This is according to a MarketWatch report:
The Senate Finance Committee is investigating the Food and Drug Administration’s handling of a marketing clearance for Cyberonics’s VNS Therapy System to treat chronic depression…
According to Cyberonics, the inquiry focuses on allegations that the FDA gave a preliminary green light to the VNS device over the objections of several agency scientists.
The VNS system, cleared by the FDA in 1997 to treat epilepsy, received an approvable letter from the agency in early February. An approvable letter means the agency considers the product worthy of approval if the company follows through on specific testing and product labeling. Formal approval of the device is still pending.