NEW ORLEANS — With visualization of dynamic airway motion in children with severe obstructive sleep apnea, cine MRI supplies unique information that enhances diagnosis, targets treatment and, in some cases, prevents unnecessary surgeries, according to findings presented at annual meeting of the American Society of Neuroradiology.
Likely candidates for cine MRI evaluation are children who have obstructive sleep apnea (OSA) and have undergone adenoidectomy or tonsillectomy and have failed using continuous positive airway pressure (CPAP). Many have congenital disorders such as Beckwith Weidemann syndrome, trisomy 21, midfacial hypoplasia, and cleft palate. “We do not use cine MRI for the typical patient who has sleep apnea and enlarged tonsils and would respond to conservative management,” said Dr. H. Coleman Herrod, of the University of Utah, Salt Lake City.
For the cine MRI, the patient is deeply sedated using propofol and then monitored for airway obstruction. During imaging, the airway is not secured, in order to elicit the obstructive pathophysiology. This requires close monitoring by the anesthesiologist to foster physiologic sleep respiratory patterns, and technologists who know exactly what they are doing to ensure the child's safety, Dr. Herrod said. Patients are imaged on a 1.5-T magnet through several different sequences.
In 29 cases, sleep was successfully induced with no adverse events. Airway obstruction was visualized in most patients. The remaining patients were found to have patent airways throughout the exam with no clinical evidence of apnea.
Cause of obstruction visible on cine imaging included macroglossia, glossoptosis, micrognathia, palatine elongation or coaptation with posterior pharynx, tonsillar hypertrophy, and dynamic multilevel airway collapse. In several cases, more than one site appeared obstructed.
The findings directed the need for surgery and the type of procedure in several cases. For example, in one case, an enlarged tongue was shown to be obstructing the airway. Subsequently, tongue reduction surgery led to a decline in the OSA score from 50.1 to 4.4. In a second case, the patient underwent Le Fort maxillary retrusion—an operation for reconstruction of the midface in which the teeth-bearing part of the maxilla is separated from its bony attachments and repositioned—to correct the problem. In at least two cases, physicians decided against surgery after reviewing the results of the cine MRI.
Traditional imaging for the evaluation of OSA in children includes radiographic, CT, and fluoroscopic imaging. Static imaging may show anatomic details but yields no information regarding dynamic airway motion. Fluoroscopy can show dynamic changes but at the risk of ionizing radiation exposure. Cine MRI adds to the traditional work-up of OSA for those patients with more severe disease, said Dr. Herrod, who added that he is getting positive feedback from referring clinicians.