Addison Lennon met all her early milestones: she sat up on time, crawled on time and walked on time. At about 4 months, however, she had a seizure, and her parents started to worry. By 9 months, her head appeared small for her age. Her neurologist reassured the family that Addison could still be within the lowest 5 percent of the normal range. "We were thinking she was typical," says Kari Lennon, "she would be in that 5 percent." At 15 months, however, Addison had another seizure that was a lot more severe. She had been tested for