Neurodevelopmental function, language, academic achievement, visuomotor integration, and motor function were evaluated in 20 nonreferred children, aged 6 to 15 years, with idiopathic megalencephaly (>98th percentile) from a suburban practice, and compared to 19 siblings with normal heads and 16 age-matched controls, at the Olson Huff Center for Child Development, Thoms Rehabilitation Hospital, Asheville, North Carolina. Megalencephaly was associated with impaired performance on upper limb motor proficiency, visuomotor integration, response speed, coordination, and increased mirror movements and other neurologic soft signs. Naming fluency was weak, but receptive vocabulary and academic performance were not affected. 
COMMENT. Idiopathic megalencephaly in school-age children, sometimes considered ‘benign.’ may be associated with subtle motor impairments and neurodevelopmental dysfunction.