The ear (Figure 32-1) is divided into (1) the external ear; (2) the middle ear, which is separated from the external auditory meatus by the tympanic membrane and is in communication anteriorly with the pharynx via the auditory tube (eustachian tube) and posteriorly with the mastoid air cells; and (3) the inner ear, consisting of the semicircular canals, which are part of the vestibular system, and the cochlea, which is the hearing sense organ. The vestibular and auditory nerves arise in the inner ear and pass to the brain stem in the internal auditory meatus.
The structure of the ear and its principal diseases.
The external ear consists of the pinna (or auricle) and the external auditory meatus. The pinna is composed of cartilage covered by skin. The meatus is lined by stratified squamous epithelium and contains wax-secreting ceruminous glands between the epithelium and the bony wall.
Preauricular Sinus & Cyst
This is a developmental anomaly associated with abnormal fusion of the facial folds. A blind-ending epithelium-lined tract opens as a small pit anterior to the meatus. Obstruction of the opening may lead to the development of an epidermal cyst; infection may cause an abscess and discharging sinus.
Inflammation of the external auditory canal is commonly caused by saprophytic fungi, commonly Aspergillus spp. This causes pain and a thick discharge. A foreign body or excessive exposure to water (swimmer's ear) predisposes to infection by low-grade pathogens.
Herpes zoster involving the facial nerve ganglion (Ramsay Hunt syndrome) results in typical viral vesicles in the external ear, commonly associated with severe pain.
Chondrodermatitis Nodularis Helicis
This is a common lesion characterized clinically by the occurrence of a painful nodule in the helix. It is thought to result from trauma and is more common in males. Microscopically, there is ulceration of the skin and a chronic inflammatory infiltrate involving the perichondrium of the underlying cartilage. Surgical excision is curative.
This is the result of trauma and is most commonly seen in professional boxers. It is caused by thickening due to multiple organized and contracted hematomas.
Neoplasms of the External Ear
The skin of the external ear is a common site for basal cell and squamous carcinoma. Nevi and malignant melanoma also occur in the skin of the ear.
Neoplasms of the external auditory meatus, such as osteoma and ceruminous gland adenoma, are very rare.