On this episode of the “First Opinion Podcast,” host Torie Bosch talks to Vijay Agarwal, the neurosurgeon who consults on “Severance.” (His day job is chief of the Division of Skull Base and Minimally Invasive Surgery at Montefiore Medical Center.) They chat about the neuroscience behind severance, how Hollywood approaches medicine, and his cameo appearance on the show as, naturally, the surgeon performing the titular procedure. Note: Severance spoilers ahead.