Criteria for differentiating superficial from deep lobe tumours of the parotid gland by computed tomography

The efficacy of clinicopathological and imaging features in differentiating benign from malignant parotid micro- and minitumors: a retrospective analysis

OBJECTIVE

To compare clinicopathological and imaging features of micro- and minitumors of the parotid gland and provide a reference for preoperative prediction of benign vs malignant status.

STUDY DESIGN

Patients with parotid gland tumors treated surgically were selected. Relevant clinicopathological and imaging data were collected for patients with maximum tumor diameters ≤20 mm on preoperative computed tomography (CT). The lesions were divided into 2 groups, microtumors and minitumors, based on maximum tumor diameter. CT imaging features of benign and malignant tumors were compared through binary logistic regression analysis.

RESULTS

Microtumors and minitumors were categorized by maximum diameters <10 mm (n = 74) and 10-20 mm (n = 611), respectively. Benign and malignant minitumors exhibited significant differences in boundary, tumor density, margin morphology, spiculation margin, and CT values in the plain and arterial phase (P ≤ .027), resembling those found in typical malignant parotid gland tumors. However, no significant differences were observed between benign and malignant microtumors. Logistic regression analysis identified boundary, margin morphology, and spiculation margin as independent predictors of malignancy. The prediction model excelled in identifying benign lesions but was less successful in identifying malignancies.

CONCLUSION

Parotid gland minitumors had imaging features similar to typical larger malignant tumors. Active exclusion of the malignant risk and early surgical treatment is recommended for these tumors.

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.

Extracapsular Dissection of Deep Lobe Parotid Mass Aided by Retromandibular Vein on Imaging: A Case Report

This report investigates the use of the retromandibular vein on imaging as a diagnostic tool for planning deep lobe parotid tumors. A unique aspect of this case is the performance of extracapsular dissection on a deep lobe parotid lesion, which is rare. Preoperative imaging showed a superficially displaced retromandibular vein, indicating a deeply seated tumor, which aided surgical planning. Under general anesthesia, extracapsular dissection was performed while protecting the facial nerve branches. The patient's postoperative course was uneventful, and the facial nerve was intact with no weakness.

Reliability of the 'M-Line' in the Prediction of the Facial Nerve Position in Patients with Parotid Neoplasms

Preoperative radiological assessment of parotid tumours represents a crucial step in the planning of a parotidectomy in order to avoid post-operative facial nerve paralysis. The purpose of this study is to determine the reliability of the novel 'M-line' in predicting the facial nerve position and compare it to various radiological methods in the same context. 66 patients whom had underwent parotidectomy for parotid tumours from January 2012 to February 2021 were analyzed. Parotid tumour location were identified using the retromandibular vein, facial nerve line, Conn's arc, Utrecht line and the 'M'-line were compared to the intraoperative location of parotid tumours.The 'M'-line is a novel hypothetical line (drawn between the lateral surface of the mandible to the lateral border of the mastoid process) used to identify the location of the facial nerve radiologically. The 'M-Line' and other methods of radiological assessments were associated with statistical significance in predicting if the parotid tumours were superficial or deep to the facial nerve (p-value < 0.05).The 'M-line' had demonstrated a sensitivity of 73.6% and 92.3% specificity.It had also yielded the highest accuracy (77.3%) in the prediction of the parotid tumour location in relation to the facial nerve. While the radiological lines represented by the Retromandibular vein,facial nerve line,Utrecht line and Conn's arc were statistically significant in predicting the location of the parotid tumour in relation to the facial nerve, the M-line was the most accurate and sensitive predictor in our study.The M-Line is a potentially useful tool to predict the location of the facial nerve in relation to a parotid tumour.

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.

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.

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.

Correlation between preoperative predictions and surgical findings in the parotid surgery for tumors

Background

To compare preoperative CT/MRI based predictions with real surgical findings for deep lobe parotid gland surgery.

Methods

The study analyzed 122 parotidectomies (2004–2014) for benign tumor removal. The facial nerve, the Utrecht line, the Conn’s arc, and the retromandibular vein were used as landmarks for CT/MRI presurgical evaluation of patients. We assessed 106 CT images and 86 MRI images. The study compared preoperative evaluation of tumor location with its actual location that was revealed during the operation and assessed the importance of the landmarks.

Results

In general, the agreement between preoperative CT prediction and actual location of the parotid tumors was achieved in 88.7 % (n = 94/106) when facial nerve line was used as a landmark. However, out of 14 tumors in the deep lobe only 5 were located correctly (35.7 %). Of the other existing CT landmarks, none showed more precision over others. The agreement between MRI based prediction and surgical results on actual location of the tumor was achieved in 94.2 %. Out of 12 MRI-investigated tumors in the deep lobe nine were located correctly that gives 75 % agreement with surgical results.

Conclusion

Our data suggests that no existing CT landmark can be accepted as completely reliable in cases when selective deep lobe parotidectomy is planned. If tumor location is suspected in the deep lobe of the gland, MRI imaging is necessary to confirm the diagnosis. An operating surgeon should be prepared that in some cases the true location of the tumor would be revealed only during surgery.

Novel differential diagnostic method for superficial/deep tumor of the parotid gland using ultrasonography

BACKGROUND

The purpose of this study was to prepare the ultrasonographic diagnostic criteria on parotid tumors for preoperative differentiation of superficial and deep tumors.

METHODS

We evaluated 154 patients with a benign parotid tumor who underwent surgery. The minimum thickness of normal parotid gland tissue between the parotideomasseteric fascia and tumor (minimum fascia-tumor distance [MFTD]) was measured on preoperative ultrasonography and compared among tumors at different locations, and the optimum cutoff value to differentiate a deep tumor was identified.

RESULTS

The MFTD showed significant differences between superficial and deep tumors and between inferior pole and deep tumors. The sensitivity, specificity, and accuracy of an MFTD ≥3 mm for the differentiation of deep tumors were 85%, 91%, and 89%.

CONCLUSION

A tumor with an MFTD ≥3 mm on preoperative ultrasonography is very likely to be a deep tumor based on a new differentiation method for deep parotid tumors considering those present at other locations.

Major and minor salivary gland tumors

Malignant salivary gland tumors are rare. The most common tumor site is the parotid. Aetiologic factors are not clear. Nutrition may be a risk factor, as well as irradiation or a long-standing histologically benign tumor that occurs at youth. Painless swelling of a salivary gland should always be considered as suspicious, especially if no sign of inflammation is present. Signs and symptoms related to major salivary gland tumors differ from those concerning minor salivary gland tumors, as they depend on the different location of the salivary gland. Surgical excision represents the standard option in the treatment of resectable tumors of both major and minor salivary glands. Neutron, heavy ions or proton radiotherapy may be a treatment option for inoperable locoregional disease. Surgery, irradiation or re-irradiation are treatment options for local relapse, whereas radical neck dissection is indicated for regional relapses. Metastatic disease may be either treated with radiotherapy or palliative chemotherapy, depending on the site of metastases. For highly selected patients the employment of anti-androgen therapy is indicated.

Do magnetic resonance imaging and ultrasound add anything to the preoperative workup of parotid gland tumors?

PURPOSE

To assess the additional value of magnetic resonance imaging (MRI) and ultrasound (US) to physical examination (PE) and fine needle aspiration cytology (FNAC) in the preoperative determination of the location and histology of parotid gland tumors.

PATIENTS AND METHODS

Prospectively, 99 patients with 77 benign and 22 malignant lesions were included; 82 underwent parotidectomy. FNAC was performed in 88 patients. On PE, the location of the tumor was predicted. Eighty-nine patients had MRI and 47 US. Various characteristics and the presumed diagnosis were assessed. Furthermore, the location of the tumor in relation to the facial nerve was predicted. The results were compared with the definite histology and the location during surgery.

RESULTS

Of the MRI characteristics, incomplete demarcation from normal parotid gland tissue showed the highest positive predictive value (PPV) for malignancy of 0.48. Of the US characteristics, enlarged lymph nodes yielded the highest PPV for malignancy of 0.5. Cytology correctly predicted the benign or malignant nature of the tumor in all cases. Superficial location was well predicted on PE with a PPV of 0.8, slightly better on MRI (PPV of 0.87), and worse on US (PPV of 0.7).

CONCLUSION

FNAC is the only accurate investigation for classifying a parotid gland tumor as benign or malignant. Palpation and MRI are superior to US in predicting tumor location. Because the results for palpation and MRI are almost equal, MRI should only be reserved for specific cases, and not routinely requested.

Preservation of the Superficial Lobe for Deep-Lobe Parotid Tumors: A Better Aesthetic Outcome

Deep-lobe parotid tumors are relatively uncommon. Most of these tumors present as external masses. They can also present in the oral cavity or oropharynx. Magnetic resonance imaging and ultrasound-guided fine-needle aspiration for biopsy and cytology have made it possible to establish a definitive diagnosis and identify the exact location of the tumor in almost all cases before surgery. Traditionally, deep-lobe tumors have been managed by a formal superficial parotidectomy and identification and preservation of the facial nerve, followed by removal of the deep lobe that contains the tumor. Superficial parotidectomy is associated in most cases with periauricular depression secondary to a loss of volume, leading to variable aesthetic deformities. A complete parotidectomy is more likely to be associated with a larger aesthetic deficit secondary to a greater loss of tissue volume. The incidence of gustatory sweating is high after superficial parotidectomy, particularly in the early postoperative period. We hypothesize that if the superficial lobe is preserved, there is less likelihood of gustatory sweating because of the interposition of tissue between the skin and the cut ends of the secretomotor fibers. Approximately 80% of parotid tissue volume is made up of the superficial lobe, and therefore preservation of the superficial lobe should be associated with less postparotidectomy depression. Therefore, we decided to preserve the superficial lobe of the gland for deep-lobe tumors. Nine patients underwent deep-lobe parotidectomy with preservation of the superficial lobe over a 6-year period. Patients were studied prospectively with regard to technical difficulty, complications, and cosmetic outcome. Follow-up ranged from 12 months to 6 years. We did not experience any undue technical difficulty, and there were no cases of facial weakness. One patient developed gustatory sweating, which almost completely resolved over a 2-year period. There were no cases of postparotidectomy depression, and both patients and surgeons were satisfied with the cosmetic appearance. We present our technique and experience.

Use of cross-sectional imaging in predicting surgical location of parotid neoplasms

OBJECTIVE

The purpose of this study was to determine the diagnostic accuracy of using the retromandibular vein as seen on cross-sectional imaging to help differentiate superficial lobe from deep lobe tumors.

METHODS

Of the patients who had parotid neoplasms between January 1997 and July 2002, we were able to identify 44 patients with preoperative imaging studies that were available for evaluation. The films were reviewed by a single head and neck radiologist to determine whether the neoplasms involved the superficial, deep, or both lobes of the parotid gland (total). The lateral margin of the retromandibular vein was used as a marker for the facial nerve, since the nerve is not always visible on CT and MRI scans. The radiologist's findings were then compared with the findings during surgery. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of predicting the location of neoplasms were then calculated.

RESULTS

For lesions in the superficial lobe, cross-sectional imaging was able to predict the location of the neoplasm with a sensitivity of 0.91 (95% CI, 0.70-0.98), specificity of 0.86 (95% CI, 0.63-0.96), PPV of 0.88 (95% CI, 0.67-0.97), and NPV of 0.90 (95% CI, 0.67-0.98). For lesions in both lobes (total), cross-sectional imaging was able to predict the location of the neoplasm with a sensitivity of 0.94 (95% CI, 0.68-0.99), specificity of 0.89 (95% CI, 0.71-0.97), PPV of 0.83 (95% CI, 0.58-0.96), and NPV of 0.96 (95% CI, 0.78-0.99).

CONCLUSION

Use of the retromandibular vein as a marker for the facial nerve is a sensitive method for identifying the location of parotid gland neoplasms on cross-sectional imaging. This supports the accuracy of using preoperative imaging to detect the position of parotid neoplasms with respect to the facial nerve.

Use of Cross-Sectional Imaging in Predicting Facial Nerve Sacrifice during Surgery for Parotid Neoplasms

BACKGROUND

Neoplasms of the parotid gland are difficult management issues because of the wide variation in their biological behavior and the potential for sacrifice of the facial nerve during resection. Because of the significant associated morbidity, prediction of facial nerve sacrifice is critically important for planning surgical procedures and preoperative counseling of patients. We hypothesize that along with the knowledge of the tumor type we would be able to accurately predict the likelihood of facial nerve sacrifice using cross-sectional imaging.

METHODS

All patients included in this study were previously untreated patients with parotid neoplasms operated on between January 1997 and July 2002. Only those patients with an available preoperative imaging were included and this resulted in 44 patients for review. Nine patients with preoperative deficits in facial nerve function were excluded from this study since these patients would require facial nerve sacrifice regardless of the radiological prediction. The prediction of facial nerve sacrifice was determined using a prediction of tumor location and an algorithm. The predicted results were compared to the operative record.

RESULTS

For all lesions, cross-sectional imaging predicted the need for sacrifice of the facial nerve with a sensitivity of 0.83 (95% CI, 0.36-0.99), specificity of 0.90 (95% CI, 0.72-0.97), PPV of 0.63 (95% CI, 0.26-0.90), and NPV of 0.96 (95% CI, 0.79-0.99). For malignant lesions only, prediction of sacrifice of the facial nerve had a sensitivity of 0.83 (95% CI, 0.36-0.99), specificity of 0.80 (95% CI, 0.51-0.95), PPV of 0.63 (95% CI, 0.26-0.90), and NPV of 0.92 (95% CI, 0.62-0.99).

CONCLUSION

Cross-sectional imaging and application of our algorithm is a sensitive method for identifying patients with parotid neoplasms who require facial nerve sacrifice. CT and MRI have a high negative predictive value for facial nerve sacrifice.

MR imaging of salivary glands

Diagnostic imaging of salivary glands has been revolutionized with the advent of cross-sectional imaging modalities like CT and MR imaging. In the era before CT, imaging of the salivary glands was relatively unrewarding and was used uncommonly by ear-nose-throat surgeons. Early diagnostic tests like plain films and sialography evaluated dilated parotid ducts and calculus disease within ducts or glands. Full evaluation of salivary glands, especially deep lobes of parotid gland and masses of minor salivary glands, was not possible by these methods, however. Imaging of the parotid glands has developed significantly since that time. CT and MR imaging greatly compliment physical and endoscopic examinations (and previous favorites like sialography) by direct visualization of previously blind areas of the salivary glands and extension of the disease process in surrounding tissue planes.

Parotid gland surgery: 4-year review of 118 cases in an Asian population

BACKGROUND

To determine the presentation and management of parotid lesions requiring excision in a largely Chinese Asian population.

METHODS

Retrospective study of 118 consecutive parotidectomies.

RESULTS

Thirty-seven percent were Warthin's tumor (WT), 33% pleomorphic adenoma (PA), 21% other benign disease (OBD), and 9% malignant tumor (MT). Mean age was significantly different between benign (51 years) and malignant (40 years) lesions. MT decreased above 50 years, but increased five times with pain and two times with a noninferior pole lesion. Sensitivity of fine-needle aspiration (FNA) for differentiating benign from MT = 78%, for WT =5 8%, for PA =82%, for OBD = 28%, and for MT = 38%. CT scans did not alter WT management. Facial nerve (FN) paresis was not associated with histology, tumor size, site, or parotidectomy type.

CONCLUSIONS

This is the first report documenting that most benign parotid tumors are WT and not PA. MT risk is greater in those less than 50 with pain and a noninferior pole lesion. Cystic lesions such as WT require great care in the evaluation of FNA findings.

MR imaging of salivary glands

In conclusion, if a parotid gland mass is bilateral, it is more likely to be Warthin's tumor, especially if it does not enhance. Less likely, it could be lymphoepithelial cyst or necrotic lymph node. A unilateral, non-enhancing mass with a high T2 signal is more likely to be a Warthin's tumor and less likely a necrotic lymph node or first branchial cleft cyst. If the mass is unilateral, shows postcontrast enhancement, has a high T2 signal, and does not invade surrounding tissue planes, it is more likely to be a pleomorphic adenoma. An intermediate to low T2 signal mass-with or without invasion of surrounding tissue planes--is more likely to be a malignant mass such as adenocystic or mucoepidermoid carcinoma. Biopsy is superior and the gold standard for diagnosis and cannot be replaced by MR imaging, however.

The location of parotid gland tumors in relation to the facial nerve on magnetic resonance images and computed tomography scans

PURPOSE

The facial nerve, which cannot be visualized radiographically in its intraparotid part, divides the parotid gland into 2 lobes. When planning surgery, it is important to know where to locate a parotid gland tumor in relation to the facial nerve, because the location can influence the duration and difficulty of the operation. In this study, an anatomic line that predicts the course of the facial nerve in the parotid gland, is applied clinically and compared with another line recently described to evaluate the usefulness of both tools in the use of computed tomography scans and magnetic resonance images.

MATERIALS AND METHODS

We reviewed 28 scans (15 computed tomography and 13 magnetic resonance) and used both lines to predict tumor location in the parotid gland. The accuracy of each prediction was checked later by referring to the surgical report.

RESULTS

This new anatomic line helped us to correctly predict tumor location in relation to the facial nerve in 24 cases (85.7%), whereas the other line was helpful in 20 cases (71.4%).

CONCLUSION

Our new line may be a very useful tool to predict the location of parotid gland tumors.

Prediction of the position of the intraparotid portion of the facial nerve on MRI and CT

Despite developments in imaging technology, visualisation of the intraparotid portion of the facial nerve is not possible. Three separate radiological techniques have been described to predict the position of the facial nerve: Conn's arc; a plane extending posteriorly from the outer surface of the mandibular ramus; and soft-tissue structures, including the posterior belly of the digastric muscle, the retromandibular vein and the lateral border of the masseter muscle. We investigated the reliability of these techniques in predicting the relationship of tumours to the facial nerve. Cross-sectional imaging of the parotid glands was performed prior to the removal of a parotid mass in 26 patients. Twenty patients underwent MRI, and six had CT scans. We removed 14 malignant neoplasms, nine benign lesions and three non-neoplastic lesions. The relationship of the tumour to the facial nerve was assessed radiologically by each of the three techniques, and compared with the findings at surgery. In 18 patients the tumour involved the parotid gland deep to the facial nerve. The above techniques predicted the position of the facial nerve in 69%, 58% and 46% of cases, respectively. When planning parotid surgery, it is important that the surgeon understands the advantages and limitations of the radiological assessment of the position of parotid tumours in relation to the facial nerve.

Preoperative determination of the location of parotid gland tumors by analysis of the position of the facial nerve

PURPOSE

This study examined the usefulness of anatomic lines in predicting the intraparotid course of the facial nerve.

MATERIALS AND METHODS

To make the comparison, 3 lines were drawn on 69 transverse sections of 5 cadaver heads. Then, the shortest and the longest distance from the lines to the facial nerve were measured.

RESULTS

Of the tested lines, the one that connects the most dorsal point on the ipsilateral half of a vertebra to the dorsal side of the retromandibular vein had the shortest distance to the facial nerve. It also ran more parallel to the facial nerve than the other 2 lines.

CONCLUSIONS

Because the line that connects the most dorsal point on the ipsilateral half of a vertebra to the dorsal side of the retromandibular vein best predicts the intraparotid course of the facial nerve, it might be useful in assessing whether parotid tumors are located in the superficial or deep lobe.