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.
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.
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.