What is the likely diagnosis and appropriate next steps for a 16‑year‑old female with nine days of nasal congestion, thick green nasal discharge, fever, throbbing temple headache radiating to the occiput, positional vertigo with tinnitus, mild gait instability, and a history of asthma treated with montelukast?

Acute Bacterial Sinusitis with Vestibular Symptoms

This 16-year-old female meets diagnostic criteria for acute bacterial sinusitis based on the "persistent illness" pattern (symptoms >10 days without improvement), and she requires antibiotic therapy with amoxicillin 80-90 mg/kg/day divided twice daily for 10 days. 1

Primary Diagnosis: Acute Bacterial Sinusitis

The clinical presentation clearly satisfies the American Academy of Pediatrics criteria for acute bacterial sinusitis through the persistent illness pattern: 1

• Thick greenish nasal discharge and headache persisting for 9 days without improvement meets the >10 days threshold for persistent symptoms 1
• The swollen turbinates on physical examination support ongoing sinus inflammation 1
• Her history of asthma is a recognized predisposing factor for developing bacterial sinusitis 1

Critical distinction: The purulent nasal discharge alone does NOT indicate bacterial infection—this is a normal evolution of viral URIs due to neutrophil influx. 1, 2 However, the persistence beyond 10 days without improvement distinguishes this from uncomplicated viral URI. 1

Vestibular Component Requiring Attention

The positional vertigo ("room spinning"), tinnitus, and mild gait instability warrant careful consideration: 1

• These symptoms likely represent viral labyrinthitis or vestibular neuritis that can accompany or follow upper respiratory infections 1
• The temporal relationship (preceding the fever by several days) suggests a concurrent viral process rather than a complication of bacterial sinusitis 1
• Red flag assessment is essential: No proptosis, no visual changes, no severe periorbital swelling described—these would indicate orbital complications requiring immediate hospitalization 3

Immediate Management Algorithm

1. Antibiotic Therapy (First Priority)

Prescribe amoxicillin 80-90 mg/kg/day divided twice daily for 10 days as first-line therapy targeting Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. 1, 4

• Do NOT use azithromycin or oral third-generation cephalosporins due to S. pneumoniae resistance 1, 2
• Expect fever resolution within 24-48 hours; if no improvement after 48 hours, switch to amoxicillin-clavulanate 90 mg/kg/day 4

2. Asthma Management Reassessment

Restart montelukast immediately given her history of asthma and current acute illness: 5, 6

• Acute sinusitis can trigger asthma exacerbations, and montelukast provides both anti-inflammatory effects and symptom control 5, 6, 7
• The once-daily oral formulation ensures better compliance than inhaled therapies 5
• Montelukast is well-tolerated with no clinically important adverse effects in this age group 5, 6

3. Vestibular Symptom Management

Provide symptomatic treatment for vertigo: 1

• Meclizine 25 mg every 6-8 hours as needed for vertigo
• Advise slow positional changes and adequate hydration
• These symptoms typically resolve spontaneously over 1-2 weeks 1

4. Supportive Care

• Continue paracetamol for headache and fever control 1
• Nasal saline irrigation to facilitate drainage 1
• Adequate hydration 2

Critical Imaging Decision

Do NOT obtain imaging studies (CT, MRI, plain films) to confirm the diagnosis of acute bacterial sinusitis. 1

• Imaging is not recommended as it does not change management in uncomplicated cases 1
• Up to 68% of symptomatic children and 42% of healthy children show sinus abnormalities on imaging 1
• Imaging is only indicated if complications are suspected (orbital involvement, intracranial extension, treatment failure) 1

Mandatory Follow-Up Protocol

Reassess in 48-72 hours: 1, 4

• Fever should resolve within 24-48 hours of starting antibiotics 4
• If no improvement or worsening, switch to amoxicillin-clavulanate and consider imaging 4

Monitor for complications requiring immediate evaluation: 3

• Periorbital swelling or erythema (preseptal cellulitis)
• Proptosis, visual changes, or painful eye movements (orbital cellulitis—requires immediate hospitalization) 3
• Severe headache, altered mental status, or neck stiffness (intracranial complications)
• Persistent vertigo worsening beyond 1 week (may require ENT or neurology referral)

Common Pitfalls to Avoid

• Do not assume bacterial infection based solely on green nasal discharge—this is a normal viral URI evolution 1, 2
• Do not delay antibiotics when persistent illness criteria are met (>10 days without improvement) 1, 4
• Do not ignore the asthma history—acute sinusitis can trigger exacerbations requiring controller therapy 1
• Do not dismiss vestibular symptoms as insignificant—document carefully and ensure no red flags for central causes 1
• Do not prescribe oral corticosteroids unless asthma exacerbation is severe—they are not indicated for uncomplicated acute bacterial sinusitis 1