During the health supervision visit for a healthy 4-month-old boy, you note that his head circumference is 46 cm (>98th percentile) and his length and weight are at the 50th percentile. He has mild frontal bossing and widely split cranial sutures. The fontanelle is flat. Arm and leg movements, tone, and reflexes are normal. In reviewing prior growth parameters, you note that his head circumference was at the 75th percentile at birth and the 90th percentile at 2 months