Diagnosis, Workup and Treatment
The examination was thought to be suggestive of a restrictive process involving the right orbit and a CT scan was ordered. The working differential diagnosis in the setting of the patient’s right enophthalmos was occult orbital fracture, silent sinus syndrome (SSS), scirrhous carcinoma of the breast, and pseudo-enophthalmos.

CT imaging was diagnostic for silent sinus syndrome. The right maxillary sinus was opacified and its walls were collapsed inward, expanding the volume of the right orbit. The right orbital floor/maxillary sinus roof was inferiorly displaced causing enophthalmos. The right ostium and infundibulum were completely opacified and the right uncinate process was laterally displaced against the inferomedial orbital wall. No fracture was appreciated (See Figure 2).

The patient underwent right maxillary sinus endoscopic drainage with septoplasty by ENT and deferred right orbital floor reconstruction as his symptoms were minimal. Spontaneous remodeling of the orbital floor and resolution of the enophthamos has been reported with sinonasal surgery alone and the patient did not want to risk potential complications of orbital surgery. He reported improvement of his symptoms and appearance postoperatively.

Silent sinus syndrome is an uncommon unilateral acquired condition causing atelectasis of the maxillary sinus leading to non-specific ocular symptoms and signs such as enophthalmos and hypoglobus.1 The term was coined in 1994 by Charles Soparker, MD, PhD, but was first described as a distinct clinical entity by William Montgomery, MD, in 1964.2,3

Its etiology remains unclear, although several theories have been proposed. In 1964, Dr. Montgomery proposed that chronic sinusitis caused pressure atrophy of the sinus walls leading to maxillary sinus atelectasis.3 This theory was dismissed, as there is no clear association with chronic sinusitis and only the orbital floor is thin, whereas the other maxillary sinus walls are typically normal thickness or thicker. In 1994, Dr. Soparker and colleagues thought the underlying cause was congenital hypoplasia of the maxillary sinus.2 This was also refuted by available imaging of patients prior to the onset of SSS, documenting normal maxillary sinus architecture. The current theory, proposed by Erik S. Kass, MD, and colleaguesl in 1997, is related to maxillary sinus outflow obstruction. Blockage of the osteomeatal complex with continued resorption of gases into the capillaries of the sinus wall leads to maxillary sinus hypoventilation and buildup of negative pressure. Maxillary sinus manometry has shown sub-atmospheric pressures. This ultimately causes the sinus walls to collapse and orbital floor thinning.4,5

SSS affects individuals in the third and fourth decade of life and affects men and women equally. For unknown reasons, non-smokers are more commonly affected than smokers. There usually is not a history of sinus disease.4,5,6

Patients may report a variety of non-specific symptoms such as “sinking of the eye,” a “pulling sensation,” or a “change in facial symmetry or appearance.” However, SSS is usually asymptomatic.1 Diplopia is unusual, as the disease process is slowly progressive.5 Of note, about 50 percent of patients with enophthalmos may come in with complaints related to the contralateral uninvolved eye such as proptosis or ptosis.7 It is up to the clinician to determine the true abnormality given the ocular findings. Motility is usually normal. Ocular findings include enophthalmos, hypoglobus and upper eyelid retraction. The clinician or patient may appreciate an audible clicking sound with blinking.7 This is caused by air trapped within a deep superior sulcus and can sometimes be seen in CT imaging as well.

The gold standard for diagnosis is CT of the orbits. CT classically shows partial or complete opacification of the maxillary sinus and inward retraction of the sinus walls. Associated ipsilateral increased orbital volume helps explain the enophthalmos and hypoglobus seen on exam. An enlarged middle meatus and lateralization of the uncinate process can be shown occluding the osteomeatal complex. The walls tend to be osteopenic, but can be thickened. Orbital soft tissue is normal.8,9 If the above radiographic findings are not suggestive of SSS, the differential diagnosis for spontaneous enophthalmos and hypoglobus is broad and includes trauma, scirrhous carcinoma, linear scleroderma, lipodystrophy, orbital varix, osteomyelitis, Parry-Romberg Syndrome and pseudo-enophthamos.1

Pathology of the sinus mucosa shows thickening, edema, chronic inflammation, but bacterial cultures are typically negative.1
Modern treatment is surgical and involves either a one- or two-step procedure. The primary goal is to reestablish ventilation of the maxillary sinus. This is typically done by endoscopic maxillary antrostomy and uncinectomy. The maxillary sinus is evacuated and decompressed, and a large patent communication between the maxillary sinus and nasal meatus is established. Recurrences are prevented by creating a large ostium.

Post-treatment imaging months later may reveal remodeling and normalization of the sinus architecture. This alone may correct the enophthalmos and hypoglobus. For this reason, some authors recommend staging the procedure, as opposed to simultaneous repair of the orbital floor. A second procedure to reconstruct the orbital floor may be required, however, and its timing is case- and surgeon-dependent. A trans-conjunctival approach is most commonly employed.1,5,10

The author would like to thank Jennifer Hall, MD, Wills Eye Institute Neuro-Ophthalmology Department and Jurij Bilyk, MD, Wills Eye Institute Oculoplastic and Orbital Surgery Department, for their time and assistance.

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