Dr. Brian Goldman talks to Keith McArthur, the creator and host of the CBC podcast "Unlocking Bryson's Brain.” McArthur’s son Bryson has a severe genetic disorder that’s so rare it took nearly a decade to get a diagnosis. Now 13, Bryson is a happy kid, but his illness means he can't walk, talk or feed himself, and he’s thought to have a mental age of a one-year-old. The “‘medical mystery” series chronicles McArthur’s search to find more information about Bryson’s condition, known as a GRIN disorder — and his quest to find a cure.