Objective        To investigate the manifestation of upper airway on cine MR imaging in children without respiratory symptoms during sleep.       Methods       One hundred and twelve subjects without sleep-related disorders were recruited from a population of patients between the ages of 2 and 7 who were referred for MR imaging of the brain because of other reasons in our department from June 2010 to February 2011. A sagittal midline cine MR sequence was performed by using a 1.5-T MR imaging system. The upper airway was segmented as nasopharynx

oropharynx and oral cavity. Motion of the nasopharynx

oropharynx and oral cavity was characterized as static patent

dynamic patent

intermittent collapse

or static collapse. The maximal diameter and greatest change in size of three segments were measured and calculated.       Results       In 112 subjects

dynamic motion (dynamic patent or intermittent collapse) was detected in the oropharynx in 50 cases (44.6%)

in the nasopharynx in 44 cases (39.3%)

and in the oral cavity in 8 cases (7.2%). The dynamic motion was 2.49±2.20 mm in the oropharynx

2.13±0.75 mm in the nasopharynx

and 1.42±0.53 mm in the oral cavity.       Conclusion       Cine MR imaging is an ideal way to measure the diameter and evaluate the dynamic motion of the upper airway in children. A certain degree of airway motion (usually less than 5 mm) is commonly encountered in children without sleep disorder and should be considered as a normal finding on cine MRI.