If you go around the bend, you go crazy. It's an informal way to describe a slight nuttiness or a more serious bout of insanity.
You might use this phrase for something that drives you batty: "I didn't go around the bend until we got our fifth dog." You could also say, more seriously, "It might drive her around the bend when she hears that her son's in trouble again." The origin isn't clear, as some word experts suspect it has a nautical origin — a bend is a series of sailors' knots — while others think it's related to long, curved driveways leading to mental hospitals.