Cyclical Vomiting Syndrome

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🔁 Cyclical Vomiting Syndrome (CVS) is a disorder characterised by recurrent stereotyped episodes of intense nausea and vomiting, separated by periods of relative or complete wellness. It is a diagnosis of pattern plus exclusion: the history is often highly suggestive, but important alternative causes of vomiting must still be considered.

📖 What is CVS?

CVS is a disorder of gut–brain interaction in which patients develop repeated attacks of severe nausea, retching, and vomiting that tend to follow a similar pattern each time. Episodes may last from hours to several days, and between attacks the patient may be entirely well or have only mild background symptoms. CVS occurs in both children and adults, and there is a well-recognised association with migraine.

🧠 Pathophysiology

The exact mechanism is not fully understood, but CVS appears to involve disordered signalling along the gut–brain axis. Proposed contributors include migraine biology, autonomic dysfunction, altered stress responses, neuroendocrine activation, and abnormal gastric motility. In practice, the strong overlap with migraine is clinically useful: many patients have a personal or family history of migraine, and some of the same preventive and abortive therapies can help.

👀 Typical clinical features

• Recurrent episodes of severe nausea and vomiting
• Stereotyped pattern: attacks are similar in onset, duration, and symptoms each time
• Symptom-free intervals between episodes
• Retching and inability to tolerate oral intake during attacks
• Abdominal pain, pallor, lethargy, sweating, dizziness, or headache may occur
• Some patients report triggers such as stress, sleep deprivation, infection, menstruation, travel, or certain foods

🪜 Clinical phases

🔎 Diagnostic pattern

CVS is diagnosed from the characteristic episodic pattern together with appropriate exclusion of other causes. The history is often striking: repeated attacks with a similar time course, separated by symptom-free intervals. A personal or family history of migraine supports the diagnosis.

• Discrete episodes of intense nausea and vomiting
• Episodes separated by periods of baseline health
• Attacks often have similar timing and duration each time
• No better explanation after appropriate assessment

⚠️ Differential diagnosis

CVS should not be diagnosed casually. Vomiting has a very broad differential, and the first task is always to exclude important surgical, metabolic, neurological, toxicological, and pregnancy-related causes.

• Cannabinoid Hyperemesis Syndrome (CHS) — especially if there is regular cannabis use
• Gastrointestinal: obstruction, peptic disease, gallbladder disease, pancreatitis, gastroparesis
• Metabolic / endocrine: DKA, adrenal insufficiency, uraemia, hypercalcaemia
• Neurological: raised intracranial pressure, migraine-associated vomiting
• Pregnancy-related: hyperemesis gravidarum
• Infective: gastroenteritis or systemic infection
• Functional GI disorders and rumination syndrome

🌿 CVS versus CHS

🚩 Red flags suggesting another diagnosis

• First presentation with severe focal abdominal findings
• Peritonism or marked localised tenderness
• GI bleeding
• Persistent vomiting without symptom-free intervals
• Neurological signs, confusion, or reduced consciousness
• Weight loss, progressive dysphagia, anaemia, or systemic features
• Fever or sepsis features
• Abnormal examination out of keeping with previous stereotyped episodes

🧪 Investigations

There is no single confirmatory test for CVS. Investigations are used to assess severity, identify complications such as dehydration, and exclude other causes.

• Bedside: observations, glucose, pregnancy test where relevant
• Bloods: FBC, U&Es, creatinine, bicarbonate, LFTs, CRP, calcium, glucose
• Urinalysis and ketones where appropriate
• ECG if significant electrolyte disturbance or QT-prolonging antiemetics are being considered
• Imaging only if history or examination suggests another pathology

💥 Complications

• Dehydration
• Acute kidney injury
• Hypokalaemia and other electrolyte abnormalities
• Hypoglycaemia
• Mallory–Weiss tear in severe cases
• Repeated emergency attendances and loss of quality of life

🏥 Acute management during an episode

Treatment in the acute phase is supportive. The aim is to relieve symptoms, correct dehydration and metabolic disturbance, and provide a calm environment while excluding dangerous mimics.

• IV or oral rehydration depending on severity
• Correct electrolyte abnormalities
• Antiemetics as needed
• Analgesia if required
• Rest in a quiet, dark environment may help some patients, particularly if there is a migraine phenotype
• Admit if unable to maintain hydration, if complications are present, or if the diagnosis is uncertain

🛡️ Preventive / long-term management

Long-term treatment focuses on trigger recognition, lifestyle measures, and prophylactic therapy when episodes are frequent, prolonged, or disabling. The migraine association matters here, because prophylactic regimens often mirror migraine practice.

• Identify and avoid triggers where possible
• Optimise sleep, hydration, regular meals, and stress management
• Treat associated conditions such as migraine, anxiety, depression, or sleep disorders
• Consider specialist review if episodes are recurrent or severe

💊 Common treatment principles

• Abortive treatment: given early in the prodrome to try to stop or blunt an attack
• Supportive treatment: antiemetics, fluids, rest, symptom relief during the vomiting phase
• Prophylactic treatment: used between episodes to reduce frequency and severity

🧠 Clinical pearls

• Think of CVS when vomiting is episodic, stereotyped, and separated by wellness.
• A migraine history is a valuable clue.
• Always ask about cannabis use because CHS can mimic CVS closely.
• Normal investigations between episodes do not exclude CVS.
• Frequent attenders may benefit from an agreed management plan to reduce repeated unnecessary investigations.

📌 Summary

Cyclical Vomiting Syndrome is a disorder of recurrent, stereotyped vomiting episodes with symptom-free intervals between attacks. Diagnosis depends on recognising the pattern, excluding other important causes, and considering the strong overlap with migraine biology. Acute care is mainly supportive, while long-term management focuses on trigger control and preventive therapy in selected patients.