Cyclic Vomiting Syndrome Association


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Cyclic Vomiting Syndrome, or cyclical vomiting syndrome, (CVS) is a chronic functional condition of unknown cause characterized by recurring attacks of intense nausea, vomiting, and sometimes abdominal pain, headaches, or migraines and prostration with no apparent cause.

CVS typically develops during childhood but it may persist into adult life. Vomiting occurs at frequent intervals for hours or days. The episodes tend to be similar to each other in symptoms and duration and are self-limited with return of normal health between episodes.

Approximately 25% of cases have coexisting neuromuscular disease manifestations (cyclic vomiting syndrome plus).

CVS sufferers are more likely than average to have a family history of migraine and/or travel sickness, but not all CVS sufferers have family histories of these problems.

The four phases of CVS

The illness has four phases:
1. The inter-episode phase, during which the patient is relatively symptom free.
2. The prodrome phase, which begins when the patient senses an oncoming episode.
3. The emetic phase, characterized by intense, persistent nausea, severe vomiting, and other symptoms.
4. The recovery phase begins with the subsidence of nausea and ends when hunger, tolerance of oral intake, and vigor return to normal.


For many with CVS there is nothing obvious that starts an attack, but for others some specific “triggers” can be identified which may initiate a CVS episode. Physical stress is one of the most common triggers. Mild viruses and minor injuries causing pain, may initiate an episode. Going without food for too long and sleep deprivation can also act as physical triggers.

Less commonly, anaesthetics, cold temperatures, food sensitivities, may start an episode. For some, excitement or emotional stress may play a role too. Negative stress such as anxiety, family problems, etc and the fear of being ill can trigger episodes in some people. In a large proportion no obvious triggering event can be recognised.

Under an episode, these symptoms may occur:

  • Severe and constant, unremitting nausea
  • Repeated vomiting and retching, often violently, peaking at up to 5-6 times per hour or more
  • Pallor, often extreme paleness of the skin
  • Low-grade fever
  • Headache
  • Abdominal pain
  • Diarrhea
  • Lethargy or unresponsiveness/conscious coma
  • “Perplexing” or unusual behaviors
  • Excessive salivation, and/or spitting
  • Extreme thirst
  • Dehydration
  • Vomiting blood
  • Weakness
  • Eye problems
  • Fatigue
  • Pathologic bathing behavior (prolonged hot baths or showers).

Symptoms of CVS

Episodes may begin at any time, but most commonly occur during the night or early morning. There is relentless nausea with repeated bouts of vomiting or retching. The vomiting has been described as the most intense kind of nausea a human can experience. The person is pale and listless. They may experience intense abdominal pain and less often headache, low-grade fever and diarrhea. Prolonged vomiting may cause mild bleeding due to irritation of the esophagus. The symptoms are frightening to the person and family and may be life-threatening if delayed treatment leads to dehydration. CVS is very different from the normal vomiting. The most obvious thing is that the vomiting doesn’t stop. Only bacillus cereus food poisoning matches this high intensity of emesis in CVS.

Attacks tend to be stereotypical, in that a patient’s attacks tend to be similar each time, although attacks vary from person to person. 50% of CVS suffers experience the same progression and character of attack with every episode. Laboratory tests often reveal a persistent presence of lactic acid in the blood.

Who gets CVS?

The onset of CVS may occur at any time, but most commonly develops between the ages of 3-7 years.  Although CVS is most commonly recognized in children, it is apparent that adult onset CVS is more common than was once thought. Females are affected slightly more than males.

How frequently do the episodes occur?

As the name suggests, cyclic activity is often a feature of this condition. Episode frequency is relatively constant for any given individual, but varies between individuals. Vomiting occurs at frequent intervals for hours or days. A patient may suffer from 1 to 70 episodes per year with an average of 12 episodes a year. Patients with uncomplicated CVS are asymptomatic between episodes; attacks have an “on-off ” pattern. About half of all sufferers show a strong regular pattern of vomiting episodes.

How long does an episode last?

The length of an episode varies from person to person, but are often consistent within the same individual. Most often the attacks last from 8 to 24 hours, but some experience only 1-2 hour episodes while others have episodes that last for days.


CVS is usually a diagnosis by exclusion of all other causes and to study the symptoms and the pattern. In CVS, the pattern of vomiting is such that at the peak this can be 5-6 times per hour. This is different from vomiting induced by most other causes.


The treatment of CVS is a difficult area, with little research to support one form of treatment over another. Treatment often progresses in an empirical manner, by trial and error on an individual basis. Treatment is otherwise supportive.  During an episode it is often helpful to provide a dark, quiet environment. Intravenous fluids may be needed if the sufferer has become dehydrated. Early use and monitoring are essential. Treatment with a range of anti-emetic and other drugs has been used. An individual may find a treatment that works for them, but there is nothing approaching a universal treatment regime. Between episodes a variety of treatments have been tried. Some can work well for some individuals, reducing frequency, duration or severity of an episode, but the same drug may provide no benefit to others. In most cases the evidence is anecdotal, relying on the opinion of the sufferer or parent, or the doctor.