Cyclic Vomiting Syndrome (CVS) is a functional gastrointestinal disorder defined by recurrent, sudden-onset episodes of severe nausea and vomiting. Attacks are highly similar for the individual patient each time they occur, followed by extended periods of complete wellness. The disorder is not caused by a structural or biochemical abnormality, setting it apart from other causes of vomiting. CVS often requires emergency medical attention due to the risk of dehydration.
Defining Cyclic Vomiting Syndrome
CVS is characterized by a distinctive, cyclical pattern of stereotyped attacks. Episodes tend to start at the same time of day and last for a similar duration. These intense vomiting episodes are separated by symptom-free intervals, ranging from weeks to months, during which the individual returns to normal health. CVS is classified as a functional disorder, indicating a disturbance in brain-gut interaction rather than a clear structural cause.
CVS was historically considered a pediatric condition, but it is now recognized in adults, sometimes with a more severe presentation and less frequent, longer-lasting episodes. Many patients with CVS also have a personal or family history of migraine headaches, suggesting a shared underlying mechanism. This connection has led some researchers to consider CVS a type of “abdominal migraine” due to the episodic nature and symptom overlap. The condition disrupts daily life, often leading to missed school or work and frequent emergency department visits.
The Phases of a CVS Episode
A typical CVS attack is characterized by three distinct phases. The Prodromal Phase signals the imminent onset of the episode and may last minutes to hours. During this time, the individual experiences intense nausea, often accompanied by pallor, sweating, and lethargy. Recognizing this phase is important because early medication intervention can sometimes halt the progression to full vomiting.
The Emetic Phase follows, marked by continuous, severe vomiting and retching that occurs rapidly, sometimes six times per hour during peak intensity. This period can be debilitating, lasting for hours or even several days. It is often accompanied by abdominal pain, headache, and sensitivity to light and sound. The severity of the vomiting carries a significant risk of dehydration and electrolyte imbalance, frequently necessitating hospitalization for intravenous fluids.
The Recovery Phase begins when the vomiting and retching stop, and the nausea gradually subsides. The individual slowly regains energy and appetite, returning to their baseline health. This recovery period leads directly into the symptom-free interval, which can last for weeks or months until the next episode is triggered. The complete return to normal function between episodes is a defining feature of CVS.
Underlying Factors and Triggers
The precise cause of CVS remains unknown, but it involves complex communication issues between the brain and the gut. Research points toward a dysfunction in the autonomic nervous system, which controls involuntary body functions like the vomiting reflex. This dysregulation may lead to the sympathetic nervous system becoming overly activated, contributing to symptoms like rapid heart rate, dizziness, and paleness during an attack.
There is also a strong association between CVS and abnormalities in the mitochondria, the energy-producing structures within cells. Specific mitochondrial DNA polymorphisms have been identified more frequently in children with CVS, suggesting a genetic predisposition that may affect cellular energy metabolism. This link helps explain why CVS often co-occurs with other conditions linked to mitochondrial dysfunction, such as migraines.
While these are underlying factors that increase susceptibility, specific events or conditions can act as triggers to precipitate an attack. Common triggers include psychological or physical stress, infections, and lack of adequate sleep. Dietary factors, such as caffeine, chocolate, or prolonged fasting, can lower the threshold for an attack, as can hormonal fluctuations associated with the menstrual cycle.
Diagnosis and Treatment Approaches
Diagnosing CVS is primarily a process of exclusion, as there is no single confirmatory test. Physicians must first rule out other possible causes of recurrent vomiting, such as metabolic disorders, structural abnormalities, or neurological conditions. This often involves extensive testing, including blood work and imaging, especially if the patient presents with “alarm features” like gastrointestinal bleeding or unexplained weight loss.
Diagnosis is confirmed using standardized criteria, most commonly the Rome IV criteria. These criteria require stereotypical vomiting episodes occurring at least one week apart, with a return to baseline health between episodes. This formalizes the cyclical nature and helps distinguish CVS from chronic vomiting disorders. Treatment addresses acute attacks and prevents future episodes.
Management is divided into two distinct strategies: acute and prophylactic.
Acute (Abortive) Treatment
Acute treatment is administered at the first sign of the prodromal phase to stop the attack from progressing. This typically involves antiemetics, such as serotonin antagonists like ondansetron, and often triptans, which are common migraine medications. Aggressive supportive care during the emetic phase, including intravenous fluids containing dextrose and sometimes sedatives, is used to manage severe symptoms and prevent dehydration.
Prophylactic (Preventative) Treatment
Prophylactic treatment involves taking daily medication during the symptom-free interval to reduce the frequency and severity of future episodes. For moderate-to-severe CVS, tricyclic antidepressants like amitriptyline are often the first-line medication, as they modulate nerve signals involved in the brain-gut axis. Alternative options include antiepileptic drugs like topiramate and mitochondrial supplements such as Coenzyme Q10 and riboflavin.