Middle Ear Cleft Opacification in Acute Otitis Externa: Sequela or Incidentaloma?

The external and middle ear are anatomically distinct regions. Middle ear cleft opacification (MECO) observed following acute otitis externa (AOE) raises questions about its occurrence mechanism and clinical significance. Previous animal studies have demonstrated that irritation of the external ear canal can lead to the development of middle ear effusion via Pars Flaccida cells. The literature lacks clinical information on middle ear involvement in AOE.

A retrospective analysis was conducted on 92 patients post-AOE who underwent brain imaging within 3 months post-uncomplicated AOE. Patients with anatomical disruptions between the external and middle ear were excluded. MECO rate and dynamics were evaluated. The involvement of middle ear cleft anatomic regions was assessed.

MECO was identified in 38.0% (35/92) of post-AOE ears compared to 10.8% (10/92) of contralateral ears (P = .002). The prevalence of MECO in post-AOE patients decreased from 58.9% (23/39) within 2 weeks post-AOE to 8.0% (2/25) 3 months post-AOE. Over time, complete middle ear opacification gradually transitioned to partial opacification. Opacification was noted in the upper middle ear cleft (epitympanum/mastoid) in 94.2% (33/35).

Middle ear effusion is a common, resolving sequela of AOE, rather than an indication of AOE deterioration or significant middle ear inflammatory involvement. This information is valuable for otolaryngologists as well as general practitioners who treat AOE patients, helping to better understand potential sequelae and avoid unnecessary treatments, and for radiologists who diagnose ME opacification in AOE patients. Further studies are warranted to explore the role of the pars flaccida in middle ear effusion.