Clinical and radiologic characteristics of the imploding antrum, or "silent sinus," syndrome

To present the clinical and radiologic details of a series of patients with the imploding antrum, or silent sinus, syndrome, together with examples of the surgical findings and management.

Retrospective, noncomparative case series.

Fourteen patients assessed in the Orbital Service at Moorfields Eye Hospital.

Changes of clinical signs, symptoms, and radiologic signs.

Seven men and seven women, between the ages of 25 and 78 years (mean, 41.3 years), had unilateral enophthalmos, their having noted the anomaly for an average of 8 months (range, 1-36 months). All patients were nonsmokers. There was no evidence of progression of the condition in eight cases followed up for up to 63 months. On the affected side, there was 1 to 4 mm enophthalmos and up to 4 mm hypoglobus, with secondary narrowing of the vertical palpebral aperture in some cases, but no effect on visual function, and there was significant disturbance of ocular motility in only one case. The condition is characterized radiologically by a smooth inward bowing of the walls of the maxillary antrum on the affected side, with secondary enophthalmos and hypoglobus. In all 14 cases, the maxillary roof (orbital floor) was drawn downwards, and the medial and posterolateral walls of the maxilla were concave in 13 cases where it could be assessed. In one patient, there was associated inward collapse of the ipsilateral ethmoid complex. There was a patchy loss of mineral from the maxillary roof in 9 of 13 cases and, where the posterolateral maxillary wall was affected, there was a concomitant increase in the radiolucency (fat) of the pterygopalatine fossa. Some soft-tissue changes were present in the affected antrum in all 14 patients, and there was an air-fluid level in three patients. In 12 patients where septal deviation was present, this was to the affected side in 10 (83%), and an abnormally directed middle turbinate was also frequently observed (10 of 14 cases).

The silent sinus syndrome mainly presents as unilateral enophthalmos in younger people and has very characteristic clinical and radiologic signs with, in many cases, abnormal intranasal anatomic characteristics on the affected side. The condition may be exclusive to nonsmokers. The acute onset and long-term stability of the condition suggests that, although chronic and largely asymptomatic sinus disease may be the underlying cause, an acute event precipitates collapse of the orbital floor or (in fact) a widespread "implosion" of all antral walls resulting from maxillary atelectasis. Therefore, we prefer the term imploding antrum syndrome-describing the relatively acute, symptomatic, event-rather than the name silent sinus syndrome, which relates to a putative underlying mechanism.