A child presents with severe facial swelling extending toward the periorbital region, and a deep carious maxillary molar is found. What is the MOST likely diagnosis?

Correct answer: D. Cellulitis of the canine/infraorbital space from an odontogenic source

• A. Cavernous sinus thrombosis is the feared COMPLICATION, not the initial diagnosis. Its hallmarks are ophthalmoplegia (loss of eye movement), proptosis, fixed dilated pupil, fever, and altered consciousness — this patient has none of these yet.
• B. Sinusitis produces facial pressure and nasal symptoms without this degree of periorbital swelling from a carious tooth.
• C. Ludwig angina is a bilateral submandibular/sublingual/submental space infection of MANDIBULAR origin with elevated tongue and airway compromise.
• D. CORRECT. Odontogenic infection from a maxillary tooth spreads superiorly into the CANINE and INFRAORBITAL spaces, producing a diffuse, warm, indurated, poorly demarcated swelling that obliterates the nasolabial fold and extends toward the lower eyelid. This is CELLULITIS — the acute, diffuse, spreading phase. It is a true urgency: source control (extraction or drainage), antibiotics, and close monitoring for spread.

Note: Periorbital swelling from a maxillary tooth is an escalating emergency — the route to the cavernous sinus via the angular vein is VALVELESS. Do not delay.