Facial Nerve In Relation Research Articles

Effect of deep learning-based reconstruction on high-resolution three-dimensional T2-weighted fast asymmetric spin-echo imaging in the preoperative evaluation of cerebellopontine angle tumors.

We aimed to evaluate the effect of deep learning-based reconstruction (DLR) on high-spatial-resolution three-dimensional T2-weighted fast asymmetric spin-echo (HR-3D T2-FASE) imaging in the preoperative evaluation of cerebellopontine angle (CPA) tumors. This study included 13 consecutive patients who underwent preoperative HR-3D T2-FASE imaging using a 3T MRI scanner. The reconstruction voxel size of HR-3D T2-FASE imaging was 0.23 × 0.23 × 0.5mm. The contrast-to-noise ratios (CNRs) of the structures were compared between HR-3D T2-FASE images with and without DLR. The observers' preferences based on four categories on the tumor side on HR-3D T2-FASE images were evaluated. The facial nerve in relation to the tumor on HR-3D T2-FASE images was assessed with reference to intraoperative findings. The mean CNR between the tumor and trigeminal nerve and between the cerebrospinal fluid and trigeminal nerve was significantly higher for DLR images than non-DLR-based images (14.3 ± 8.9 vs. 12.0 ± 7.6, and 66.4 ± 12.0 vs. 53.9 ± 8.5, P < 0.001, respectively). The observer's preference for the depiction and delineation of the tumor, cranial nerves, vessels, and location relation on DLR HR-3D T2FASE images was superior to that on non-DLR HR-3D T2FASE images in 7 (54%), 6 (46%), 6 (46%), and 6 (46%) of 13 cases, respectively. The facial nerves around the tumor on HR-3D T2-FASE images were visualized accurately in five (38%) cases with DLR and in four (31%) without DLR. DLR HR-3D T2-FASE imaging is useful for the preoperative assessment of CPA tumors.

Augmented reality presentation of the extracranial facial nerve: an innovation in parotid surgery

Surgeons used to be unaware of the facial nerve's position during parotid surgery. Now, with special magnetic resonance imaging (MRI) sequences, it can be located and converted into a 3D model displayed on an augmented reality (AR) device for surgeons to study and manipulate. This study explores the accuracy and usefulness of the technique for the treatment of benign and malignant parotid tumours. A total of 20 patients with parotid tumours had 3-Tesla MRI scans, and their anatomical structures were segmented using Slicer software. The structures were imported into a Microsoft HoloLens 2® device, displayed in 3D, and shown to the patient for consent. Intraoperative video recording was used to record the position of the facial nerve in relation to the tumour. The predicted path of the nerve taken from the 3D model was combined with surgical observation and video recording in all cases. The imaging proved to have application in both benign and malignant disease. It also improved the process of informed patient consent. Three-dimensional MRI imaging of the facial nerve within the parotid gland and its display in a 3D model is an innovative technique for parotid surgery. Surgeons can now see the nerve's position and tailor their approach to each patient's tumour, providing personalised care. The technique eliminates the surgeon's blind spot and is a significant advantage in parotid surgery.

Five-year experience in surgical treatment of temporal bone paragangliomas

Objectives to discuss a five-year experience in surgical treatment of temporal bone paragangliomas from the point of view of U. Fisch and D. Mattox classification modified by М. Sanna in 2013.&#x0D; Material and methods. In the period from February 2015 till December 2020, we performed 130 operations to remove temporal bone paraganglioma. The examined and operated patients included 34 men and 96 women aged from 2 to 82 years. The paraganglioma types A, B and C were distributed as follows: type A in 22 patients (A1 12 cases, A2 10 cases); type B in 73 patients (B1 25 cases, B2 16 cases, B3 32 cases); type C in 35 patients (С1 10 cases, С2 12 cases, С3 7 cases, С4 5 cases)&#x0D; Results. The evaluated results included the quality of tumor removal, the auditory function and the function of the facial nerve in relation to the size of the neoplasm, registered during the early and late postoperative periods. Based on the study data, we developed an algorithm of tactics of surgical treatment of patients with this type of temporal bone pathology aimed to avoid damage to the vital structures of the lateral skull base.

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.

An Observational Study for Localization of Temporal and Marginal Mandibular Branch of Facial Nerve in Indian Cadavers

The aim of this study was to observe the variation in the course of frontotemporal and marginal mandibular branch of the facial nerve in Indian cadavers, by using fixed anatomical landmarks. A total of 30 hemi faces of 15 embalmed formalin-preserved cadavers were aged between 18 and 70 years, and dissection was carried to expose parotid and submandibular gland. Fronto-temporal and marginal mandibular branch of facial nerve were identified within the parotid gland. Retrograde dissection and identification of the fronto-temporal branch and marginal mandibular branch of the facial nerve were done to measure the distance, and anatomical landmarks were given. We found that mean distance between temporal branch of facial nerve and root of the zygomatic arch was 25.4 ± 4.6 mm. Mean distance from the lateral canthus to the temporal nerve was 21.1 ± 4.0 mm. Mean distance from the lateral canthus to the temporal nerve, superiorly was 17.7 ± 4.2 mm. Marginal mandibular branch of the facial nerve runs with the mean distance of 6.3 ± 1.7 mm inferiorly from anatomical angle. Mean distance from the antegonial notch to the marginal mandibular nerve was 6.1 ± 1.6 mm. Mean distance from the lower border of the mandible at the level of mental foramen was 1.1 ± 6.3 mm. Course and variations of the facial nerve in relation to fixed anatomical landmarks can guide the surgeon to avoid facial nerve injuries and further postoperative complications.

Инфракохлеарный доступ к верхушке пирамиды височной кости (морфометрическое исследование)

Aim: to study morphometrics data of the infracochlear tunnel on the cadaveric temporal bones, sufficient for its rehabilitation. Patients and Methods: the study was performed on 30 cadaveric temporal bones. The measurement was made using a measurement probe, a micrometer ruler, and a digital caliper. The following parameters were studied: the distances concerning the location of the facial nerve in relation to the infracochlear tunnel; the distances between the anatomical structures of the infracochlear tunnel in its various sections (from the internal carotid artery to the jugular vein); the length of the infracochlear tunnel (bisector drawn between the internal carotid artery and the jugular bulb to the basal whorl of the cochlea); the depth of the infracochlear tunnel (distance to the petrous apex from the basal whorl of the cochlea). A comparative analysis of the results obtained with the data of other scientific studies was conducted. Results: infracochlear access on the cadaveric temporal bones was performed in our study only on 18 cadaveric temporal bones (60% of cases). During surgical access to the petrous apex, a 2 mm cutter was used to avoid injury to adjacent vessels. Based on the obtained data, differences in the structure of the infracochlear tunnel were noted depending on the pneumatization of the petrous apex. The main parameters of the infracochlear tunnel have been determined, which can be applied in the choice of surgical tactics for the removal of pathological formation from the petrous apex. Conclusions: there are the following anatomical prerequisites for conducting infracochlear access to the petrous apex for its lavage: infracochlear tunnel width from 5 mm, infracochlear tunnel length from 5.5 mm, the distance between the mastoid part of the facial nerve to the anterior margin of the cochlea window from 4.8 mm. These parameters can be applied in the assessment of patients’ CT scans to determine the indications for infracochlear access to the petrous apex. KEYWORDS: petrous pyramid, petrous apex, infracochlear tunnel, infracochlear access, cadaveric temporal bones, morphometrics. FOR CITATION: Anikin I.A., Khamgushkeeva N.N. Infracochlear access to the petrous apex (morphometrics). Russian Medical Inquiry. 2021;5(7):486–491 (in Russ.). DOI: 10.32364/2587-6821-2021-5-7-486-491.

Cadaveric Study of Topographic Anatomy of Temporal and Marginal Mandibular Branches of the Facial Nerve in Relation to Temporomandibular Joint Surgery

Detailed anatomy of the facial nerve, including the variations among different ethnic groups, is essential to prevent an iatrogenic injury. The purpose of the study was to document topographic anatomy of temporal and marginal mandibular (MM) branches of the facial nerve in relation to temporomandibular joint (TMJ) surgery. The specific aim was to demonstrate detailed course of temporal and MM nerves, their surgical implications, and to compare the results obtained with the previous studies. The investigators implemented a prospective cadaveric study. A dissection was carried out on 52 facial halves. The facial nerve was dissected according to the instructions described in the Cunningham's dissection manual. Anatomic landmarks were selected as determined by Al-Kayat and Bramley, and results obtained were compared with previous published articles. The study sample was composed of 52 facial halves (males, n=35; females, n=17). The number of branches of temporal nerve varied in dissected facial halves from 3 (n=37 [70%]), 2 (n=14 [26%]), to 1 (n=1 [2%]). The distance between the lowest concavity of the bony external auditory meatus to the point at which the facial nerve bifurcates (distance B) was considerably less in the study population (1.79cm) when compared with the reported literature (2.3cm). There was no significant influence of gender and cephalic index on distances measured. There was 1 branch in 15% of the dissected facial halves (1 in 52) and 2 branches in 85% (44 of 52). The MM nerve was seen coursing below the inferior border of the mandible, and in 44 (85%), the nerve was present above the inferior border of mandible all along the course. The topographic anatomy of the temporal and MM nerves is the same as reported in the literature. The only considerable difference was found in distance B; hence, surgical procedures involving the distance B require special consideration.

Morphometric study of Intratemporal course of facial nerve in relation to pneumatization of temporal bone—An original study

IntroductionFacial nerve (C.N VII) is the nerve of facial expression and communication. The intratemporal part of this nerve comprising tympanic and mastoid segments, is very vulnerable to injury during ear surgeries. Hence to safely navigate around this part of the nerve one has to be very familiar with 3D anatomy of the temporal bone and crucial landmarks present in relation to the nerve. Aim of this study is to know the exact morphometry of Intratemporal part of the facial nerve in relation to Pneumatization of temporal bone. Material and methodsThe present study was carried out on 54 cadaveric temporal bones obtained from the department of anatomy, Santosh Medical College, Santosh University, Delhi-NCR. With the pneumatization determined by computerized tomography (CT), the dissection was performed by standard techniques of ‘canal wall up’ mastoidectomy and ‘canal wall down’ mastoidectomy. Temporal bones have been classified into 3 groups: Group I-Well Pneumatised bones, Group II- Mixed type of Pneumatised bones and Group III- Sclerosed bones. The mean, standard deviation (S.D), maximum and minimum values were calculated in all the groups for the lengths of the facial nerve. ResultsThe total length of the intratemporal part of facial nerve ranged between 19.71–30.13mm for group I, 21.77–27.27mm in group II and 16.21–25.19mm in group III respectively. DiscussionThe distal segment of nerve is most commonly injured during otologic surgeries. Incus pointer can be considered as a landmark to identify the facial nerve. Accordingly the tympano mastoid part of the facial nerve can be divided into proximal, distal and stylomastoid foramen segments. Radiological evaluations such as Computed Tomographic (CT) imaging techniques and MRI techniques like FIESTA (Fast Imaging Employing Steady-state Acquisition) have become popular in identifying these segments. The morphometric values of facial nerve provided in the present study can help in assessment during procedures, like end to end anastamosis and cable nerve graft repairs in iatrogenic injuries.

In Reply to “Predicting Shape, Location, and Course of Facial Nerve in Relation to Large Vestibular Schwannoma on Diffusion Tensor Imaging with Intraoperative Correlation: Important Surgical Adjunct”

In Reply to “Predicting Shape, Location, and Course of Facial Nerve in Relation to Large Vestibular Schwannoma on Diffusion Tensor Imaging with Intraoperative Correlation: Important Surgical Adjunct”

NIMG-09. PREDICTION OF FACIAL NERVE POSITION IN LARGE VESTIBULAR SCHWANNOMA USING DIFFUSION TENSOR IMAGING TRACTOGRAPHY AND ITS INTRA-OPERATIVE CORRELATION

Resection of large vestibular schwannomas (VS), can be associated with postoperative facial nerve injury. Diffusion-based tractography has emerged as a powerful tool for three- dimensional imaging and reconstruction of white matter fibers; however, tractography of the cranial nerves has not been well studied. In this prospective study, we aim to predict the position of facial nerve in large vestibular schwannomas (> 3cm) using Diffusion Tensor Imaging (DTI) tractography and correlate it with intra-operative finding of the position of facial nerve. Twenty patients with large vestibular schwannomas (>3cm) undergoing surgery were subjected to preoperative DTI imaging to predict the position of facial nerve in relation to the tumor. The surgeon was blinded to the results of the preoperative DTI tractography. A comparative analysis was then made during operation. The location of the facial nerve in relation to the tumor was recorded during surgery using facial nerve stimulator. Out of the twenty patients who underwent DTI tractography, it was not possible to preoperatively identify facial nerve in one patient. In another patient, although DTI tractography predicted the position of facial nerve, it was not identified intraoperatively. Out of the remaining 18 patients, DTI tractography predicted facial nerve position was in sync with intraoperative facial nerve position in 16 patients (89 % concordance). It was discordant in two patients (11%), but this was not found to be statistically significant (p value -0.3679). This study validates the reliability of facial nerve diffusion tensor (DT) imaging–based fiber tracking for prediction of facial nerve position in patients with large vestibular schwannomas. The reliable preoperative visualization of facial nerve location in relation to VS would allow surgeons to plan tumor removal accordingly and may increase the safety of surgery.

Prediction of facial nerve position in large vestibular schwannomas using diffusion tensor imaging tractography and its intraoperative correlation.

Resection of large Vestibular Schwannomas (VSs) can be associated with postoperative facial nerve injury. Diffusion-based tractography has emerged as a powerful tool for three-dimensional imaging and reconstruction of white matter fibers; however, tractography of the cranial nerves has not been well studied. In this prospective study, we aim to predict the position of facial nerve in large VSs (>3 cm) using Diffusion Tensor Imaging (DTI) tractography and correlate it with the intraoperative finding of the position of facial nerve. Twenty patients with a large VS (>3 cm) undergoing surgery were subjected to preoperative DTI to predict the position of the facial nerve in relation to the tumor. The surgeon was blinded to the results of the preoperative DTI tractography. A comparative analysis was then made during operation. The location of the facial nerve in relation to the tumor was recorded during surgery using facial nerve stimulator. Of the 20 patients who underwent DTI tractography, it was not possible to preoperatively identify facial nerve in one patient. In another patient, although DTI tractography predicted the position of facial nerve, it was not identified intraoperatively. In the remaining 18 patients, DTI tractography accurately predicted the facial nerve position. The predicted position was in synchronization with the intraoperative facial nerve position in 16 patients (89% concordance). It was discordant in two patients (11%), but this was not found to be statistically significant (P = -0.3679). This study validates the reliability of facial nerve DTI-based fiber tracking for prediction of the facial nerve position in patients with large VSs. The reliable preoperative visualization of facial nerve location in relation to the VS will allow surgeons to plan tumor removal accordingly and may increase the safety of surgery.

Reliability of Diffusion Tensor Imaging Tractography for Facial Nerve Imaging in Patients with Vestibular Schwannoma

Introduction: The ability to reliably visualize the facial nerve in relation to the location of vestibular schwannoma (VS) is crucial for preoperative surgical planning and may increase the safety of surgery. Diffusion tensor imaging (DTI) tractography has enabled unprecedented in vivo preoperative visualization of the facial nerve. We conducted a meta-analysis to assess the accuracy of DTI tractography for locating the facial nerve in preoperative VS resection planning.

Preoperative identification of facial nerve in vestibular schwannomas surgery using diffusion tensor tractography.

ObjectiveFacial nerve palsy is a common complication of treatment for vestibular schwannoma (VS), so preserving facial nerve function is important. The preoperative visualization of the course of facial nerve in relation to VS could help prevent injury to the nerve during the surgery. In this study, we evaluate the accuracy of diffusion tensor tractography (DTT) for preoperative identification of facial nerve.MethodsWe prospectively collected data from 11 patients with VS, who underwent preoperative DTT for facial nerve. Imaging results were correlated with intraoperative findings. Postoperative DTT was performed at postoperative 3 month. Facial nerve function was clinically evaluated according to the House-Brackmann (HB) facial nerve grading system.ResultsFacial nerve courses on preoperative tractography were entirely correlated with intraoperative findings in all patients. Facial nerve was located on the anterior of the tumor surface in 5 cases, on anteroinferior in 3 cases, on anterosuperior in 2 cases, and on posteroinferior in 1 case. In postoperative facial nerve tractography, preservation of facial nerve was confirmed in all patients. No patient had severe facial paralysis at postoperative one year.ConclusionThis study shows that DTT for preoperative identification of facial nerve in VS surgery could be a very accurate and useful radiological method and could help to improve facial nerve preservation.

Vestibular Schwannoma Surgical Treatment

Neurosurgical intervention remains the main step in the effective management of vestibular schwannomas. Extensive studies on vestibular schwannoma treatment have placed emphasis on preserving quality of life and neurological functions, particularly of the facial and vestibulocochlear nerves. Facial nerve preservation and hearing preservation have been achieved by significant advances in skull base microsurgical techniques and intraoperative neuromonitoring. Diffusion tensor imaging is a powerful and accurate method for preoperatively identifying the facial nerve in relation to vestibular schwannomas. Endoscopy offers excellent illumination of the anatomical structures and provides panoramic vision inside the surgical area. In this report, we focused on facial nerve and vestibulocochlear nerve preservation and analyzed the major techniques used for identifying the nerve-tumor relationship.

Preoperative identification of the facial nerve in patients with large cerebellopontine angle tumors using high-density diffusion tensor imaging

Facial nerve paresis can be a devastating complication following resection of large (> 2.5 cm) cerebellopontine angle (CPA) tumors. The authors have developed and used a new high-density diffusion tensor imaging (HD-DT imaging) method, aimed at preoperatively identifying the location and course of the facial nerve in relation to large CPA tumors. Their study objective was to preoperatively identify the facial nerve in patients with large CPA tumors and compare their HD-DT imaging method with a traditional standard DT imaging method and correlate with intraoperative findings. The authors prospectively studied 5 patients with large (> 2.5 cm) CPA tumors. All patients underwent preoperative traditional standard- and HD-DT imaging. Imaging results were correlated with intraoperative findings. Utilizing their HD-DT imaging method, the authors positively identified the location and course of the facial nerve in all patients. In contrast, using a standard DT imaging method, the authors were unable to identify the facial nerve in 4 of the 5 patients. The HD-DT imaging method that the authors describe and use has proven to be a powerful, accurate, and rapid method for preoperatively identifying the facial nerve in relation to large CPA tumors. Routine integration of HD-DT imaging in preoperative planning for CPA tumor resection could lead to improved facial nerve preservation.

Diffusion tensor imaging–based fiber tracking for prediction of the position of the facial nerve in relation to large vestibular schwannomas

Diffusion tensor imaging–based fiber tracking for prediction of the position of the facial nerve in relation to large vestibular schwannomas

Determination of a Facial Nerve Safety Zone for Navigated Temporal Bone Surgery

Transtemporal approaches require surgeons to drill the temporal bone to expose target lesions while avoiding the critical structures within it, such as the facial nerve and other neurovascular structures. We envision a novel protective neuronavigation system that continuously calculates the drill tip-to-facial nerve distance intraoperatively and produces audiovisual warnings if the surgeon drills too close to the facial nerve. Two major problems need to be solved before such a system can be realized. To solve the problems of (1) facial nerve segmentation and (2) calculating a safety zone around the facial nerve in relation to drill-tip tracking inaccuracies. We developed a new algorithm called NerveClick for semiautomatic segmentation of the intratemporal facial nerve centerline from temporal bone computed tomography images. We evaluated NerveClick's accuracy in an experimental setting of neuro-otologic and neurosurgical patients. Three neurosurgeons used it to segment 126 facial nerves, which were compared with the gold standard: manually segmented facial nerve centerlines. The centerlines are used as a central axis around which a tubular safety zone is built. The zone's thickness incorporates the drill tip tracking errors. The system will warn when the tracked tip crosses the safety zone. Neurosurgeons using NerveClick could segment facial nerve centerlines with a maximum error of 0.44 ± 0.23 mm (mean ± standard deviation) on average compared with manual segmentations. Neurosurgeons using our new NerveClick algorithm can robustly segment facial nerve centerlines to construct a facial nerve safety zone, which potentially allows timely audiovisual warnings during navigated temporal bone drilling despite tracking inaccuracies.

Diffusion tensor imaging–based fiber tracking for prediction of the position of the facial nerve in relation to large vestibular schwannomas

The reliable preoperative visualization of facial nerve location in relation to vestibular schwannoma (VS) would allow surgeons to plan tumor removal accordingly and may increase the safety of surgery. In this prospective study, the authors attempted to validate the reliability of facial nerve diffusion tensor (DT) imaging-based fiber tracking in a series of patients with large VSs. Furthermore, the authors evaluated the potential of this visualization technique to predict the morphological shape of the facial nerve (tumor compression-related flattening of the nerve). Diffusion tensor imaging and anatomical images (constructive interference in steady state) were acquired in a series of 22 consecutive patients with large VSs and postprocessed with navigational software to obtain facial nerve fiber tracking. The location of the cerebellopontine angle (CPA) part of the nerve in relation to the tumor was recorded during surgery by the surgeon, who was blinded to the results of the fiber tracking. A correlative analysis was performed of the imaging-based location of the nerve compared with its in situ position in relation to the VS. Fibers corresponding to the anatomical location and course of the facial nerve from the brainstem to the internal auditory meatus were identified with the DT imaging-based fiber tracking technique in all 22 cases. The location of the CPA segment of the facial nerve in relation to the VS determined during surgery corresponded to the location of the fibers, predicted by the DT imaging-based fiber tracking, in 20 (90.9%) of the 22 patients. No DT imaging-based fiber tracking correlates were found with the 2 morphological types of the nerve (compact or flat). The current study of patients with large VSs has shown that the position of the facial nerve in relation to the tumor can be predicted reliably (in 91%) using DT imaging-based fiber tracking. These are preliminary results that need further verification in a larger series.

The Course of the Frontal Branch of the Facial Nerve in Relation to Fascial Planes: An Anatomic Study

Despite a wealth of literature describing the anatomy of the temporal region, controversy still exists over the depth of the frontal branch of the facial nerve as it travels over the zygomatic arch. It is commonly stated that the frontal branch travels within the superficial musculoaponeurotic system (SMAS) as it crosses the zygomatic arch. Clinically, however, it is apparent that the nerve runs at a deeper level as it crosses the arch, allowing for safe elevation and division of the SMAS to a point at or above the superior border of the zygomatic arch. The purpose of this study was to define the path of the frontal branches along fascial planes and to clarify the relationship of the fascial layers of the cheek and temporal region. Eighteen fresh-frozen cadaver hemifaces were dissected in a layer-by-layer fashion to evaluate the relationship between the nerve and the fascial planes above and below the zygomatic arch. Histologic evaluation was performed on six hemifaces. In all dissections, the frontal branch traveled within the innominate fascia as it crossed the zygomatic arch into the temporal region. A fascial transition zone was identified in a region 1.5 to 3.0 cm above the zygomatic arch and 0.9 to 1.4 cm posterior to the lateral orbital rim, where the frontal branches crossed from the innominate fascia to run within the superficial temporal fascia. As the frontal branch crosses the zygomatic arch, it is within the innominate fascia, a plane deep to the SMAS and superficial temporal fascia.

In Situ Location of the Temporal Branch of the Facial Nerve

The purpose of this radiologic study was to determine the precise location of the temporal branch of the facial nerve in relation to the most anterior aspect of the bony external acoustic canal without distortion of the position of the nerve by surgical manipulation or cadaveric fixation artifact. This was a retrospective study of 30 patients with a mean age of 38 years (range, 22 to 67 years) with no history of previous surgery or trauma. Thirty axial high-resolution magnetic resonance imaging examinations at the level of the zygomatic arch were examined to determine the location of the temporal branch. The nerve was identified by following its course from the stylomastoid foramen to an area lateral to the frontozygomatic suture. Three individuals made 3 measurements of each image with digimatic calipers. The high and low values were discarded, and the remaining 3 values were analyzed. These examiners were trained in locating the nerve and bony landmarks and were tested for accuracy in measurement. No inter- or intraoperative variability was noted. The mean distance of the most posterior ramus of the temporal branch of the facial nerve to the most anterior aspect of the external acoustic canal was 2.12 cm +/- 0.21 cm (range, 1.68 to 2.49 cm). The course of the temporal branch was easily identified, and the examiners were consistent in their measurements. In all cases examined, there was no evidence of facial trauma or other facial surgery in the patient histories. All nerves were found superficial to the zygomatic arch, just deep to the superficial musculoaponeurotic system, or the temporozygomatic fascia, which is the connective tissue layer just deep to the subcutaneous fat. The temporal branch of the facial nerve is at risk for injury during a variety of facial surgical procedures because of its location. This study found the nerve to be in a slightly less vulnerable position during a preauricular approach than Al-Kayat and Bramley's classic study (0.8-3.5 cm), and also established a narrower range of nerve position variability.