The sphenoid sinus is one of four paired air-filled cavities within the skull, known collectively as the paranasal sinuses. It connects to the nasal cavity and contributes to various bodily functions. Though less commonly discussed, the sphenoid sinus plays a role in respiratory health and can be associated with specific conditions.
Anatomy and Location
The sphenoid sinus is a paired cavity deep within the sphenoid bone, a complex, butterfly-shaped bone positioned centrally in the skull. It lies behind the upper part of the nasal cavity. Each sinus varies in size and shape, rarely symmetrical, and is often separated by an asymmetrical bony septum. They connect to the nasal cavity through an opening into the sphenoethmoidal recess, a small space in the superior nasal meatus.
The sphenoid sinus’s deep placement brings it into close proximity with several important structures. Directly superior and lateral are the optic nerves, which can be adjacent to, indenting, or even traversing the sinus. The pituitary gland, a small endocrine gland, sits just above, making the sinus a common surgical access point for procedures involving this gland. Internal carotid arteries lie laterally, and the cavernous sinuses are positioned superiorly and laterally. The bone separating the sphenoid sinus from these sensitive structures can be remarkably thin.
Role in the Body
The sphenoid sinus contributes to several physiological functions. It helps condition inhaled air by humidifying and warming it before it reaches the lungs. Mucus produced within the sinus traps airborne particles like germs and allergens, flushing them out and maintaining a healthy lining. The inner surface is lined with cilia that move this mucus towards the sinus opening for drainage, a process known as mucociliary clearance.
Beyond air conditioning and defense, the sphenoid sinus also reduces skull weight. As an air-filled cavity, it lightens the cranial structure. The presence of this air-filled space also plays a role in voice resonance, influencing the sound and quality of speech. Some research suggests the sphenoid sinus may also help absorb impact during head injuries, potentially offering a degree of protection.
Common Conditions
The sphenoid sinus can be affected by various conditions, with inflammation or infection being common. Sphenoid sinusitis occurs when germs or allergens become trapped, leading to inflammation and swelling. Though less common than other sinusitis types, infections here can be problematic due to the sinus’s deep location and proximity to vital structures.
Symptoms of sphenoid sinusitis can be distinct and sometimes severe. Headaches are a frequent symptom, often described as deep and intense, felt behind the eyes, in the forehead, temples, or the back of the head, and may worsen when lying down. Facial pain or pressure, and occasionally numbness, can also occur. Given the sphenoid sinus’s close relationship with the optic nerves, vision changes are possible symptoms, including blurred or double vision, vision loss, or sensitivity to light.
Other indicators may include:
Neck pain
Nasal congestion
Discharge
Post-nasal drip
Sore throat
Dizziness
Vertigo
Toothache
Untreated sphenoid sinusitis can lead to serious complications, such as brain abscesses, damage to cranial nerves, or meningitis. While less common, other conditions like tumors can also affect the sphenoid sinus.