Elsevier

Clinical Radiology

Volume 60, Issue 3, March 2005, Pages 349-354
Clinical Radiology

High-resolution magnetic resonance of the extracranial facial nerve and parotid duct: demonstration of the branches of the intraparotid facial nerve and its relation to parotid tumours by MRI with a surface coil

https://doi.org/10.1016/j.crad.2004.06.018Get rights and content

AIM

To investigate the usefulness of high-resolution MR imaging in the evaluation of the extracranial facial nerve, compared with surgical findings.

MATERIALS AND METHODS

Thirteen patients with benign parotid tumours were studied on a 1.5-T MR system with a 3 in circular surface coil. High-resolution T1-weighted spin-echo, T2-weighted fast spin-echo, and three-dimensional gradient-recalled acquisition in the steady state (GRASS) images were obtained in the axial planes. Oblique reformatted images were generated. Tumours, parotid ducts and facial nerves were identified on these images. The relationship of the tumours to the facial nerves was confirmed at surgery.

RESULTS

Facial nerves appeared as linear structures of low intensity on all pulse sequences. The main trunks and cervicofacial and temporofacial divisions of the facial nerves were identified in 100%, 84.1% and 53.8% of GRASS images, respectively. Parotid ducts appeared as structures of low intensity on T1-weighted (66.6%) and GRASS images (81.8%), and as structures of very high intensity on T2-weighted images (91.7%). The relationships of the tumours to the facial nerves were correctly diagnosed in 11 (91.7%) of 12 cases.

CONCLUSION

High-resolution MR imaging depicts the extracranial facial nerve and the parotid duct, and is useful for preoperative evaluation of parotid gland tumours.

Introduction

Determining the relationship of parotid gland tumours to the facial nerve is of value in planning surgical approaches. Some investigators reported that the extracranial facial nerve was detected accurately on high-resolution three-dimensional (3-D) MR imaging.1, 2 However, these data lacked anatomical confirmation.

We studied prospectively parotid lesions in clinical patients using high-resolution MR imaging with a surface coil, and confirmed the relationship of the lesions to the facial nerve during surgery. The purpose of this study was to determine the usefulness of high-resolution MR imaging in evaluation of the course of the extracranial facial nerve and the parotid duct.

Section snippets

Materials and methods

From May 1999 to June 2000, 17 patients with parotid gland tumours experienced high-resolution MR imaging at our university hospital; 13 patients who underwent surgery (3 men and 10 women, age range 32–75 years, mean age 50.3 years) were included in this study. The study protocol followed the human research guidelines of the Internal Review Board of our institution, and informed consent was obtained from all subjects.

All MR imaging examinations were performed using a 1.5-T (Signa Lightening; GE

Results

All lesions were histologically confirmed benign parotid tumours: 8 pleomorphic adenomas, 3 recurrent pleomorphic adenomas, one Warthin's tumour, and one lymphoepithelial cyst. The maximum diameters of the tumours ranged from 10 mm to 40 mm.

Table 1 shows the rate of demonstration of tumours, parotid ducts and facial nerves seen on the images. All parotid lesions had well-defined margins on T2-weighted and GRASS images (2, 3). T1-weighted images were successful in 12 of 13 cases; one pleomorphic

Discussion

Various authors have cited anatomical landmarks for predicting the course of the facial nerve on computed tomography and MR imaging.4, 5, 6, 7, 8, 9, 10, 11 There has been some controversy about the linear structures of low signal intensity in the parotid gland on T1-weighted images and what they actually represent.3, 5, 12, 13, 14 It was initially reported that a curvilinear structure of low signal intensity on T1-weighted images was the facial nerve.13, 14 Subsequently, MR imaging was

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