The human skull contains four pairs of air-filled spaces known as the paranasal sinuses; the maxillary sinuses are the largest. Located in the cheekbones, below the eyes and above the upper teeth, these spaces reduce skull weight, humidify inhaled air, and affect voice resonance. The lining produces mucus, which normally drains through a small opening into the nasal cavity. Maxillary sinus cysts are common, fluid-filled sacs that appear as dome-shaped masses on imaging. Though these lesions are almost always benign, they can grow large enough to obstruct the sinus or press on surrounding structures, leading to noticeable symptoms.
Defining Maxillary Sinus Cysts
A maxillary sinus cyst is a non-cancerous, fluid-filled lesion that develops on the inner wall of the sinus cavity. The most frequent type is the mucous retention cyst, which forms due to a mechanical blockage. This occurs when the microscopic ducts of the seromucous glands—which secrete fluid to keep the sinus lining moist—become obstructed. When the duct is blocked, the gland continues to produce fluid, causing the area to swell and accumulate mucus beneath the sinus lining, eventually forming the retention cyst. This mechanism distinguishes cysts from conditions like sinusitis (generalized inflammation) or nasal polyps (soft tissue growths). The fluid inside the cyst is sterile and typically clear or yellowish in color. The cyst’s size dictates its potential for causing problems; a small cyst is often inconsequential, but one that expands can occupy a significant portion of the sinus cavity. Since the maxillary sinus floor houses the roots of the upper teeth, the cyst’s location places it in close proximity to sensitive structures.
Common Symptomatic Presentations
When a maxillary sinus cyst expands, it exerts pressure on the thin bony walls of the sinus and adjacent nerves, leading to a variety of symptoms. One of the most common complaints is facial pain or pressure, often localized directly over the cheekbone and mid-face area. This discomfort may be constant or intermittent, and it typically worsens as the cyst grows large enough to fill the sinus space. The cyst’s pressure can also result in referred pain, which is pain felt in a location different from the source. Patients frequently report chronic headaches concentrated behind the cheek or eye. Because the floor of the maxillary sinus is close to the roots of the upper molars and premolars, the cyst can cause a feeling of tenderness or a dull ache in the teeth, mimicking a dental problem. The physical presence of a large cyst can disrupt the normal airflow and drainage of the sinus. If the mass blocks the ostium (the small opening connecting the sinus to the nasal cavity), it can cause persistent nasal congestion or obstruction, typically on only the affected side. This obstruction impairs the natural clearance of mucus, sometimes leading to a post-nasal drip or a feeling of fullness and stuffiness in the face. Pressure exerted by the cyst on nerves like the infraorbital nerve can produce sensations, such as numbness or tingling in the cheek or upper lip.
The Path to Detection
For a majority of individuals, maxillary sinus cysts remain completely silent, causing no symptoms throughout their lifetime. These asymptomatic cysts are frequently discovered by chance when a patient undergoes imaging for an unrelated issue, such as a dental examination or an evaluation for a head injury. This phenomenon is known as an incidental finding. When a patient presents with facial pain, congestion, or referred tooth pain, medical professionals must confirm the cyst’s existence and rule out other potential causes. Initial plain film X-rays, such as a panoramic dental view, may show a classic dome-shaped opacity in the sinus. However, the computed tomography (CT) scan is the definitive tool for diagnosis, providing detailed, cross-sectional images of the sinus cavity. The CT scan allows a clinician to precisely visualize the cyst’s size, exact location, and relationship to the sinus walls and drainage pathway. Imaging clearly differentiates the fluid-filled cyst from other pathologies, such as bone-destroying tumors or the diffuse mucosal thickening characteristic of chronic sinusitis. Ultimately, detection through imaging confirms the nature of the lesion, which is important if the symptoms are severe enough to warrant further management.