Chronic maxillary atelectasis is an infrequent entity and data on its prevalence are lacking. This study investigated the prevalence of chronic maxillary atelectasis and aimed to determine the bilaterality of this entity.

The data for 5835 patients who underwent paranasal sinus computed tomography from 2016 to 2020 were retrospectively analysed.

Fifty-four patients were diagnosed with chronic maxillary atelectasis; its prevalence was 0.92 per cent. The mean age of these 54 patients was 42.98 ± 18.89 years (range, 18–85 years); 17 of the patients were female and 37 were male. Chronic maxillary atelectasis was unilateral in 42 patients and bilateral in 12 patients (22.2 per cent). Eight patients were found to have enophthalmos with apparent facial asymmetry.

The prevalence of bilateral chronic maxillary atelectasis may be higher than previously reported and bilaterality may increase as the number of diagnosed cases increases. A unified classification is also proposed, which describes the silent sinus syndrome as chronic maxillary atelectasis IIIS.

Silent sinus syndrome is characterised by spontaneous enophthalmos and hypoglobus, in association with chronic atelectasis of the maxillary sinus, and in the absence of signs or symptoms of intrinsic sinonasal inflammatory disease. Traditionally, correction of the enophthalmos involved reconstruction of the orbital floor, which was performed simultaneously with sinus surgery. Recently, there has been increasing evidence to support the performance of uncinectomy and antrostomy alone, then orbital floor reconstruction as a second-stage procedure if needed.

We performed a retrospective review of 23 cases of chronic maxillary atelectasis managed in our unit with endoscopic uncinectomy and antrostomy alone. All patients were operated upon by the same surgeon.

Twenty-two of the 23 patients had either complete or partial resolution. One patient had ongoing enophthalmos, and was considered for an orbital floor reconstruction as a second-stage procedure.

Our case series demonstrates that dynamic changes in orbital floor position can occur after sinus re-ventilation. These findings support the approach of delaying orbital floor reconstruction in cases of silent sinus syndrome treated with sinus re-ventilation, as such reconstruction may prove unnecessary over time.

We describe a previously unreported case of ethmoid silent sinus syndrome.

Case report and review of the world literature regarding silent sinus syndrome.

A 33-year-old woman developed medial displacement of the left orbital contents in the absence of trauma, surgery or other significant pathology. Imaging showed opacification of the left ethmoid sinus and implosion of the medial orbital wall. Previously reported cases of silent sinus syndrome have all involved the maxillary sinus, with subsequent implosion of the orbital floor. Computed tomography scans of our patient showed wide, flat ethmoidal bulla and surrounding cells, with few horizontal bony septae reinforcing the area of collapse.

This case represents the first report of ethmoid silent sinus syndrome. We argue that, in anatomically susceptible individuals, the silent sinus syndrome can present due to chronic ethmoidal sinusitis.