- Painless enophthalmos, hypoglobus and facial asymmetry
Description
Silent Sinus Syndrome (SSS) is a rare and progressive condition characterised by asymptomatic or minimally symptomatic chronic maxillary sinusitis, leading to painless, spontaneous enophthalmos and hypoglobus.
Pathogenesis
The accepted theory for SSS pathogenesis involves the chronic obstruction of the ostiomeatal complex, leading to negative sinus pressure, gradual collapse of the maxillary sinus walls, and consequent enophthalmos and hypoglobus. The syndrome is “silent” due to its indolent nature and the absence of typical sinusitis symptoms, which makes its early diagnosis challenging.
Epidemiology, Risk Factors & Associations
- The exact prevalence of SSS is unknown due to its rarity and asymptomatic nature.
- It most commonly affects adults, with a mean age of presentation around 40 years, though cases have been reported in patients ranging from 14 to 72 years.
- There’s no clear gender predominance.
- Risk factors are not well defined but the condition has been associated with prior nasal or sinus surgery and with history of nasal or facial trauma.
Clinical Features
- The hallmark clinical features of SSS are enophthalmos (a sunken eye appearance) and hypoglobus (downward displacement of the eye), which often lead to cosmetic concerns and may cause diplopia.
- Patients often lack symptoms typically associated with sinusitis. This relative symptom silence contributes to the diagnostic challenge and delay.
- A minority of patients might have mild nonspecific symptoms such as dull facial ache or pressure.
Complications
- Possible complications include persistent diplopia due to muscle imbalance from the hypoglobus, and orbital floor fractures due to weakening of the maxillary bone structure.
Pathological Features
Histopathological examination of the sinus mucosa typically reveals chronic inflammation, fibrosis, and remodeling.
Radiological Features
General Features
- The maxillary sinus appears opacified with a reduced volume (atelectasis).
- There is a characteristic inward bowing or retraction of the antral walls, most notably the inferomedial wall, leading to enophthalmos and hypoglobus.
CT
- CT is the modality of choice for the diagnosis of SSS.
- Demonstrates opacification and atelectasis (reduced volume) of the maxillary sinus
- Inferior bowing of the sinus roof (orbital floor) resulting in increased orbital volume and enophthalmos
- Lateral bowing of the medial wall resulting in lateral displacement of the middle and inferior turbinate
- Posterior bowing of the anterior wall resulting in flattening of the malar eminence
- Anteromedial bowing of the posterolateral wall
- Enophthalmos can be measured by comparing the anterior projection of the globe relative to the external orbital rim with the unaffected side.
MRI
- MRI can confirm the diagnosis and exclude other causes of enophthalmos, but it’s typically not the first line of imaging.
Diagnosis
- The diagnosis of SSS is typically made based on characteristic clinical and imaging features.
- The definitive diagnosis is usually made on CT scans showing maxillary sinus opacification, sinus wall retraction, and orbital floor lowering.
Differential Diagnosis
- Chronic sinusitis: Mucoperiosteal reaction and sinus wall hyperostosis.
- Congenital Maxillary Sinus Hypoplasia: More common. Facial deformity not present.
Clinically-based
- Orbital floor fracture: Sudden onset, usually related to trauma, with acute symptoms like pain and bruising.
Management
- Primarily managed surgically with endoscopic maxillary sinus surgery aimed at re-establishing maxillary sinus ventilation.
- The orbital floor may be reconstructed in severe cases with significant enophthalmos, hypoglobus or persistent diplopia post sinus surgery.
- Despite treatment, some degree of enophthalmos may persist due to irreversible changes in the sinus walls and floor.