For years, in part due to the significance and frequency of obstructive sleep apnea syndrome (OSA), and also in part due to frustrations of eliminating optimal treatments for selected patients, imaging techniques have been used to attempt to gain insights into the disorder. In hopes of defining the exact site of obstruction in a selected patient, a therapy could be tailor to that person.
Some of the more standard imaging techniques that have been used include x-ray cephalometry which measures the cranio-facial dimensions in relationship to oro-pharyngeal diameters (the area behind the tongue) on a person's head and neck. This attempts to predict OSA in patients by selecting those with reduced diameters in the throat area. Unfortunately these measures are low in both sensitivity and specificity for the disorder. Cephalometry has also been combined with CT scanning of the posterior tongue and soft palate to predict this better, but again this has been limited in defining the population at risk. Another option is to have videoendoscopy with Muller's maneuver. This is where an otolaryngologist inserts a laryngoscope (flexible optical fiber) down one nostril into your nasal / throat area. You then plug the other nostril and mouth and try to breathe in. This creates a vacuum and can show how much your airway collapses. This has been more effective in predicting patients with OSA if the area behind the palate is less than 0.8cm squared in males and less than 0.54 cm squared in females.
More recent attempts have included performing nasopharyngoscopy under sedation, and having the patient's jaw advanced during the procedure to assess if visualized obstruction and snowing improved. If so, these patients were either fitted with a dental appliance advancing the mandible, or underwent surgical mandibular advancement. This seems to have some beneficial results in small population studies. Also MR techniques are being studied to assess the anatomical risks of patients who may have OSA, but to date pre-and post-operative tests by MRI have not been able to show consistent changes that allow predictability of success or failures of various treatments.
Perhaps the future will find more secure diagnostics for imaging in real-time imaging techniques. One currently being investigated is anatomical optical coherence tomography which can be performed without sedation. A small probe is passed from the nose to mid-esophagus, and within this an optical probe is inserted. As it passes down it directly visualizes and measures the anatomy of the upper airway by creating images from the phase characteristics of light that bounces back from the surrounding tissues. This procedure still has limitations, but may hold the key for both better therapeutics and diagnostics since construction is being measured real-time.