Abstract
The purpose of this study was to evaluate a magnetic resonance imaging (MRI) protocol for direct visualization of the inferior alveolar nerve in the setting of mandibular fractures. Fifteen patients suffering from unilateral mandible fractures involving the inferior alveolar nerve (15 affected IAN and 15 unaffected IAN from contralateral side) were examined on a 3 T scanner (Elition, Philips Healthcare, Best, the Netherlands) and compared with 15 healthy volunteers (30 IAN in total). The sequence protocol consisted of a 3D STIR, 3D DESS and 3D T1 FFE sequence. Apparent nerve-muscle contrast-to-noise ratio (aNMCNR), apparent signal-to-noise ratio (aSNR), nerve diameter and fracture dislocation were evaluated by two radiologists and correlated with nerve impairment. Furthermore, dislocation as depicted by MRI was compared to computed tomography (CT) images. Patients with clinically evident nerve impairment showed a significant increase of aNMCNR, aSNR and nerve diameter compared to healthy controls and to the contralateral side (p < 0.05). Furthermore, the T1 FFE sequence allowed dislocation depiction comparable to CT. This prospective study provides a rapid imaging protocol using the 3D STIR and 3D T1 FFE sequence that can directly assess both mandible fractures and IAN damage. In patients with hypoesthesia following mandibular fractures, increased aNMCNR, aSNR and nerve diameter on MRI imaging may help identify patients with a risk of prolonged or permanent hypoesthesia at an early time.
Highlights
Abbreviations aNMCNR Apparent nerve-muscle contrast-to-noise ratio apparent signal-to-noise ratio (aSNR) Apparent signal-to-noise ratio cone beam computed tomography (CBCT) Cone beam computed tomography CI Confidence interval CT Computed tomography CNR Contrast-to-noise ratio DESS Double echo steady state inferior alveolar nerve (IAN) Inferior alveolar nerve
The primary goal of the present study is to evaluate the applicability of a protocol consisting of a 3D STIR, 3D DESS and 3D T1 FFE sequence for rapid imaging assessment of mandible fractures affecting the IAN in the emergency room setting
Fifteen IANs involved in mandible fractures were included in this study
Summary
Abbreviations aNMCNR Apparent nerve-muscle contrast-to-noise ratio aSNR Apparent signal-to-noise ratio CBCT Cone beam computed tomography CI Confidence interval CT Computed tomography CNR Contrast-to-noise ratio DESS Double echo steady state IAN Inferior alveolar nerve. X-rays, CT, and CBCT imaging can only visualize the bony cortical walls surrounding the mandibular canal[6]. These radiation-based imaging techniques lack the ability to directly visualize neural structures. The IAN is at potential risk of injury in wisdom tooth removal, implant placement and orthognathic surgery as well. All of these injuries vary in nature, but the signs and symptoms following nerve damage remain rather uniform, and differ primarily in degree. The required resolution to visualize the continuity loss of endo- and perineurium was not achieved with a 3 T MRI in that study
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