Differentiation of geniculate ganglion venous malformation from schwannoma: dynamic T1-weighted imaging provides unique diagnostic value.

OBJECTIVE: To distinguish geniculate ganglion venous malformation (GGVM) from schwannoma (GGS) by using high-resolution CT (HRCT), routine MRI, and dynamic T1-weighted imaging (T1WI) characteristics. METHODS: Surgically confirmed GGVMs and GGSs between 2016 and 2021 were retrospectively included. Preoperative HRCT, routine MR, and dynamic T1WI were performed on all patients. Clinical data, imaging characteristics including lesion size, involvement of facial nerve (FN), signal intensity, enhancement pattern on dynamic T1WI, and bone destruction on HRCT were evaluated. Logistic regression model was developed to identify independent factors for GGVMs, and the diagnostic performance was accessed by receiving operative curve (ROC) analysis. Histological characteristics were explored for both GGVMs and GGSs. RESULTS: Twenty GGVMs and 23 GGSs with mean age of 31 were included. On dynamic T1WI, 18 GGVMs (18/20) showed "pattern A" enhancement (a progressive filling enhancement), while all 23 GGSs showed "pattern B" enhancement (a gradual whole-lesion enhancement) (p < 0.001). Thirteen GGVMs (13/20) showed the "honeycomb" sign whereas all GGS (23/23) showed extensive bone changes on HRCT (p < 0.001). Lesion size, involvement of FN segment, signal intensity on non-contrast T1WI and T2-weighted imaging (T2WI), and homogeneity on enhanced T1WI were obviously differed between two lesions (p < 0.001, p = 0.002, p < 0.001, p = 0.01, p = 0.02, respectively). Regression model showed the "honeycomb" sign and "pattern A" enhancement were independent risk factors. Histologically, GGVM was characterized by interwoven dilated and tortuous veins, while GGS was characterized by abundant spindle cells with dense arterioles or capillaries. CONCLUSIONS: The "honeycomb" sign on HRCT and "pattern A" enhancement on dynamic T1WI are the most promising imaging characteristics for differentiating GGVM from GGS. CLINICAL RELEVANCE STATEMENT: The characteristic sign and enhancement pattern on HRCT and dynamic T1-weighted imaging allow preoperative differentiation of geniculate ganglion venous malformation and schwannoma feasible, which will improve clinical management and benefit patient prognosis. KEY POINTS: • The "honeycomb" sign on HRCT is a reliable finding to differentiate GGVM from GGS. • GGVM typically shows "pattern A" enhancement (focal enhancement of the tumor on early dynamic T1WI, followed by progressive contrast filling of the tumor in the delayed phase), while "pattern B" enhancement (gradual heterogeneous or homogeneous enhancement of the whole lesion) is observed in GGS on dynamic T1WI.

Schwannomas of the greater superficial petrosal nerve - case series, discussion of surgical techniques, and review of literature.

BACKGROUND: Facial nerve schwannomas account for about 0.8% of all petrous mass lesions. Schwannomas of the greater superficial petrosal nerve (GSPN) are a rare subtype with few case-reports up to date. CASE PRESENTATIONS: A retrospective analysis of clinical outcomes, radiographic findings and postoperative complication between June 2007 and December 2020 was performed. Four cases of GSPN schwannomas were reported. The presenting symptoms were facial nerve palsy and hearing loss. Imaging studies showed a subtemporal mass on the anterosuperior aspect of the petrous bone, in one case with extraordinary petrous bone and mastoid infiltration and destruction. Three cases were removed through a subtemporal extra- or intradural approach, one case via a combined pre- and retrosigmoid approach. Improvement of facial nerve palsy occurred in one case; new hearing loss was observed in another case. Xeropthalmia was a short-term temporary deficit in three cases. Short- to mid-term follow-up of the patients has not shown any tumor recurrence. CONCLUSIONS: GSPN schwannomas are rare entities presenting with heterogenous symptoms. Our surgical findings emphasize safe resection. Complete remission is possible by GTR. Since the small data set limits the expressiveness of statements regarding standard of care and alternative therapy options, additional data is needed.

[Differential diagnosis and management of hemangioma at geniculate ganglion].

Objective: To investigate the clinical characteristics, differential diagnosis, treatments and prognosis of facial nerve hemangioma and schwannoma at genicular ganglion, so as to provide reference for clinical diagnosis and treatments of facial nerve tumor at genicular ganglion. Methods: Clinical data of 13 patients with facial nerve tumors at genicular ganglion confirmed by postoperative pathology in the Ninth People's Hospital affiliated to Shanghai Jiaotong University School of Medicine from March 2018 to April 2020 were retrospectively analyzed, including seven cases of hemangioma and six cases of schwannoma. There were eight males and five females. Their ages ranged from 20 to 65, with an average age of 40. The course of disease ranged from 3 to 118 months, with an average of 52 months. All the patients underwent preoperative HRCT of the temporal bone and facial nerve dynamic contrast-enhanced(DCE) MRI examinations. All the patients had detailed surgical procedures and at least one-year postoperative follow-up. Results: On HRCT of the temporal bone, (4/7) hemangioma at geniculate ganglion showed characteristic honeycomb appearance, while 6/6 schwannoma and 3/7 hemangiomas showed expansive bone changes. On DCE-MRI, geniculate ganglion hemangioma (7/7) showed characteristic "point-to-surface" enhancement, and schwannoma (6/6) showed characteristic "face-to-surface" enhancement. For five hemangioma-patients with HB-Ⅱ-Ⅳ before surgery, the facial nerve anatomy was completely preserved through transcanal endoscopic approach(TEA), and the facial nerve function improved one year after surgery (two cases of HB-I, two cases of HB-Ⅱ, and one case of HB-Ⅲ). For two patients, with preoperative facial nerve function HB-Ⅴ-Ⅵ, since their tumors was inseparable from the nerves, they were performed with facial nerve anastomosis during the surgery, and the facial nerve function was improved to HB-Ⅳ level one year after surgery. For six patients with meningioma whose facial nerve function was greater than or equal to HB-Ⅲ, based on the preoperative hearing level, the involved segments, and duration of facial paralysis, three of them were conducted surgeries through middle cranial fossa approach, one by translabyrinthine approach, and one via mastoid approach. Two patients among them with complete facial paralysis over three years preoperatively were not performed facial nerve anastomosis after total resections of the tumors, and there was no improvement in facial nerve function one year after surgery. Three patients underwent facial nerve anastomosis after total tumor resections, and their facial nerve function was HB-Ⅲ in one patient, HB-Ⅳ in two patients one year after surgery. One patient (preoperative HB-Ⅲ) had a normal hearing level preoperatively, and the tumor involved the labyrinth segment. To protect the hearing, partial tumor was resected through the middle cranial fossa approach, and facial nerve function improved to HB-Ⅱ one year after surgery. Conclusions: Temporal bone HRCT combined with DCE-MRI are useful for the differential diagnosis of hemangioma and schwannoma at geniculate ganglion and provide references for preoperative clinical decision makings. It is extremely necessary to select the appropriate surgical approach based on the patient's hearing and involved segments. For geniculate ganglion hemangioma, early surgery can improve the possibilities of anatomical integrity of facial nerve, thereby improving facial nerve function postoperatively.TEA is a kind of surgical method worth consideration, with the characteristics of minimally invasive, favorable postoperative features, and so on. For schwannoma, one-stage functional reconstruction of the facial nerve is recommended during the resection of the tumors because of the inevitable damage to the anatomical integrity of the facial nerve.

Endoscopic Transcanal Approach to Geniculate Ganglion Hemangioma and Simultaneous Facial Nerve Reinnervation: A Case Report.

Hemangioma of the facial nerve (FN) is a very rare benign tumor whose origin is the vascular plexi that surround the nerve. The transpetrous, retrosigmoid, and middle cranial fossa (MCF) routes are the traditional and most widely used approaches to reach these lateral skull base neoformations. However, this very complex region can be reached through an exclusive transcanal endoscopic procedure in selected cases. One of these was a 42-year-old patient who had been presenting a worsening left FN paralysis (grade VI according to the House-Brackmann scale at the time of visit) for 22 months without a history of trauma or infection. Radiological studies showed a lesion in the region of the geniculate ganglion. A suprageniculate endoscopic approach was performed to remove the lesion, with the sacrifice of the FN and a simultaneous hypoglossal-facial anastomosis. The aim of this minimally invasive surgery is the complete excision of the disease, maintaining the hearing function intact and restoration of facial function, whenever possible, avoiding more invasive approaches.

Regenerative Failure Following Rat Neonatal Chorda Tympani Transection is Associated with Geniculate Ganglion Cell Loss and Terminal Field Plasticity in the Nucleus of the Solitary Tract.

Neural insult during development results in recovery outcomes that vary dependent upon the system under investigation. Nerve regeneration does not occur if the rat gustatory chorda tympani nerve is sectioned (CTX) during neonatal (≤P10) development. It is unclear how chorda tympani soma and terminal fields are affected after neonatal CTX. The current study determined the impact of neonatal CTX on chorda tympani neurons and brainstem gustatory terminal fields. To assess terminal field volume in the nucleus of the solitary tract (NTS), rats received CTX at P5 or P10 followed by chorda tympani label, or glossopharyngeal (GL) and greater superficial petrosal (GSP) label as adults. In another group of animals, terminal field volumes and numbers of chorda tympani neurons in the geniculate ganglion (GG) were determined by labeling the chorda tympani with DiI at the time of CTX in neonatal (P5) and adult (P50) rats. There was a greater loss of chorda tympani neurons following P5 CTX compared to adult denervation. Chorda tympani terminal field volume was dramatically reduced 50 days after P5 or P10 CTX. Lack of nerve regeneration after neonatal CTX is not caused by ganglion cell death alone, as approximately 30% of chorda tympani neurons survived into adulthood. Although the total field volume of intact gustatory nerves was not altered, the GSP volume and GSP-GL overlap increased in the dorsal NTS after CTX at P5, but not P10, demonstrating age-dependent plasticity. Our findings indicate that the developing gustatory system is highly plastic and simultaneously vulnerable to injury.

Facial nerve neuroma in the geniculate ganglion extending into the internal auditory canal: A case report.

Facial nerve schwannoma is a very rare benign tumor representing less than 1% of intrapetrous lesions. Our patient is a forty-one year old female who has suffered from recurrent right facial palsy for the last six years. She was first misdiagnosed as having Bell's palsy and received corticosteroids which resulted in little improvement. She then had facial nerve decompression surgery which resulted in a partial improvement. Since then, she has suffered from recurrent attacks of facial palsy. Two years ago, she came to our hospital seeking further treatment options. The final diagnosis made by MRI was a possible facial nerve tumor. To obtain a better facial outcome, total tumor removal was performed through the middle cranial fossa approach along with facial-hypoglossal nerve end-to-side anastomosis through transmastoid approach. Her hearing was preserved, and she obtained a better facial outcome than that of her preoperative level. In conclusion, facial nerve schwannoma has the potential to be misdiagnosed as Bell's palsy which might lead to a delay in diagnosis, and end-to-side neurorrhaphy may be an effective alternative in a selected case.

Geniculate Ganglion Tumors: Clinical Presentation and Surgical Results.

OBJECTIVE: Facial nerve tumors are rare lesions mostly located in the geniculate ganglion. This study aims to compare those tumors limited to the geniculate ganglion in terms of clinical features and postoperative outcomes. STUDY DESIGN: Case series with chart review. SETTINGS: University tertiary reference center. SUBJECTS AND METHODS: Medical charts were reviewed for 17 patients who had surgery for geniculate ganglion tumor removal (10 hemangiomas, 6 schwannomas, 1 meningioma). Hemangiomas and schwannomas were compared for preoperative facial nerve function, hearing, tumor size, and postoperative outcomes. RESULTS: Facial palsy was observed in all cases. Regarding the preoperative facial nerve function, severe facial palsy (House-Brackmann grades V and VI) was present in 70% of cases for hemangiomas and for no case of schwannoma (P = .01), although hemangiomas were significantly smaller tumors (P = .01). Hearing loss was observed in 4 cases (23.5%) and was related to tumor volume (P < .0001). A complete excision was achieved in all cases, and a facial nerve graft was performed immediately after interruption in 16 patients (94%). Postoperative facial nerve function was improved or stabilized in 94% of cases. A preoperative House-Brackman grade VI was shown as a negative factor for postoperative facial nerve function. CONCLUSIONS: Differences in clinical presentations could help in establishing the good therapeutic option depending on the tumor type. Surgery, when indicated, is safe and effective, and postoperative outcomes are not related to tumor type.

Intratemporal facial nerve schwannoma: clinical presentation and management.

Facial nerve schwannoma is the most common facial nerve tumor, but its therapeutic strategy remains debated. The aim of this study is to analyze the facial nerve function and the hearing outcomes after surgery or wait-and-scan policy in a facial nerve schwannoma series. A monocentric retrospective review of medical charts of patients followed for an intratemporal facial nerve schwannoma between 1988 and 2013 was performed. Twenty-two patients were included. Data were extracted pertaining to the following variables: patient demographics, tumor localization, clinical and imaging features, facial nerve function and hearing levels, and details of surgical intervention. The majority of tumors were located at the geniculate ganglion. Initial symptoms were mainly facial palsy and hearing loss. The average follow-up was 4.8 ± 4.5 years. Nineteen patients underwent surgery, and three patients were observed. After surgery, 11 patients had a stable or improved facial nerve function (57.9 %), and 8 patients had a worsened facial nerve function (42.1 %). Facial nerve function was in the majority of cases a HB grade III, depending on surgical strategy. No patient presented a postoperative HB grade V or VI. Regarding the hearing, it remained stable after surgery in 52.6 % of cases, and improved in 10.5 % of cases. Among monitored patients, facial nerve function and hearing remained stable. Surgery for facial nerve schwannoma is a safe and effective option in the treatment of these tumors.

Management of Geniculate Ganglion Hemangiomas: Case Series and Systematic Review of the Literature.

OBJECTIVE: To analyze facial nerve (FN) outcomes based on duration of FN palsy and surgical strategy in patients with geniculate ganglion hemangiomas (GGH). STUDY DESIGN: Case series and systematic review of the literature. SETTING: Tertiary care center. SUBJECTS AND METHODS: All patients undergoing surgical resection of GGH from 1992 to 2014 were studied and a review of the English literature was performed. RESULTS: One hundred twenty unique patients (mean age 41.4 yrs, 44% female) were identified with GGH: 8 in the current series and 112 from the literature review. Of these patients, 94% presented with FN weakness, 18% reported hemifacial spasm, and 16% had hearing loss at presentation. Eleven patients underwent an initial period of observation, 6 of which experienced either growth or progression of FN dysfunction. One hundred fourteen subjects ultimately underwent surgical intervention. The average preoperative House-Brackmann (HB) score was 4.6 and the mean duration of preoperative FN palsy was 27 months (range, 1-132). The average postoperative HB score was 3.5 at the last follow-up. Anatomical FN preservation was reported in 44% of patients. Duration of FN palsy ≤12 months was associated with better pre- and postoperative FN outcome (HB 4.1 vs 5.1, p = 0.01 and 2.9 vs 4.0, p < 0.001, respectively). FN preservation was also associated with better postoperative FN outcome compared with interposition grafting (HB 2.6 vs 3.9, p < 0.001). CONCLUSION: GGHs are rare benign vascular malformations that present with progressive FN palsy. In most patients, early surgical intervention should be considered since shorter duration of FN paralysis and anatomical preservation of the FN are significant predictors of final FN outcome.

Changes in transient receptor potential channels in the rat geniculate ganglion after chorda tympani nerve injury.

We reported differential expression of the transient receptor potential vanilloid 1 (TRPV1), the transient receptor potential ankyrin 1 (TRPA1), and the (TRPM8) in the geniculate ganglions (GGs) of naive rats. In medical practice, the chorda tympani nerve (CTN) is injured in some patients during middle-ear surgery, and results in tongue numbness and taste disorder. We investigated changes in the expression of these receptors in GGs after CTN injury. In naive-rat GGs, 11.4, 11.8, and 0.5% of neurons were found to express the TRPV1, the TRPA1, the TRPM8, respectively. At 3 days after CTN injury, 5.2 and 4.0% of activating transcription factor 3-immunoreactive neurons, considered as injured neurons, were found to express the TRPV1 and the TRPA1, respectively. Among activating transcription factor 3-immunonegative neurons, considered as uninjured neurons, 3.9 and 3.8% were found to express the TRPV1 and the TRPA1, respectively. The TRPM8 was not detected in GGs after CTN injury. We found decreased mRNA levels of the TRPV1 and the TRPA1 in all neurons, as well as in uninjured neurons of ipsilateral GGs after CTN injury. CTN injury changes the gene expression in GGs and may have effects on the tongue.

Primary tumors of the facial nerve.

This article describes the pathophysiology, diagnosis, treatment, and outcomes of primary tumors of the facial nerve. These tumors include facial nerve schwannomas, geniculate ganglion hemangiomas, glomus facialis, and granular cell tumors. Although these tumors are rare, collected data help to form a consensus with regard to optimal treatment methods.

Facial nerve palsy after reactivation of herpes simplex virus type 1 in diabetic mice.

OBJECTIVES/HYPOTHESIS: Bell's palsy is highly associated with diabetes mellitus (DM). Either the reactivation of herpes simplex virus type 1 (HSV-1) or diabetic mononeuropathy has been proposed to cause the facial paralysis observed in DM patients. However, distinguishing whether the facial palsy is caused by herpetic neuritis or diabetic mononeuropathy is difficult. We previously reported that facial paralysis was aggravated in DM mice after HSV-1 inoculation of the murine auricle. In the current study, we induced HSV-1 reactivation by an auricular scratch following DM induction with streptozotocin (STZ). STUDY DESIGN: Controlled animal study. METHODS: Diabetes mellitus was induced with streptozotocin injection in only mice that developed transient facial nerve paralysis with HSV-1. Recurrent facial palsy was induced after HSV-1 reactivation by auricular scratch. RESULTS: After DM induction, the number of cluster of differentiation 3 (CD3)(+) T cells decreased by 70% in the DM mice, and facial nerve palsy recurred in 13% of the DM mice. Herpes simplex virus type 1 deoxyribonucleic acid (DNA) was detected in the facial nerve of all of the DM mice with palsy, and HSV-1 capsids were found in the geniculate ganglion using electron microscopy. Herpes simplex virus type 1 DNA was also found in some of the DM mice without palsy, which suggested the subclinical reactivation of HSV-1. CONCLUSIONS: These results suggested that HSV-1 reactivation in the geniculate ganglion may be the main causative factor of the increased incidence of facial paralysis in DM patients.

Facial nerve hemangiomas at geniculate ganglion: preservation of nerve integrity is correlated with duration of facial palsy.

OBJECTIVE: To study preservation of nerve integrity in 16 cases with facial nerve hemangiomas at geniculate ganglion (GG). METHODS: 16 cases with facial nerve hemangiomas at GG, who presented with facial palsy, were included in the study. Preservation of nerve integrity was attempted by the same surgeon during surgical removal, and those who failed to preserve nerve integrity underwent nerve grafting. The patients were divided into longer duration group (>12months) and shorter duration group (≤12months) according to duration of facial palsy, and preservation of nerve integrity in the couple of groups was compared. RESULTS: Nerve integrity was preserved in 2 of 10 cases (20%) among longer duration group, while it was preserved in 5 of 6 cases (83.3%) among shorter duration group (p<0.05). All the cases with nerve integrity preserved recovered to grade III or better, among which 3 cases recovered to grade I or grade II, while only 3 of 9 cases (33.3%) with nerve grafting recovered to grade III at the best. CONCLUSIONS: Preservation of nerve integrity was correlated with duration of facial palsy in cases with hemangiomas at GG. Patients with nerve integrity preserved showed better outcomes of facial nerve.

Nueva entidad en el diagnóstico diferencial de los tumores del ganglio geniculado: lesión del tejido conectivo fibroso del nervio facial / A new entity in the differential diagnosis of geniculate ganglion tumours: fibrous connective tissue lesion of the facial nerve

Dentro del diagnóstico diferencial de las lesiones del ganglio geniculado nos encontramos principalmente con los schwannomas, hemangiomas y meningiomas. Se presenta el caso de un paciente cuya clínica y hallazgos radiológicos imitaban la presentación de un schwannoma del nervio facial. Los estudios anatomopatológicos revelaron una lesión con fascículos nerviosos desestructurados por intensa colagenización, por lo que se denominó lesión fibrosa del tejido conectivo fibroso del nervio facial (AU)

Differential diagnosis of geniculate ganglion tumours includes chiefly schwannomas, haemangiomas and meningiomas. We report the case of a patient whose clinical and imaging findings mimicked the presentation of a facial nerve schwannoma. Pathological studies revealed a lesion with nerve bundles unstructured by intense collagenisation. Consequently, it was called fibrous connective tissue lesion of the facial nerve (AU)

Intra-parotid facial nerve schwannoma with intra-temporal extension; a case report. Is there a role for stereotactic radiotherapy?

Facial nerve schwannoma (FNS) is an extremely rare benign tumour that may arise anywhere along the course of the facial nerve; the standard treatment is total removal via microsurgery. Stereotactic radiotherapy has been shown to be effective in the treatment of skull base tumours, in particular for acoustic neuromas; it is interesting to notice that also the few data existing in literature about the use of radiotherapy for non acoustic schwannomas show an excellent local control rate and few adverse effects. Here we report a case of facial nerve neuroma, involving the nerve sheath from the geniculate ganglion to the parotid gland, treated with fractionated stereotactic radiotherapy after debulking surgery.

Meningioma of geniculate ganglion: case report and review of the literature.

Although meningioma is a frequent intracranial tumor, it rarely affects the geniculate ganglion of the facial nerve. Facial palsy is the most common symptom. When hearing is preserved (class A or B, AAO-HNS), tumor is best removed through a middle cranial fossa approach. We report the case of a geniculate ganglion meningioma and present its clinical, radiological, and pathological features. Surgical management is discussed. A literature review revealed that only 17 previous cases have been reported during the last 50 years.

Infranuclear facial palsy: importance of imaging the geniculate fossa.

OBJECTIVE: To highlight the importance of imaging the geniculate fossa in patients with solitary infranuclear facial palsy. STUDY DESIGN: Prospective. SETTING: Tertiary referral center. ELIGIBILITY CRITERIA: Patients with solitary infranuclear facial palsy sent for imaging. INTERVENTION: Diagnostic. MAIN OUTCOME MEASURE: Imaging specifics concerning high-resolution computed tomography (HRCT) and magnetic resonance imaging (MRI) are described in detail for evaluation of the intratemporal part of the facial nerve with special focus on the geniculate fossa. RESULTS: Normal appearances of the geniculate fossa on HRCT and MRI and its normal anatomic variant, that is, dehiscence of the overlying bone are described. Imaging findings in a range of pathologies involving the geniculate fossa in a clinical setting of infranuclear facial nerve palsy is demonstrated. These include infections (tuberculosis), trauma, schwannoma, hemangioma, meningioma, and perineural spread of parotid malignancy. CONCLUSION: The geniculate fossa is a small bony hiatus in the temporal bone and is situated at the junction of the labyrinthine and the tympanic segments of the intratemporal facial nerve canal. It houses important neural structures and is best visualized by a combination of HRCT and high-resolution MRI examination of the temporal bone. It is therefore imperative for imaging specialists to be familiar with the normal appearance of this structure on HRCT and MRI examinations of the temporal bone as subtle imaging findings involving the geniculate fossa can be indicators of a variety of abnormalities.

The nervus intermedius as a variable landmark and critical structure in cerebellopontine angle surgery: an anatomical study and classification.

BACKGROUND: An understanding of the normal topography during cerebellopontine angle surgery is necessary to obviate the anatomical distortions caused by tumors. OBJECTIVE: The aim of this study was to analyze the morphological features of the nervus intermedius (NI) and its related structures in the cerebellopontine angle (CPA). METHODS: Forty-three isolated human brainstems were examined to collect comprehensive morphometric and topographical data of the NI in its course from the brainstem to the ganglion geniculi, and discover its anatomical relationship with the other neurovascular structures in the CPA as well as within the meatus acusticus internus. RESULTS: A total of 84 NI were analyzed. The number of bundles comprising the NI varied from one to five. The mean length of the cisternal segment of the NI was 11.47 mm. In most cases, a vein between the root entry/exit zones of the facial and the vestibulocochlear nerve (VN) was documented. In all cases the NI joined the facial nerve, typically (85 %) distally to the the porus within the meatus acusticus internus. The entry/exit zone of the NI can be categorized into four types: in type A, they arise directly from the brainstem; in type B, they arise solely from the facial nerve; in type C solely from the VN; and in type D, where the bundle or bundles arise from both the brainstem and the VN or the facial nerve. CONCLUSION: The anatomical features of the NI can provide an additional variable landmark and critical structure during cerebellopontine microsurgery. Our study of the nerve's anatomy and topographical relations may contribute to preventing intraoperative nerve injuries.