A 3-month-old infant is brought with increasing head circumference (above 99th percentile), bulging anterior fontanelle, and setting-sun sign. CT scan shows dilatation of lateral and third ventricles with a normal fourth ventricle. What is the MOST likely type of hydrocephalus?
- A Non-communicating (obstructive) hydrocephalus ✓
- B Communicating hydrocephalus
- C Hydrocephalus ex vacuo
- D Benign external hydrocephalus
Correct answer: A. Non-communicating (obstructive) hydrocephalus
Explanation
Dilatation of the lateral and third ventricles with a normal-sized fourth ventricle suggests obstruction at the level of the cerebral aqueduct (Aqueduct of Sylvius), resulting in non-communicating obstructive hydrocephalus. Aqueductal stenosis is the most common cause of congenital hydrocephalus. The setting-sun sign (downward conjugate gaze) reflects pressure on the dorsal midbrain (Parinaud's syndrome). Treatment is ventriculoperitoneal shunting or endoscopic third ventriculostomy.
Reference: Ghai Essential Pediatrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.