Here's a peer reviewed account of the study from about six months ago: https://www.sciencedirect.com/science/article/pii/S0094730X2500049X The authors claim that the patient stuttered less frequently/severely, and also that he reported improved quality of life. The effect built up slowly, and similarly when the stimulation was turned off there was a lag effect in the return of stuttering. The authors acknowledge that some of the effect is probably placebo. This is a case study of a single patient, which means that the treatment is still in its early stages. While very exciting results, it's still important to keep in mind that the treatment still has to pass a lot more tests before we can think of it as a reliable option.