The gold standard for the diagnosis of obstructive sleep apnea (OSA) is polysomnography (PSG) Sleep Study. Although PSG helps identify individuals who have OSA and help the management, it does not identify the site of obstruction or predict surgical outcome. Both CT Scans and MRIs are beginning to play a crucial role in the evaluation of patients before oral appliance therapy, and other non-surgical therapies. It is also playing a critical role as well with surgeries such as uvulopalatopharyngoplasty (UPPP), reduction of tongue base, mandibular advancement, or geniohyoid muscle surgery.
Magnetic resonance imaging (MRI), although expensive, is probably the best imaging study for patients with obstructive sleep apnea because of its excellent resolution in the supine position. This radiographic modality provides a detailed view of the fat and soft tissue of the pharyngeal walls and its relation with the airway. Obtaining sagittal, coronal, and axial images, as well as 3-dimensional reconstructions, is also possible. MRI has the advantage of being radiation free, thus making performance of several studies without exposing the patient to any radiation at all..
Sleep MRI is a novel and reliable approach to simultaneously evaluate airway obstructions and respiratory events in real time during natural sleep. Sleep MRI can define the dynamic characteristics of airway obstruction in preoperative stage.
Airway obstructions visualized on Sleep MRI during natural sleep can include retropalatal, retroglossal, and combined obstruction. According to the obstructive site, different types of obstructive type sleep disordered breathing are classified as the soft palate type, palatine tonsil type, soft palate and depressed lingual root type, depression of the lingual root type, and epiglottis type.
Dynamic MRI in awake/sleep OSA patients is an excellent diagnostic tool for localizing the upper airway collapse before appropriate selection of non-surgical or surgical therapy.