An 18-month-old has a head circumference at the 98th centile with a bulging anterior fontanelle and setting-sun sign. CT head shows dilated lateral and third ventricles with a normal fourth ventricle. The most likely etiology of hydrocephalus in this child is:

• A Aqueductal stenosis ✓
• B Dandy-Walker malformation
• C Communicating hydrocephalus from post-meningitic adhesions
• D Choroid plexus papilloma

Explanation

Aqueductal stenosis (stenosis of the cerebral aqueduct of Sylvius connecting the third and fourth ventricles) is the most common cause of obstructive non-communicating hydrocephalus in children. On CT, dilated lateral and third ventricles with a normal-sized fourth ventricle is the hallmark — obstruction is at the aqueduct level, preventing CSF passage. Dandy-Walker shows a posterior fossa cyst with fourth ventricle dilation. Communicating hydrocephalus (post-meningitic) involves all four ventricles being dilated due to impaired CSF absorption at the arachnoid villi. Choroid plexus papilloma causes communicating hydrocephalus by CSF overproduction. The setting-sun sign indicates elevated ICP from ventricular dilation.

Reference: Ghai Essential Pediatrics, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.