**Core Concept**
Pott's puffy tumor is a rare but serious complication of frontal sinusitis, characterized by subperiosteal abscess formation in the frontal bone. This condition occurs due to the spread of infection from the frontal sinuses to the surrounding bone and soft tissues.

**Why the Correct Answer is Right**
The infection in Pott's puffy tumor typically originates from the frontal sinuses, which contain mucous membranes that can become infected. The infection then spreads to the frontal bone, leading to the formation of a subperiosteal abscess. This condition can be life-threatening if left untreated, as it can cause increased intracranial pressure, meningitis, and sepsis. The frontal sinuses are closely associated with the anterior cranial fossa, and the infection can spread to the brain, causing severe neurological complications.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Pott's puffy tumor is not primarily caused by mastoiditis. Mastoiditis is a different condition that affects the mastoid bone and is often associated with otitis media.
**Option B:** This option is incorrect because epidural abscess is a different type of abscess that occurs between the dura mater and the inner surface of the skull. While both conditions are serious and can be life-threatening, they have distinct underlying pathologies.
**Option C:** This option is incorrect because osteomyelitis is a more general term that refers to infection of the bone. Pott's puffy tumor is a specific type of osteomyelitis that occurs in the frontal bone.

**Clinical Pearl / High-Yield Fact**
Pott's puffy tumor is a classic example of an "open sinus" infection, where the infection spreads from the paranasal sinuses to the surrounding bone and soft tissues. This type of infection can occur in anyone with a compromised immune system, including those with diabetes, HIV/AIDS, or taking immunosuppressive medications.

**Correct Answer:** C.