Extracranial facial nerve imaging in parotid surgery candidates. Could 1.5 T MRI be beneficial?

Background and aim: Despite improvements in the imaging modalities, the optimal protocol for extracranial facial nerve imaging using 1.5 T MRI is still debatable. Pre-operative mapping of the facial nerve could provide valuable information for surgeons. The current study aimed to evaluate and choose proper 1.5 T MRI protocols for the extracranial segment of facial nerve pre-op imaging.Patients and methods: Extracranial facial nerves on the tumoral and normal side of 19 patients (38 nerves) were imaged by 1.5 T MRI, using five sequences including T1-weighted, T2-weighted, T1 weighted-fat-saturated with contrast, Three-dimensional (3D) T1-weighted and 3D T2-weighted. The visibility of each of the three segments of the extracranial facial nerve (the main trunk, cervicofacial and temporofacial divisions and terminal branches) in each sequence was assessed.Results: On the normal side, segments 1 and 2 of the nerve were identifiable in all patients and segment 3 was identifiable in 89.5% of patients in both 3D T1-weighted and 3D T2-weighted sequences. On the tumoral side, segments 1, 2 and 3 were identifiable in 89.5, 84.2 and 68.4% of patients, respectively, in 3D T1-weighted and T2-weighted sequences. 3D sequences showed significant improvement in visualizing extracranial facial nerve and its branches compared to routine T1 weighted and T2-weighted sequences.Conclusions: Our protocol showed favourable results in visualizing the extracranial facial nerve and its branches. We believe the protocol used in this study could be used as a pre-operative facial nerve mapping method using 1.5 T MRI.