The external auditory meatus (external auditory canal, EAC) is the bony channel from the auricle to the tympanic membrane, formed by the tympanic plate of the temporal bone anteriorly and inferiorly and the squamosal temporal bone superiorly and posteriorly. The bony EAC is approximately 16 mm long and the outer third is cartilaginous. The anterior wall is closely related to the temporomandibular joint.
The EAC is the primary access route for otoscopy, middle ear procedures, and tympanoplasty. Exostoses (bony outgrowths from cold water exposure) and osteomas narrow the EAC and can cause conductive hearing loss and recurrent otitis externa managed by canalplasty. EAC carcinoma, while rare, erodes the tympanic plate and spreads to the TMJ, parotid, and mastoid. TMJ trauma may fracture the anterior EAC wall. Necrotising otitis externa destroys the tympanic plate and EAC floor.
Chronic cold water exposure in surfers and swimmers stimulates bony exostosis formation from the EAC walls, narrowing the canal and causing conductive hearing loss, recurrent otitis externa from cerumen impaction, and occasionally requiring canalplasty to restore adequate canal width.
Squamous cell carcinoma of the EAC erodes the tympanic plate and adjacent bone, producing a bloodstained otorrhoea initially mistaken for otitis externa; CT-confirmed bone erosion requires aggressive multimodal treatment including lateral temporal bone resection, radiotherapy, and neck dissection for regional nodes.
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