Assessment of Sinus Infections
The diagnosis of acute sinusitis is best made through clinical history and physical examination alone, without routine imaging, reserving CT scanning for complicated cases, recurrent disease, or preoperative planning. 1
Clinical Assessment: The Primary Diagnostic Approach
Key Historical Features
The most reliable clinical predictor combines:
- Purulent nasal secretions (yellow-green, green, or gray)
- Maxillary pain or pressure
- Colored rhinorrhea persisting beyond 10 days (or worsening after 5-7 days)
- Poor response to decongestants 1
Additional symptoms to assess include nasal congestion, postnasal drip, hyposmia/anosmia, fever, cough, fatigue, maxillary dental pain, and ear fullness 1
Physical Examination Technique
Facial inspection and palpation:
- Apply gentle pressure to the maxillary sinuses (below the cheekbones) - the most common site of sinusitis 2
- Assess the frontal sinuses (supraorbital ridge area above eyebrows) for tenderness 2
- Evaluate the ethmoid sinuses (medial canthal area between the eyes) 2
- Check for facial swelling, orbital involvement (diplopia, proptosis), or forehead swelling - these require urgent evaluation 2
Nasal examination:
- Decongest the nasal mucosa with a vasoconstrictor before examination to improve visualization 1, 2
- Purulent exudates in the middle meatus are highly predictive of bacterial sinusitis but may be difficult to see without decongestion 1, 2
- Red, swollen nasal tissue suggests infectious rhinitis/sinusitis; pale boggy turbinates suggest allergic rhinitis 1
- Persistence of purulent secretions beyond 10 days in the middle meatus area is characteristic of sinusitis 1
Additional examination components:
- Inspect the oropharynx for posterior pharyngeal mucopurulent secretions 1
- Examine for dental tenderness, as maxillary tooth roots project into the maxillary sinus floor 1, 2
- Check ears for otitis media, particularly in children 1
Advanced Clinical Techniques
Fiberoptic endoscopy allows direct visualization of the middle meatus, with 60-85% concordance between endoscopically-guided middle meatal cultures and maxillary sinus aspirates, though this is not routinely recommended for standard cases 1
When Imaging Is Indicated
Do NOT obtain imaging for uncomplicated acute sinusitis - the diagnosis should be clinical. 3
Appropriate Indications for Imaging:
- Recurrent or chronic sinusitis 3
- Persistent symptoms despite optimal medical therapy 2
- Suspected complications (orbital or intracranial involvement) 1, 3
- Preoperative evaluation before endoscopic sinus surgery 1
- Immunocompromised patients (lower threshold due to invasive fungal sinusitis risk) 3
Imaging Modality Selection
CT Scanning (First-Line When Imaging Needed)
Non-contrast CT is the optimal imaging technique for evaluating sinusitis when imaging is clinically indicated. 1, 3
Advantages:
- Best for evaluating ethmoid sinuses and ostiomeatal complex 1
- Excellent delineation of complex ethmoidal anatomy and anatomic variations 1
- Essential for preoperative planning 1
- Sensitivity and specificity superior to plain films 1
Important caveat: CT abnormalities are frequently found in patients with viral respiratory disease and may persist up to 8 weeks beyond microbiologic resolution, so clinical correlation is essential. 1
MRI (Selective Use)
MRI is NOT first-line but is indicated for:
- Suspected fungal sinusitis 1, 3
- Differentiating inflammatory disease from malignant tumors 1, 3
- Suspected intracranial complications 3
- Evaluating soft-tissue structures when CT findings are equivocal 1
Limitation: MRI cannot define bony anatomy as well as CT 1, 4
Plain Radiographs (Limited Role)
Plain films have poor sensitivity (76%) and specificity (79%) compared to maxillary sinus puncture, with particularly poor visualization of ethmoid sinuses. 1, 5
Single Waters view may detect maxillary sinusitis (80% sensitivity for maxillary sinus), but negative films cannot exclude disease in other sinuses. 1, 5
Obsolete Modalities
- Ultrasound: Poor sensitivity (36%) and specificity (90%); cannot distinguish bacterial from viral infection 1
- Transillumination: Cannot differentiate bacterial from viral infection 1
Critical Pitfalls to Avoid
Do not routinely image uncomplicated acute sinusitis - this leads to overdiagnosis due to nonspecific findings in viral infections 3, 4
Do not miss dental causes - examine for dental tenderness as dental root infections can erode into the maxillary sinus 1, 2
Do not miss red flags requiring urgent evaluation: orbital swelling, diplopia, proptosis, forehead swelling, or neurological symptoms 2
Do not assume absence of purulent secretions excludes sinusitis - protracted inflammation may not produce visible purulence 1
In recurrent sinusitis, evaluate for underlying conditions: immunodeficiency, cystic fibrosis (especially if nasal polyps in children), ciliary dysfunction, anatomic abnormalities 1