STEPTRACKERSPECIAL SENSES | PATHOLOGY + MICROBIOLOGY + ANATOMY | HIGH-YIELD REVIEW

External & Middle Ear

Infections of the canal and middle ear, fluid behind the drum, the skin cyst that erodes bone, and the stapes that won't move.

FOCUS ON
Otitis externa: swimmer, pain on pulling the pinna, Pseudomonas; malignant form in elderly diabetics spreads to skull base. Acute otitis media: child, bulging red drum, S pneumoniae, nontypeable H influenzae, Moraxella → amoxicillin. Effusion: dull immobile drum, conductive loss. Cholesteatoma: keratin cyst, foul discharge, bone erosion. Otosclerosis: young adult, stapes fixation.
DISORDER
CAUSE · MECHANISM
FEATURES
CLUE · TREATMENT
Otitis externa
Moisture/trauma breaks canal skin; Pseudomonas, S aureus
Ear pain worse when pulling the pinna or pressing tragus; swollen canal, discharge
Topical antibiotic ± steroid drops
Malignant (necrotizing) otitis externa
Pseudomonas invades bone in elderly diabetics or immunocompromised
Severe pain, granulation tissue in canal, skull-base osteomyelitis, CN VII palsy
↑ ESR, CT/MRI · IV antipseudomonal antibiotics
Acute otitis media
Eustachian tube dysfunction after URI; S pneumoniae, nontypeable H influenzae, Moraxella
Child with ear pain, fever, tugging; bulging red immobile drum
High-dose amoxicillin (± clavulanate)
Otitis media with effusion
Fluid without acute infection after AOM or eustachian dysfunction
Dull, retracted, immobile drum with air-fluid level; conductive hearing loss, speech delay
Persistent → tympanostomy tubes
Complications of otitis media
Spread to bone and brain
Mastoiditis (postauricular swelling, ear pushed forward), TM perforation, meningitis, brain abscess, venous sinus thrombosis
Displaced pinna → CT, IV antibiotics
Cholesteatoma
Squamous epithelium in the middle ear (retraction pocket, perforation) → keratin mass
Painless foul-smelling discharge, conductive loss; white mass behind drum; erodes ossicles
Can reach inner ear, facial nerve, brain · surgery
Tympanic membrane perforation
Infection, trauma (Q-tips, slaps, blasts), barotrauma
Sudden pain relieved by discharge; conductive loss
Most heal spontaneously · keep dry
Barotrauma
Pressure change with blocked eustachian tube (flying, diving)
Ear pain, fullness, hemotympanum
Decongestants, Valsalva
Otosclerosis
Abnormal bone remodeling fixes the stapes footplate; often AD, worse in pregnancy
Young adult with progressive conductive hearing loss, normal drum
Hearing aid or stapedectomy
Cerumen & foreign body
Canal obstruction
Conductive loss, fullness
Batteries in the ear → urgent removal
Branchial anomalies of the ear
First pharyngeal arch/cleft remnants
Preauricular pits/tags, first cleft cysts near the angle of the jaw
Preauricular tags → check hearing and kidneys

Mechanism — why children get otitis media

URINasopharyngeal swelling
→
Short, horizontal eustachian tubeBlocked
→
Negative pressure → fluid
→
Bacteria multiplyAcute otitis media
→
Persistent fluidConductive loss

Risk ↑ with daycare, smoke exposure, bottle-feeding lying down, cleft palate and Down syndrome; ↓ with breastfeeding and pneumococcal vaccine.

Ear structures from the arches

STRUCTURE
ORIGIN
NOTE
Malleus, incus
1st arch (Meckel cartilage)
Tensor tympani (CN V3)
Stapes
2nd arch (Reichert cartilage)
Stapedius (CN VII) → hyperacusis if lost
External canal
1st cleft
Ectoderm
Middle ear, eustachian tube
1st pouch
Endoderm
Tympanic membrane
1st membrane
All three germ layers

How it's tested

COMMON CONFUSIONOtitis externa hurts when the pinna is pulled and the drum may be normal; otitis media hurts deep in the ear with a bulging drum and fever.
THE TRAPAn elderly diabetic with "ear infection" that won't settle, severe pain and facial weakness has malignant otitis externa — skull-base osteomyelitis, not a simple swimmer's ear.
YOUR APPROACHAge + pain pattern + drum appearance (normal, bulging, retracted, white mass) + hearing type → diagnosis → organism → treatment and complications.

If you see… think…

Swimmer with pain when the ear is pulled → otitis externa (Pseudomonas)
Elderly diabetic with ear pain, granulation tissue and facial palsy → malignant otitis externa
Toddler with fever, ear tugging, bulging red drum → acute otitis media
Most common bacterial cause of AOM → S pneumoniae
Dull immobile drum with fluid line and hearing loss → otitis media with effusion
Ear pushed forward with postauricular swelling → mastoiditis
Foul painless discharge and white mass behind the drum → cholesteatoma
Young woman with conductive loss worsening in pregnancy, normal drum → otosclerosis
Ear pain and hemotympanum after a flight → barotrauma
Facial palsy with hyperacusis → CN VII lesion (stapedius)