Diagnosis and management of presumptive cyclic vomiting syndrome in a dog: first report in veterinary medicine

Cyclic vomiting syndrome (CVS) is an idiopathic chronic disorder characterized by recurrent episodes of vomiting that are often triggered by psychological stressors and circadian rhythms. Although CVS is well documented in human medicine, it has not been previously reported in dogs. This case describes a dog provisionally diagnosed with neurogenic vomiting exhibiting clinical features consistent with a CVS phenotype. A 16-year-old neutered male Maltese was evaluated for persistent daily vomiting that did not respond to standard antiemetic therapies including maropitant, ondansetron, and metoclopramide. A comprehensive diagnostic workup was performed, including hematology, serum biochemistry, abdominal radiographs, ultrasonography, contrast fluoroscopy, computed tomography, endoscopy with histopathology, brain magnetic resonance imaging, cerebrospinal fluid analysis, and electroencephalography. These investigations ruled out gastrointestinal, metabolic, and structural neurologic causes. The vomiting episodes consistently followed a stereotyped pattern that included stress-related prodromal behavior, clusters of emesis, symptom-free intervals, and early-morning onset. These clinical signs fulfilled adapted human CVS criteria, defined as at least three vomiting episodes occurring within an hour period on two or more days within six months, separated by symptom-free intervals. Based on these findings, a presumptive diagnosis of neurogenic vomiting consistent with a CVS phenotype was made. Treatment with phenobarbital led to rapid resolution of vomiting and associated respiratory signs. Levetiracetam was introduced during phenobarbital tapering to maintain seizure threshold. At 462 days following discharge, the dog remained clinically normal without recurrence or adverse effects. This case represents the first veterinary report of suspected CVS in a dog and emphasizes the importance of considering functional vomiting syndromes in the differential diagnosis of episodic vomiting that does not respond to conventional treatment. Further studies are warranted to define diagnostic criteria specific to canine patients, investigate neurogenic and neuroendocrine mechanisms, and develop validated treatment strategies.