CVS Plus: A Distinct Subgroup of Cyclic Vomiting Syndrome

While most individuals with Cyclic Vomiting Syndrome (CVS) are otherwise healthy between episodes, research has identified a significant subgroup of patients who experience CVS alongside additional neurological or neuromuscular features. This subgroup is commonly referred to as CVS Plus.

CVS Plus describes individuals with CVS who have two or more objective neuromuscular or neurodevelopmental manifestations in addition to cyclic vomiting episodes. These additional features are present between episodes, while the vomiting, nausea, and lethargy remain episodic.

Clinical Characteristics of CVS Plus

Neuromuscular and neurological features seen in CVS Plus may include:

• Cognitive or developmental delay

• Skeletal muscle weakness or myopathy

• Seizure disorders

• Cranial nerve abnormalities

• Ataxia

• Cardiomyopathy

• Autism spectrum or related developmental disorders

These manifestations are not randomly distributed among people with CVS. Instead, they tend to cluster within a distinct subset of patients, supporting the concept of CVS Plus as a recognizable clinical phenotype rather than coincidental comorbidity.

Differences Between CVS Plus and Other Forms of CVS

Compared with individuals who have CVS without neuromuscular involvement, those with CVS Plus tend to:

• Develop symptoms at a younger age

• Have a higher burden of associated conditions, including:

  • migraine

  • chronic fatigue

  • dysautonomia-related symptoms

  • growth delay or congenital abnormalities

Despite these differences, CVS Plus does not appear to represent a completely separate genetic disorder. Instead, it is best understood as a phenotypic subgroup within CVS, with overlapping but more complex clinical features.

Possible Role of Mitochondrial Dysfunction

Many of the neurological and neuromuscular features seen in CVS Plus overlap with conditions commonly observed in mitochondrial disorders. Supporting this, individuals with CVS Plus more frequently show:

• Elevated lactate levels

• Biochemical patterns suggestive of impaired energy metabolism

• Family histories consistent with maternal inheritance

These findings suggest that CVS Plus may represent a form of CVS with a greater contribution from mitochondrial dysfunction, rather than a distinct disease entity.

Treatment Considerations

Patients with CVS Plus generally receive the same core treatments used for CVS, including preventive, abortive, and supportive therapies. Available data suggest that:

• Response patterns to medications are broadly similar between CVS Plus and other CVS subgroups

• Some preventive treatments may be particularly helpful in this subgroup

• Management often requires a multidisciplinary approach, involving neurology, gastroenterology, and other specialists as needed

Because CVS Plus is associated with higher medical complexity, early recognition may help guide appropriate evaluation and long-term care planning.

Summary

CVS Plus represents a clinically meaningful subgroup of Cyclic Vomiting Syndrome characterized by coexisting neuromuscular or neurodevelopmental features. These individuals often experience earlier disease onset and increased medical complexity. Recognition of CVS Plus supports more individualized assessment and highlights the potential role of mitochondrial dysfunction in a subset of CVS patients.