**Core Concept:** Neurocysticercosis is a parasitic infection caused by the larval form of the tapeworm Taenia solium. The infection primarily affects the central nervous system (CNS), leading to symptoms and complications.

**Why the Correct Answer is Right:** Cysticerci, the larval form of Taenia solium, can invade the CNS and cause inflammation, leading to symptoms such as seizures, focal neurological deficits, and mass effect. The correct answer, **Option C: Cysticerci can cause inflammation and mass effect within the CNS**, is correct because these events lead to the clinical manifestations of neurocysticercosis.

**Why Each Wrong Option is Incorrect:**

A. **Option A: Cysticerci primarily affect the gastrointestinal tract** is incorrect because neurocysticercosis results from the migration of cysticerci to the CNS, not their primary location.

B. **Option B: Cysticerci do not cause seizures** is incorrect because seizures are a common manifestation of neurocysticercosis due to the inflammation and mass effect caused by the cysticerci in the CNS.

D. **Option D: Cysticerci do not cause focal neurological deficits** is incorrect as focal neurological deficits can result from the direct involvement of nerves and brain structures by the cysticerci in the CNS.

**Clinical Pearl:** Neurocysticercosis is an important differential diagnosis to consider in patients presenting with seizures, focal neurological deficits, or mass lesions on imaging studies, especially in endemic regions where Taenia solium is prevalent.

**Correct Answer:** **Option C: Cysticerci can cause inflammation and mass effect within the CNS**. The correct answer highlights the key pathological mechanisms of neurocysticercosis, which result in the clinical manifestations seen in patients.