A 9-month-old infant with rapidly enlarging head circumference (crossing centiles), bulging fontanelle, sunset sign (downward gaze deviation), and scalp vein prominence is diagnosed with communicating hydrocephalus. MRI shows dilation of all four ventricles. Which is the most likely etiology in this age group?
- A Post-infectious (post-meningitis) arachnoid fibrosis ✓
- B Aqueductal stenosis (congenital or secondary)
- C Dandy-Walker malformation
- D Choroid plexus papilloma with CSF overproduction
Explanation
Communicating hydrocephalus (all ventricles dilated, CSF circulation not obstructed within the ventricular system but impaired in subarachnoid space/arachnoid villi) is most commonly caused in infants by post-infectious arachnoid fibrosis following bacterial meningitis or intraventricular hemorrhage (IVH) in preterm neonates. Aqueductal stenosis causes non-communicating (obstructive) hydrocephalus with dilation of lateral and third ventricles only. Dandy-Walker malformation causes posterior fossa cyst with fourth ventricle dilation. Choroid plexus papilloma is rare. A lumbar puncture in communicating hydrocephalus will show elevated opening pressure and the CSF is accessible, unlike in obstructive types.
Reference: Ghai Essential Pediatrics, 10th ed.
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Written and medically reviewed by the StethoPrep medical team.