Case Report: Right-sided vagus nerve stimulation for treatment-resistant affective disorders with complex cardiac...

Vagus nerve stimulation (VNS) is a well-established treatment option for treatment-resistant affective disorders. Due to potential concerns about increased cardiac innervation on the right side, devices are almost exclusively implanted on the left cervical vagus nerve. Clinical data on right-sided VNS for psychiatric indications are often very scarce.

We present a case series involving three patients-two with MDD and one with bipolar depression-each with extensive prior unsuccessful treatments, frequent hospitalizations, and severe psychiatric and medical comorbidities. In each case, the right cervical side was chosen for primary implantation or re-implantation due to cardiac disease, pre-existing devices, or anatomical constraints (including high-grade atrioventricular block with pacemaker and recurrent laryngeal nerve palsy). All patients underwent standard titration of stimulation parameters and long-term clinical follow-up.

All three patients showed significant and lasting mood stabilization within approximately 12 months after right-sided VNS implantation. Hospital admission rates decreased markedly, and in two cases, maintenance electroconvulsive therapy (ECT) was discontinued or notably reduced. In all cases, VNS was generally well tolerated. During right-sided stimulation, no clinically significant bradyarrhythmia, device interactions, or other serious cardiac adverse events were observed.

This series highlights the usefulness of right-sided VNS in sustaining long-term mood stability and reducing hospitalizations for patients with highly treatment-resistant, comorbid mood disorders. The findings expand existing epilepsy-focused data on right-sided VNS to the psychiatric field and support systematic evaluation of this approach in future prospective studies. Multidisciplinary coordination is essential to minimize risks and improve outcomes. Additional long-term research is needed to assess its lasting effectiveness, optimal candidate selection, and cost-efficiency in routine clinical practice.