The ability to identify the intraparotid facial nerve for locating parotid gland lesions in comparison to other indirect landmark methods: evaluation by 3.0 T MR imaging with surface coils

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.

An updated protocol for mandibular reconstruction in nongrowing patients with craniofacial microsomia with temporomandibular joint total prosthesis

The authors aim to present an updated protocol for mandibular reconstruction in nongrowing patients with Pruzansky/Kaban type IIb/III congenital craniofacial microsomia with customized temporomandibular joint (TMJ) prosthesis to reduce facial nerve (FN) damage and improve surgical accuracy. This is illustrated (using 3 cases) and is based on preoperative mapping of the FN using MRI for better virtual surgical planning of custom-made TMJ prosthesis. Intraoperative FN mapping and monitoring, as well as verification of the final result with intraoperative cone-beam computed tomography (CBCT) and 3D-reconstructed images is also achieved. All 3 patients presented mild transient postoperative facial palsy due to surgical soft tissue stretching which resolved within 2 months of surgery. All patients presented proper occlusion and mouth opening without pain, with an average incisal opening of 38.8 mm (range 35.5-42 mm) at two months of follow-up. Moreover, superposition of intraoperative and preoperative 3D reconstruction images ensured surgical accuracy and avoided the need for a potential reintervention. In conclusion, the proposed surgical protocol for mandibular reconstruction with customized alloplastic TMJ prosthesis in nongrowing patients with type IIb/III Pruzansky-Kaban congenital mandibular hypoplasia may reduce FN morbidity, improve surgical accuracy and final outcomes.

The external jugular vein axis: a new anatomical landmark for pre-operative prediction of the location of parotid gland tumours

The relationships between parotid tumours and the facial nerve determine duration of surgical procedure and risks involved. As the division of the facial nerve is not visible using standard imaging techniques, other anatomical landmarks are used to determine the pre-operative location of tumours. This retrospective study aimed to evaluate reliability of the 'external jugular vein axis' compared with other landmarks generally used in imaging, such as the retromandibular vein, Conn's arc, the facial nerve line and the Utrecht line. Forty-eight pre-operative imaging exams of patients who underwent parotid benign tumour surgery between 2010 and 2016 were examined. We determined the location of tumour using the five markers. A pre-operative simulation was compared with the description given by the surgeon intraoperatively, in terms of sensitivity and specificity for each marker. External jugular vein axis and retromandibular vein are the most sensitive markers for locating suprafacial tumours (Se = 1). External jugular vein axis and Conn's arc are the most specific markers for locating suprafacial tumours (Spe = 0.92). External jugular vein axis is reproducible and present on all radiological sections, thereby overcoming any anatomical and nomenclature variations. This landmark appears to be the most representative marker of the dividing branches of the facial nerve.

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.

Identification of the intraparotid facial nerve on MRI: a systematic review and meta-analysis

OBJECTIVES

Accurate preoperative localization of the intraparotid facial nerve (IFN) on MRI could reduce intraoperative injury. This study aimed to assess the detection rate of the IFN and its branches on MRI.

METHODS

PubMed-MEDLINE and Embase databases were searched for articles published up to October 2019. The inclusion criteria were (a) adults, (b) MRI-based identification of IFN by radiologists, (c) original articles, and (d) detailed results to assess the proportion of visible IFN. Two radiologists reviewed the original articles. The Quality Assessment of Diagnostic Accuracy Studies-2 tool was used to determine the quality of the selected studies. The DerSimonian-Laird random effects model was utilized to calculate the pooled estimates. Between-studies heterogeneity was evaluated using the chi-squared statistic test and Higgins' inconsistency index (I²). A subgroup meta-regression was performed to explore the factors causing study heterogeneity.

RESULTS

Nine original articles with 209 subjects were included. MRI reported a high pooled detection rate of 99.8% (95% CI, 98.4-100%) for the main trunk of the IFN. The pooled rates for the temporofacial and cervicofacial branches were 90.4% (95% CI, 84.1-96.7%) and 96.3% (95% CI, 96.1-99.5%), respectively. Heterogeneity was detected only in the temporofacial branch (I² = 83%) as a result of both slice thickness and the use of steady-state sequences with diffusion-weighted imaging (DWI) implementation.

CONCLUSIONS

MRI showed an overall high detection rate of the IFN and its branches. Furthermore, an increased identification was observed in studies that used a slice thickness of < 1 mm and steady-state sequences with DWI implementation.

KEY POINTS

• MRI showed an overall high detection rate of the intraparotid facial nerve and its branches. • Higher detection rate was observed in studies that used a slice thickness of < 1 mm and steady-state sequences with diffusion-weighted imaging.

Evaluation of preoperative Ultrasonography in the Differentiation between Superficial and Deep Parotid Gland Tumors

Imaging of the intraparotid course of the facial nerve remains a challenge and is not an established routine procedure. The aim of this study was to evaluate ultrasound in localizing a parotid tumor in relation to the facial nerve. The ultrasound findings and operative reports of all patients treated for parotid gland tumors were studied retrospectively. Eight hundred sixty-eight parotid lesions formed our study sample. The unit of measurement was the minimal distance between the parotideomasseteric fascia and the superficial capsule of the tumor, measured in millimeters by means of ultrasound. The mean value for this parameter was 1.3 mm for superficial and 4.6 mm for deep lobe tumors (p < 0.001). When the cutoff value was set at 2.6 mm, the sensitivity and specificity of ultrasound were 89.6 and 88.4%, respectively. Our study revealed that ultrasound can help in the pre-operative differentiation between tumors of the superficial and deep lobes of the parotid gland.

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

BACKGROUND AND PURPOSE

Reliable preoperative facial nerve mapping may help avoid or minimize facial nerve injury during parotid tumor resection. The purpose of this study was to investigate the diagnostic performance of the 3D double-echo steady-state with water excitation sequence in localizing parotid gland tumors through direct visualization of the intraparotid facial nerve in comparison with indirect methods of estimating the facial nerve location.

MATERIALS AND METHODS

We retrospectively reviewed 91 parotid gland tumors in 90 patients who underwent surgical resection and preoperative MR imaging, including the 3D double-echo steady-state with water excitation sequence. The tumor locations were categorized as deep or superficial on the basis of direct and 3 indirect methods: the facial nerve line, retromandibular vein, and Utrecht line. Surgical localization was considered the criterion standard. The diagnostic performance for localizing deep lobe lesions using direct and indirect methods was calculated and compared using the McNemar test.

RESULTS

Surgical localization confirmed 75 superficial lesions and 16 deep lesions. The interobserver variability of the 3D double-echo steady-state with water excitation sequence was excellent (κ = 0.870). The diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value for localizing deep lobe lesions using the 3D double-echo steady-state with water excitation method were 97.8%, 87.5%, 100%, 100%, and 97.4%, respectively. These findings were significantly higher than the facial nerve line in sensitivity, the retromandibular vein in sensitivity, and the Utrecht line in accuracy and specificity (P < .05). Overall, the direct method was the most accurate, sensitive, and specific in localizing parotid gland tumors.

CONCLUSIONS

We can achieve higher diagnostic performance in localizing parotid gland tumors by directly visualizing the intraparotid facial nerve using the 3D double-echo steady-state with water excitation sequence compared with indirect methods.

The multiplanar analysis of the retromandibular vein in surgical planning for parotid gland tumors

OBJECTIVE

To analyze the effectiveness of the multiplanar analysis of the retromandibular vein in establishing the position of the parotid gland tumor and its relationship with the facial nerve, together with the most common radiological criteria (facial nerve line, Utrecht line, retromandibular vein and parapharyngeal space variations) using the magnetic resonance imaging.

STUDY DESIGN

Retrospective study SETTING: Tertiary Academic Hospital SUBJECTS AND METHODS: 128 preoperative magnetic resonances were analyzed to study preoperative tumor location (medial or lateral to the expected course of the facial nerve) based on comparison between the radiological criteria and the surgical findings.

RESULTS

FN line had the lowest accuracy at 77%, whereas the retromandibular vein achieved 85% accuracy and the UT line achieved accuracy of 93%. The retromandibular vein could not be identified in 11 cases (9%). The multiplanar evaluation of the retromandibular vein allowed us to identify it on almost all MR images (99% of cases) and reach 87% of accuracy. The parapharyngeal space evaluation achieved 92% of accuracy. In the subgroup of 66 cases where the neoplasms were strictly related to the main trunk, where the surgery entailed manipulation if situated laterally to the tumor, the multiplanar evaluation of the retromandibular vein reached 98% of accuracy and UT line achieved 94%.

CONCLUSIONS

The multiplanar modality, combined with the evaluation of the parapharyngeal space, is effective in helping the surgeon to achieve accurate planning: it enables the tumor to be located and the facial nerve course predicted with a good precision.

Preoperative transcutaneous electrical nerve stimulation for localizing superficial nerve paths

During surgery, peripheral nerves are often seen to follow unpredictable paths because of previous surgeries and/or compression caused by a tumor. Iatrogenic nerve injury is a serious complication that must be avoided, and preoperative evaluation of nerve paths is important for preventing it. In this study, transcutaneous electrical nerve stimulation (TENS) was used for an in-depth analysis of peripheral nerve paths. This study included 27 patients who underwent the TENS procedure to evaluate the peripheral nerve path (17 males and 10 females; mean age: 59.9 years, range: 18-83 years) of each patient preoperatively. An electrode pen coupled to an electrical nerve stimulator was used for superficial nerve mapping. The TENS procedure was performed on patients' major peripheral nerves that passed close to the surgical field of tumor resection or trauma surgery, and intraoperative damage to those nerves was apprehensive. The paths of the target nerve were detected in most patients preoperatively. The nerve paths of 26 patients were precisely under the markings drawn preoperatively. The nerve path of one patient substantially differed from the preoperative markings with numbness at the surgical region. During surgery, the nerve paths could be accurately mapped preoperatively using the TENS procedure as confirmed by direct visualization of the nerve. This stimulation device is easy to use and offers highly accurate mapping of nerves for surgical planning without major complications. The authors conclude that TENS is a useful tool for noninvasive nerve localization and makes tumor resection a safe and smooth procedure.

Management of salivary gland tumors

Surgery after proper imaging (MRI or CT scan) is the main stay of treatment for salivary gland tumors. Although excision margins should be ≥5 mm for malignant tumors in cases of parotid gland carcinoma, the facial nerve should be preserved whenever it is not infiltrated. Adjuvant external radiation is indicated for malignant tumors with high-risk features such as close (or invaded) margins, perineural speed, lymphatic and/or vascular invasion, lymph-node involvement and high-grade histology. A Phase II trial testing adjuvant concomitant cisplatin plus radiation therapy versus adjuvant radiation therapy alone after surgery is currently under investigation for high-risk salivary gland cancer. For inoperable cancers, photons combined with proton boost seem to be a valuable option. Even if protons or carbon ions are promising, access to the latter is limited for usual treatment. For recurrent and/or metastatic cancer, polychemotherapy (cisplatin based) gives a 25% response rate in adenoid cystic carcinoma and should be used when the disease is overtly in progression. Targeted therapies with anti-EGF receptor molecules, antiangiogenic agents and tyrosine kinase inhibitors are ongoing, but more trials are needed to establish their efficacy, as is the use of bortezomib followed by doxorubicin. The products of fusion oncogenes, which have a pathogenic role in some adenoid cystic carcinoma and mucoepidermoid carcinomas, are of interest as potential therapeutic targets.