Localization of Parotid Gland Tumors in Relation to the Intraparotid Facial Nerve on 3D Double-Echo Steady-State with Water Excitation Sequence

Double echo steady-state free precession technique in MR neurography to evaluate extracranial facial nerve involvement in a case of Bell's palsy

Bell's palsy is the most common cause of facial weakness involving the facial nerve. While brain MRI is often acquired to evaluate for pathology along the intracranial course of the facial nerve, evaluation of inflammation affecting the extracranial segments of the facial nerve, particularly the intraparotid segments, is uncommon. We present a case report of acute Bell's palsy in a 35-year-old pregnant patient at 38 weeks' gestation. A double-echo steady state MR neurography technique, MENSA (Multi-Echo iN Steady-state Acquisition), acquired with a conformable prototype neck coil, was utilized to visualize abnormal enlargement and signal hyperintensity of the left intraparotid facial nerve. The case highlights a presentation of Bell's palsy affecting the extracranial segments of the facial nerve. This technique may be useful for longitudinal monitoring of Bell's palsy, planning of targeted treatments, and for evaluating other pathologies affecting the facial nerve.

MR-Neurography of the facial nerve in parotid tumors: intra-parotid nerve visualization and surgical correlation

PURPOSE

One of the most severe complications in surgery of parotid tumors is facial palsy. Imaging of the intra-parotid facial nerve is challenging due to small dimensions. Our aim was to assess, in patients with parotid tumors, the ability of high-resolution 3D double-echo steady-state sequence with water excitation (DE3D-WE) (1) to visualize the extracranial facial nerve and its tracts, (2) to evaluate their relationship to the parotid lesion and (3) to compare MRI and surgical findings.

METHODS

A retrospective study was conducted including all patients with parotid tumors, who underwent MRI from April 2022 to December 2023. Two radiologists independently reviewed DE3D-WE images, assessing quality of visualization of the facial nerve bilaterally and localizing the nerve's divisions in relation to the tumor. MRI data were compared with surgical findings.

RESULTS

Forty consecutive patients were included (M:F = 22:18; mean age 56.3 ± 17.4 years). DE3D-WE could excellently visualize the nerve main trunk and the temporofacial division in all cases. The cervicofacial branch was visible in 99% of cases and visibility was good. Distal divisions were displayed in 34% of cases with a higher visibility on the tumor side (p < 0.05). Interrater agreement was high (weighted kappa 0.94 ± 0.01 [95% CI 0.92-0.97]). Compared to surgery accuracy of MRI in localizing the nerve was 100% for the main trunk, 96% for the temporofacial and 89% for the cervicofacial branches.

CONCLUSIONS

Facial nerve MR-neurography represents a reliable tool. DE3D-WE can play an important role in surgical planning of patients with parotid tumors, reducing the risk of nerve injury.

Comparing the Double-Echo Steady-State with Water Excitation and Constructive Interference in Steady-State Sequence Techniques for Identifying Extracranial Facial Nerve and Tumor Positions in Patients with Parotid Tumors

BACKGROUND AND PURPOSE

Reliable preoperative visualization of facial nerve morphology and understanding the spatial relationship between the facial nerve and tumors in the parotid gland can help clinicians perform safe and effective surgeries. Hence, this study aimed to compare the image quality of extracranial facial nerves obtained by using double-echo steady state with water excitation (DESS-WE) and CISS sequences and evaluate their diagnostic efficacy in the localization of parotid tumors.

MATERIALS AND METHODS

In total, 32 facial nerves of 16 healthy volunteers and 25 facial nerves of 25 patients with parotid tumors were included in this retrospective study. All participants underwent noncontrast-enhanced extracranial facial nerve MR imaging with DESS-WE and CISS with a 3T MR scanner equipped with a 64-channel head and neck coil. Image quality was subjectively evaluated by using a 5-point Likert scale by 2 radiologists. Inter- and intrarater agreements were assessed by using the Cohen κ coefficient. Receiver operating characteristic analysis was performed, and the diagnostic efficacies of DESS-WE and CISS images in localizing parotid tumors were calculated.

RESULTS

For healthy volunteers (11 men and 5 women; median age, 26 years), image quality scores for CISS were significantly higher than those for DESS-WE for the discrimination of the temporofacial and cervicofacial trunks (both, P < .001). In patients with parotid tumors (12 men and 13 women; median age, 58 years), CISS performed better than DESS-WE in terms of visualizing the spatial relationship of the facial nerve to the tumor and diagnostic confidence (both, P < .001). Regarding the localization of parotid tumors, CISS showed excellent performance, comparable to that of DESS-WE (area under the curve, 0.981 versus 0.942, P = .1489).

CONCLUSIONS

CISS achieved diagnostic performance comparable to DESS-WE in parotid tumor localization, with favorable image quality and more reliable morphologic visualization of the facial nerve.

Sporadic neurofibroma of facial nerve presenting as parotid gland tumor: a rare case report

Intraparotid gland neurofibroma is a rare benign tumor that arises from Schwann cells of the facial nerve within the parotid gland. This case report discusses a 41-year-old woman who experienced a painless preauricular swelling on her right side for over 5 years. Clinical examination and ultrasound revealed a well-defined mass in the parotid gland. The patient underwent total mass excision, resulting in transient facial nerve dysfunction but complete recovery. These tumors often manifest as solitary masses in the parotid region and may compress nearby structures, causing facial paralysis or numbness. Their diagnosis can be challenging due to similarities with other parotid gland tumors and possible associations with neurofibromatosis. Managing intraparotid tumors, including neurofibromas, involves a multidisciplinary approach with input from cytopathologists, radiologists, and surgeons.

Direct visualization of intraparotid facial nerve assisting in parotid tumor resection

Precise recognition of the intraparotid facial nerve (IFN) is crucial during parotid tumor resection. We aimed to explore the application effect of direct visualization of the IFN in parotid tumor resection. Fifteen patients with parotid tumors were enrolled in this study and underwent specific radiological scanning in which the IFNs were displayed as high-intensity images. After image segmentation, IFN could be preoperatively directly visualized. Mixed reality combined with surgical navigation were applied to intraoperatively directly visualize the segmentation results as real-time three-dimensional holograms, guiding the surgeons in IFN dissection and tumor resection. Radiological visibility of the IFN, accuracy of image segmentation and postoperative facial nerve function were analyzed. The trunks of IFN were directly visible in radiological images for all patients. Of 37 landmark points on the IFN, 36 were accurately segmented. Four patients were classified as House-Brackmann Grade I postoperatively. Two patients with malignancies had postoperative long-standing facial paralysis. Direct visualization of IFN was a feasible novel method with high accuracy that could assist in recognition of IFN and therefore potentially improve the treatment outcome of parotid tumor resection.

Diagnostic imaging of salivary gland cancers: REFCOR recommendations by the formal consensus method

OBJECTIVE

To define the indications for each imaging modality in the screening, characterization, extension and follow-up of salivary gland tumors.

MATERIAL AND METHODS

The French Network of Rare Head and Neck Tumors (REFCOR) formed a steering group who drafted a narrative review of the literature published on Medline and proposed recommendations. The level of adherence to the recommendations was then assessed by a rating group, according to the formal consensus method.

RESULTS

If a swelling of a salivary gland is palpable for 3 weeks, an ultrasound scan is recommended to confirm a tumoral lesion and rule out differential diagnoses. For a salivary gland tumor, MRI is recommended with diffusion-weighted and dynamic contrast-enhanced techniques. In the case of histologically proven malignancy or a highly suspicious lesion, a CT scan of the neck and chest is recommended to assess the tumor, lymph nodes and metastases. FDG-PET is not currently recommended in routine clinical practice for initial diagnosis, assessment of extension, evaluation of response to treatment, staging of recurrence, or follow-up of salivary gland tumors.

CONCLUSION

Assessing salivary tumors is based on MRI. Extension assessment is based on neck and chest CT.

An Updated Review of Magnetic Resonance Neurography for Plexus Imaging

Magnetic resonance neurography (MRN) is increasingly used to visualize peripheral nerves in vivo. However, the implementation and interpretation of MRN in the brachial and lumbosacral plexi are challenging because of the anatomical complexity and technical limitations. The purpose of this article was to review the clinical context of MRN, describe advanced magnetic resonance (MR) techniques for plexus imaging, and list the general categories of utility of MRN with pertinent imaging examples. The selection and optimization of MR sequences are centered on the homogeneous suppression of fat and blood vessels while enhancing the visibility of the plexus and its branches. Standard 2D fast spin-echo sequences are essential to assess morphology and signal intensity of nerves. Moreover, nerve-selective 3D isotropic images allow improved visualization of nerves and multiplanar reconstruction along their course. Diffusion-weighted and diffusion-tensor images offer microscopic and functional insights into peripheral nerves. The interpretation of MRN in the brachial and lumbosacral plexi should be based on a thorough understanding of their anatomy and pathophysiology. Anatomical landmarks assist in identifying brachial and lumbosacral plexus components of interest. Thus, understanding the varying patterns of nerve abnormalities facilitates the interpretation of aberrant findings.

Imaging of Facial Nerve With 3D-DESS-WE-MRI Before Parotidectomy: Impact on Surgical Outcomes

OBJECTIVE

The intra-parotid facial nerve (FN) can be visualized using three-dimensional double-echo steady-state water-excitation sequence magnetic resonance imaging (3D-DESS-WE-MRI). However, the clinical impact of FN imaging using 3D-DESS-WE-MRI before parotidectomy has not yet been explored. We compared the clinical outcomes of parotidectomy in patients with and without preoperative 3D-DESS-WE-MRI.

MATERIALS AND METHODS

This prospective, non-randomized, single-institution study included 296 adult patients who underwent parotidectomy for parotid tumors, excluding superficial and mobile tumors. Preoperative evaluation with 3D-DESS-WE-MRI was performed in 122 patients, and not performed in 174 patients. FN visibility and tumor location relative to FN on 3D-DESS-WE-MRI were evaluated in 120 patients. Rates of FN palsy (FNP) and operation times were compared between patients with and without 3D-DESS-WE-MRI; propensity score matching (PSM) and inverse probability of treatment weighting (IPTW) were used to adjust for surgical and tumor factors.

RESULTS

The main trunk, temporofacial branch, and cervicofacial branch of the intra-parotid FN were identified using 3D-DESS-WE-MRI in approximately 97.5% (117/120), 44.2% (53/120), and 25.0% (30/120) of cases, respectively. The tumor location relative to FN, as assessed on magnetic resonance imaging, concurred with surgical findings in 90.8% (109/120) of cases. Rates of temporary and permanent FNP did not vary between patients with and without 3D-DESS-WE-MRI according to PSM (odds ratio, 2.29 [95% confidence interval {CI} 0.64-8.25] and 2.02 [95% CI: 0.32-12.90], respectively) and IPTW (odds ratio, 1.76 [95% CI: 0.19-16.75] and 1.94 [95% CI: 0.20-18.49], respectively). Conversely, operation time for surgical identification of FN was significantly shorter with 3D-DESS-WE-MRI (median, 25 vs. 35 min for PSM and 25 vs. 30 min for IPTW, P < 0.001).

CONCLUSION

Preoperative FN imaging with 3D-DESS-WE-MRI facilitated anatomical identification of FN and its relationship to the tumor during parotidectomy. This modality reduced operation time for FN identification, but did not significantly affect postoperative FNP rates.

Ultrasonographic Localization of Parotid Gland Tumor Relative to the Facial Nerve Using Stensen's Duct Criterion

PURPOSE

During the preoperative evaluation of parotid gland tumors, 1 of the main concerns is to determine the location of the tumors in relation to the facial nerve. This study aims to assess the value of ultrasound for determination of the location of parotid gland tumors in relation to the facial nerve using Stensen's duct.

METHODS

This is a retrospective cross-sectional study at a single institute. The subjects who underwent preoperative ultrasound and parotidectomy for parotid gland tumors were included. The subjects with incomplete operative records or no reference standard for the location of parotid gland tumor were excluded. The primary predictor was ultrasound tumor location, which was defined as the location of parotid gland tumors determined by preoperative ultrasound as to whether the tumors were superficial or deep to the facial nerve. The operative records were used as the reference standard for the location of parotid gland tumors. The primary outcome was diagnostic performances of preoperative ultrasound in predicting the location of parotid gland tumors, which were calculated by comparing ultrasound tumor location to the reference standard. Covariates were sex, age, type of surgery, tumor size, and tumor histology. Data analysis involved descriptive and analytic statistics; P < .05 was considered significant.

RESULTS

One hundred and two of 140 eligible subjects met inclusion and exclusion criteria. There were 50 male and 52 female, with a mean age of 53.3 years. Ultrasound tumor location was classified as deep in 29 subjects, superficial in 50, and indeterminate in 23. The reference standard was deep in 32 subjects and superficial in 70. Indeterminate ultrasound tumor location results were grouped as either deep or superficial to make every possible cross table in which ultrasound tumor location results were presented as a dichotomy. The mean sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the ultrasound to predict the deep location of parotid tumors were 87.5, 82.1, 70.2, 93.6, and 83.8%, respectively.

CONCLUSIONS

Stensen's duct on ultrasound can be a useful criterion to determine the location of parotid gland tumor relative to the facial nerve.

Preoperative Magnetic Resonance Image and Computerized Tomography Findings Predictive of Facial Nerve Invasion in Patients with Parotid Cancer without Preoperative Facial Weakness-A Retrospective Observational Study

Simple Summary

Facial nerve invasion in parotid cancer affects survival outcomes as well as functional outcomes after surgery-based treatment. Normal facial muscle function before surgery does not always exclude the possibility of involvement of the facial nerve by a tumor. Especially in patients without facial palsy, accurate evaluation of invasion before surgery is necessary to plan optimal facial nerve resection and reconstruction. Various findings are obtained from preoperative radiological findings, such as CT and MRI. We evaluated the role of these radiological findings in predicting nerve invasion. Large tumor, spiculated margin, and anterolateral location may suggest a high risk of nerve involvement even in patients with normal preoperative facial function. These findings may help surgeons to avoid unexpected facial nerve invasion and to make adequate surgical plans to get optimal oncological and functional outcomes.

Abstract

(1) Background: Facial nerve resection with reconstruction helps achieve optimal outcomes in the treatment of facial nerve invasion (FNI) of parotid cancer. Preoperative imaging is crucial to predict facial nerve reconstruction. The radiological findings of CT or MRI may predict FNI in the parotid cancer even without facial paralysis. Methods: We retrospectively reviewed the records of 151 patients without facial nerve paralysis before surgery who had undergone tumor resection. Previously untreated parotid cancers were included. (2) Results: The median follow-up duration was 62 months (range: 24–120 months). The FNI (+) group (n = 30) showed a significantly worse 5-year overall survival compared with the FNI (−) group (75.5 vs. 93.9%; hazard ratio = 4.19; 95% confidence interval: 1.74–10.08; p = 0.001). The tumor margin, tumor size, presence in the anterolateral parotid region (area 3), retromandibular vein involvement, distance from the stylomastoid foramen to the upper tumor margin, and a high tumor grade were significant factors related to FNI in the univariate analysis. A spiculated tumor margin, the tumor size (2.2 cm), and presence in area 3 were factors predicting FNI in the logistic regression model (p = 0.020, 0.005, and 0.050, respectively; odds ratio: 4.02, 6.40, and 8.16, respectively). (3) Conclusions: The tumor size (≥2.2 cm), spiculated margin, and presence in area 3 as presented in CT and MRI may help clinicians preoperatively predict FNI in patients with parotid cancer and establish an appropriate surgical plan.

New and Advanced Magnetic Resonance Imaging Diagnostic Imaging Techniques in the Evaluation of Cranial Nerves and the Skull Base

The skull base and cranial nerves are technically challenging to evaluate using magnetic resonance (MR) imaging, owing to a combination of anatomic complexity and artifacts. However, improvements in hardware, software and sequence development seek to address these challenges. This section will discuss cranial nerve imaging, with particular attention to the techniques, applications and limitations of MR neurography, diffusion tensor imaging and tractography. Advanced MR imaging techniques for skull base pathology will also be discussed, including diffusion-weighted imaging, perfusion and permeability imaging, with a particular focus on practical applications.

MRI of the intraorbital ocular motor nerves on three-dimensional double-echo steady state with water excitation sequence at 3.0 T

PURPOSE

To explore the capability of three-dimensional double-echo steady state with water excitation sequence (3D-DESS-WE) to determine the intraorbital ocular motor nerves (IOMN).

MATERIALS AND METHODS

A 3.0 T scanner was applied to investigate 30 healthy volunteers based on the 3D-DESS-WE sequence. Dunnett t test was conducted to evaluate the signal intensity (SI) of the left oculomotor nerve (CNIII), frontal white matter, cerebrospinal fluid (CSF), and lateral rectus (LR). The oculomotor nerve's detectability, trochlear nerve (CNIV), and abducens nerve (CNVI) were evaluated independently by two observers. The average assessment scores were determined, and interobserver variability for these nerves' detectability was determined using a weighted kappa analysis.

RESULTS

The SI of CNIII is similar to that of the frontal white matter (t = 2.26, P > 0.05), lower than the CSF, and higher than the LR (t = 3.81, - 3.45, P < 0.05). The average scores of the superior division of CNIII and the branch to medial rectus (MR), inferior rectus (IR), inferior oblique (IO), CNIV, and CNVI were 3.01, 3.07, 3.78, 2.98, 2.88, and 3.97, respectively. The interobserver variability was excellent (κ = 0.83-1.00).

CONCLUSION

The 3D-DESS-WE sequence shows an ability to detect the IOMN course in healthy volunteers effectively.

Three-dimensional double-echo steady-state with water excitation magnetic resonance imaging to localize the intraparotid facial nerve in patients with deep-seated parotid tumors

PURPOSE

To assess the utility of three-dimensional double-echo steady-state with water excitation (3D-DESS-WE) imaging for localizing deep-seated parotid tumors in relation to the facial nerve.

METHODS

A prospective study comparing the surgical outcomes of parotidectomy with or without 3D-DESS-WE sequence is currently enrolling the patients. Magnetic resonance imaging data from the first 25 patients with 3D-DESS-WE sequence were reviewed. Visibility of the intraparotid facial nerve was independently assessed by two neuroradiologists. The diagnostic performance of the 3D-DESS-WE sequence for prediction of deep lobe involvement was compared with that of two conventional methods based on the retromandibular vein line (RMVL) and facial nerve line (FNL). The relationship between the tumor and the main trunk of the facial nerve was also evaluated on the 3D-DESS-WE sequence.

RESULTS

On 3D-DESS-WE images, the main trunk, temporofacial division, and cervicofacial division of the intraparotid facial nerve were visualized in 100% (25/25), 48% (12/25), and 36% (9/25) of patients, respectively. The diagnostic accuracy of the 3D-DESS-WE sequence for prediction of deep lobe involvement was 92% (23/25), which was significantly superior to that of the RMVL (68% [17/25]; p = 0.008) and FNL (64% [16/25]; p = 0.004) methods. The relationship between the tumor and the main trunk of the facial nerve was correctly predicted in 92% (23/25) of 3D-DESS-WE images.

CONCLUSION

By direct visualization of the facial nerve, the 3D-DESS-WE sequence improved the preoperative localization of the intraparotid facial nerve in deep-seated parotid tumors. This information may help better surgical planning for deep-seated parotid tumors.

Magnetic resonance neurography of the head and neck: state of the art, anatomy, pathology and future perspectives

Magnetic resonance neurography allows for the selective visualization of peripheral nerves and is increasingly being investigated. Whereas in the past, the imaging of the extracranial cranial and occipital nerve branches was inadequate, more and more techniques are now available that do allow nerve imaging. This basic review provides an overview of the literature with current state of the art, anatomical landmarks and future perspectives. Furthermore, we illustrate the possibilities of the three-dimensional CRAnial Nerve Imaging (3D CRANI) MR-sequence by means of a few case studies.

Visualization of the morphology and pathology of the peripheral branches of the cranial nerves using three-dimensional high-resolution high-contrast magnetic resonance neurography

PURPOSE

To assess the feasibility and advantages of high-resolution high-contrast magnetic resonance neurography (HRHC-MRN) for visualizing the morphology and pathology of the peripheral branches of cranial nerves.

MATERIALS

cMRN (3D SPACE STIR sequence) and HRHC-MRN (contrast enhanced 3D SPACE STIR sequence) were performed at 3 T MR unit on 16 volunteers and 12 patients with head and neck tumors. Quantitative measurements such as SNR, CNR and CR were calculated. Three readers evaluated the continuity of the 10 major peripheral branches of cranial nerves using a 5-score scale (scores 0-4). Interobserver variability was tested. Quantitative measurements and scores were compared between cMRN and HRHC-MRN. The imaging features of the nerve pathology were analyzed.

RESULTS

The CRs of nerve to bone marrow, nerve to muscle, and nerve to gland were significantly higher with HRHC-MRN than with cMRN (P = 0.014, P = 0.02, P <0.001, respectively). The scores of all nerve trunks were significantly higher with HRHC-MRN than with cMRN (all, P < 0.001). For all nerves on HRHC-MRN, the interobserver consistency was excellent across the three readers (all κ > 0.8). The scores of the inferior alveolar nerve, hypoglossal nerve, lingual nerve, facial nerve, infraorbital nerve, masseteric nerve, glossopharyngeal/vagus nerve, supraorbital nerve, auriculotemporal nerve and buccal nerve were 3.95, 3.77, 3.63, 3.25, 3.15, 3.04, 3.04, 2.87, 2.79, 1.88, respectively.

CONCLUSION

HRHC-MRN provides improved visualization of the peripheral branches of cranial nerves and is a promising nerve-selective imaging method for evaluating cranial nerve morphology and pathology.

Normal Anatomy of Cranial Nerves III–XII on Magnetic Resonance Imaging

복잡한 해부학적 구조와 기능 때문에 뇌신경 질환의 신경영상검사는 항상 어려운 과제이다. 최근 자기공명영상(이하 MRI) 기법의 발달로 많은 경우에서 뇌신경 질환의 원인이 규명되고 있으며, 신경영상의학 의사들은 다학제 팀의 핵심적 팀원으로서 다양한 뇌신경 질환의 원활한 진단을 위하여 MRI에서 관찰되는 뇌신경의 세밀한 해부학적 구조를 잘 알아야 한다. 이 종설에서는 말초성 뇌신경 III–XII에 대해 뇌간으로부터 두개 밖까지 해부학적으로 비슷한 구조를 가지는 구역별로 분류하여 각 구역에서 보이는 뇌신경의 정상 해부학 및 MRI 소견을 설명하고자 한다. 또한 각 구역에서 가장 적합한 MRI 기법에 관하여도 기술하고자 한다.

Incidence of postoperative facial weakness in parotid tumor surgery: a tumor subsite analysis of 794 parotidectomies

Background

The reported incidence of facial weakness immediately after parotid tumor surgery ranges from 14 to 65%. The purpose of this study was to evaluate the incidence of postoperative facial weakness related to parotidectomy with use of preoperative computed tomography (CT), intraoperative facial nerve monitoring, and surgical magnification. Also, we sought to elucidate additional information about risk factors for postoperative facial weakness in parotid tumor surgery, particularly focusing on the tumor subsites.

Methods

We retrospectively reviewed 794 cases with parotidectomy for benign and malignant tumors arising from the parotid gland (2009–2016). Patients with pretreatment facial palsy were excluded from the analyses. Tumor subsites were stratified based on their anatomical relations to the facial nerve as superficial, deep, or both. Multivariable logistic regression analyses were conducted to identify risk factors for postoperative facial weakness.

Results

The overall incidences of temporary and permanent (more than 6 months) facial weakness were 9.2 and 5.2% in our series utilizing preoperative CT, intraoperative facial nerve monitoring, and surgical magnification. Multivariable analysis revealed that old age, malignancy, and recurrent tumors (revision surgery) were common independent risk factors for both temporary and permanent postoperative facial weakness. In addition, tumor subsite (tumors involving superficial and deep lobe) was associated with postoperative facial weakness, but not tumor size. Extent of surgery was strongly correlated with tumor pathology (malignant tumors) and tumor subsite (tumors involving deep lobe).

Conclusion

Aside from risk factors for facial weakness in parotid tumor surgery such as old age, malignant, or recurrent tumors, the location of tumors was found to be related to postoperative facial weakness. This study result may provide background data in a future prospective study and up-to-date information for patient counseling.

MR Imaging of the Extracranial Facial Nerve with the CISS Sequence

BACKGROUND AND PURPOSE

MR imaging is not routinely used to image the extracranial facial nerve. The purpose of this study was to determine the extent to which this nerve can be visualized with a CISS sequence and to determine the feasibility of using that sequence for locating the nerve relative to tumor.

MATERIALS AND METHODS

Thirty-two facial nerves in 16 healthy subjects and 4 facial nerves in 4 subjects with parotid gland tumors were imaged with an axial CISS sequence protocol that included 0.8-mm isotropic voxels on a 3T MR imaging system with a 64-channel head/neck coil. Four observers independently segmented the 32 healthy subject nerves. Segmentations were compared by calculating average Hausdorff distance values and Dice similarity coefficients.

RESULTS

The primary bifurcation of the extracranial facial nerve into the superior temporofacial and inferior cervicofacial trunks was visible on all 128 segmentations. The mean of the average Hausdorff distances was 1.2 mm (range, 0.3-4.6 mm). Dice coefficients ranged from 0.40 to 0.82. The relative position of the facial nerve to the tumor could be inferred in all 4 tumor cases.

CONCLUSIONS

The facial nerve can be seen on CISS images from the stylomastoid foramen to the temporofacial and cervicofacial trunks, proximal to the parotid plexus. Use of a CISS protocol is feasible in the clinical setting to determine the location of the facial nerve relative to tumor.