Pathophysiology
Clinical meaning
Otitis media encompasses a spectrum of middle ear inflammatory conditions including acute otitis media (AOM), otitis media with effusion (OME), and chronic suppurative otitis media (CSOM). The pathophysiology begins with eustachian tube (ET) dysfunction, most commonly triggered by viral upper respiratory infection. The ET mucosa is contiguous with the nasopharyngeal and middle ear mucosa, so viral-induced inflammation causes mucosal edema throughout this system. When the ET becomes obstructed, three pathological consequences follow: negative middle ear pressure develops (from gas absorption by the middle ear mucosa without ventilatory replacement), transudate fluid accumulates in the middle ear space, and nasopharyngeal bacteria are aspirated retrograde through the dysfunctional tube. The three cardinal AOM pathogens -- Streptococcus pneumoniae, non-typeable Haemophilus influenzae, and Moraxella catarrhalis -- colonize the nasopharynx in up to 60% of children. S. pneumoniae remains the most virulent organism, responsible for the majority of treatment failures and complications (mastoiditis, meningitis, epidural abscess), though its prevalence has declined by 50-60% since widespread PCV13 vaccination. H. influenzae has become the most commonly isolated AOM pathogen in the post-PCV13 era. Importantly, AOM must be distinguished...