What is the fine-grained topic of the following text: HOUSTON, Feb. 2 — Cyberonics, Inc. today announced that the United States Food and Drug Administration (FDA) has deemed the Vagus Nerve Stimulation Therapy System (VNS Therapy) approvable as a long-term adjunctive treatment for patients over the age of 18 with chronic or recurrent treatment-resistant depression in a major depressive episode that has not responded to at least four adequate antidepressant treatments. Only return the topic.
FDA's approval of Cyberonics' VNS Therapy for treatment-resistant depression