The External Ear

General compartments External Middle Inner

External ear Embryology: Condensation of the mesoderm of the 1st and 2nd pharyngeal/brachial arches occurs to give rise to 6 hillocks of His 20th week gestation: It has reached adult shape 9 years: reach adult size (this is the age of performing plastic surgery)

Anterior part: Auriculotemporal branch of mandibular branch of trigeminal (V) Posterior and central part: auricular branch of Vagus Nerve (X), Facial nerve (VII) Posterior and inferior part: cervical C2, C3 Understanding innervation is important to understand referred ear pain

Pinna embryology Condensation of the mesoderm of the 1st and 2nd pharyngeal/brachial arches occurs to give rise to 6 hillocks of His 20th week: It has reached adult shape 9 years: reach adult size (this is the age of performing plastic surgery)

Congenintal anomalies of the Pinna Preauricular tag Remnant of one of the hillocks. Uncertain risk factor for hearing loss. Preauricular sinus results from improper fusion of the 1st & 2nd brachial arches May be associated with branchio-oto-renal syndrome Surgery is only indicated when it is complicated by recurrent infection or abscesses Microtia: underdeveloped ear pinna Bat ears: protruding ears, loss of antihelix

Infections of the auricle Erysipelas: infection of the overlying skin Caused by group A beta hemolytic strep. Rapid treatment with oral or IV antibiotic cellulitis (infection of the soft tissue) Cellulitis of the ear typically results from a spreading otitis externa or a penetrating injury. It is distinguished from perichondritis by the lack of induration Rapid treatment with Anti-staph oral or IV antibiotic Perichondiritis to chondritis : represent infections of the auricular perichondrium or cartilage infection involving the cartilage itself of the auricle & external auditory canal. The lobule, which contains no cartilage, is spared Most common cause is Pseudomonas aeruginosa

Relapsing Polychondritis Auto-immune disease Pathophysiology: Chronic multisystemic Inflammation of types of cartilage and may involve other proteoglycan-rich structures, such as the eyes and the cardiovascular system. presentation: acute phase: fever sudden sever painful uniform swelling and erythema of the auricle Chondritis rapidly develops and resolves in 5-10 days Spares: external auditory canal, lobule

External auditory canal anatomy It is tortuous S shaped to protects the Tympanic membrane Dimensions: 24 mm in length from the concha to the Tympanic membrane Bony part: 2/3 of the canal = 16 mm Cartilaginous part: 1/3 of the canal = 8 mm Made of yellow elastic fibrocartilage Auditory canal constrictions: at the junction of the cartilaginous and bony portions the isthmus The isthmus: The narrowest point of the EAC, 5 mm from the tympanic membrane, which is taller more than wider (important note for foreign body retrieval)

Cerumen consists of desquamated epithelium mixed with the sebum produced from sebaceous glands and the watery secretions of modified apocrine sweat glands (apopilo-sebaceous unit) acidic: bacteriostatic + fungostatic contains lysozymes which are bactericidal

External auditory canal infections Furunculosis Furuncle is a localized abscess of the apopilo-sebaceous unit Most common organism: S. aureus Treatment: Analgesia Anti-staphylococcal oral and topical antibiotics should be administered. A fluctuant lesion should be incised and drained under local anesthetic.

Otitis externa Acute otitis externa affects approximately 4- 8/1000 per year. Approximately 10% of the population during their lifetime. Approximately 80% of cases occur in the summer, particularly in warm, humid environments. Other predisposing factors include anatomic obstructions of the ear canal (e.g., stenosis, impacted cerumen), hearing aid or ear plug use, self-induced trauma (e.g., by cotton swabs), and swimming. Systemic: Immune compromise, DM. Bacterial > Fungal (only 2%)

Otitis externa Most common micro-organism: Pseudomonus aeruginosa Second most common: Staph species (epidermidis + aureus) Presentation: Pain: due to high innervation, closely adherent skin May be severe and is exacerbated by manipulation of the auricle or the tragus (due to cartilage continuity) Discharge: scanty… Aural fullness: due edema, discharge. Treatment : Frequent aural toileting Local antibiotic Analgesics Avoid water contact

Fungal otitis externa (otomycosis) Aspergillus Aspergillus accounts for 80-90 % of cases with Candida being responsible for the remaining 10-20%. Presentation: Itchiness, Pain, aural fullness. Treatment : Frequent aural toileting Local antifungal Avoid water contact Candida

Malignant (Necrotizing) otitis externa Malignant Otitis Externa: otitis externa + osteomyelitis of the tympanic plate of the temporal bone which may extend to involve skull base Clinical Presentation: Persistent Otalgia more than 1 month Persistent Otorrhea with granulation tissue Persistent Otorrhea in the immunocompromised patients (Diabetics with microangiopathy and cellular immune dysfunction), HIV. Deep-seated aural pain (pain out of proportion to examination findings). Most cases are caused by P. aeruginosa followed by S. aureus Diagnostic: CT scan with IV contrast MRI Technetium-99m bone scanning

Malignant (Necrotizing) otitis externa Treatment: Regular aural toilet Blood sugar control Correct immunodeficiency if possible Pain killer Infectious disease consult IV antibiotic for 6 weeks, with anti-pseudomonal coverage Prognosis: Mortality is 5-20%

Herpes Zoster Oticus prodrome of otalgia, which may be severe. A vesicular eruption is seen in the canal and concha. Ultimately, these vesicles rupture and form crusts. Etiology: After primary infection (chickenpox), varicella-zoster virus is harbored in a latent state in sensory ganglia, and reactivates with infection spreading along dermatomes. Harbored in the facial nerve VII and the vestibular ganglia of VIII A subgroup of patients manifest Ramsay Hunt syndrome: SNHL, tinnitus or vertigo or both, Palsy: lower motor neuron palsy of the ipsilateral facial nerve 2nd commonest cause of lower facial nerve palsy after bell's palsy (9%) Prognosis for facial nerve recovery worse than Bell’s palsy (only 60% regain normal function, where as up 90% regain normal function in bell’s palsy). Symptoms: Auricular pain: the 1st symptom to appear Vesicular Rash: location: concha, EAC, mucosa of the palate, anterior 2/3 of the tongue Treatment: acyclovir or valacyclovir High-dose steroids Corneal protection