The airway space includes the nasal cavity, nasopharynx, velopharynx, oropharynx and hypopharynx. Large FOV CBCT studies, such as those acquired to assess the craniofacial skeleton for orthodontics and orthognathic surgery, will typically include the airway spaces. In MDCT units where the patient is in a supine (lying with face up) position, gravitational forces on the tongue and soft palate will result in narrowing of the airway space.21 With most CBCT units the patient is in a seating position which does not replicate the sleeping position. The visualized airway is not only influenced by the position of the soft tissue of the neck, it is also influenced by the position of the tongue during acquisition, which can cause the airway to appear narrower.22 CBCT can help identify patients with a high predisposition for obstructive sleep apnea (OSA), although the final diagnosis is typically made through a medical sleep study (polysomnography).
CBCT studies provide only a static image of the airway space, and can be helpful in the detection of anatomical or pathological changes. The airway space should be evaluated systematically for patency and symmetry, with the capability to measure airway dimensions or provide 3D modeling. Although CBCT imaging provides excellent visualization of static airway morphology, it does not provide any direct information on airflow or airway resistance.
Hyperplasia of the nasal turbinates is the most common form of nasal obstruction, and can be caused either by infection or chronic inflammation. Other causes of nasal obstruction are nasal septum deviation, nasal polyps, benign tumors (such as osteoma), and malignant tumors (such as squamous cell carcinoma). Neoplasms in the nasopharynx and oropharynx can cause narrowing and/or asymmetry of the airway space. The most common pathological conditions that can affect the airway in children are enlarged pharyngeal and palatine tonsils.2
An airway analysis may be performed prior to orthognathic surgery. Volumetric measurements can be taken for the patient with surgical treatment options considered according to the severity in the position of the jaws.