**Core Concept**
Paranasal sinusitis is an inflammatory condition of the paranasal sinuses, which can lead to various complications due to the spread of infection, altered anatomy, or impaired drainage. The paranasal sinuses are air-filled cavities in the skull that are lined by mucous membranes and are connected to the nasal cavity.

**Why the Correct Answer is Right**
Complications of paranasal sinusitis can arise from the spread of infection to adjacent structures, such as the orbit, cavernous sinus, or intracranial structures. This can lead to orbital cellulitis, cavernous sinus thrombosis, or intracranial abscesses. Additionally, altered anatomy or impaired drainage can cause chronic sinusitis, leading to persistent symptoms and potential complications.

**Why Each Wrong Option is Incorrect**
* **Option A:** Orbital cellulitis is a recognized complication of paranasal sinusitis, making this option incorrect.
* **Option B:** Cavernous sinus thrombosis is a potential complication of paranasal sinusitis, particularly in cases of frontal or ethmoid sinusitis, making this option incorrect.
* **Option C:** Meningitis is a possible complication of paranasal sinusitis, especially in cases of frontal or ethmoid sinusitis, making this option incorrect.

**Clinical Pearl / High-Yield Fact**
Meningitis is a potential complication of paranasal sinusitis, particularly in cases where the infection spreads to the frontal or ethmoid sinuses.

**Correct Answer: D.**