High resolution 3-T MR imaging in the evaluation of the trigeminal nerve course.

BACKGROUND The evaluation of the trigeminal course and his anatomical relationships with surrounding structures, is important for the assessment of the injury that may occur in tumors and several orofacial trauma and for avoiding the damage during surgeries. AIM The aim of this retrospective study was to assess the use of 3-T MRI in the evaluation of the course of the four segments of the trigeminal nerve: cisternal and Meckels's cave, cavernous sinus, skull base and mandibular extracranial segments. PATIENTS AND METHODS 78 patients were studied, for a total of 156 trigeminal nerves examined. T2-weighted 3D Fast imaging employing steady-state acquisition and T1-weighted Fast spoiled gradient recalled echo sequences were used. Two radiologists (reader A and B), independently, evaluated the course of the four segments of the trigeminal nerve according to a qualitative scale. The Intraclass correlation coefficient (ICC) and Pearson correlation coefficient were used to assess the intraobserver and interobserver variability in the nerve course evaluation. RESULTS Reader A evaluated 47 trigeminal nerves excellent, 94 good, 12 fair and 3 poor. Reader B rated 43 trigeminal nerves excellent, 92 good, 16 fair and 5 poor. The intraobserver variability was ICC = 0.937 in reader A and ICC = 0.894 in reader B. The interobserver variability was 0.734 (p ≤ 0.01). CONCLUSIONS High resolution 3-T MRI imaging allows an accurate study of the trigeminal nerve and especially of its mandibular branch. The knowledge of the course and of the anatomic relationships of these nerve bundles with surrounding structures, as well as of the anatomical variants, allow oral and maxillofacial surgical plannings thus reducing the risk of nerve damage.