Commonest cause of obstructive hydrocephalus in children:
**Core Concept**
Obstructive hydrocephalus is a condition where there is an accumulation of cerebrospinal fluid (CSF) in the brain due to an obstruction in the CSF pathways. In children, the most common cause of this condition is a blockage in the cerebral aqueduct, which connects the third and fourth ventricles.
**Why the Correct Answer is Right**
The cerebral aqueduct is a narrow tube that allows CSF to flow from the third to the fourth ventricle. Blockage of the aqueduct can occur due to various reasons such as congenital anomalies, tumors, or inflammation. When the aqueduct is blocked, CSF accumulates in the third and lateral ventricles, leading to hydrocephalus. This condition can cause increased intracranial pressure, impaired cerebrospinal fluid circulation, and eventually, brain damage.
**Why Each Wrong Option is Incorrect**
* **Option A:** Aqueductal stenosis is a condition where the cerebral aqueduct is narrowed or blocked, leading to obstructive hydrocephalus. However, it is not the most common cause of this condition in children.
* **Option B:** Congenital hydrocephalus refers to hydrocephalus present at birth, but it is not the most common cause of obstructive hydrocephalus in children.
* **Option C:** Meningitis is an infection of the meninges, which can cause hydrocephalus, but it is not the most common cause of obstructive hydrocephalus in children.
**Clinical Pearl / High-Yield Fact**
The Dandy-Walker malformation is a congenital anomaly that involves the formation of a cyst in the fourth ventricle and agenesis of the cerebellar vermis. It is often associated with obstructive hydrocephalus and is a common cause of hydrocephalus in children.
**Correct Answer: C. Meningitis.**