGZ, TRPA1) CVS related. Nine additional genes (OTC, ATP1A3, ATP1A2, GFAP, SLC2A1, TUBB3, PPM1D, CHAMP1, HMBS) had sufficient evidence in the literature but not from our study participants. Candidate status for mitochondrial DNA was confirmed by the literature and our study data. Among the above-listed 22 CVS candidate genes, a Key Qualifying variant was identified in 31/80 (34%), and any Qualifying variant was present in 61/80 (76%) of participants. These findings were highly statistically significant (p < 0.0001, p = 0.004, respectively) compared to an alternative hypothesis/control group regarding brain neurotransmitter receptor genes. Additional, post-analyses, less-intensive review of all genes (exome) outside our paroxysmal genes identified 13 additional genes as "Possibly" CVS related.

Conclusion

All 22 CVS candidate genes are associated with either cation transport or energy metabolism (14 directly, 8 indirectly). Our findings suggest a cellular model in which aberrant ion gradients lead to mitochondrial dysfunction, or vice versa, in a pathogenic vicious cycle of cellular hyperexcitability. Among the non-paroxysmal genes identified, 5 are known causes of peripheral neuropathy. Our model is consistent with multiple current hypotheses of CVS.

Cyclic Vomiting Syndrome and Cannabis Hyperemesis Syndrome: The State of the Science

This article provides a narrative review of the state of the science for both cyclic vomiting syndrome and cannabis hyperemesis syndrome along with a discussion of the relationship between these 2 conditions. The scope of this review includes the historical context of these conditions as well as the prevalence, diagnostic criteria, pathogenesis, and treatment strategies for both conditions. A synopsis of the endocannabinoid system provides a basis for the hypothesis that a lack of cannabidiol in modern high-potency Δ 9 -tetrahydrocannabinol cannabis may be contributory to cannabis hyperemesis syndrome and possibly other cannabis use disorders. In concluding assessment, though the publications addressing both adult cyclic vomiting syndrome and cannabis hyperemesis syndrome are steadily increasing overall, the state of the science supporting the treatments, prognosis, etiology, and confounding factors (including cannabis use) is of moderate quality. Much of the literature portrays these conditions separately and as such sometimes fails to account for the confounding of adult cyclic vomiting syndrome with cannabis hyperemesis syndrome. The diagnostic and therapeutic approaches are, at present, based generally on case series publications and expert opinion, with a very limited number of randomized controlled trials and a complete absence of Level 1 evidence within the cyclic vomiting literature overall as well as for cannabis hyperemesis syndrome specifically.

Cyclic vomiting syndrome, a common language? A 20-year bibliometric study

BACKGROUND

Cyclic vomiting syndrome (CVS) is recognized as an episodic syndrome associated with migraine in the last version of the International Classification of Headache Disorders (ICHD-3). It manifests as stereotypical episodes of intense nausea and vomiting, occurring preferentially in childhood. Over the last 2 decades, the knowledge of this disorder has increased. The diagnostic criteria have been modified, through the evolution of several successive classifications. Actually, two classifications are prominent in the literature: the ICHD-3 and the Rome IV classification. The predictable periodicity of episodes is only recognized in the ICHD-3.

OBJECTIVE

We aimed to analyze the evolution of CVS literature in the last 2 decades, with a focus on CVS criteria used in these papers.

METHODS

We conducted a bibliometric study. We searched in the Web of Science database all papers in English literature with the term CVS in the abstract or title, in the category "article" or "review", published from 2001 to 2020. We searched within the paper which classification was used or mentioned.

RESULTS

In total, 213 papers were analyzed. 116 papers exclusively concerned childhood and adolescence CVS, or were written by pediatric practitioners. For most of the papers, the corresponding author was specialized in the field of gastroenterology. The Rome III classification was the main classification used or mentioned. The ICHD-3 and its beta version were mostly used or mentioned by the authors affiliated to the neurologic field.

CONCLUSION

This study shows the growth in the number of publications on CVS. It highlights the lack of reference to the ICHD, in particular by practitioners in the field of gastroduodenal disorders. This should encourage the achievement of a common classification with the different scientific societies.

Diagnosis and Management of Cyclic Vomiting Syndrome: A Critical Review

Cyclic vomiting syndrome (CVS) is a chronic disorder of gut-brain interaction characterized by recurrent disabling episodes of nausea, vomiting, and abdominal pain. CVS affects both children and adults with a prevalence of approximately 2% in the United States. CVS is more common in female individuals and affects all races. The pathophysiology of CVS is unknown and a combination of genetic, environmental, autonomic, and neurohormonal factors is believed to play a role. CVS is also closely associated with migraine headaches and likely have a shared pathophysiology. The diagnosis of CVS is based on the Rome criteria, and minimal recommended testing includes an upper endoscopy and imaging studies of the abdomen. CVS is frequently associated with anxiety, depression, and autonomic dysfunction. Patients with CVS commonly use cannabis therapeutically for symptom relief. By contrast, cannabinoid hyperemesis syndrome is believed to be a subset of CVS with chronic heavy cannabis use leading to hyperemesis. Due to the recalcitrant nature of the illness, patients often visit the emergency department and are hospitalized for acute CVS flares. Guidelines on the management of CVS recommend a biopsychosocial approach. Prophylactic therapy consists of tricyclic antidepressants (amitriptyline), antiepileptics (topiramate), and aprepitant in refractory patients. Abortive therapy consists of triptans, antiemetics (ondansetron), and sedation. Treatment of comorbid conditions is extremely important to improve overall patient outcomes. CVS has a significant negative impact on patients, families, and the healthcare system, and future research to understand its pathophysiology and develop targeted therapies is needed.

Cardiac Vagal Regulation Is Impeded in Children With Cyclic Vomiting Syndrome

INTRODUCTION

The pathophysiology underlying cyclic vomiting syndrome (CVS) remains undefined. Scant data and distinct clinical features point to altered autonomic nervous system function. Autonomic signaling can be noninvasively assessed through cardiac indices of parasympathetic vagal regulation, which is reduced in children with disorders of gut-brain interaction. We aimed to examine dynamic cardiac vagal regulation in children with CVS compared with that in healthy controls (HC).

METHODS

A total of 31 children with CVS evaluated in a tertiary care CVS center and 66 HC (ages 8-18 years) underwent cardiac autonomic function assessment. Electrocardiogram recordings were conducted during 3-minute sit/stand/sit posture challenges. The electrocardiogram-derived variables heart period, respiratory sinus arrhythmia (RSA), and vagal efficiency (VE) were analyzed using linear regression and mixed-effects modeling.

RESULTS

After exclusion of medication confounders, 23 patients with CVS were included in analyses. Both groups were comparable in age, gender, and body mass index. Compared with HC, children with CVS had shorter heart period (standardized mean difference range: 1.15-1.22, all P values < 0.05) and lower RSA (SMD range: 0.66-0.88, all P values < 0.05). Patients with CVS had significantly lower VE during the entire course of posture shifts, compared with HC ( B = -19.87, SE = 6.95, t = -2.86, P = 0.005, SMD = 0.76).

DISCUSSION

Children with CVS have suboptimal parasympathetic autonomic regulation compared with HC, indexed by reduced RSA and VE, even during their interepisodic well phase. Abnormal vagal modulation may underlie CVS pathophysiology, comorbidities, and triggers. Assessing VE during posture stressors could inform therapeutic interventions.

Prevalence and incidence of cyclic vomiting syndrome in Japan: A study using Japanese claims data

Cyclic vomiting syndrome (CVS) is a gastrointestinal disorder that is characterized by recurrent episodes of vomiting. Previous studies have provided reliable data on the prevalence of CVS among children in Japan; however, neither prevalence data nor incidence of CVS is available for adults. Hence, we obtained detailed prevalence and incidence data for CVS and estimated the total number of CVS cases in Japan. This retrospective cross-sectional study was conducted using the JMDC (JMDC, Inc.; formerly known as Japan Medical Data Center Co., Ltd.,) database, which is a de-identified Japanese claims database. Individuals enrolled between January 2017 and December 2017 were included in this study. Longitudinal data for eligible populations were used to identify patients who displayed CVS symptoms throughout the follow-up period. Due to the lack of a specific diagnosis code for CVS in 2017, the Rome IV criteria were applied to identify CVS cases in the pediatric and adult populations. The prevalence was standardized to the 2017 Japanese census and extrapolated to estimate the number of CVS cases. A total of 2,093 patients with CVS were identified from 3,506,144 individuals. The overall age-and-sex-standardized prevalence was 0.32 per 1,000 population (95% confidence interval [CI]: 0.30-0.34), projected to approximately 49,000 patients with CVS across Japan. The pediatric age-and-sex-standardized prevalence was 2.10 per 1,000 population (95% CI: 2.01-2.19), and the adult prevalence was 0.05 per 1,000 population (95% CI: 0.04-0.06). Marked sex differences were observed before and after 12 years of age. Thus our study provides the first large-population-based estimates of CVS prevalence and incidence in Japan, and currently, the only estimates for adult CVS in Japan.

Current understanding of the etiology of cyclic vomiting syndrome and therapeutic strategies in its management

INTRODUCTION

Cyclic vomiting syndrome is a chronic debilitating disorder of the gut-brain interaction and is characterized by recurrent episodes of nausea and vomiting.Recent studies indicate that it is common and affects 2% of the US population. Unfortunately, there is significant heterogeneity in the management of these patients in the medical community. This review article aims to bridge this gap and will review the epidemiology and etiology with a focus on management of CVS.

AREAS COVERED

This article reviews the epidemiology, and pathophysiology of CVS and impact on patients. It also discusses management based on recent guidelines based on which is intended for the busy clinician. A literature search was done using PubMed and key words "cyclic vomiting", "management", "etiology", and pathophysiology were used to identify articles of importance.

EXPERT OPINION

CVS is a complex, poorly understood disorder of gut-brain interaction (DGBI) and has a significant negative impact on patients, families and the healthcare system. Recent guidelines recommend a multidisciplinary approach to management using prophylactic therapy in moderate-severe CVS and abortive medication for acute flares. However more research is needed to better understand the pathophysiology and develop targeted therapies for CVS.

The Role of Neuro-Immune Interaction in Chronic Pain Conditions; Functional Somatic Syndrome, Neurogenic Inflammation, and Peripheral Neuropathy

Functional somatic syndromes are increasingly diagnosed in chronically ill patients presenting with an array of symptoms not attributed to physical ailments. Conditions such as chronic fatigue syndrome, fibromyalgia syndrome, or irritable bowel syndrome are common disorders that belong in this broad category. Such syndromes are characterised by the presence of one or multiple chronic symptoms including widespread musculoskeletal pain, fatigue, sleep disorders, and abdominal pain, amongst other issues. Symptoms are believed to relate to a complex interaction of biological and psychosocial factors, where a definite aetiology has not been established. Theories suggest causative pathways between the immune and nervous systems of affected individuals with several risk factors identified in patients presenting with one or more functional syndromes. Risk factors including stress and childhood trauma are now recognised as important contributors to chronic pain conditions. Emotional, physical, and sexual abuse during childhood is considered a severe stressor having a high prevalence in functional somatic syndrome suffers. Such trauma permanently alters the biological stress response of the suffers leading to neuroexcitatory and other nerve issues associated with chronic pain in adults. Traumatic and chronic stress results in epigenetic changes in stress response genes, which ultimately leads to dysregulation of the hypothalamic-pituitary axis, the autonomic nervous system, and the immune system manifesting in a broad array of symptoms. Importantly, these systems are known to be dysregulated in patients suffering from functional somatic syndrome. Functional somatic syndromes are also highly prevalent co-morbidities of psychiatric conditions, mood disorders, and anxiety. Consequently, this review aims to provide insight into the role of the nervous system and immune system in chronic pain disorders associated with the musculoskeletal system, and central and peripheral nervous systems.

Differential Diagnosis of Cyclic Vomiting and Periodic Headaches in a Child with Ventriculoperitoneal Shunt: Case Report of Chronic Shunt Overdrainage

Fourteen months after the implantation of a ventriculoperitoneal shunt catheter, a six-year-old boy developed recurrent, severe headaches and vomiting every three weeks. The attacks were of such severity that hospitalizations for analgesic and antiemetic therapies and intravenous rehydration and electrolyte substitution were repeatedly required. The patient was asymptomatic between the attacks. After an extensive diagnostic workup-including repeated magnetic resonance imaging (MRI) and neurosurgical examinations-common differential diagnoses, including shunt overdrainage, were ruled out. The patient was transferred to a specialized pediatric pain clinic with suspected cyclic vomiting syndrome (CVS). Despite intensive and in part experimental prophylactic and abortive pharmacological treatment, there was no improvement in his symptoms. Consecutive MRI studies reinvestigating the initially excluded shunt overdrainage indicated an overdrainage syndrome. Subsequently, the symptoms disappeared after disconnecting the shunt catheter. This case report shows that even if a patient meets CVS case definitions, other differential diagnoses must be carefully reconsidered to avoid fixation error.

Kynurenine Pathway of Tryptophan Metabolism in Migraine and Functional Gastrointestinal Disorders

Migraine, the leading cause of disability in the population aged below 50, is associated with functional gastrointestinal (GI) disorders (FGIDs) such as functional nausea, cyclic vomiting syndrome, and irritable bowel syndrome (IBS). Conversely, changes in intestinal GI transit may cause diarrhea or constipation and are a component of the autonomic symptoms associated with pre- and post-dorsal phases of migraine attack. These mutual relationships provoke a question on a common trigger in migraine and FGIDs. The kynurenine (l-kyn) pathway (KP) is the major route for l-tryptophan (l-Trp) metabolism and transforms l-Trp into several neuroactive compounds. Changes in KP were reported in both migraine and FGIDs. Migraine was largely untreatable, but several drugs approved lately by the FDA, including monoclonal antibodies for calcitonin gene-related peptide (CGRP) and its receptor, create a hope for a breakthrough in migraine treatment. Derivatives of l-kyn were efficient in pain relief with a mechanism including CGRP inhibition. KP products are important ligands to the aryl hydrocarbon receptor (AhR), whose activation is implicated in the pathogenesis of GI and migraine. Toll-like receptors (TLRs) may play a role in migraine and IBS pathogeneses, and KP metabolites detected downstream of TLR activation may be an IBS marker. The TLR4 signaling was observed in initiating and maintaining migraine-like behavior through myeloid differentiation primary response gene 88 (MyD88) in the mouse. The aim of this review is to justify the view that KP modulation may provide common triggers for migraine and FGIDs with the involvement of TLR, AhR, and MyD88 activation.

A link between gastrointestinal disorders and migraine: Insights into the gut-brain connection

Background

Migraine is a complex, multifaceted, and disabling headache disease that is often complicated by gastrointestinal (GI) conditions, such as gastroparesis, functional dyspepsia, and cyclic vomiting syndrome (CVS). Functional dyspepsia and CVS are part of a spectrum of disorders newly classified as disorders of gut–brain interaction (DGBI). Gastroparesis and functional dyspepsia are both associated with delayed gastric emptying, while nausea and vomiting are prominent in CVS, which are also symptoms that commonly occur with migraine attacks. Furthermore, these gastric disorders are comorbidities frequently reported by patients with migraine. While very few studies assessing GI disorders in patients with migraine have been performed, they do demonstrate a physiological link between these conditions.

Objective

To summarize the available studies supporting a link between GI comorbidities and migraine, including historical and current scientific evidence, as well as provide evidence that symptoms of GI disorders are also observed outside of migraine attacks during the interictal period. Additionally, the importance of route of administration and formulation of migraine therapies for patients with GI symptoms will be discussed.

Methods

A literature search of PubMed for articles relating to the relationship between the gut and the brain with no restriction on the publication year was performed. Studies providing scientific support for associations of gastroparesis, functional dyspepsia, and CVS with migraine and the impact these associations may have on migraine treatment were the primary focus. This is a narrative review of identified studies.

Results

Although the association between migraine and GI disorders has received very little attention in the literature, the existing evidence suggests that they may share a common etiology. In particular, the relationship between migraine, gastric motility, and vomiting has important clinical implications in the treatment of migraine, as delayed gastric emptying and vomiting may affect oral dosing compliance, and thus, the absorption and efficacy of oral migraine treatments.

Conclusions

There is evidence of a link between migraine and GI comorbidities, including those under the DGBI classification. Many patients do not find adequate relief with oral migraine therapies, which further necessitates increased recognition of GI disorders in patients with migraine by the headache community.

Cyclic vomiting syndrome: A narrative review and guide to management

OBJECTIVES/BACKGROUND

Cyclic vomiting syndrome (CVS) is a disabling disorder of gut-brain interaction manifested by stereotypical and severe episodes of nausea and vomiting. Prevalence data indicate that CVS affects 1-2% of children and there has been a recent dramatic rise in diagnosed adults.

METHODS

This narrative review summarizes relevant literature pertaining to pediatric and adult CVS and provides a guide to management based on extensive clinical experience.

RESULTS

More timely diagnosis is facilitated by an expert consensus diagnostic approach and limited testing. Some diagnostic tests of exclusion remain essential. These include an upper gastrointestinal (GI) contrast study to exclude intestinal malrotation and basic laboratory screening. An abdominal ultrasound is recommended to exclude renal hydronephrosis in children and biliary disease in adults. Exclusion of metabolic/genetic conditions is warranted in those with specific warning signs, presentation in infants/toddler age, and in those with refractory disease. In the absence of chronic GI symptoms, referral to a GI specialist for upper endoscopy is generally not necessary in children but recommended in adults. A large subset termed migraine-equivalent CVS display strong clinical and genetic features of migraine. A unifying pathophysiologic core concept involves neuronal hyperexcitability and aberrant central modulation of autonomic signals. This is coupled with multiple susceptibility factors including mitochondrial dysfunction/cellular energy deficits, a hyper-responsive hypothalamic-pituitary-adrenal axis and many comorbidities that increase vulnerability to triggering events. CVS episodes are frequently triggered by stressors and intercurrent illnesses. Lifestyle and non-pharmacological interventions thus play a pivotal role in successful management. Pharmacological therapies are categorized into abortive, supportive/rescue, and prophylactic treatments. The majority respond particularly well to migraine-focused treatment strategies.

CONCLUSION

Despite improved characterization and understanding, CVS remains classified as a functional disorder of brain-gut interaction that is often disjointly managed by generalists and subspecialists. Early recognition, evaluation, and management will facilitate care and improve outcomes. Further research into its natural history with common progression to migraine headaches, neuroendocrine mechanisms, and the pathophysiologic relation to migraine diathesis is much needed.

Sumatriptan as abortive treatment in cyclic vomiting syndrome: A cross-sectional study

Cyclic vomiting syndrome (CVS) is characterized by episodic vomiting and shares similarities with migraine headache. Guidelines recommend using triptans as abortive therapy in CVS, but there are limited data on its efficacy. Methods: We thus sought to characterize sumatriptan use and performed a cross-sectional study of adults with CVS episodes within the previous 6 months. Questionnaires about demographics, clinical characteristics, and response to sumatriptan (defined as >50% reduction in symptoms) were administered via e-mail. We investigated differences between responders and nonresponders, using χ 2 and Student’s t test. Results: Of 101 participants (age 41 ± 15 years, 74% female, 83% Caucasian), 39 (38%) used sumatriptan during their last CVS attack. Most reported an improvement in nausea (55%), vomiting (59%), and abdominal pain (43%) within 2 h and at 24 h (67%, 73%, and 67%) respectively. Eighteen (46%) reported that sumatriptan helped them avoid emergency department visits and 20 (51%) avoided being hospitalized. Nonresponse to sumatriptan was associated with depression ( p = 0.01), current cannabis use ( p = 0.02), use of benzodiazepines ( p = 0.04), and opioids (0.02) during an episode. No serious side effects were noted. Conclusions: Sumatriptan use reduced symptoms of CVS but did not abort them. Prospective studies to determine its independent effects are needed.

Highlighting the importance of early diagnosis of cyclic vomiting syndrome in adults: A case report

INTRODUCTION

Cyclic vomiting syndrome (CVS) is a potentially exhausting disorder and has an adverse impact on quality of life, but it is poorly recognized and is always misdiagnosed leading to a diagnostic delay of several years, especially in adults.

PATIENT CONCERNS

We report a case of a 32-year-old woman with recurrent severe nausea, vomiting, and abdominal pain, and repeated visits to the emergency department or the outpatient department for 4 years. Each time she was diagnosed with gastroenteritis or gastritis, and recovered after supportive treatment including antiemetics, maintenance of water and electrolyte balance, and a proton pump inhibitor.

DIAGNOSIS

Laboratory examinations, gastroenteroscopy, chest and abdominal computed tomography, and brain magnetic resonance imaging all failed to reveal abnormalities that would explain her symptoms. Based on typical symptoms and the exclusion of other diseases associated with repeated vomiting, the diagnosis was made as CVS.

INTERVENTIONS

She was given orally amitriptyline, 50 mg per night, and olanzapine, 1.25 mg per night.

OUTCOMES

The treatment was effective in inducing remission, and symptoms did not recur after treatment. The treatment lasted for 2 months and stopped. Her symptoms did not recur over the 10-month follow up.

CONCLUSION

CVS is not rare in adults, but its diagnosis is usually delayed due to poor recognition of the condition. Clinician awareness of CVS should be enhanced to improve early diagnosis.Core tip: Cyclic vomiting syndrome has a tremendous impact on the quality of life, but it is poorly recognized and is always misdiagnosed leading to a diagnostic delay of several years, especially in adults. The article presented a case report of cyclic vomiting syndrome of adult; we hope the article will attribute to increased awareness of physician and reduce delayed diagnosis.

Cyclic vomiting syndrome: Pathophysiology, comorbidities, and future research directions

Cyclic vomiting syndrome (CVS) is characterized by severe episodic emesis in adults and children. Cannabinoid hyperemesis syndrome is an increasingly recognized CVS-like illness that has been associated with chronic cannabis use. There are significant gaps in our understanding of the pathophysiology, clinical features, comorbidities, and effective management options of CVS. Recommendations for treating CVS are based on limited clinical data, as no placebo-controlled, randomized trials have yet been conducted. Diseases associated with CVS, including migraine, mitochondrial disorders, autonomic dysfunction, and psychiatric comorbidities, provide clues about pathophysiologic mechanisms and suggest potential therapies. We review our current understanding of CVS and propose future research directions with the aim of developing effective therapy. Establishing a multicenter, standardized registry of CVS patients could drive research on multiple fronts including developing CVS-specific outcome measures to broaden our understanding of clinical profiles, to serve as treatment end points in clinical trials, and to provide a platform for patient recruitment for randomized clinical trials. Such a robust database would also facilitate conduct of research that aims to determine the underlying pathophysiological mechanisms and genetic basis for CVS, as well as identifying potential biomarkers for the disorder. Soliciting government and industry support is crucial to establishing the necessary infrastructure and achieving these goals. Patient advocacy groups such as the Cyclic Vomiting Syndrome Association (CVSA), which partner with clinicians and researchers to disseminate new information, to promote ongoing interactions between patients, their families, clinicians, investigators, to support ongoing CVS research and education, must be an integral part of this endeavor.