Silent Sinus Syndrome is a rare, acquired condition involving the spontaneous, gradual collapse of the maxillary sinus, the large air-filled cavity located in the cheekbone area. The syndrome is distinct because it occurs without the typical symptoms of a sinus infection, such as pain, pressure, or nasal discharge, which is why it is referred to as “silent.” The primary consequence of this implosion is a visible change in the appearance and function of the eye on the affected side.
How the Maxillary Sinus Collapses
The underlying cause of Silent Sinus Syndrome is chronic obstruction of the sinus’s natural drainage pathway, known as the ostium. This small opening allows the maxillary sinus to ventilate and drain into the nasal cavity. When the ostium becomes blocked, often subtly and without causing noticeable symptoms, the air trapped inside the sinus cannot be replenished.
The mucosal lining within the sinus cavity continues to absorb gases into the bloodstream through its capillary network. Because the ostium is obstructed, the air is slowly absorbed from the closed-off space, but no new air can enter to equalize the pressure. This resorption of air creates a chronic negative pressure gradient—a vacuum effect—within the sinus cavity.
This subatmospheric pressure is the driving force behind the structural changes, causing the thin, bony walls of the sinus to be pulled inward, a process called atelectasis. The negative pressure causes the sinus to gradually reduce in volume. The orbital floor, which forms the roof of the maxillary sinus, is particularly vulnerable and bows downward into the contracting cavity, slowly distorting the anatomy of the face and eye socket.
Key Physical Symptoms and Signs
The inward collapse of the orbital floor creates noticeable changes in the position of the eyeball. The two primary physical signs are enophthalmos and hypoglobus. Enophthalmos describes the posterior displacement, or sinking, of the eyeball deeper into the eye socket, which is present in nearly all cases.
Hypoglobus is the downward displacement of the eyeball. The extent of these changes is often gradual, meaning the patient may not notice the changes until facial asymmetry becomes pronounced.
The change in the eye’s position can also lead to functional problems, most commonly diplopia, or double vision. The shifting of the orbital floor subtly alters the alignment of the eye muscles, making it difficult for the eyes to work together to focus. Patients may also notice aesthetic changes, such as a deepening of the upper eyelid crease or a droopy appearance of the eyelid.
Identifying and Treating the Syndrome
Diagnosis of Silent Sinus Syndrome relies heavily on imaging. The most definitive tool is a Computed Tomography (CT) scan of the orbits and sinuses. CT images characteristically show a reduced volume of the maxillary sinus, inward bowing of the sinus walls, and a distinct downward displacement of the orbital floor. The scan also typically reveals opacification (the sinus cavity filled with soft tissue or fluid) and a blockage of the ostiomeatal complex.
Treatment for the syndrome is surgical and has two distinct goals: restoring normal sinus ventilation and correcting the orbital and visual defects. The first step involves an endoscopic sinus procedure, such as a wide maxillary antrostomy, to create a permanent opening and relieve the negative pressure. This procedure restores proper airflow and drainage to the sinus, addressing the root cause.
The second goal is to restore the normal position of the eye, which may require orbital floor augmentation. The orbital floor is repaired using an implant to lift the displaced eye socket and increase its volume. This repair is often performed concurrently with the endoscopic surgery. In some cases, the enophthalmos may improve slightly after the antrostomy alone, potentially avoiding the need for a separate orbital floor reconstruction.