A 2-year-old child with myelomeningocele develops worsening headache, irritability, and upgaze palsy (Parinaud's sign) with dilated scalp veins. Head circumference has increased 3 cm over 2 months. Which type of hydrocephalus is present and its MOST common cause in this condition?
- A Communicating hydrocephalus due to impaired CSF absorption at arachnoid granulations
- B Communicating hydrocephalus due to overproduction of CSF by choroid plexus
- C Non-communicating hydrocephalus due to aqueductal stenosis unrelated to myelomeningocele
- D Non-communicating (obstructive) hydrocephalus due to Chiari II malformation obstructing CSF flow at the aqueduct/4th ventricle outflow ✓
Explanation
Myelomeningocele (open spina bifida) is invariably associated with Chiari II malformation (Arnold-Chiari), where the cerebellar vermis, medulla, and 4th ventricle herniate downward through the foramen magnum. This herniation obstructs CSF outflow at the level of the 4th ventricle foramina and/or the aqueduct of Sylvius, causing non-communicating (obstructive) hydrocephalus in 80–90% of children with myelomeningocele. Parinaud's syndrome (failure of upgaze) arises from dorsal midbrain compression by the dilated supratentorial ventricles. Communicating hydrocephalus due to impaired absorption occurs in post-hemorrhagic hydrocephalus of prematurity and post-meningitic hydrocephalus. Choroid plexus overproduction is extremely rare.
Reference: Ghai Essential Pediatrics, 10th ed.
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