Today is special. For devotees of the 1984 film This Is Spinal Tap, 11/11/11 is the day to honor the genius of Nigel Tufnel. The guitarist played by Christopher Guest rocked the world with amplifiers that "go to 11." In the popular imagination, spinal taps get top symbolic billing when it comes to medically induced pain and foreboding. But Paola Sandroni, a neurologist at the Mayo Clinic in Rochester, Minn., says that reputation is undeserved: "It's a benign procedure overall."