Brooke Ellison, who after being paralyzed from the neck down by a childhood car accident went on to graduate from Harvard and became a professor and a devoted disability rights advocate, died on Sunday in Stony Brook, N.Y., on Long Island. She was 45.Her death, in a hospital, was caused by complications of quadriplegia, her mother, Jean Ellison, said.As an 11-year-old, Brooke had been taking karate, soccer, cello and dance lessons and singing in a church choir. But on Sept. 4, 1990, she was struck by a car while running across a road near her home in Stony Brook. Her skull, her spine and almost every major bone in her body were fractured.After waking from a 36-hour coma, she spent six weeks in the hospital and eight months in a rehabilitation center. And for the rest of her life she was de...