<s>[INST] context: Maxillary and ethmoid sinuses are large enough to harbor infections from infancy. Frontal sinuses are rarely large enough to harbor infections until the sixth to tenth year of life. Sphenoid sinuses do not become large until about the third to fifth year of life. In general, a "cold" lasting longer than 10 to 14 days with fever and facial pain is suggestive of rhinosinusitis. Examination of the nose can reveal pus draining from the middle meatus in maxillary, frontal, or anterior ethmoid sinusitis. Pus in the superior meatus indicates sphenoid or posterior ethmoid sinuses. Diagnosis is on clinical grounds and can be difficult. Positive findings on plain sinus films in a symptomatic child are supportive of sinusitis. CT scans are more sensitive, but are usually reserved for the more complicated cases. The treatment is usually oral antibiotics for 10 to 14 days. Decongestants and antihistamines have not been shown to be helpful or necessary.Brain abscess is unlikely in this patient who demonstrates no neurologic symptoms. A streptococcal throat infection should present with acute onset of sore throat without other signs and symptoms of upper respiratory infection. Sphenoid sinusitis usually does not cause facial pain or drainage from the middle meatus. The child might have a middle-ear infection coincident with a sinusitis, but her lack of ear pain suggests otherwise. [/INST] question: A 10-year-old girl has had a "cold" for 14 days. In the 2 days prior to the visit to your office, she has developed a fever of 39degC (102.2degF), purulent nasal discharge, facial pain, and a daytime cough. Examination of the nose after topical decongestants shows pus in the middle meatus. Which of the following is the most likely diagnosis? | options: A: Brain abscess B: Maxillary sinusitis C: Streptococcal throat infection D: Sphenoid sinusitis | answer: B </s>