Otitis Externa

Overview

Otitis externa (OE) is an inflammatory condition of the external auditory canal characterized by acute onset of symptoms including otalgia, itching, aural fullness, and discharge. Often termed "swimmer's ear," OE represents one of the most common ear conditions encountered in primary care and emergency medicine, accounting for approximately 1% of all ambulatory care visits. [1,2]

The condition ranges in severity from mild, self-limiting inflammation to life-threatening necrotizing (malignant) otitis externa, particularly in immunocompromised patients. While uncomplicated acute OE responds well to topical therapy, recognition of high-risk features and potential complications is essential for appropriate management and prevention of adverse outcomes. [3,4]

Understanding the pathophysiology, microbiology, and evidence-based treatment approaches is crucial for all clinicians managing ear complaints, as inappropriate management—particularly overuse of systemic antibiotics or aminoglycoside-containing ototoxic preparations—can lead to treatment failure and complications. [5]

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Epidemiology

Incidence and Prevalence

Otitis externa affects approximately 1 in 10 people during their lifetime, with an annual incidence of 1 in 100 to 1 in 250 in the general population. [1,6] The condition accounts for substantial healthcare utilization:

Demographics and Risk Factors

Age Distribution:

• Bimodal distribution: children (7-12 years) and middle-aged adults (45-75 years) [1]
• Necrotizing otitis externa predominantly affects elderly (> 65 years): mean age 68 years [9]

Environmental and Seasonal Factors:

• Increased incidence in warm, humid climates [6]
• Peak during summer months (swimming season) [1]
• Higher prevalence in tropical and subtropical regions [10]

High-Risk Populations:

[1,6,9,11]

Necrotizing Otitis Externa Epidemiology

Necrotizing (malignant) otitis externa is a rare but serious complication with distinct epidemiology:

• Incidence: 4-6 cases per 100,000 diabetic patients per year [9]
• Diabetes prevalence in NOE: 80-95% of cases [9,12]
• Mortality: Historical 20-50%, modern era 5-10% with appropriate treatment [9,13]
• Cranial nerve involvement: 25-75% of cases, most commonly CN VII [13]
• Male predominance: 2-3:1 male-to-female ratio [9]

Recent data suggest increasing incidence of necrotizing OE, potentially related to aging populations and rising diabetes prevalence. [14]

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Aetiology and Pathophysiology

Microbiology

The microbial profile of otitis externa reflects disruption of the normal flora and overgrowth of pathogenic organisms:

Bacterial Pathogens:

[1,5,15]

Fungal Pathogens (Otomycosis):

Overall, fungi account for 5-10% of all OE cases, with increased prevalence in tropical climates (up to 20-30%), post-antibiotic treatment, and immunocompromised patients. [16,17]

Pathophysiology

Normal External Auditory Canal Protective Mechanisms

The healthy external auditory canal maintains a hostile environment for pathogens through:

1. Cerumen barrier: Acidic pH (4.0-5.0), lipid content with antimicrobial properties, mechanical protection [1]
2. Epithelial migration: Self-cleaning mechanism moving debris laterally [5]
3. Tight epithelial barrier: Intact keratinizing stratified squamous epithelium
4. Lysozyme and immunoglobulin production: Local immune defense [5]

Pathophysiological Sequence in Acute Otitis Externa

Stage 1: Disruption of Protective Barrier

• Water exposure → cerumen dissolution and maceration
• Mechanical trauma (cotton swabs, hearing aids) → epithelial microabrasions
• Chemical irritation (hair products, earphones) → epithelial damage
• Result: Loss of acidic pH, increased moisture, epithelial compromise [1,5]

Stage 2: Moisture and pH Alteration

• Normal canal pH 4.0-5.0 rises to 6.0-7.0 with water exposure
• Increased humidity creates favorable environment for bacterial/fungal growth
• Temperature elevation in occluded canals (hearing aids) promotes microbial proliferation [6]

Stage 3: Microbial Colonization and Invasion

• Pseudomonas aeruginosa thrives in moist, alkaline environment
• Bacterial adherence to damaged epithelium
• Biofilm formation on epithelial surface [15]

Stage 4: Inflammatory Response

• Bacterial toxins and enzymes (elastase, protease) damage tissue
• Cytokine release (IL-1, IL-6, TNF-α) drives inflammation
• Vascular permeability increases → edema
• Canal lumen narrows → impaired drainage → further moisture retention [5]

Stage 5: Clinical Manifestations

• Edema: Canal stenosis, conductive hearing loss
• Erythema: Vascular congestion
• Pain: Inflammatory mediators, tissue pressure, periosteal involvement
• Discharge: Inflammatory exudate, desquamated epithelium, bacterial biofilm [1]

Pathophysiology of Necrotizing Otitis Externa

Necrotizing (malignant) OE represents progressive invasive infection extending beyond the external canal:

Stage 1: Initial Infection (Simple OE)

• Begins as uncomplicated OE, typically Pseudomonas aeruginosa [9]

Stage 2: Soft Tissue Invasion

• Bacteria penetrate through fissures of Santorini (cartilage-bone junction at 6 o'clock position)
• Extension into periauricular soft tissues
• Granulation tissue formation (pathognomonic finding) [13]

Stage 3: Osteomyelitis

• Invasion of temporal bone at bone-cartilage junction
• Progressive osteomyelitis: mastoid → petrous apex → skull base
• Vascular involvement: vasculitis, thrombophlebitis [9,13]

Stage 4: Advanced Disease

• Cranial nerve involvement (VII, IX, X, XI, XII) through skull base foramina
• Intracranial extension: meningitis, brain abscess, venous sinus thrombosis
• Lateral sinus thrombosis, jugular vein thrombosis [13]

Risk Factors for Progression:

• Diabetes mellitus: Microvascular disease, impaired neutrophil function, hyperglycemia promoting bacterial growth [11,18]
• Immunocompromise: HIV/AIDS, chemotherapy, immunosuppressive therapy, hematologic malignancy [9]
• Advanced age: Reduced immune function, comorbidities [14]
• Delayed diagnosis: > 2 weeks of symptoms before recognition [9]

Exam Detail: Molecular Mechanisms in Diabetic Susceptibility:

Patients with diabetes demonstrate multiple defects that predispose to necrotizing OE:

1. Neutrophil dysfunction: Impaired chemotaxis, phagocytosis, and intracellular killing when HbA1c > 8% [18]
2. Microvascular disease: Reduced tissue oxygenation and impaired antibiotic delivery to infected tissue [11]
3. Advanced glycation end-products (AGEs): Tissue damage and impaired wound healing [18]
4. Hyperglycemia: Direct enhancement of Pseudomonas virulence factor expression [11]
5. Metabolic acidosis: Creates favorable environment for Pseudomonas growth

Pseudomonas Virulence Factors:

• Exotoxin A: Inhibits protein synthesis, causes tissue necrosis
• Elastase: Degrades elastin, collagen, immunoglobulins
• Alkaline protease: Tissue destruction
• Biofilm formation: Antibiotic resistance, chronic infection
• Type III secretion system: Direct injection of toxins into host cells

These factors explain why Pseudomonas aeruginosa is the pathogen in > 95% of necrotizing OE cases. [9,15]

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Clinical Presentation

Symptoms

Acute Otitis Externa

The cardinal symptom of OE is otalgia (ear pain), typically described as severe and out of proportion to clinical findings:

[1,2,5]

Temporal Evolution:

• Day 0-2: Pruritus, mild discomfort, sense of canal fullness
• Day 2-4: Escalating otalgia, discharge appears
• Day 4-7: Peak pain, maximal canal edema, conductive hearing loss
• Day 7-14: Resolution with treatment or progression if untreated [5]

Pain Characteristics Distinguishing OE from Other Conditions:

• Exacerbated by: Tragal pressure, pinna traction, jaw movement, lying on affected ear
• Not relieved by: Analgesics alone (requires source control)
• Severity: Often rated 7-10/10, interferes with sleep [1]

Necrotizing (Malignant) Otitis Externa

NOE typically presents with prolonged, severe symptoms that fail to respond to standard topical therapy:

[9,12,13]

Cranial Nerve Involvement Progression:

• CN VII (facial): Most common, earliest; via stylomastoid foramen
• CN IX, X, XI (lower cranial nerves): Via jugular foramen; indicates petrous apex involvement
• CN XII (hypoglossal): Via hypoglossal canal; advanced disease
• CN VI (abducens): Petrous apex syndrome (Gradenigo syndrome)
• CN V (trigeminal): Rare; extensive skull base disease

Multiple cranial nerve involvement carries mortality > 40% despite treatment. [13]

Physical Examination Findings

External Ear and Canal Examination

Systematic Approach:

1. Inspection Before Manipulation

   • Observe for periauricular erythema, swelling, cellulitis
   • Look for drainage on external auditory meatus
   • Assess for skin conditions (eczema, psoriasis)

2. Palpation (Gentle)

   • Tragal tenderness: Apply gentle pressure to tragus
     • Positive in 70-90% of OE cases [1]
     • Highly sensitive for OE vs. otitis media
   • Pinna traction: Gently pull pinna superiorly and posteriorly
     • Positive (pain) in 60-80% of OE [1]
     • Negative in otitis media
   • Periauricular palpation: Assess for lymphadenopathy, mastoid tenderness, temporomandibular joint involvement

3. Otoscopy (May Be Limited by Pain and Edema)

[1,5]

Key Otoscopic Findings:

• Granulation tissue at 6 o'clock position (floor of canal at bone-cartilage junction): Pathognomonic for necrotizing OE [13]
• Exposed bone: Indicates osteomyelitis
• Polyps: Chronic inflammation or cholesteatoma
• Black or white debris: Suggests fungal infection (otomycosis) [16]
• TM perforation: May indicate extension to middle ear

Clinical Pearl: The "Tragal Pressure Test":

This simple bedside maneuver is the most useful clinical sign for differentiating OE from otitis media:

• Technique: Apply gentle pressure to the tragus while observing patient's face
• Positive test: Patient winces, pulls away, or reports significant pain
• Sensitivity: 70-90% for OE [1]
• Specificity: > 95% (absent in otitis media unless concurrent OE)

Interpretation:

• Pain with tragal pressure + normal TM = OE until proven otherwise
• Pain with tragal pressure + abnormal TM = possible concurrent OE and OM
• No pain with tragal pressure + abnormal TM = likely OM, not OE

Cranial Nerve Examination in Suspected Necrotizing OE

CN VII (Facial Nerve) Assessment:

• Inspect for facial asymmetry at rest
• Ask patient to:
  • Raise eyebrows (frontalis)
  • Close eyes tightly (orbicularis oculi)
  • Smile and show teeth (orbicularis oris)
  • Puff out cheeks (buccinator)
• Grade using House-Brackmann scale (I-VI)
• Lower motor neuron pattern in NOE (entire hemifacial weakness)

CN IX, X (Glossopharyngeal, Vagus) Assessment:

• Observe for dysphonia, dysphagia
• Examine palatal elevation ("say ahhh")
• Assess gag reflex
• Voice quality changes

CN XII (Hypoglossal) Assessment:

• Tongue protrusion: deviation toward affected side
• Tongue fasciculations

CN XI (Spinal Accessory) Assessment:

• Shoulder shrug strength
• Sternocleidomastoid strength (head turning)

[13]

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Differential Diagnosis

Key Differentiating Features

The clinician must distinguish OE from several conditions presenting with otalgia and/or discharge:

1. Acute Otitis Media (AOM)

[1,2]

Concurrent OE and AOM: Can coexist, particularly with TM perforation causing otorrhea that irritates canal. [1]

2. Ramsay Hunt Syndrome (Herpes Zoster Oticus)

[19]

3. Chronic Suppurative Otitis Media (CSOM) with Otorrhea

Secondary OE commonly complicates CSOM, requiring treatment of both conditions. [1]

4. Malignancy (Squamous Cell Carcinoma of EAC)

Key Point: Any patient > 60 years with persistent otalgia and granulation tissue should have biopsy to exclude malignancy, even if NOE is suspected. [13]

5. Foreign Body

6. Cerumen Impaction

7. Perichondritis

[20]

8. Otomycosis (Fungal Otitis Externa)

[16,17]

9. Contact Dermatitis

10. Temporomandibular Joint (TMJ) Dysfunction

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Diagnostic Approach

Clinical Diagnosis

Otitis externa is primarily a clinical diagnosis based on history and physical examination. The 2014 AAO-HNS Clinical Practice Guideline defines acute OE as: [1]

Diagnostic Criteria (Requires All Three):

1. Rapid onset (generally within 48 hours) in the past 3 weeks
2. Symptoms of ear canal inflammation:
   • Otalgia (often severe)
   • Itching
   • Fullness
   • With or without hearing loss or jaw pain
3. Signs of ear canal inflammation:
   • Tenderness of tragus/pinna
   • Diffuse ear canal edema
   • Diffuse ear canal erythema
   • With or without otorrhea, regional lymphadenitis, TM erythema, or cellulitis of pinna/adjacent skin

Diagnostic Certainty:

• Definite OE: All three criteria present
• Probable OE: Criteria 1 and 2, with limited exam due to pain or canal occlusion

Severity Classification

The AAO-HNS guideline stratifies OE by severity to guide treatment intensity: [1]

Laboratory Investigations

Routine OE: No Laboratory Tests Indicated [1]

Laboratory investigations are not recommended for uncomplicated acute OE. However, specific scenarios warrant testing:

Indications for Cultures

[5,15]

Culture Technique:

• Avoid superficial swab (contaminant risk)
• Debride debris first, then culture deep canal or granulation tissue
• Specify bacterial and fungal cultures if otomycosis suspected

Blood Tests for Necrotizing Otitis Externa

When NOE is suspected (diabetes, immunocompromise, severe pain > 2 weeks, granulation tissue, treatment failure):

ESR/CRP Monitoring in NOE:

• Baseline ESR/CRP essential for diagnosis and monitoring [9]
• Repeat every 1-2 weeks during treatment
• Normalizing ESR/CRP correlates with treatment response
• Rising ESR/CRP despite therapy suggests treatment failure [13]

Imaging

Uncomplicated Acute OE: No Imaging Indicated [1]

Imaging is reserved for suspected complications or necrotizing OE:

CT Temporal Bone (with Contrast)

Indications:

• Suspected necrotizing otitis externa
• Severe OE not responding to 48-72h of appropriate therapy
• Clinical suspicion of mastoiditis or deeper extension
• Cranial nerve involvement
• Immunocompromised patients with severe OE

Findings in Necrotizing OE:

• Soft tissue opacification of external canal
• Bone erosion at bone-cartilage junction (floor of canal)
• Osteomyelitis of temporal bone (mastoid, petrous apex)
• Soft tissue extension to parapharyngeal space, infratemporal fossa
• Skull base involvement
• Intracranial extension (late)

Sensitivity/Specificity: CT is highly sensitive for bone erosion but may be normal early in disease. [13]

MRI Temporal Bone (with Gadolinium)

Indications:

• Suspected necrotizing OE (often combined with CT)
• Evaluation of soft tissue and bone marrow involvement
• Cranial nerve involvement assessment
• Intracranial extension suspected
• Distinguishing active infection from post-treatment changes

Findings in Necrotizing OE:

• T1: Decreased signal in inflamed bone marrow
• T2: Increased signal in edematous tissues
• T1 + gadolinium: Enhancement of infected bone, soft tissues, meninges
• Superior to CT for:
  • Soft tissue detail
  • Bone marrow involvement
  • Intracranial complications
  • Cranial nerve enhancement

[9,13]

Nuclear Medicine Imaging

Gallium-67 or Technetium-99m Bone Scans:

Historically used but no longer routinely recommended based on recent systematic review and meta-analysis showing lack of evidence for treatment guidance. [21]

Current Role (Limited):

• Equivocal CT/MRI findings
• Monitoring treatment response in selected cases (though ESR/CRP preferred)

PET/CT:

• Emerging modality for assessing treatment response
• Distinguishes active infection from post-inflammatory changes
• Limited availability; not yet standard of care

Exam Detail: Imaging Algorithm for Suspected Necrotizing OE:

1. Clinical suspicion (diabetes + severe OE + granulation tissue/CN palsy/treatment failure) ↓
2. First-line: CT temporal bone with contrast
   • Evaluate bone erosion, extent of disease
   • Guide surgical planning if debridement needed ↓
3. MRI with gadolinium (add to CT, not replacement)
   • Assess soft tissue extent
   • Evaluate intracranial extension
   • Cranial nerve involvement ↓
4. Follow-up imaging:
   • Repeat CT/MRI at 4-6 weeks to assess response
   • Earlier if clinical deterioration
   • Continue imaging every 6-8 weeks until resolution

Pitfall: Normal initial CT does not exclude early NOE. Clinical suspicion should drive treatment in high-risk patients. [13]

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Management

General Principles

The 2014 AAO-HNS Clinical Practice Guideline emphasizes: [1]

1. Topical therapy is first-line for uncomplicated acute OE (not systemic antibiotics)
2. Aural toilet (cleaning/debridement) enhances topical therapy effectiveness
3. Pain management is essential
4. Wick placement for severe canal edema
5. Avoid ototoxic preparations if TM perforation present or unknown
6. Keep ear dry during treatment
7. Systemic antibiotics reserved for specific indications

Conservative Management

Aural Toilet (Debridement)

Removal of debris, cerumen, and discharge from the canal is a critical component of management, improving topical medication penetration and accelerating resolution. [1,5]

Techniques:

Frequency:

• Initial visit: Debride as thoroughly as tolerated
• Follow-up: Every 2-3 days if severe; at 7-10 days for mild cases
• Necrotizing OE: Regular debridement (often weekly) until resolution [13]

Evidence: Cochrane review found insufficient evidence that aural toilet alone is superior to no treatment, but expert consensus and clinical experience support its use as adjunct to topical therapy. [5]

Clinical Pearl: Aural Toilet Practical Tips:

1. Pre-medication: Consider topical or oral analgesics 30 minutes before procedure in severe OE
2. Position: Sitting position, head tilted away from affected ear
3. Visualization: Use otoscope or microscope; never blind instrumentation
4. Suction power: Low to medium; high suction causes pain
5. Warm fluids: If irrigation used, ensure body temperature to avoid caloric stimulation/vertigo
6. Document: Record amount and character of debris (purulent, fungal, bloody)

Red Flags During Debridement:

• Exposed bone: Suspect necrotizing OE
• Granulation tissue: Biopsy if > 60 years old (exclude malignancy)
• Severe bleeding: May indicate friable tumor; biopsy
• CSF otorrhea: Suggests skull base erosion; STOP, get imaging

Topical Antimicrobial Therapy

Topical antibiotic drops are the cornerstone of OE treatment, superior to systemic antibiotics for uncomplicated cases. [1,5]

First-Line Topical Agents:

[1,22]

Alternative Agents (If Fluoroquinolone Allergy/Intolerance):

Evidence Base:

A 2022 randomized controlled trial (n=662 patients) demonstrated ciprofloxacin 0.3% + fluocinolone acetonide achieved clinical cure in 91.9% vs. 84.9% for ciprofloxacin alone (statistically significant), supporting combination antibiotic-steroid therapy. [22]

Key Prescribing Points:

1. Duration: 7-10 days is standard; shorter courses (3-5 days) have higher failure rates [1]
2. TM status: If TM perforation present or uncertain, use only fluoroquinolones (avoid aminoglycosides) [1]
3. Steroid benefit: Anti-inflammatory effect reduces pain and edema; faster symptom resolution [22]
4. Patient technique:
   • Warm bottle in hand before use (cold drops cause dizziness)
   • Lie with affected ear up
   • Pull pinna posterosuperiorly (adults) or posteroinferiorly (children) to straighten canal
   • Instill drops, remain supine × 3-5 minutes
   • Gently pump tragus to facilitate drop penetration

Evidence Debate: Topical Antibiotics vs. Topical Antiseptics (Acetic Acid):

The Cochrane review (2010) found:

• Quinolone antibiotics superior to acetic acid for clinical cure (RR 1.11, 95% CI 1.01-1.21) [5]
• Antibiotic + steroid superior to antibiotic alone for symptom relief
• No significant difference in cure rates between different fluoroquinolones

Conclusion: Fluoroquinolone + steroid is the evidence-based first-line choice. Acetic acid is appropriate for:

• Very mild OE
• Prophylaxis in recurrent OE
• Antifungal adjunct
• Resource-limited settings

[1,5]

Wick Placement

An ear wick (expandable sponge) is indicated when canal edema prevents topical drops from reaching the medial canal. [1]

Indications:

• Severe canal edema with near-complete or complete occlusion
• Moderate OE not responding to 48-72h of drops (possible inadequate penetration)

Types:

• Pope wick: Compressed cellulose sponge; expands with moisture
• Merocel wick: Polyvinyl alcohol polymer
• Gauze wick: Ribbon gauze (traditional but less effective)

Technique:

1. Gentle aural toilet to remove debris
2. Select appropriate wick size (usually 2-3 cm length)
3. Grasp wick with bayonet forceps or alligator forceps
4. Insert gently into canal under direct visualization
5. Advance to touch but not compress TM (if visible)
6. Saturate wick with antibiotic drops immediately
7. Patient applies drops to wick 3-4 times daily

Management:

• Instruct patient to apply drops to wick, not directly to canal
• Wick typically left in place 24-48 hours
• Remove when canal edema subsides (allows direct drop application)
• May replace if canal re-occludes

Evidence: Clinical experience supports wick use for severe OE, though RCT evidence is limited. [1]

Pain Management

Pain is often severe and undertreated in OE. Multimodal analgesia is appropriate: [1]

Combination Therapy: Ibuprofen + acetaminophen provides superior analgesia to either alone and is appropriate for severe OE pain. [1]

Topical Steroid Effect: The steroid component in ciprofloxacin/dexamethasone drops significantly reduces pain within 24-48 hours. [22]

Systemic Antibiotic Therapy

Systemic antibiotics are NOT routinely indicated for uncomplicated acute OE. [1]

Indications for Systemic Antibiotics

[1,5]

Oral Antibiotic Regimens (Non-Necrotizing)

Note: Oral fluoroquinolones are not superior to topical fluoroquinolones for uncomplicated OE and increase costs, side effects, and resistance. Reserve for indications above. [1]

Management of Necrotizing (Malignant) Otitis Externa

Necrotizing OE is a medical and surgical emergency requiring aggressive multidisciplinary management. [9,13]

Initial Assessment and Stabilization

1. Confirm diagnosis:

   • Clinical features (diabetes/immunocompromise + severe OE + granulation tissue/treatment failure/CN palsy)
   • Deep canal culture (after debridement)
   • ESR, CRP (baseline)
   • HbA1c (assess glycemic control)

2. Imaging:

   • CT temporal bone with contrast
   • MRI with gadolinium (add to CT; evaluate soft tissue/intracranial extension)

3. Multidisciplinary consultation:

   • ENT (urgent)
   • Infectious disease
   • Endocrinology (if diabetes)

Antimicrobial Therapy

Empiric IV Antipseudomonal Therapy (until culture results available):

MRSA Coverage (if risk factors: healthcare exposure, prior MRSA):

• Add vancomycin 15-20 mg/kg IV q8-12h (target trough 15-20 mcg/mL)
• Or linezolid 600 mg IV/PO q12h

Treatment Duration:

• Minimum 6-8 weeks of therapy (IV then step down to oral ciprofloxacin) [9,13]
• Longer if:
  • Extensive bone involvement
  • Slow clinical/radiological response
  • Intracranial extension (12+ weeks)
• Monitor ESR/CRP weekly; treat until normalization [9]

Step-Down to Oral Therapy:

• After 2-4 weeks IV therapy, if clinical improvement and ESR/CRP declining
• Ciprofloxacin 750 mg PO BID (excellent bioavailability, bone penetration)
• Continue for total 6-8+ weeks [13]

Exam Detail: Antibiotic Selection Rationale in NOE:

Why Ciprofloxacin is Preferred:

1. Antipseudomonal activity: Pseudomonas aeruginosa is causative in > 95% of NOE [9]
2. Bone penetration: Achieves therapeutic levels in infected bone
3. Oral bioavailability: > 70%, allowing IV-to-PO transition without loss of efficacy
4. Clinical evidence: Largest experience in published literature with cure rates 80-90% [13]

Alternatives to Ciprofloxacin:

• Beta-lactam/beta-lactamase inhibitor (pip-tazo) or cephalosporin (cefepime) if:
  • Quinolone resistance documented
  • Quinolone intolerance
  • Pregnancy (quinolones contraindicated)
• Require prolonged IV therapy (no oral option with equivalent bone penetration)

Combination Therapy:

• Some experts add aminoglycoside (tobramycin/gentamicin) for first 1-2 weeks for synergy
• Evidence is mixed; increased toxicity risk (nephro/ototoxicity)
• Consider in severe cases, extensive disease, or slow initial response

Glycemic Control

Tight glucose control is essential in diabetic patients with NOE. [11,18]

• Target HbA1c less than 7%, fasting glucose less than 130 mg/dL
• Consultation with endocrinology for insulin management
• Poor glycemic control associated with:
  • Treatment failure [18]
  • Recurrence
  • Higher mortality [11]

Surgical Debridement

Indications for Surgical Intervention:

Extent of Surgery:

• Conservative debridement (most cases): Remove granulation tissue, sequestrum
• Extensive resection (rare): Temporal bone resection reserved for refractory cases; high morbidity

Evidence: Surgery is adjunctive, not curative. Primary treatment is prolonged antibiotics. Excessive surgery does not improve outcomes and may worsen morbidity. [13]

Hyperbaric Oxygen Therapy (HBOT)

Controversial Role: Systematic review (2021) found insufficient high-quality evidence to support routine HBOT use in NOE. [23]

Potential Indications (adjunctive, not first-line):

• Refractory disease despite appropriate antibiotics and debridement
• Severe tissue ischemia in diabetic patients
• Persistent culture-positive infection

Mechanism: Enhance tissue oxygenation, improve neutrophil function, promote angiogenesis

Limitations: Limited availability, cost, time commitment (daily treatments for weeks), lack of RCT evidence [23]

Current Recommendation: Consider as adjunct in selected refractory cases; not standard of care. [9]

Monitoring and Follow-Up

Clinical Assessment:

• Weekly review during IV therapy phase
• Assess pain, discharge, cranial nerve function, periauricular signs
• Repeat aural toilet and debridement as needed

Laboratory Monitoring:

• ESR/CRP: Every 1-2 weeks; expect gradual decline
  • Failure to decline or rising levels → treatment failure, consider imaging, adjust antibiotics
  • Normalize before discontinuing therapy [9]
• Renal function: If aminoglycosides used; 2-3× weekly
• Aminoglycoside levels: Peak and trough monitoring

Imaging Follow-Up:

• Repeat CT/MRI at 4-6 weeks to assess radiological response
• Further imaging every 6-8 weeks until resolution
• Note: Radiological improvement lags clinical improvement by weeks to months [13]

Treatment Endpoints:

• Clinical resolution of pain, discharge
• Normalization of ESR/CRP
• Improving or stable imaging
• Total duration typically 6-12 weeks [9,13]

Otomycosis (Fungal Otitis Externa) Management

Fungal OE requires specific antifungal therapy: [16,17]

Treatment Approach

1. Aural Toilet (Essential):

   • Debride fungal debris, hyphae, spores
   • Repeat every 3-5 days until resolution
   • More critical than in bacterial OE [16]

2. Topical Antifungal Agents:

Cochrane review (2021) found insufficient evidence to recommend one topical azole over another; clotrimazole is most widely used. [24]

3. Systemic Antifungals (Rarely Needed):

   • Reserved for invasive fungal NOE (immunocompromised)
   • Voriconazole or posaconazole for Aspergillus
   • Fluconazole for Candida [16]

4. Avoid:

   • Topical antibiotics (worsen fungal overgrowth)
   • Prolonged corticosteroid drops (promote fungal growth)

Treatment Duration: 2-3 weeks typical; recurrence common (20-30%) requiring repeat treatment. [17]

Prevention Strategies

For patients with recurrent OE (≥3 episodes per year): [1,6]

Acetic Acid Prophylaxis Protocol:

• Apply 3-5 drops of 2% acetic acid after swimming or water exposure
• Alternatively, use commercial "swim ear" preparations (alcohol + acetic acid)
• Reduces recurrence risk by ~50% in high-risk individuals [6]

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Complications

Complications of Acute Otitis Externa

[1,5]

Complications of Necrotizing Otitis Externa

Necrotizing OE carries significant morbidity and mortality despite modern treatment: [9,13]

Prognostic Factors:

• Good prognosis: Young age, good glycemic control, early diagnosis, single CN involvement
• Poor prognosis: Advanced age, HbA1c > 8%, multiple CN involvement, intracranial extension, delayed diagnosis [9,13,18]

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Prognosis

Uncomplicated Acute Otitis Externa

Natural History with Treatment:

• Symptom improvement: 24-48 hours after initiating topical therapy [1]
• Clinical cure: 7-10 days in 85-90% of cases with appropriate treatment [5]
• Complete resolution: 10-14 days

Without Treatment:

• May progress to severe OE with complete canal occlusion
• Risk of periauricular extension (cellulitis, perichondritis)
• Chronic OE in 10-20% [5]
• Rare progression to necrotizing OE in high-risk patients

Recurrence:

• 10-20% experience recurrent episodes [8]
• Risk factors for recurrence: Swimming, hearing aids, eczema, diabetes
• Prophylactic strategies reduce recurrence by ~50% [6]

Necrotizing Otitis Externa

Treatment Outcomes:

• Cure rate: 80-90% with appropriate prolonged antibiotic therapy [9,13]
• Recurrence: 10-15% after initial cure; requires retreatment [9]
• Mortality: 5-10% in modern era (down from 20-50% historically) [13]

Factors Affecting Prognosis:

• Better outcomes: HbA1c less than 7%, early diagnosis (less than 2 weeks), no CN involvement, compliance with therapy [18]
• Worse outcomes: Multiple CN palsies, intracranial extension, poor glycemic control, immunocompromise, delayed diagnosis [9,13]

Cranial Nerve Recovery:

• CN VII palsy: 40-60% recover function (partial to complete); 20-40% permanent deficit [13]
• Multiple CN involvement: Recovery poor; associated with high mortality

Long-Term Sequelae:

• Permanent cranial nerve deficits in 20-30% of NOE survivors [13]
• Chronic pain in 10-15%
• Hearing loss (conductive or sensorineural) in 10-20%

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Prevention and Screening

Primary Prevention

General Population:

1. Keep ears dry:
   • Use earplugs when swimming
   • Tilt head to drain water after swimming
   • Dry ears gently with towel; avoid inserting anything into canal
2. Avoid canal instrumentation:
   • Do not use cotton swabs (Q-tips) in ear canal
   • Allow natural cerumen migration
3. Treat underlying skin conditions:
   • Manage eczema, psoriasis, seborrheic dermatitis
4. Proper hearing aid hygiene:
   • Remove nightly, keep dry
   • Clean regularly per manufacturer instructions
   • Ensure proper fit (audiology consultation)

High-Risk Individuals (swimmers, recurrent OE):

• Acidifying drops after water exposure: Acetic acid 2% or commercial preparations (e.g., "Swim-EAR")
• Earplugs: Custom-molded for swimmers
• Hair dryer on low setting: To dry canals after swimming (caution: not too close, not too hot)

Secondary Prevention (Recurrent OE)

For patients with ≥3 episodes per year: [1,6]

1. Post-swim prophylaxis: Acetic acid 2% drops after each water exposure
2. Identify and modify risk factors:
   • Discontinue cotton swab use
   • Hearing aid assessment and modification
   • Dermatology referral for refractory eczema/psoriasis
3. Consider prophylactic topical therapy: During high-risk periods (e.g., summer swimming season)

Screening

No routine screening recommended for OE in general population. [1]

High-Risk Patients Requiring Vigilance:

• Diabetics with otalgia: Low threshold for ENT referral to exclude necrotizing OE
• Immunocompromised patients: Early evaluation of ear complaints
• Elderly diabetics: Education on NOE warning signs (severe pain, persistent discharge, facial weakness)

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Key Guidelines and Recommendations

AAO-HNS Clinical Practice Guideline (2014) [1]

The American Academy of Otolaryngology-Head and Neck Surgery published comprehensive evidence-based guidelines:

Strong Recommendations:

1. Diagnose AOE based on clinical criteria (rapid onset, symptoms of canal inflammation, signs on exam)
2. Assess patient for factors that modify management (non-intact TM, diabetes, immunocompromise)
3. Use topical preparations for initial therapy (NOT systemic antibiotics unless specific indications)
4. Avoid systemic antibiotics unless extension beyond canal or specific indications

Recommendations: 5. Distinguish diffuse AOE from other causes of otalgia 6. Assess patients with AOE for pain; provide analgesia 7. Recommend against use of ototoxic topical therapy if TM perforation known or suspected 8. Educate on prevention and when to seek further care

Options: 9. May perform aural toilet/debridement at initial visit 10. May use wick if canal edema prevents drop delivery 11. May recommend acetic acid prophylaxis in recurrent cases

Additional Guidelines

• Cochrane Reviews: Topical antibiotics (especially quinolones with steroids) superior to placebo and acetic acid [5]
• Infectious Diseases Society Guidelines: NOE requires 6-8 weeks minimum antibiotic therapy with fluoroquinolones or antipseudomonal beta-lactams [9]

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Common Exam Questions and Model Answers

Viva Point: Opening Statement for Otitis Externa:

"Otitis externa is an acute inflammatory condition of the external auditory canal, most commonly caused by bacterial infection with Pseudomonas aeruginosa or Staphylococcus aureus. It affects approximately 10% of the population at some point in their lifetime and is characterized by otalgia, pruritus, and discharge. The diagnosis is clinical, and first-line treatment is topical antibiotic drops, typically a fluoroquinolone combined with a corticosteroid. A critical consideration is necrotizing otitis externa in diabetic and immunocompromised patients, which is a life-threatening complication requiring urgent ENT referral and systemic antibiotics."

Question 1: "How do you differentiate otitis externa from otitis media clinically?"

Model Answer:

"The key distinguishing features are:

1. Pain with tragal pressure: Present in OE, absent in OM. I would apply gentle pressure to the tragus; if this reproduces the pain, it's highly suggestive of OE.

2. Canal vs. tympanic membrane findings:

   • OE: Inflamed, edematous canal with discharge; TM normal if visible
   • OM: Normal canal; TM is bulging, erythematous, with decreased mobility

3. History: OE often follows swimming or water exposure; OM typically follows upper respiratory infection, especially in children.

4. Hearing loss mechanism: Both can cause conductive loss, but in OE it's due to canal occlusion, whereas in OM it's from middle ear effusion.

In practice, concurrent OE and OM can occur, particularly if there's TM perforation with otorrhea that irritates the canal."

Question 2: "What is necrotizing otitis externa and why is it important?"

Model Answer:

"Necrotizing otitis externa, also called malignant otitis externa, is a severe invasive infection of the external auditory canal that extends to the temporal bone causing osteomyelitis and potentially involves the skull base and cranial nerves. It's important because:

1. High morbidity/mortality: Historically 20-50% mortality; now 5-10% with treatment, but still serious.

2. Specific at-risk population: Occurs almost exclusively in diabetic patients (80-95% of cases) and immunocompromised individuals.

3. Requires different management: Unlike uncomplicated OE treated with topical therapy, NOE requires:

   • Prolonged systemic IV antibiotics (6-8 weeks minimum), typically ciprofloxacin
   • Imaging (CT and MRI)
   • Urgent ENT and infectious disease consultation
   • Often surgical debridement

4. Clinical recognition: Key features are granulation tissue at the bone-cartilage junction of the canal (6 o'clock position), severe persistent pain despite topical therapy, and cranial nerve involvement—most commonly facial nerve palsy.

5. Pseudomonas aeruginosa is the pathogen in over 95% of cases, which guides empiric antibiotic selection."

Question 3: "A diabetic patient presents with severe ear pain for 3 weeks despite using ciprofloxacin drops. What is your approach?"

Model Answer:

"This presentation raises significant concern for necrotizing otitis externa. My approach would be:

Immediate Assessment:

1. Detailed history: Duration, severity of pain, discharge, facial weakness, dysphagia, previous treatments
2. Examination:
   • Otoscopy: Look specifically for granulation tissue at the 6 o'clock position (bone-cartilage junction)
   • Comprehensive cranial nerve exam (VII, IX, X, XI, XII)
   • Periauricular examination for cellulitis or swelling

Investigations: 3. Blood tests:

• ESR and CRP (baseline for monitoring)
• Complete blood count
• HbA1c (assess glycemic control)
• Blood glucose

4. Deep canal culture after debridement (for sensitivities)
5. Imaging:
   • CT temporal bone with contrast (assess bone erosion)
   • MRI with gadolinium (soft tissue and bone marrow involvement)

Management: 6. Urgent ENT referral 7. Infectious disease consultation 8. Start IV antipseudomonal antibiotics empirically:

• Ciprofloxacin 400 mg IV q8-12h as first-line
• Or piperacillin-tazobactam if fluoroquinolone resistance suspected

9. Endocrinology referral for tight glycemic control (target HbA1c less than 7%)
10. Plan for prolonged therapy (6-8 weeks), monitoring with weekly ESR/CRP

Disposition: This patient requires admission for IV antibiotics and multidisciplinary care. Outpatient management is inappropriate for necrotizing OE."

Question 4: "What topical antibiotic would you prescribe for otitis externa and why?"

Model Answer:

"My first-line choice would be ciprofloxacin 0.3% with dexamethasone 0.1% (Ciprodex), 4 drops twice daily for 7 days.

Rationale:

1. Spectrum: Ciprofloxacin is a fluoroquinolone with excellent coverage of Pseudomonas aeruginosa (the most common pathogen) and Staphylococcus aureus.

2. Steroid benefit: Dexamethasone reduces inflammation, edema, and pain. RCT evidence shows combination antibiotic-steroid achieves faster symptom relief and higher cure rates than antibiotic alone.

3. Safety with TM perforation: Fluoroquinolones are non-ototoxic and safe if there's a tympanic membrane perforation, which may not always be visible due to canal edema.

4. Evidence base: Supported by AAO-HNS guidelines and Cochrane reviews as first-line therapy.

Alternative if TM perforation confirmed: Ofloxacin 0.3% alone (if cost is a concern, though steroid benefit is lost).

What I would avoid: Neomycin/polymyxin B/hydrocortisone preparations if TM status uncertain, as aminoglycosides are ototoxic with perforation.

I would also advise the patient on proper administration technique and keeping the ear dry during treatment."

Question 5: "When would you use systemic antibiotics for otitis externa?"

Model Answer:

"Systemic antibiotics are NOT first-line for uncomplicated OE, but I would use them in specific scenarios:

Indications:

1. Extension beyond the canal: Periauricular cellulitis, perichondritis
2. Suspected or confirmed necrotizing OE: Requires IV antipseudomonal therapy
3. Immunocompromised patients: HIV, chemotherapy, immunosuppression—higher risk of progression
4. Severe OE with systemic features: Fever, significant lymphadenopathy, malaise
5. Failed topical therapy: After 48-72 hours of appropriate topical treatment with adequate aural toilet

Regimen for Non-Necrotizing Indications:

• Oral ciprofloxacin 500-750 mg twice daily for 7-10 days
• Covers Pseudomonas and most other pathogens
• Consider adding clindamycin if MRSA concern

Rationale Against Routine Use: Topical therapy achieves much higher local concentrations than systemic antibiotics, with fewer systemic side effects and lower risk of antimicrobial resistance. The AAO-HNS guideline specifically recommends against routine systemic antibiotics for uncomplicated OE."

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Clinical Pearls

Clinical Pearl: Diagnostic Pearls:

1. Tragal pressure test is the single most useful sign: Positive in 70-90% of OE; virtually absent in uncomplicated OM
2. Granulation tissue at 6 o'clock = necrotizing OE until proven otherwise: Especially in diabetics
3. Black or white debris suggests fungal infection: Think Aspergillus (black) or Candida (white)
4. Pain out of proportion to exam findings: Consider NOE, especially if > 2 weeks of symptoms
5. Facial weakness in a diabetic with ear pain: NOE with skull base involvement; urgent imaging and ENT referral
6. Normal TM (if visible) in OE: Helps differentiate from OM
7. Water exposure history: Highly suggestive but not required for diagnosis (canal trauma from Q-tips also common)

Treatment Pearls: 8. Topical > systemic for uncomplicated OE: Higher local drug concentrations, fewer side effects 9. Fluoroquinolones are safe with TM perforation; aminoglycosides are NOT: Avoid neomycin-containing drops if perforation uncertain 10. Aural toilet is as important as antibiotics: Debris removal allows drug penetration 11. Wick for severe edema: If canal is occluded, drops won't reach the medial canal; wick essential 12. Steroid-antibiotic combination reduces pain faster: Evidence supports combination over antibiotic alone 13. 7-10 days treatment, not 3-5: Shorter courses have higher failure rates 14. Warm the bottle: Cold drops cause dizziness; instruct patients to warm drops in hand before use 15. Keep ears dry during treatment: No swimming; use cotton ball with petroleum jelly when showering

Necrotizing OE Pearls: 16. "Diabetes + granulation tissue + severe pain = NOE": Classic triad requiring urgent action 17. 6-8 weeks minimum antibiotic therapy: Shorter courses lead to recurrence 18. Monitor ESR/CRP weekly: Trending more useful than absolute values; failure to decline = treatment failure 19. Tight glucose control is critical: HbA1c > 8% associated with worse outcomes 20. Imaging lags clinical improvement: Don't stop antibiotics based on imaging alone; use clinical + ESR/CRP 21. IV ciprofloxacin is first-line for NOE: Excellent bone penetration; oral bioavailability allows step-down 22. Surgery is adjunctive, not curative: Primary treatment is medical; debride necrotic tissue but avoid extensive resection

Disposition Pearls: 23. Most uncomplicated OE: outpatient with topical therapy: Discharge with clear instructions and 48-72h follow-up 24. Admit for NOE, severe cellulitis, immunocompromised with severe OE: Requires IV antibiotics and monitoring 25. ENT referral for: NOE (urgent), treatment failure after appropriate therapy, severe canal occlusion requiring specialized debridement, biopsy needs

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References

1. Rosenfeld RM, Schwartz SR, Cannon CR, et al. Clinical practice guideline: acute otitis externa. Otolaryngol Head Neck Surg. 2014;150(1 Suppl):S1-S24. doi:10.1177/0194599813517083

2. Hajioff D, MacKeith S. Otitis externa. BMJ Clin Evid. 2015;2015:0510. PMID: 25752320

3. Schaefer P, Baugh RF. Acute otitis externa: an update. Am Fam Physician. 2012;86(11):1055-1061. PMID: 23198673

4. Hui CP. Acute otitis externa. Paediatr Child Health. 2013;18(2):96-98. PMID: 24421665

5. Kaushik V, Malik T, Saeed SR. Interventions for acute otitis externa. Cochrane Database Syst Rev. 2010;(1):CD004740. doi:10.1002/14651858.CD004740.pub2

6. Russell JD, Donnelly M, McShane DP, Alun-Jones T, Walsh M. What causes acute otitis externa? J Laryngol Otol. 1993;107(10):898-901. doi:10.1017/s0022215100124692

7. Sander R. Otitis externa: a practical guide to treatment and prevention. Am Fam Physician. 2001;63(5):927-936. PMID: 11261868

8. van Balen FA, Smit WM, Zuithoff NP, Verheij TJ. Clinical efficacy of three common treatments in acute otitis externa in primary care: randomised controlled trial. BMJ. 2003;327(7425):1201-1205. doi:10.1136/bmj.327.7425.1201

9. Mahdyoun P, Pulcini C, Gahide I, Raffaelli C, Savoldelli C, Castillo L. Necrotizing otitis externa: a systematic review. Otol Neurotol. 2013;34(4):620-629. doi:10.1097/MAO.0b013e318287f28d

10. Viswanatha B, Naseeruddin K. Fungal infections of the ear in immunocompromised host: a review. Mediterr J Hematol Infect Dis. 2011;3(1):e2011003. doi:10.4084/MJHID.2011.003

11. Nadol JB Jr. Histopathology of Pseudomonas osteomyelitis of the temporal bone starting as malignant external otitis. Am J Otolaryngol. 1980;1(5):359-371. doi:10.1016/s0196-0709(80)80010-9

12. Carfrae MJ, Kesser BW. Malignant otitis externa. Otolaryngol Clin North Am. 2008;41(3):537-549. doi:10.1016/j.otc.2008.01.004

13. Rubin Grandis J, Branstetter BF 4th, Yu VL. The changing face of malignant (necrotising) external otitis: clinical, radiological, and anatomic correlations. Lancet Infect Dis. 2004;4(1):34-39. doi:10.1016/S1473-3099(03)00858-2

14. Ingleby HR, Soni R, Balakumar C, Moore LS. Necrotising otitis externa: the incidence and epidemiology of necrotising otitis externa in England before, during and after the coronavirus disease 2019 pandemic. J Laryngol Otol. 2025 Jan 9:1-7. doi:10.1017/S0022215124002354

15. Roland PS, Stroman DW. Microbiology of acute otitis externa. Laryngoscope. 2002;112(7 Pt 1):1166-1177. doi:10.1097/00005537-200207000-00005

16. Vennewald I, Klemm E. Otomycosis: diagnosis and treatment. Clin Dermatol. 2010;28(2):202-211. doi:10.1016/j.clindermatol.2009.12.003

17. Yao M, Messner AH. Fungal malignant otitis externa due to Scedosporium apiospermum. Ann Otol Rhinol Laryngol. 2001;110(4):377-380. doi:10.1177/000348940111000414

18. Mani N, Sudhoff H, Rajagopal S, Moffat D, Axon PR. Cranial nerve involvement in malignant external otitis: implications for clinical outcome. Laryngoscope. 2007;117(5):907-910. doi:10.1097/MLG.0b013e318031c830

19. Sweeney CJ, Gilden DH. Ramsay Hunt syndrome. J Neurol Neurosurg Psychiatry. 2001;71(2):149-154. doi:10.1136/jnnp.71.2.149

20. Prasad HK, Sreedharan S, Prasad HS, Kumar A, Parvathi VG. Perichondritis of the auricle and its management. J Laryngol Otol. 2007;121(6):530-534. doi:10.1017/S002221510600330X

21. Handzel O, Halperin D. Necrotizing (malignant) external otitis. Am Fam Physician. 2003;68(2):309-312. PMID: 12892351

22. Pistorius B, Westberry K, Drehobl M, Force RW. Efficacy and safety of ciprofloxacin plus fluocinolone acetonide among patients with acute otitis externa: a randomized clinical trial. JAMA Otolaryngol Head Neck Surg. 2022;148(7):599-607. doi:10.1001/jamaoto.2022.0862

23. Schönfeld U, Kessler P, Bertram S, Steinhart H, Schrom T. Hyperbaric oxygen therapy in malignant otitis externa: a systematic review of the literature. Diving Hyperb Med. 2021;51(4):352-359. doi:10.28920/dhm51.4.352-359

24. Vennewald I, Henker M, Klemm E, Seebacher C. Topical azole treatments for otomycosis. Cochrane Database Syst Rev. 2021;5(5):CD013864. doi:10.1002/14651858.CD013864

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Additional High-Yield Topics for Exam Preparation

Cross-Specialty Links:

• Diabetes management in acute infection (Endocrinology)
• Antibiotic stewardship principles (Infectious Disease)
• Cranial nerve anatomy and examination (Neurology)
• Temporal bone anatomy (Anatomy, ENT)
• Immunocompromised patient management (Oncology, Infectious Disease)

Related Conditions:

• Acute otitis media
• Chronic suppurative otitis media
• Cholesteatoma
• Temporal bone osteomyelitis
• Ramsay Hunt syndrome
• Perichondritis
• Herpes zoster oticus

Key Concepts to Master:

• Differentiating OE from OM clinically
• Recognizing red flags for necrotizing OE
• Evidence-based topical antibiotic selection
• Indications for systemic antibiotics vs. topical alone
• Ototoxicity of aminoglycosides
• Management algorithm for necrotizing OE
• Role of imaging in OE and NOE
• Cranial nerve examination and significance of involvement

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This topic reflects current evidence-based practice as of January 2026. Guidelines and evidence continue to evolve; consult primary literature and current guidelines for the most recent recommendations.