Meningitis
Cavernous sinus thrombosis (ethmoid/sphenoid)
Intracranial abscess
Orbital cellulitis (ethmoid)
Frontal bone osteomyelitis (Pott's puffy tumor)
Extradural or subdural empyema
Sinusitis
Upper respiratory infection, influenza
Laryngitis
Mastoiditis
Juvenile nasopharyngeal angiofibroma
Croup
Nasal polyp
Pharyngitis