The tympanic part of the temporal bone is a curved bony plate forming the anterior wall, floor, and inferoposterior wall of the external auditory meatus. It extends from the tympanosquamosal suture anterosuperiorly to the tympanomastoid suture posteriorly. Its medial edge forms the tympanic ring, which holds the tympanic membrane. Superiorly it is deficient at the tympanic notch of Rivinus where the pars flaccida of the tympanic membrane attaches.
The tympanic plate is eroded by cholesteatoma in the external auditory canal (keratosis obturans), by necrotising otitis externa causing temporal bone osteomyelitis, and by carcinoma of the EAC. Fractures of the tympanic plate can cause anterior EAC haemorrhage and communication with the temporomandibular joint. In congenital aural atresia, the tympanic plate is absent or malformed, replacing the normal EAC with a bony atretic plate requiring surgical reconstruction.
Keratosis obturans or EAC cholesteatoma erodes the tympanic plate by enzymatic activity of the cholesteatoma matrix, causing progressive expansion of the EAC, erosion into the mastoid or middle ear, and risk of lateral sinus or facial nerve exposure requiring surgical exenteration.
Malignant (necrotising) otitis externa from Pseudomonas aeruginosa in diabetic or immunocompromised patients invades the tympanic plate and spreads to the skull base, producing severe ear pain, cranial nerve palsies, and osteomyelitis managed with prolonged antipseudomonal antibiotics and surgical debridement.
