1. The External Ear

2. General compartments
External
Middle
Inner

3. 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)

4. 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

5. 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)

6. 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

8. 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

9. 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 days
Spares: external auditory canal, lobule

10. 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)

11. 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

12. 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.

13. 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%)

14. 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

15. Fungal otitis externa (otomycosis)
Aspergillus
Aspergillus accounts for % 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

16. 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

17. 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%

18. 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