A 22-month-old male infant had been followed up from birth because of "macrocrania," which had been associated with consistently normal neurologic examination results and normal growth and development.
The infant was born to a 30-year-old primigravida who experienced a normal pregnancy, labor, and delivery. Delivery was vaginal by "elective" low-outlet forceps. Apgar scores were 9 and 9 at one and five minutes, respectively. The results of his examination at birth were normal, with a head circumference of 35.5 cm (at the 50th percentile), weight of 3.9 kg (at the 75th percentile), and height of 50 cm (at the 50th percentile). There had been no history of trauma.
At 2 weeks of age, the anterior fontanelle was soft, and the infant's development and neurologic examination findings were normal, but the head circumference was abnormal (37.5 cm) and continued to progress to greater than 2 SDs above normal at 6 months of