What is CVS?
CVS has been recognised for over 100 years, but we still know relatively little about the cause of the problem. There is increasing evidence that mitochondrial DNA mutations play a role in some people developing CVS.
CVS is characterised by recurrent, prolonged attacks of severe vomiting, nausea and lethargy, with no apparent cause. Vomiting persists at frequent intervals, 5-6 times per hour at the peak, for periods ranging from hours to 10 days or more. It most commonly lasts for between 1 and 4 days. The episodes are self-limiting and tend to be similar to each other in symptoms and duration. The sufferer is generally in good health between episodes.
There are no diagnostic clinical or laboratory tests for CVS itself, but when all specific conditions that could cause the symptoms have been eliminated by testing, doctors may classify the illness as Cyclical Vomiting Syndrome. This means that people with CVS may show a range of symptoms. One goal of the CVSA is to help develop better diagnostic criteria, so that sufferers are diagnosed more quickly and accurately than has been the case previously.
Dr Venkatesan is a CVS expert and an advisor to the North American CVS society.
This video was prepared to introduce gastroenterologists, about to attend a conference, to information about CVS.
Who gets CVS?
It is thought that anyone can potentially get CVS. CVS sufferers are more likely than average to have a family history of migraine, and/or travel sickness, but the association is not complete, and not all CVS sufferers have family histories of these problems.
A number of studies have been performed to estimate how common CVS is. Studies on school age children from Australia and Scotland have suggested that about 2% may be affected.
In a sub-set of CVS sufferers a mitochondrial DNA mutation is thought to be responsible (see research section and this article).
Professor Li is a paediatric CVS expert based in the USA and in this video talks about childhood CVS.
What triggers a vomiting episode?
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 (e.g. colds or ‘flu, and throat or chest infections) 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 (e.g. on a birthday or on holiday) can trigger episodes in some people. In a large proportion no obvious triggering event can be recognised.
When does it start?
The onset of CVS can occur at any time. CVS most commonly develops between the age of 3-7 years and it can persist for periods of time ranging from months to decades. Although CVS is most commonly recognised in children, it is apparent that adult onset CVS is more common than was once thought. It affects males and females equally. As the name suggests, cyclic activity is often a feature of this condition. About 50% of sufferers show a strong regular pattern of vomiting episodes. The episodes may occur as often as several times a month or as little as several times a year. The frequency of episodes is relatively constant in any given individual, but varies between individuals.
How long does an episode last?
Episodes are typically very consistent for any given individual (i.e. stereotypic) but can vary from a few hours to days between individuals. Most commonly the duration is between 12 hours-2 days. Remember this is the duration of vomiting - sufferers often experience symptoms prior to vomiting including severe nausea, headache, dizziness etc, (see Symptoms). Although families often become expert at recognising the onset of an episode, there are few studies which have tried to quantitate this. It is important to realise that the symptoms, even in those with short vomiting durations, can be spread over days.