**Core Concept**
Neuroregression in a child refers to a decline in previously acquired cognitive, motor, or language skills, often associated with underlying neurological or systemic disorders. This condition can result from various causes, including infections, metabolic disorders, and structural brain abnormalities.

**Why the Correct Answer is Right**
Neuroregression is often linked to conditions that affect the brain's development or function. Infections such as bacterial meningitis or encephalitis can lead to inflammation and damage to brain tissue, resulting in neuroregression. Metabolic disorders, like phenylketonuria (PKU), can cause an accumulation of toxic substances that impair brain development. Structural brain abnormalities, including congenital malformations or acquired injuries, can also contribute to neuroregression.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while certain medications can have adverse effects on the developing brain, they are not typically associated with neuroregression. However, certain medications like steroids can cause regression in cases of certain conditions but this is not directly related to neuroregression.
**Option B:** This option is incorrect because genetic disorders, such as Down syndrome, can be associated with developmental delays or cognitive impairments, but they are not typically characterized by neuroregression.
**Option C:** This option is incorrect because nutritional deficiencies, such as those caused by inadequate maternal nutrition during pregnancy, can have long-term effects on fetal brain development, but they are not typically associated with neuroregression in children.

**Clinical Pearl / High-Yield Fact**
It's essential to consider the child's medical history, developmental milestones, and physical examination findings when evaluating neuroregression. A thorough diagnostic workup, including imaging studies and laboratory tests, can help identify underlying causes and guide appropriate management.

**Correct Answer: D. Nutritional deficiencies are generally not a direct cause of neuroregression in children.