**Core Concept:** Hydrocephalus is a condition characterized by an abnormally increased intracranial pressure due to accumulation of cerebrospinal fluid (CSF) within the brain ventricles. It can be categorized as either obstructive or communicative, depending on the obstruction in the CSF circulation. This question is related to a case of communicative hydrocephalus in a 6-month-old child.

**Why the Correct Answer is Right:** The correct answer, option D (Meningitis), is chosen due to the presence of calcified lesions on the CT scan and impaired movement of the extremities, hypotonia, and retinal abnormalities. These findings are consistent with the neurological complications of meningitis.

**Why Each Wrong Option is Incorrect:**

A. Infantile spasms (hypotonic seizures): Although seizures are present, the other clinical features like hydrocephalus and retinal abnormalities are not typical of infantile spasms.

B. Encephalomalacia: This refers to the necrosis of brain tissue, not calcified lesions and retinal abnormalities seen in meningitis.

C. Congenital hydrocephalus: Hydrocephalus can be present at birth or develop later, and the combination of calcification, impaired movement, hypotonia, and retinal abnormalities is more consistent with meningitis.

D. Encephalitis: Encephalitis is inflammation of the brain, but the calcified lesions and retinal abnormalities are indicative of meningitis.

**Clinical Pearl:** Encephalitis is a serious neurological condition that requires prompt evaluation and treatment. Early diagnosis and intervention can prevent severe neurological deficits and improve the outcome.

**Correct Answer:** D. Encephalitis