Variability of morphology and signal intensity of alar ligaments in healthy volunteers using MR imaging.

BACKGROUND AND PURPOSE Evaluation of alar traumatic injuries by using MR imaging is frequently performed. This study investigates the variability of morphology and signal intensity of alar ligaments in healthy volunteers so that pathology can be more accurately defined. MATERIALS AND METHODS Fifty healthy volunteers were examined on a 1.5T MR imaging scanner with 2-mm PD-weighted sequences in 3 planes. Delineation of the alar ligaments in 3 planes and signal-intensity characteristics on sagittal planes were analyzed by using a 4-point grading scale. Variability of courses and morphologic characteristics were described. RESULTS Delineation of alar ligaments was best viewed in the coronal plane, followed by the sagittal and axial planes. In the sagittal view, 6.5% of alar ligaments appeared homogeneously dark. Hyperintense signal intensity in up to one-third of the cross-sectional area was present in 33% of cases; in up to two-thirds of the cross-sectional area, in 45% of cases; and in more than two-thirds of the cross-sectional area, in 15% of cases. Of alar ligaments, 58.5% ascended laterally, 40.5% ran horizontally, and 1% descended laterally. The cross-sectional area was round in 41.5%, oval in 51.5%, and winglike in 6.5%. CONCLUSIONS On 1.5T MR imaging, the alar ligaments can be delineated best in the coronal and sagittal planes. Our data indicate a remarkable variability of morphology and course as well as signal intensity. This finding is contradictory to former publications assigning such alterations exclusively to patients with trauma.