Introduction: In patients refractory to vestibular rehabilitation in the management of bilateral vestibulopathy, the cochleo-vestibular implant has emerged as a viable alternative to enhance both audiovestibular function and quality of life. The main objective of this study is to pioneer the use of PET to assess cortical modifications in patients with cochleo-vestibular implants, aiming to evaluate the safety and functional improvements in individuals with bilateral vestibulopathy and severe to profound hearing loss. Methods: A phase I pilot clinical trial was conducted with participants who received a BIONIC-VEST CI24RE cochleo-vestibular implant, with pre- and post-implantation assessments conducted for twelve months. Audiovestibular testing and two PET studies with 18F-FDG under baseline conditions and with active stimulus to observe cortical-level differences were performed. Results: Five patients were included in the study, all of them treated with a cochleo-vestibular implant, none of whom presented postoperative adverse effects. Audiologically, the mean post-implant gain was 56.63 ± 14.53 dB and 50.40 ± 35.54% in terms of speech intelligibility. From a vestibular perspective, the most remarkable findings were observed at the graviceptive pathway level, where a mean posturographic improvement was observed, with a sensory organization test score of 24.20 ± 13.74 and a subjective visual vertical of 1.57° ± 0.79°, achieving, in most cases, results within the normal range (<2.3°) by the end of the follow-up. PET images confirmed that with the electrical stimulus active (implant ON), there was a supratentorial activation pattern, particularly in areas related to somatosensory integration, emotional regulation, and autonomic control. Conclusions: The BIONIC-VEST implant significantly improved the vestibular system, particularly the graviceptive pathway, enhancing balance and SVV and reducing fall risk. PET revealed distinct uptake patterns in baseline and activated conditions, highlighting a cortical-level response with the use of the cochleo-vestibular implant.