**Core Concept**
The question is testing the association between congenital intrauterine infections and their impact on the central nervous system (CNS) in neonates. Intrauterine infections can cause various complications, including CNS involvement, which is a significant concern for neonatal health.

**Why the Correct Answer is Right**
Toxoplasmosis is a well-documented cause of congenital CNS involvement. When a pregnant woman becomes infected with Toxoplasma gondii, the parasite can cross the placenta and infect the fetus. This can lead to a range of complications, including hydrocephalus, microcephaly, intracranial calcifications, and chorioretinitis. The exact mechanism of Toxoplasma-induced CNS damage is not fully understood, but it is thought to involve the parasite's ability to evade the maternal immune response and infect neural cells.

**Why Each Wrong Option is Incorrect**
**Option A:** Cytomegalovirus (CMV) is another common cause of congenital infection, but it is not the most common cause of symptomatic neonatal CNS involvement. CMV can also cause CNS damage, including microcephaly and intracranial calcifications, but it tends to cause more subtle symptoms than Toxoplasmosis.
**Option B:** Rubella is a viral infection that can cause congenital anomalies, including CNS involvement. However, the introduction of rubella vaccination has significantly reduced the incidence of congenital rubella syndrome, making it a less common cause of symptomatic neonatal CNS involvement.
**Option C:** Syphilis is a bacterial infection that can cause congenital CNS involvement, including hydrocephalus and meningitis. However, the incidence of congenital syphilis has declined significantly in recent decades, making it a less common cause of symptomatic neonatal CNS involvement.
**Option D:** Herpes simplex virus (HSV) is a viral infection that can cause congenital CNS involvement, including encephalitis and seizures. However, HSV is typically associated with more severe and acute CNS symptoms, rather than the more subtle and chronic symptoms seen with Toxoplasmosis.

**Clinical Pearl / High-Yield Fact**
Toxoplasmosis is often referred to as the "silent killer" of congenital infections, as it can cause significant CNS damage without overt symptoms in the mother. This highlights the importance of routine prenatal screening and testing for Toxoplasma antibodies.

**Correct Answer: A. Toxoplasmosis**