What is silent sinus syndrome?

What is Silent Sinus Syndrome?

Silent sinus syndrome (SSS) is atelectasis (collapse) of the maxillary sinus caused by chronic obstruction of the sinus outflow tract, resulting in negative intrasinus pressure that leads to progressive, painless enophthalmos (sunken eye) and hypoglobus (downward displacement of the eye). 1

Pathophysiology

• SSS develops when chronic obstruction of the maxillary sinus ostium or infundibulum creates negative pressure within the sinus cavity 1
• This negative pressure causes progressive inward bowing and collapse of the sinus walls, particularly the orbital floor 1
• The orbital floor resorption and maxillary sinus volume reduction lead to the characteristic orbital findings 2
• The condition is typically acquired rather than congenital, though the exact trigger for ostial obstruction remains debated 2, 3

Clinical Presentation

The hallmark features are painless enophthalmos and hypoglobus, distinguishing it from other sinus pathology that typically causes pain or pressure 3:

• Enophthalmos (posterior displacement of the globe) is present in most patients, averaging 2.67 ± 1.39 mm at presentation 3
• Hypoglobus (inferior displacement of the globe) occurs in most cases, averaging 2.22 ± 1.43 mm 3
• Facial asymmetry with retraction of the malar eminence, best appreciated on frontal and cranio-caudal photographs 2
• Diplopia (double vision) from altered orbital mechanics 3
• Headache or facial pressure may occur but are not the predominant symptoms 3
• Mean age at diagnosis is approximately 39 years with relatively equal gender distribution 3

Diagnostic Imaging

CT without contrast is the imaging modality of choice for diagnosis and surgical planning 1:

• Demonstrates decreased maxillary sinus volume with inward bowing of the sinus walls 1
• Shows obstruction of the infundibulum (the drainage pathway) 1
• Reveals osseous thinning of the sinus walls and orbital floor 1
• Demonstrates lateralization of the uncinate process 1
• CT provides superior delineation of these bony changes compared to MRI 1

A common pitfall is that nasal septum deviation is frequently present on the same side as the affected maxillary sinus, and this association should prompt consideration of SSS when combined with facial asymmetry 2.

Treatment Approach

Functional endoscopic sinus surgery (FESS) is the primary treatment, performed in 87% of reported cases 3:

• FESS with maxillary antrostomy restores sinus ventilation and equalizes pressure 2, 3
• The procedure involves postero-anterior uncinectomy and enlargement of the maxillary ostium 2
• Orbital floor reconstruction is required in 23.5% of cases when significant bony deficits persist after FESS 3
• Patient-specific implants (such as Medpor) can be used for orbital floor reconstruction when needed 4, 5

Treatment Outcomes

Post-surgical results demonstrate significant improvement 3:

• Enophthalmos reduces from 2.67 mm to 0.33 ± 0.75 mm
• Hypoglobus reduces from 2.22 mm to 0.23 ± 0.62 mm
• 83.2% of patients achieve partial or total resolution of clinical symptoms

FESS should be performed promptly to prevent progression of enophthalmos, hypoglobus, and facial deformities 2.

Key Clinical Pearls

• Suspect SSS in patients presenting with painless progressive enophthalmos, hypoglobus, and ipsilateral nasal septal deviation 2
• Obtain paranasal sinus CT when a patient has deviated nasal septum combined with retraction of the malar eminence and hypoglobus 2
• The "silent" nature refers to the absence of typical sinus pain or pressure symptoms, not the absence of all symptoms 1
• SSS can be idiopathic or occur following trauma or previous sinus surgery 6
• Cranio-caudal facial photographs are essential for documenting facial asymmetries that may be subtle on standard frontal views 2