A 4-month-old male infant is brought to the pediatric clinic by his parents due to concerns about rapid head growth and developmental delay. The parents report that the infant’s head size has been noticeably larger than normal since birth, and over the last month, they noticed that he has difficulty lifting his head and appears less active compared to other infants his age. He has also had poor feeding and irritability over the past week. Prenatal and Birth History: •No complications during pregnancy. •No significant family history of hydrocephalus or genetic disorders. •Delivered via normal vaginal delivery at 39 weeks. Birth weight and APGAR scores were within normal limits. Physical Examination: •Head circumference: >95th percentile for age •Cranial examination: •Bulging anterior fontanelle •Widened cranial sutures •Prominent forehead •Neurological examination: •Poor head control •Increased muscle tone and spasticity in the lower limbs •Positive Babinski reflex •No focal deficits •Developmental assessment: Delayed milestones (unable to lift head when prone) Diagnostic Tests: •Cranial ultrasound: Shows dilated lateral and third ventricles with a normal fourth ventricle. •MRI of the brain: Confirms aqueductal stenosis and ventricular enlargement. •Genetic testing: Positive for mutation in the L1CAM gene. What is the most likely diagnosis?
