Visualization of the Peripheral Branches of the Mandibular Division of the Trigeminal Nerve on 3D Double-Echo Steady-State with Water Excitation Sequence

Abstract

Background and purpose: Although visualization of the extracranial branches of the cranial nerves has improved with advances in MR imaging, only limited studies have assessed the detection of extracranial branches of the mandibular nerve (V3). We investigated the detectability of the branches of V3 on a 3D double-echo steady-state with water excitation sequence.

Materials and methods: We retrospectively evaluated the detectability of the 6 branches of the V3, the masseteric, buccal, auriculotemporal, lingual, inferior alveolar, and mylohyoid nerves, by using a 5-point scale (4, excellent; 3, good; 2, fair; 1, poor; and 0, none) in 86 consecutive patients who underwent MR imaging with the 3D double-echo steady-state with water excitation sequence. Weighted κ analysis was used to calculate interobserver variability among the 3 readers.

Results: The detection of the lingual and inferior alveolar nerves was the most successful, with excellent average scores of 3.80 and 3.99, respectively. The detection of the masseteric, the buccal, and the auriculotemporal nerves was good, with average scores of 3.31, 2.67, and 3.11, respectively. The mylohyoid nerve was difficult to detect with poor average scores of 0.62. All nerves had excellent interobserver variability across the 3 readers (average weighted κ value, 0.95-1.00).

Conclusions: The 3D double-echo steady-state with water excitation sequence demonstrated excellent visualization of the extracranial branches of V3 in most patients. The 3D double-echo steady-state with water excitation sequence has the potential for diagnosing V3 pathologies and preoperatively identifying peripheral cranial nerves to prevent surgical complications.

Fig 1.

A and B, Axial source images of the 3D-DESS-WE sequence. C and D, Coronal reformatted images of the 3D-DESS-WE sequence. Axial image shows the masseteric nerve (A, arrow) and buccal nerve (A, solid arrowhead) arising from the V3 trunk. The intermediate point is established, where the masseteric nerve enters the deep surface of the masseter muscle (B, arrow), to divide the nerve into proximal and distal portions. The intermediate point for the buccal nerve is established as the anterolateral edge of the lateral pterygoid muscle (B, solid arrowhead). Reformatted coronal images show the course of the buccal nerve running inferiorly (C, arrows) and the auriculotemporal nerve running inferolaterally (D, arrows). The intermediate point is established where the auriculotemporal nerve enters the pterygoid venous plexus (B and D, open arrowheads).

Fig 2.

A and B, Coronal reformatted image of the 3D-DESS-WE sequence. C, Axial source image of the 3D-DESS-WE sequence. Reformatted coronal images show the lingual nerve (A, arrows) and the inferior alveolar nerve (B, arrows). The intermediate points are established where the lingual nerve running laterally starts to change direction medially (A, arrowhead) and where the inferior alveolar nerve enters the mandibular foramen (B; arrowhead). Axial image shows that the mylohyoid nerve runs at the medial surface of the mandible (C, arrow). The intermediate point is established where the nerve enters the mylohyoid muscle (C, arrowhead).