Study II (recently diagnosed CHI): Patients undergo neurobehavioral and psychological testing as in study I once during hospitalization or soon after discharge, and then at 3, 6, 12, and 24 months. Patients undergo brain MRI at 3 months. While each patient undergoes testing, the patient's parent/guardian answers interview questions as in study I. Prior to each visit, the same questionnaire as in study I is mailed to each patient's teacher.