Cyclic Vomiting Syndrome

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What is CVS?

Cyclic vomiting syndrome or cyclical vomiting syndrome (CVS) is a chronic functional condition of unknown cause characterised by recurring attacks of intense nausea, vomiting, and sometimes abdominal pain, headaches, or migraines and prostration with no apparent cause. Approximately 25% of cases have coexisting neuromuscular disease manifestations (cyclic vomiting syndrome plus).

It has long been thought that CVS was a condition of childhood and adolescence. We now åknow that adults also suffer from CVS. There is CVS that begins in childhood and may extend into adulthood as well as adult onset CVS.

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. The episodes tend to be similar to each other in symptoms and duration and are self-limited with return of normal health between episodes. 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.

A CVS cycle 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, characterised 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 vigour return to normal. 

The following symptoms of CVS occur:

Severe and constant, unremitting nausea

Repeated vomiting, peaking at up to 5-6 times per hour or more

Retching, often violently

Pallor, often extreme paleness of the skin

Low grade fever


Abdominal pain


Lethargy or unresponsiveness 


«Perplexing» or unusual behaviours

Excessive salivation, and/or spitting

Extreme thirst


Vomiting blood


Eye problems


May be associated with pathologic bathing behaviour (prolonged hot baths or showers).  (You can read more about this in Adult CVS here. This text is in English)


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.


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. 

Each phase has therapeutic goals.  

  1. The goal of the inter‐episodic phase is prevention of episodes.  
  2. The goal of the prodromal phase is to abort the vomiting phase.
  3. The therapeutic goal during the vomiting phase is termination of the nausea and vomiting or, if this cannot be achieved, sedating the patient until the episode passes; deep sleep makes the vomiting cease and makes the patient insensible to the misery of the attack.  
  4. The goal of the recovery phase is resumption of oral intake without causing a relapse of nausea and vomiting.