ObjectivesVagus nerve stimulation (VNS) has been shown to be effective for treatment-resistant depression (TRD). However, long-term (>5 years) studies on the efficacy and tolerability of this treatment have been lacking. Here, we report a long-term clinical follow-up of 5 patients with severe and long-standing TRD, who received a VNS implant.MethodsOf the initial 6 patients with TRD implanted with VNS at our center, 5 of them were followed for 6 to 12 years after implantation. Primary efficacy outcomes were clinical response and improved functioning at follow-up visits. The primary safety outcome was all-cause discontinuation, and the secondary safety outcomes were the number and the severity of adverse events.ResultsThe VNS implant was associated with a sustained response (>10 years) in terms of clinical response and social, occupational, and psychological functioning in 3 patients. Two patients dropped out after 6 and 7 years of treatment, respectively. Vagus nerve stimulation was well tolerated by all patients, who reported only mild adverse effects. One patient, who discontinued concomitant drug treatment, had a hypomanic episode in the 10th year of treatment. The parameters of the VNS device were fine-tuned when life stressors or symptom exacerbation occurred.ConclusionsOur case series showed that VNS can have long-term and durable effectiveness in patients with severe multiepisode chronic depression, and this could be associated with its neuroplastic effects in the hippocampus. In light of good general tolerability, our findings support VNS as a viable treatment option for TRD.

I ntroduction Vagus nerve stimulation (VNS) is a neuromodulation technique approved for Treatment-Resistant Depression (TRD).Evidence regarding its long-term efficacy and safety is still scarce. Objectives To descriptively report a case series of 3 patients undergoing adjunctive VNS for TRD with an over 10-year follow-up. Methods We investigated outcomes of clinical interest in patients with ongoing VNS for at least 10 years after the device implantation. They had participated in a larger single-arm interventional study conducted at the University Hospital of Padua. They were diagnosed with chronic unipolar (1), recurrent unipolar (1), and bipolar (1) TRD. Results Our 3 cases had an average 14-year history of psychiatric disease before surgery. Afterward, all subjects achieved clinical remission within two years. 2 patients experienced relapses within the first 4 years of treatment (respectively, 1 and 2 episodes). The other case showed a recurrent trend of brief relapses every two years. Only 1 individual needed to be admitted to the psychiatric unit once. None of them committed suicidal attempts. Prescription of antidepressants remained almost unchanged after the first two years. 2 individuals improved and 1 maintained their working position. Common adverse events were voice alteration (3/3), neck pain (2/3), and cough (2/3). Conclusions Very few cases of 10-year VNS for TRD have been reported so far. For our subjects, VNS was most likely to have a major impact on the clinical course of the disease. This treatment can be a safe and effective adjunctive intervention in a subgroup of patients with TRD.

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