Acute Suppurative Otitis Media (ASOM) vs. Chronic Suppurative Otitis Media (CSOM)

ASOM (Acute Suppurative Otitis Media)

Definition

Epidemiology

• ~85% of all children experience at least one episode - the most common bacterial infection of childhood
• Predisposing factors: young age, male sex, bottle-feeding, daycare exposure, crowded living, passive smoking, cleft palate, Down syndrome, cystic fibrosis, ciliary dyskinesia, immunodeficiency

Pathogenesis

• Frequently follows a viral URTI - about 1/3 of children with viral URTI develop AOM within 4 weeks
• Viral URTI causes nasopharyngeal inflammation, altered mucous properties, reduced mucociliary clearance, Eustachian tube (ET) dysfunction, and changes in bacterial adherence
• Viral-bacterial interactions play a significant role
• Key viruses: rhinovirus, RSV (most common), adenovirus, coronavirus, parainfluenza

Causative Organisms (in order of frequency)

Clinical Features

• Severe deep throbbing otalgia
• Fever and leukocytosis
• Hearing loss (conductive)
• Acute purulent otorrhea (if TM perforates)
• Otoscopy: red, bulging or perforated tympanic membrane
• Pre- and post-auricular lymphadenopathy may be present

Complications of AOM (if untreated)

Treatment

• Broad-spectrum antibiotics: amoxicillin is first-line (dose escalated to 80-90 mg/kg/day in children with risk for resistant organisms), amoxicillin-clavulanate, cefuroxime, azithromycin, or erythromycin
• Note: M. catarrhalis is almost always beta-lactamase-producing and resistant to plain amoxicillin
• Myringotomy + ventilating tube: for AOM with complications, to drain pus and obtain culture
• Tympanocentesis: if CT/MRI shows intracranial complication, surgical drainage is required

CSOM (Chronic Suppurative Otitis Media)

Definition

Types

Pathogenesis

1. ET dysfunction → persistent middle ear effusion (serous or purulent)
2. Effusion → mucosal edema → granulation tissue formation
3. Bacterial toxins + inflammatory mediators rupture basement membrane of epithelium → lamina propria extrudes into middle ear lumen → fibrous/polyp formation
4. Enzymes from granulation tissue break down the collagen skeleton of TM → weakening + perforation
5. ET-driven negative middle ear pressure + weak TM → retraction pockets → cholesteatoma formation

Clinical Features

• Intermittent, often foul-smelling otorrhea (the cardinal symptom)
• Conductive hearing loss (CHL): CHL > 30 dB suggests ossicular erosion
• Some patients have concurrent sensorineural hearing loss (5-33 dB range in studies)
• Otalgia and headache are NOT typical of CSOM - if present, suspect intracranial involvement or malignancy
• Vertigo should raise suspicion for labyrinthitis or labyrinthine fistula
• Otomicroscopy: TM perforation, retraction, middle ear granulation tissue, polyps, scutal/ossicular erosion, cholesteatoma

Diagnosis

• Full audiometric evaluation is essential
• CT temporal bone: to assess disease extent, ossicular erosion, cholesteatoma
• Diffusion-weighted MRI: useful for detecting cholesteatoma recurrence (note: cochlear implant artifact can limit DW-MRI)

Medical Treatment

• Aural toilet + ototopical antibiotics - primary medical management
• Goal: dry ear, reduce inflammation
• Multiple failed medical treatments or symptoms suggesting complications (vertigo, facial weakness, headache) = indication for surgery

Surgical Treatment

• Tympanoplasty: closes perforation, restores hearing; may suffice for uncomplicated tubotympanic disease
• Mastoidectomy: indicated for eradication of disease, removal of cholesteatoma, and establishing aeration
  • Canal Wall Up (CWU): preserves posterior EAC; less postoperative care but higher recurrence risk
  • Canal Wall Down (CWD): removes posterior EAC; better access, lower recurrence, but open cavity requires lifelong follow-up and debridement

Key Differences at a Glance

• Cummings Otolaryngology Head and Neck Surgery, Chapter 141 - Complications of Otitis Media
• Scott-Brown's Otorhinolaryngology Head & Neck Surgery Vol. 1 & 2 - AOM and CSOM chapters
• Shambaugh Surgery of the Ear - Etiology and Diagnosis/Medical Treatment of CSOM
• Berek & Novak's Gynecology - Otitis Media summary (as cross-reference)
• Goodman & Gilman's Pharmacological Basis of Therapeutics - antibiotic dosing