Postoperative Facial Palsy Research Articles

Traumatic arteriovenous fistula of the left parotid region: A case report.

The formation of arteriovenous fistula beneath the parotid is relatively rare. To the best of our knowledge, the present study reports the first case of a 48-year-old man with a pulsatile mass on the left parotid region, which had been present for >3 years following penetrating wounds. Computed tomography angiography and digital subtraction angiography revealed a fistula between the left external carotid artery and the left jugular vein. The patient was successfully managed through surgical excision without embolization. Intraoperative facial nerve monitoring was employed to prevent postoperative facial paralysis. The present study briefly reviewed the current literature, illustrating the pathophysiology, symptoms, imaging studies and treatment for arteriovenous fistula in the head and neck region. To conclude, arteriovenous fistula located near the facial nerve may be successfully managed by surgical treatment, without permanent facial paralysis.

Risk factors for recurrence of pleomorphicadenoma.

Pleomorphic adenoma is the most frequent benign tumor of the salivary glands. It is characterized by a tendency to recur, which is determined by the biological characteristics of the tumor as well as the mode of its treatment. Recurrence of the tumor is associated with a high risk of postoperative facial palsy, risk of subsequent recurrence after revision surgery, and an increased risk of malignant transformation. Knowledge of the recurrence risk factors could allow selection of treatments that minimize the risk. Among the factors in this study the most important are: incomplete excision, intraoperative capsule rupture, myxoid subtype, presence of the satellite nodules and tumor extensions (pseudopodia), lack of the glandular tissue margin and the experience of the surgeon. The possible factors are: the female sex, young age, location and size of the tumor, and the duration of the tumor growth. The technique of tumor enucleation of pleomorphic adenoma carries a high risk of recurrence and should be replaced by parotidectomy. In cases of recurrence the treatment is individually tailored and may: further follow up, limited resection of the tumor, lateral parotidectomy or extended radical parotidectomy with concurrent reconstruction of the facial nerve. The role of radiotherapy is discussed.

Functional Outcome of the Facial Nerve After Surgery for Vestibular Schwannoma: Prediction of Acceptable Long-Term Facial Nerve Function Based on Immediate Postoperative Facial Palsy

To examine the relationship between immediate postoperative facial palsy and long-term facial palsy and identify a treatment strategy for vestibular schwannoma considering long-term outcomes of facial nerve function and tumor control. Patients (N= 385) who underwent surgery in a single institution were reviewed retrospectively; 12 patients with neurofibromatosis, 6 with preoperative radiosurgery, and 14 with multiple surgeries were excluded. The generalized estimating equation method was used to show the correlation between immediate and later postoperative facial palsy and to identify the cutoff grade of immediate postoperative facial palsy. The tumor control rates for 1 year, 3 years, and 5 years were 88.7%, 83.9%, and 80.0%. Preservation of facial function above House-Brackmann (H-B) grades 1 and 2 was achieved in 47.9% of patients immediately postoperatively, in 50.1% after 1 month, and in 74.5% after >2 years. The immediate postoperative facial palsy grade showed a statistically significant relationship with the facial palsy grade on long-term follow-up (P < 0.001). H-B grade 3 immediate postoperative facial palsy was identified as the cutoff grade that showed the most significant relationship between the grade of immediate postoperative facial palsy and the grades above the cutoff (H-B grade 1-3) on long-term follow-up (P < 0.001). H-B grade of immediate postoperative facial palsy can predict facial palsy at long-term follow-up. H-B grade 3 immediate postoperative facial palsy is the lowest tolerable grade that guarantees functional improvement on long-term follow-up. Planned facial nerve preservation surgery followed by radiosurgery is thought to be optimal treatment in patients with vestibular schwannoma for both tumor control and facial nerve function.

Telovelar Approach for Midline Posterior Fossa Tumors in Paediatrics: 25 Cases Experience

Background: The classic transvermian route for excision of fourth ventricular tumors could be associated with postoperative cerebellar mutism. The Telovelar approach leads to the fourth ventricle via the cerebellomedullary fissure, avoiding retraction on the dentate nuclei and vermian incisions, hence lowering the incidence of cerebellar mutism. Objective: The aim of this study is to evaluate the Telovelar approach for excision of fourth ventricular tumors. Patients and methods: This retrospective study was conducted on 25 cases with midline posterior fossa tumors collected between 2012 and 2014. All cases were operated upon via the telovelar approach succeeded by microscopic tumor excision. Follow up data were collected regarding the degree of excision (total, near total, and subtotal), and postoperative complications. Mean follow up period was 5 months. Results: Age ranged from 2 to 8 years (mean 5.6 years). The most common was medulloblastoma (13 cases), followed by ependymoma (10 cases), and then choroid plexus papilloma (2 cases). Gross total excision was achieved in 8 cases (32%), near total excision (Eƒ80% of tumor volume) in 14 cases (56%), and subtotal excision (E‚80% of tumor volume) in 3 cases (12%). We experienced cerebellar mutism in 2 cases (8%) which improved in one case in the long term postoperative follow up. None of the cases had truncal ataxia. Two cases (8%) had postoperative facial palsy, while 3 cases (12%) had postoperative bulbar affection. There were two mortalities in this study, which were related to bulbar palsy and chest infection. Conclusion: Telovelar approach to the fourth ventricle is becoming a widespread technique for removing midline posterior fossa tumors. It gives excellent access and visualization to the fourth ventricle, with a low incidence of postoperative cerebellar mutism.

Microvascular decompression for atypical hemifacial spasm: lessons learned from a retrospective study of 12 cases.

Typical hemifacial spasm (HFS) commonly initiates from the orbicularis oculi muscle to the orbicularis oris muscle. Atypical HFS (AHFS) is different from typical HFS, in which the spasm of muscular orbicularis oris is the primary presenting symptom. The objective of this study was to analyze the sites of compression and the effectiveness of microvascular decompression (MVD) for AHFS. The authors retrospectively analyzed the clinical data for 12 consecutive patients who underwent MVD for AHFS between July 2008 and July 2013. Postoperatively, complete remission of facial spasm was found in 10 of the 12 patients, which gradually disappeared after 2 months in 2 patients. No recurrence of spasm was observed during follow-up. Immediate postoperative facial paralysis accompanied by hearing loss occurred in 1 patient and temporary hearing loss with tinnitus in 2. All 3 patients with complications had gradual improvement during the follow-up period. The authors conclude that most cases of AHFS were caused by neurovascular compression on the posterior/rostral side of the facial nerve distal to the root entry zones. MVD is a safe treatment for AHFS, but the incidence of postoperative complications, such as facial paralysis and decrease in hearing, remains high.

Management of vessels passing through the facial nerve in the treatment of hemifacial spasm.

In hemifacial spasm, it is extremely rare to find a vessel passing through the facial nerve. In this study, we present our experience of the surgical treatment of four such patients. From January 2010 to Match 2015, we treated 2,576 hemifacial spasm patients with microvascular decompression in our department. Of these, four had an intraneural vessel. Intraoperative findings and treatment were recorded, and postoperative outcomes were analyzed. In three patients, the intraneural vessel was the anterior inferior cerebellar artery, which we wrapped with small pieces of wet gelatin and Teflon sponge. A small vein found in the fourth patient was treated with facial nerve combing. Complete decompression was achieved and abnormal muscle response disappeared. Three patients got an excellent result and one patient got a good result. One patient had postoperative facial paralysis, which improved over 10 months of follow-up. If an artery passes through the facial nerve, it can be decompressed by wrapping the vessel with wet gelatin and Teflon sponge. If a vein passes through the facial nerve, combing can be used. Intraoperative abnormal muscle response monitoring is very helpful in achieving complete decompression.

Intraoperative facial nerve monitoring during cochlear implant surgery: an observational study.

Iatrogenic facial nerve injury is one of the most severe complications of cochlear implantation (CI) surgery. Intraoperative facial nerve monitoring (IFNM) is used as an adjunctive modality in a variety of neurotologic surgeries. The purpose of this retrospective study was to assess whether the use of IFNM is associated with postoperative facial nerve injury during CI surgery. The medical charts of 645 patients who underwent CI from 1999 to 2014 were reviewed to identify postoperative facial nerve palsy between those who did and did not receive IFNM. Four patients (3 children and 1 adult) were found to have delayed onset facial nerve weakness. IFNM was used in 273 patients, of whom 2 had postoperative facial nerve weakness (incidence of 0.73%). The incidence of facial nerve weakness was 0.54% (2/372) in the patients who did not receive IFNM. IFNM had no significant effect on postoperative delayed facial palsy (P = 1.000). All patients completely recovered within 3 months after surgery. Interestingly, all 4 cases of facial palsy received right CI, which may be because all of the surgeons in this study used their right hand to hold the drill. When right CI surgery is performed by a right-handed surgeon, the shaft of the drill is closer to the inferior angle of the facial recess, and it is easier to place the drilling shaft against the medial boundary (facial nerve) when the facial recess is small. The facial nerve sheaths of another 3 patients were unexpectedly dissected by a diamond burr during the surgery, and the monitor sounded an alarm. None of these 3 patients developed facial palsy postoperatively. This suggests that IFNM could be used as an alarm system for mechanical compression even without current stimulation. Although there appeared to be no relationship between the use of monitoring and delayed facial nerve palsy, IFNM is of great value in the early identification of a dehiscent facial nerve and assisting in the maintenance of its integrity. IFNM can still be used as an additional technique to optimize surgical success.

Patientin mit intrameatalem Meningeom und postoperativer Fazialisparese

Meningioma in a broader sense is among the most common type of brain tumor. About one third of all intracranial tumors evolve from a meningeal origin. Localization and size of this mostly benign neoplasia will define the type and severity of resulting neurological failure. This clinician's corner presents a female patient with a rare localization of meningioma. The initial symptoms consisted of vertigo, which lead to the diagnosis of acoustic neurinoma. After surgery, a meningioma in the meatus acusticus internus was diagnosed histologically. Due to left sided postoperative facial palsy, the patient was assigned to acupuncture. The palsy was controlled after 15 treatment sessions, however, two years after the final acupuncture treatment the meningioma recurred.

Removing Mastoid Tip Procedure for Advanced Parotid Cancer Results in Easy Identification of the Facial Nerve and Adequate Surgical Margin

Background: Advanced parotid cancers larger than 4 cm were firmly fixed around the tissue, and the main trunk of the facial nerve could hardly be detected in the narrow working space between the mastoid tip and parotid gland with cancer. Though the facial nerve was preserved, facial nerve stretching during surgery can have the serious effect of postoperative facial palsy. Methods: The study was performed on 23 advanced parotid cancers that were larger than 4 cm and invaded firmly around the parotid. Seventeen cases were fresh cases and 6 were recurrent cases. Number of Stage III, IVA, and IVB were 4, 11, and 8, respectively. Results: Twenty-three patients required either mastoid tip removal (n: 19) or extended temporal bone resection (n: 4) for advanced parotid cancer. In nine cases, the main trunk of the facial nerve was sacrificed, and in five cases, tumors in the lower division of the nerve were resected. Theses facial nerves were reconstructed immediately. Negative margins were achieved in 100% of the patients. Conclusion: Removing the mastoid tip for advanced parotid tumors facilitates identification of the facial nerve and, therefore, better preservation of the normal facial nerve function.

Canal wall reconstruction in cholesteatoma surgeries: rate of residual.

To evaluate the rates of residual and recurrent cholesteatoma following canal wall reconstruction (CWR) tympano-mastoidectomy with mastoid obliteration, for the treatment of chronic otitis with cholesteatoma. Consecutive cohort study. We included patients following surgical cholesteatoma removal by CWR tympano-mastoidectomy with hydroxyapatite mastoid obliteration from 2008 to 2012. We analyzed audiometric and postoperative radiologic data. We determined the rates of residual disease and recurrence, and evaluated postoperative complications. Thirty-six ears were included in this study. The mean follow-up after surgery was 24 months (range 12.3-51.4 months). The recurrence rate was 3.1% (one case) and the rate of residual disease was 6.2% (two cases including one of iatrogenic cholesteatoma). No canal-wall-down tympanoplasty was required. Local infection was detected in 33% of cases and was successfully treated with appropriate antibiotics. Postoperative audiometry showed no impairment of the cochlear reserve. No postoperative facial palsy or deafness was observed. CWR permits well exposure of the lesion, making complete excision of the cholesteatoma possible. This study showed a decreasing of the rate of residual cholesteatoma and must be confirmed with further studies. CWR makes it possible to use hearing aids for auditory rehabilitation.

Intraoperative continuous monitoring of facial motor evoked potentials in acoustic neuroma surgery.

The preservation of facial nerve function is one of the primary objectives in acoustic neuroma surgery. We detail our method of continuous intraoperative facial motor evoked potential (MEP) monitoring and present criteria for the preservation of facial nerve function to avoid postoperative facial nerve palsy. Our study population was comprised of 15 patients who did not (group 1), and 20 who did (group 2) undergo facial MEP monitoring during surgery to remove acoustic neuromas. In group 2, we continuously stimulated the facial motor cortex at 5- or 10-s intervals throughout surgery. Electromyograms (EMGs) were recorded from the contralateral orbicularis oculi- and orbicularis oris muscles. Optimal anode and cathode placement was at the facial motor cortex and the vertex, respectively. Postoperative facial palsy occurred in 8 of the 15 group 1 patients; in 2 it improved to grade II at 6 months after the operation. Of the 20 group 2 patients, 7 suffered postoperative facial palsy. At 6 months after the operation, their facial nerve function was normal. At the end of the operation, the ratio of the amplitude of the supramaximal EMG to the amplitude at the dural opening was 39.6 % in patients with- and 94.3 % in patients without transient postoperative facial palsy. Continuous facial MEP monitoring not only alerts to surgical invasion of the facial nerves but also helps to predict postoperative facial nerve function. To preserve a minimum amplitude ratio of 50 %, even transient postoperative facial palsy must be avoided. MEP monitoring is an additional useful modality for facial nerve monitoring during acoustic neuroma surgery.

Usefulness of facial nerve monitoring for confirmation of greater superficial petrosal nerve in anterior transpetrosal approach.

The greater superficial petrosal nerve (GSPN) is especially important in anterior transpetrosal approach (ATPA) as the most reliable superficial landmark of Kawase's triangle. The GSPN can be considered as the superficial lateral border of anterior petrosectomy on the middle fossa to avoid internal carotid artery (ICA) injury. Although experienced operators can find the GSPN, its confirmation is not always easy to achieve. We introduce our recent GSPN confirmation methods using facial nerve monitoring. In 10 recent cases, antidromic GSPN stimulation and free-running facial muscle electromyography (EMG) monitoring were performed. Facial nerve evoked-EMG by antidromic GSPN stimulation confirmed the location of the GSPN course with precision in all cases. Free-running facial muscle EMG informed the mechanical stress of facial nerves through the GSPN. There was no postoperative facial palsy or dry eye in these cases. GSPN confirmation and preservation are not always easy to achieve. These monitoring methods are useful for the confirmation of the GSPN, which is a landmark for safe extradural anterior petrosectomy, and for the preservation of the GSPN itself.

27. Facial nerve palsy after vestibular schwannoma surgery: Dynamic risk-stratification based on continuous EMG-monitoring

A-trains are a pathological pattern in intraoperative EMG-monitoring. Traintime, a parameter calculated by automated EMG-analysis, quantifies A-train activity. Its extent is associated with the degree of postoperative facial nerve palsy. However, false positive results have been observed. A systematic flaw in automated analysis was hypothesized. Facial nerve EMG-data from 79 patients undergoing vestibular schwannoma surgery were analysed visually. Automated traintime was compared with these results. The progressive risk for postoperative paresis was calculated with respect to traintime (visual and automated). Automated analysis identified a small (1.46%), but highly representative fraction of overall A-train activity: Pearson’s correlation coefficient between both values was 0.944 ( p < 0.001). Both were correlated with clinical outcome in a highly significant way ( p < 0.001) with Spearman Rho 0.592 (automated) and 0.563 (visual). Progressive risk development was visualized as an inverse sigmoid curve with traintime on a logarithmic scale. After an initial steep rise in the curve, a short plateau ( ∼ 15% risk) is reached. This changes to a shallow slope with constantly rising risk, which is then (at ∼ 50% risk) followed by a steep rise again, quickly reaching 100% of relative risk. With the ratio of 0.0146 between mean automated an visual traintime factored in, the risk-curves for both measures are basically identical concerning form and dimension. Automated traintime is a representative and reliable expression for overall A-train activity. Rigid thresholds are problematic, as they are either set too high or too low and do not reflect the complexity of risk-development. Individual risk for postoperative palsy can be estimated on the basis of the calculated curve presented.

Recurrent Pleomorphic Adenoma of the Parotid Gland: Intraoperative Facial Nerve Monitoring during Parotidectomy

To determine the benefit to postoperative facial function of intraoperative facial nerve monitoring (IFNM) during recurrent pleomorphic adenoma (RPA) parotid surgery. Cohort study with planned data collection. Chinese PLA General Hospital. Fifty-eight RPA parotidectomies were performed between 2004 and 2012. Recurrence was confirmed by histopathologic examination. None of the patients had preoperative facial palsy. Electromyography-based IFNM was used in 28 patients; 30 patients were unmonitored. The durations of surgery and the severity of postoperative facial nerve palsy were compared between the 2 groups. There were no significant differences between the 2 groups in the incidence of immediate or permanent facial paralysis after RPA parotidectomy (P = .95 and P = .36, respectively). However, the differences in the average duration of surgery and the severity of postoperative facial nerve palsy after total parotidectomy or wide resection were significant (P < .01 and P = .01, respectively). In contrast, these differences were not significant after superficial parotidectomies (P = .43 and P = .49, respectively). The average recovery time of temporary facial nerve paralysis was significantly shorter in the monitored group compared with the unmonitored group, independent of surgical technique (P < .01). The use of IFNM during total or wide resection RPA parotidectomy reduced the duration of surgery and the incidence of postoperative facial paralysis and enhanced recovery. However, there was little impact on facial nerve outcomes when IFNM was used during superficial RPA parotidectomy.

Parotid Gland Surgery for Benign Tumours: Have We Come Full Circle?

Parotid gland surgery has been described for over two centuries. The surgical philosophies in management of parotid gland tumors started off in the 18th century from a conservative approach of simple enucleation so as to minimize post-operative facial nerve palsy rate. This occurred, as there was a lack of understanding of surgical anatomy of the parotid gland and facial nerve. However unacceptably high recurrence rates ensued and this encouraged the further study of parotid gland anatomy till the 1950s when, deriving from a better understanding of the surgical anatomy, superficial parotidectomy with facial nerve identification and preservation became the new standard of care. This method then evolved to a partial superficial parotidectomy as this slightly more conservative approach allowed adequate parotid tumour resection with low recurrence rates and yet minimising post-operative complication such as Frey's syndrome. Over the last two decades, a more conservative approach known as an extracapsular dissection of parotid tumour emerged in certain high-volume centers as an alternative to a partial superficial parotidectomy. These centers published better post-operative results with lower postoperative facial nerve palsy rates, less Frey's syndrome and faster patient recovery. Dissection of parotid tumours via this technique involves following a plane close to the tumour and is similar to enucleation in terms of its conservative approach with very significant differences post-operatively. This article presents a summary on the surgical philosophies pertaining to parotid gland surgery since its inception two centuries ago.

Congenital Tri–Cavernous Hemangiomas of the Right Buccal Region, Right Accessory Parotid Gland, and Masseter Muscle Region

We report a rare case of congenital tri-cavernous hemangiomas of the right buccal region, right accessory parotid gland, and masseter muscle region in an adult. The patient, a 25-year-old woman, complained of 3 masses in her right midcheek. Ultrasonographic and computed tomographic findings showed an irregular-shaped mass (multiple calcifications) with a well-defined margin in the masseter muscle region, an ellipse-shaped mass (multiple calcifications) with a well-defined margin in the right buccal region, and a comma-shaped mass (no calcifications) with a well-defined margin separate from the parotid gland in the right accessory parotid gland region. These iconographic findings suggested that the masses were all hemangiomas separately originating from the parotid gland, accessory parotid gland, and masseter muscle. The masses were completely removed through a standard parotid incision without postoperative facial palsy, skin deformity, and difficulty in secreting saliva. Findings from histologic examination of the tumor revealed multiple, thin-walled, and dilated blood vessels, confirming the diagnosis of cavernous hemangiomas. Ultrasonographic and computed tomographic findings were extremely useful in diagnosing the mass/masses as hemangioma before surgery, clarifying relationships between the mass and adjacent structures, and determining the surgical approach to the mass/masses.

Transient facial nerve palsy after auriculotemporal nerve block in awake craniotomy patients.

In this case series, we describe transient postoperative facial nerve palsy in patients after awake craniotomy using selective scalp nerve blocks. In a 1-year period, 7 of the 42 patients receiving scalp nerve blocks at our institutions developed this complication. This is significant because there is only 1 previously reported case of postoperative facial nerve palsy related to scalp nerve blocks. The exact cause of transient postoperative facial nerve palsy after auriculotemporal nerve block is unknown and likely multifactorial. This technique may need to be refined to avoid such complications.

Results of Anterior Facial Nerve Rerouting Procedures for Removing Skull Base Tumors

The purpose of this study was to estimate the rates of functional recovery of the facial nerve and of total tumor resection in patients who undergo short anterior rerouting and long anterior rerouting of the facial nerve in removal of skull base tumors. We retrospectively collected data on 37 patients with skull base tumors who underwent facial nerve rerouting during the procedure for tumor removal. Information on the rerouting technique, the completeness of tumor resection, and changes in facial nerve function were obtained from the medical records. Rerouting techniques were classified as short anterior rerouting or long anterior rerouting. Ten of 16 patients (62.5%) in the group with short anterior rerouting showed postoperative facial palsy, and all completely recovered within 1 year. In the group with long anterior rerouting, 18 of 21 patients (85.7%) showed postoperative facial palsy, and recovery to a preoperative level of facial function was found in 10 patients at 1 year of follow-up. Total tumor resection was possible in 94% and 81% of patients with short rerouting and long rerouting, respectively. The mean operation time was not significantly related to the postoperative recovery of facial function. Short rerouting techniques, when appropriately chosen on the basis of tumor and patient characteristics, offer excellent preservation of facial function and tumor resection, comparable to those of long rerouting techniques.

Stratifying the risk of facial nerve palsy after benign parotid surgery

Post-operative facial palsy is the most important potential complication of parotid surgery for benign lesions. The published prevalence of facial weakness is up to 57 per cent for temporary weakness and up to 7 per cent for permanent weakness. We aimed to identify potential risk factors for post-operative facial palsy. One hundred and fifty patients who had undergone parotid surgery for benign disease were retrospectively reviewed. Tumour factors (size, location and histopathology), patient factors (age and sex) and operative factors (operation, surgeon grade, surgeon specialty and use of intra-operative facial nerve monitoring) were all analysed for significant associations with post-operative facial palsy. The overall incidence of facial palsy was 26.7 per cent for temporary weakness and 2.6 per cent for permanent weakness. The associations between facial palsy and all the above factors were analysed using Pearson's chi-square test and found to be non-significant. These outcomes compare favourably with the literature. No significant risk factors were identified, suggesting that atraumatic, meticulous surgical technique is still the most important factor affecting post-operative facial palsy.

Clinical Features and Surgical Outcomes of Glomus Tumors in the Temporal Bone and Skull Base

Background and ObjectivesZZGlomus tumors are benign, slow-growing tumors which cause various symptoms such as pulsatile tinnitus and hearing loss. The aim of this study was to analyze the clinical manifestation and surgical outcomes of the glomus tumors in the temporal bone and skull base. Subjects and MethodZZMedical records of 17 patients who were surgically managed for glomus tumors of the temporal bone and skull base from 1997 to 2013 were retrospectively reviewed. The location and the size of the tumor were analyzed by CT and MRI, and the Fisch classifica tion method was used to classify the tumor. Pre- and postoperative facial function measured by House-Brackmann (H-B) grade and lower cranial nerve (LCN) function were collected. ResultsZZThe mean age of 17 patients was 50.6 (18-83) years, and male to female ratio was 4:13. The most common symptom of glomus tumors was pulsatile tinnitus, and this symptom disappeared or changed naturally postoperatively. The majority of patients with glomus jugulare showed various degrees of immediate postoperative facial nerve palsy, and 8 out of 9 patients showed improvement of facial nerve function to H-B grade I in 3 months. LCN palsy occurred in 5 out of 9 patients immediately following the operation and remained in 3 patients with Fisch type C2 tumor. ConclusionZZGlomus tumors of the temporal bone and skull base were successfully removed by surgery. The surgical outcome of glomus jugulare shows that facial nerve function is acceptable and the incidence of lower cranial nerve palsy may be related to the classification of tumor. Korean J Otorhinolaryngol-Head Neck Surg 2014;57(11):752-8 Key WordsZZFacial nerve ㆍGlomus tumor ㆍLower cranial nerve ㆍSkull base, surgery.