What causes the cyclic pattern of vomiting with periods of remission in between?

Understanding the Cyclic Pattern of Vomiting in Cyclic Vomiting Syndrome (CVS)

The cyclic pattern of vomiting with periods of remission between episodes is a defining characteristic of Cyclic Vomiting Syndrome (CVS), which is caused by a complex interplay of neurological, autonomic, and psychological factors that create stereotypical episodes of vomiting separated by symptom-free intervals.1

Pathophysiology of the Cyclic Pattern

• CVS is characterized by stereotypical episodes of acute-onset vomiting lasting less than 7 days, with at least three discrete episodes in a year, separated by at least one week of baseline health 1

• The cyclic nature is believed to share pathophysiological mechanisms with migraine headaches, with approximately 20-30% of CVS patients also experiencing migraines 1

• Episodes follow a predictable pattern for each individual patient:

  • Prodromal phase (warning signs before vomiting begins)
  • Emetic phase (active vomiting)
  • Recovery phase
  • Inter-episodic phase (period of wellness between attacks) 1

• During the inter-episodic phase, patients typically return to baseline health, though some may experience milder symptoms such as occasional nausea, vomiting, or dyspepsia 1

Triggers That Initiate the Cycle

• Psychological and physiological stressors trigger the cyclic pattern in 70-80% of patients 1:

  • Negative stress (work conflicts, family issues)
  • Positive stress (birthdays, vacations)
  • Sleep deprivation
  • Hormonal fluctuations related to menstrual cycles
  • Travel or motion sickness
  • Acute infections or surgery
  • Prolonged fasting or intense exercise 1

• These triggers activate a cascade of neurological and hormonal responses that initiate the vomiting cycle 2

Associated Conditions and Comorbidities

• Mood disorders are present in 50-60% of CVS patients (anxiety, depression, panic disorder) 1

• Autonomic imbalances, including postural orthostatic tachycardia syndrome, are observed in a substantial subgroup of patients 1

• These comorbid conditions may contribute to the cyclic pattern by lowering the threshold for episode triggering 1

Clinical Patterns and Variations

• The Rome IV criteria define typical CVS episodes as lasting less than 7 days, though approximately 15% of patients experience episodes lasting longer than 7 days 1

• Episode frequency varies widely, with more severe forms characterized by greater frequency 1

• The ANMS-CVSA guidelines classify CVS severity based on:

  • Mild CVS: <4 episodes/year each lasting <2 days, without ED visits or hospitalizations
  • Moderate-severe CVS: ≥4 episodes/year, each lasting >2 days, requiring ED visits or hospitalizations 1

• Most episodes tend to occur in the early morning hours, though they can present at any time of day 1

Breaking the Cycle: Management Approaches

• Prophylactic therapy aims to prevent episodes and break the cycle:

  • Tricyclic antidepressants (amitriptyline)
  • Antiepileptics (topiramate)
  • Aprepitant for refractory cases 2

• Abortive therapy during the prodromal phase is critical to terminate episodes early:

  • Sumatriptan (nasal spray or subcutaneous)
  • Antiemetics (ondansetron, promethazine, prochlorperazine)
  • Sedating medications (alprazolam, lorazepam, diphenhydramine) 1

• Combination therapy is typically required, with most patients needing at least two agents to reliably abort CVS attacks 1

• Emergency department management focuses on:

  • IV fluids with dextrose
  • IV antiemetics
  • Sedation (often with benzodiazepines)
  • Non-narcotic pain control (IV ketorolac preferred) 1

Key Clinical Considerations

• The cyclic pattern is stereotypical within individuals but varies between patients 3

• Recognizing triggers and developing strategies to mitigate them can help reduce episode frequency 1

• Early intervention during the prodromal phase significantly increases the chance of successfully aborting an episode 1

• Treatment of comorbid conditions (especially anxiety) may decrease the frequency of CVS episodes and improve inter-episodic symptoms 1, 2

• Cannabis use patterns should be evaluated, as cannabinoid hyperemesis syndrome (CHS) is considered a subset of CVS when prolonged (>1 year) and heavy cannabis use precedes symptom onset 1