MR imaging of traumatic lesions of the inferior alveolar nerve in patients with fractures of the mandible.

BACKGROUND AND PURPOSE The objective of this study was to assess whether MR imaging can image the neurovascular bundle in patients with fractures of the mandible. In addition, an attempt was made to evaluate whether MR images provide information regarding the continuity of the inferior alveolar nerve before surgery and regarding signal intensity changes after trauma. METHODS We analyzed preoperative MR images of 23 patients with mandibular fractures. Object-oriented sagittal view proton density- and T1-weighted sequences (before and after the administration of contrast agent) were used not only in an attempt to obtain purely qualitative information regarding nerve continuity in the neurovascular bundle (inferior alveolar nerve, artery, vein) but also to perform quantitative region-of-interest measurements of signal intensities at four defined measurement sites. The measurements were compared with those obtained for a patient population with healthy mandibles. RESULTS It was possible to interpret MR images in 21 cases. MR imaging findings showed that the neurovascular bundle had been cut in two patients and was intact in the remaining 19 patients. These MR imaging findings were confirmed intraoperatively in all cases. Although we found no significant signal intensity differences between patients with intact nerves and patients with cut nerves, we found significant differences between patients with mandibular fractures and patients with unremarkable mandibles. CONCLUSION It is possible to diagnose the interruption of nerve continuity by using MR imaging. Signal intensity measurements in the neurovascular bundle provide no information regarding nerve continuity.