Management of 1000 vestibular schwannomas (acoustic neuromas): the facial nerve--preservation and restitution of function

OBJECTIVE

Although the rate of reported facial nerve preservation after surgery for vestibular schwannomas continuously increases, facial nerve paresis or paralysis is a frequent postsurgical sequelae of major concern. The major goal of this study was to define criteria for the right indication, timing, and type of therapy for patients with palsies despite anatomic nerve continuity and those with loss of anatomic continuity.

METHODS

One thousand vestibular schwannomas were surgically treated at the Department of Neurosurgery at Nordstadt Hospital from 1978 to 1993. Of 979 cases of complete removal and 21 cases of deliberately partial removal, the facial nerve was anatomically preserved in 929 cases (93%). The rate of preservation is increasing, as is evidenced in the most recent cases, and preservation is supported by special electrophysiological monitoring. The facial nerve was anatomically severed in 60 cases (6%). It was anatomically lost in previous operations that were performed elsewhere in 11 cases (1%). In case of nerve discontinuity (42 cases), immediate nerve reconstruction by one of three available intracranial procedures (within the cerebellopontine angle, intracranial-intratemporal, intracranial-extracranial) was performed in the same surgical setting. In case of loss of the proximal facial nerve stump at the brain stem, early reanimation by combination with the hypoglossal nerve was achieved in most patients within weeks after tumor surgery. In a few patients with anatomic nerve continuity but absence of reinnervation for 10 to 12 months, a hypoglossal-facial combination was applied. All the patients with partial or with complete palsies were treated in a special follow-up program of regular controls and of modulation of physiotherapeutic treatment every 3 to 6 months.

RESULTS

In intracranial nerve reconstruction at the cerebellopontine angle, 61 to 70% of patients regained complete eye closure and an overall result equivalent to House-Brackmann Grade 3. Hypoglossal-facial reanimation led to Grade 3 in 79%. The duration between the onset of paralysis and the reconstructive procedure is decisive for the quality of the outcome. These data are discussed in view of other treatment options and certain parameters influencing outcome.

CONCLUSIONS

This management contains three major principles as follows: 1) preservation of facial nerve continuity in function by the aid of intraoperative monitoring, 2) early nerve reconstruction in case of lost continuity, and 3) scheduled follow-up program for all patients with incomplete or complete palsies.

Improved preservation of hearing and facial nerve function in vestibular schwannoma surgery via the retrosigmoid approach in a series of 200 patients

Object

The aim of this study was to evaluate and present the results of current surgical treatment of vestibular schwannomas (VSs) and to report the refinements in the operative technique.

Methods

The authors performed a retrospective study of 200 consecutive patients who had undergone VS surgery over a 3-year period. Patient records, operative reports, follow-up data, and neuroradiological findings were analyzed. The main outcome measures were magnetic resonance imaging, neurological status, patient complaints, and surgical complications.

Complete tumor removal was achieved in 98% of patients. Anatomical preservation of the facial nerve was possible in 98.5% of patients. In patients treated for tumors with extension Classes T1, T2, and T3, the rate of facial nerve preservation was 100%. By the last follow-up examination, excellent or good facial nerve function had been achieved in 81% of the cases. By at least 1 year postsurgery, no patients had total facial palsy. In the patients with preserved hearing, the rate of anatomical preservation of the cochlear nerve was 84%. The overall rate of functional hearing preservation was 51%. There was no surgery-related permanent morbidity in this series of patients. Cerebrospinal fluid leakage was diagnosed in 2% of the patients. The mortality rate was 0%.

Conclusions

The goal of VS treatment should be total removal in one stage and preservation of neurological function, as they determine a patient’s quality of life. This goal can be safely and successfully achieved using the retrosigmoid approach.

Avoiding facial nerve injuries in rhytidectomy. Anatomical variations and pitfalls

Injury to the facial nerve in rhytidectomy has been occurring in less than one percent of the cases, and a spontaneous return of function in more than 80 percent of these injuries has resulted within 6 months. With the introduction of the newer and more aggressive techniques of platysmal and subplatysmal flaps and SMAS dissections, the risk of injury to facial nerve branches is obviously increased. Though there has not yet been an increase in the facial nerve injuries reported, these techniques are still relatively recent additions to the face-lift operation-and usually they have been done by more experienced surgeons, taking more time and working under direct vision with a more careful dissection. More care is needed to prevent injuries. We discuss here the detailed anatomy of the muscular branches of the facial nerve, how to prevent injuries to them during rhytidectomy, and how to manage injuries when they do occur.

Preservation of hearing and facial nerve function in resection of acoustic neuroma

The surgical results in 78 recent cases of total removal of unilateral acoustic neuroma in which an attempt was made to preserve cochlear function have been added to the authors' previous series of 66 cases to evaluate the factors influencing the ability to preserve useful hearing. Useful hearing was defined by speech reception threshold no poorer than 70 dB and a discrimination score of at least 15%. Analysis using a logistic regression model showed that certain preoperative clinical parameters such as tumor size, speech discrimination score, and gender were significantly correlated with hearing outcome. Favorable outcome was significantly correlated with smaller tumor size, higher preoperative speech discrimination score, and male sex. From this data, an explicit formula was devised for predicting hearing outcome for an individual patient. In four cases with useful hearing preserved, there was improvement of greater than 15 percentage points in speech discrimination scores. While preoperative auditory brainstem responses were not predictive of hearing preservation, monitoring of intraoperative auditory evoked potentials was predictive of hearing outcome in selected cases. Specifically, when wave V was unchanged at the end of the operation, even if it may have been transiently lost during surgery, useful hearing was invariably preserved.

Improved preservation of facial nerve function with use of electrical monitoring during removal of acoustic neuromas

Continuous spontaneous electromyographic activity and responses to electrical stimulation of the facial nerve in the surgical field were monitored in 48 patients undergoing primary removal of an acoustic neuroma. The operative and postoperative results in these patients were compared with the results in 48 patients who were matched for age and size of tumor and who underwent the same surgical procedure without intraoperative monitoring. Eighty-three percent of the patients had preoperative evidence of facial neuropathy, which was more severe with larger tumors. Postoperative facial nerve function was most accurately predicted on the basis of the extent of facial neuropathy on preoperative electrophysiologic testing. Anatomic preservation of the facial nerve in patients with large tumors was substantially improved in the monitored patients (67%) in comparison with those without monitoring (33%). No difference was noted in facial nerve function in the two groups of patients immediately postoperatively. By 3 months, the degree of improvement in the monitored group exceeded that in those who were not monitored, particularly in patients with medium-sized and large tumors.

Radiosurgery for acoustic neuromas: results of low-dose treatment

OBJECTIVE

The results of radiosurgical treatment of acoustic neuromas have improved by reducing the tumor marginal doses. We report relatively long-term follow-up results (>5 yr) for patients who underwent low-dose radiosurgery.

METHODS

We treated and followed 51 consecutive patients with unilateral acoustic neuromas who were treated from January 1994 to December 1996 by gamma knife radiosurgery at low doses (</=12 Gy to the tumor margin). The average age of the patients was 55 years (range, 32-76 yr). The treatment volume was 0.7 to 24.9 cm(3) (median, 3.6 cm(3)). The marginal radiation dose was 8 to 12 Gy (median, 12 Gy), and the follow-up period ranged from 18 to 96 months (median, 60 mo).

RESULTS

Clinical tumor growth control (without tumor resection) was achieved in 96% of patients, and the 5-year tumor growth control rate was 92%. Hearing was preserved in 59% of those with preradiosurgical hearing preservation (Gardner-Robertson Classes 1-4), and improvements (>20 dB of improvement) were noted in 9% of the patients with any hearing. Hearing was preserved at a useful level (Gardner-Robertson Classes 1 and 2) in 56% of patients. Although preexisting trigeminal neuropathy worsened in 4% of the patients, our patients did not experience new facial palsies or trigeminal neuropathies after radiosurgery. Facial spasm occurred in 6% of the patients, and intratumoral bleeding occurred in 4% of patients.

CONCLUSION

Low-dose radiosurgery (</=12 Gy at the tumor margin) can achieve a high tumor growth control rate and maintain low postradiosurgical morbidity (including hearing preservation) for acoustic neuromas.

Viral infections of the CNS with special emphasis on herpes simplex infections

Within the past decade the management of acute HSV I encephalitis has been improved dramatically by the advent of the polymerase chain reaction (PCR), a method which has become the gold standard of diagnosis of HSV I encephalitis, replacing diagnostic uncertainties and, avoiding, in particular, invasive brain biopsy. Early detection of HSV II in the neonate is mandatory; however, prevention by Caesarean section and/or prenatal therapy of the mother are for this the best option. Very recently the causative agent of Mollaret's meningitis has proved to be, at least in part, HSV I or II. So far prospective randomized therapeutic trials are awaited for the treatment of Mollaret's meningitis using intravenous acyclovir or the more modern oral forms of virostatics (famciclovir, valaciclovir). For decades the causative agent of facial palsy (Bell's palsy) has been sought; only with the advent of PCR has this question been answered. Although one single study indicates the superiority of a combination of acyclovir plus prednisone, this finding has to be confirmed by a large scale prospective randomised double blind study. Nevertheless, if other causes for the clinical/neurological syndrome of peripheral facial palsy have been excluded, a combination therapy with acyclovir plus prednisone seems to be indicated in a patient with Bell's palsy.

Resection of large vestibular schwannomas: facial nerve preservation in the context of surgical approach and patient-assessed outcome

Object. Vestibular schwannoma surgery has evolved as new therapeutic options have emerged, patients' expectations have risen, and the psychological effect of facial nerve paralysis has been studied. For large vestibular schwannomas for which extirpation is the primary therapy, the goals remain complete tumor resection and maintenance of normal neurological function. Improved microsurgical techniques and intraoperative facial nerve monitoring have decreased the complication rate and increased the likelihood of normal to near-normal postoperative facial function. Nevertheless, the impairment most frequently reported by patients as an adverse effect of surgery continues to be facial nerve paralysis. In addition, patient assessment has provided a different, less optimistic view of outcome. The authors evaluated the extent of facial function, timing of facial nerve recovery, patients' perceptions of this recovery and function, and the prognostic value of intraoperative facial nerve monitoring following resection of large vestibular schwannomas; they then analyzed these results with respect to different surgical approaches.

Methods. The authors retrospectively reviewed a database of 67 patients with 71 vestibular schwannomas measuring 3 cm or larger in diameter. The patients had undergone surgery via translabyrinthine, retrosigmoid, or combined approaches. Clinical outcomes were analyzed with respect to intraoperative facial nerve activity, responses to intraoperative stimulation, and time course of recovery.

Eighty percent of patients obtained normal to near-normal facial function (House—Brackmann Grades I and II). Patients' perceptions of facial nerve function and recovery correlated well with the clinical observations.

Conclusions. Trends in the data lead the authors to suggest that a retrosigmoid exposure, alone or in combination with a translabyrinthine approach, offers the best chance of facial nerve preservation in patients with large vestibular schwannomas.

Preservation of facial, cochlear, and other nerve functions in acoustic neuroma treatment

Between March 1966 and September 1992, 1400 acoustic neuromas were treated in Paris, France, by surgical excision. The findings over the last 7 years are presented. The translabyrinthine approach has been used in more than 85% of cases. Where hearing preservation is attempted, the middle fossa approach has been adapted for intracanilicular tumors and the retrosigmoid approach for small tumors extending into the cerebellopontine angle, in which the fundus of the internal meatus is free of tumor. The main goal is to achieve a grade I or II result in facial function within 1 month of surgery. Results improved during 1991 after the introduction of continuous facial nerve monitoring and the use of the Beaver mini-blade for dissection of tumor from nerve. With these techniques, facial function of grade I or II at 1 month improved from 20% to 52% for large tumors (larger than 3 cm), from 42% to 81% for medium tumors (2 to 3 cm). and from 70% to 92% for small tumors (up to and including 2 cm extracanalicular). The facial nerve was at greater risk using the retrosigmoid or middle fossa approaches than by the translabyrinthine route. Since 1985, success in hearing preservation has changed little, with useful hearing being preserved in 38.2% of cases operated on by means of the retrosigmoid route and a 36.4% of cases after the middle fossa approach. In older patients with good hearing and small tumors, observation with periodic MRI scanning is recommended. Despite earlier diagnosis, the number of patients suitable for hearing preservation surgery remains very limited and careful selection is required. Trigeminal nerve signs were present in 20% of cases preoperatively, in 10% postoperatively, and recovered spontaneously. Palsies of the other cranial nerves after surgery were much rarer and were as follows: sixth nerve (abducens), 0.5%; ninth nerve (glossopharyngeal), 1.4%; and tenth nerve (vagus), 0.7%. The importance of preservation of function of the nervus intermedius of Wrisberg is stressed. These results emphasize the advantages of the translabyrinthine approach, offering greater security to the facial nerve and lower morbidity.

Hearing Preservation and Facial Nerve Outcomes in Vestibular Schwannoma Surgery: Results Using the Middle Cranial Fossa Approach

OBJECTIVE

To evaluate surgical results using the middle cranial fossa approach for hearing preservation vestibular schwannoma surgery.

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary referral academic center.

PATIENTS

Seventy-three consecutive patients with vestibular schwannoma operated on using the middle cranial fossa approach between February 1999 and February 2005.

INTERVENTIONS

The tumors were removed via the middle cranial fossa approach with modifications to improve exposure. Standard auditory brainstem and facial nerve monitoring were used.

MAIN OUTCOME MEASURES

Pre- and postoperative hearing measures and facial function, tumor size, and postoperative complications. Hearing status was categorized into Classes A, B, C, and D as described by the American Academy of Otolaryngology-Head and Heck Surgery "Guidelines for the Evaluation of Hearing Preservation in Acoustic Neuroma, 1995."

RESULTS

Thirty-four patients presented with Class A hearing preoperatively. Among patients presenting with Class A hearing, a total of 27 (80%) maintained Class A or B hearing postoperatively. Of these, 21 (62%) remained in Class A, 6 (18%) deteriorated slightly to Class B, and 7 (20%) deteriorated to Class D postoperatively. Twenty-eight patients presented with Class B hearing preoperatively. Of these, 18 (64%) remained in Class B, 3 (11%) deteriorated to Class C, and 7 (25%) deteriorated to Class D. Three patients had Class C hearing preoperatively. Of these, 2 (66%) remained in Class C and 1 (33%) deteriorated to Class D. Eight patients presented in Class D and one of these improved to Class C postoperatively. Overall, 62 patients presented with useful (Class A or B) hearing and 45 (73%) remained in Class A or B. Nineteen patients had tumors larger than 10 mm in greatest dimension and had Class A or B hearing preoperatively. Of these, 11 (58%) retained Class A or B hearing postoperatively. At 4 months or greater follow-up, facial nerve outcome were excellent in 96%: House-Brackmann Grade I in 61 (85%), Grade II in 8 (11%), and Grade III in 3 (4%). There were no Grade IV, V, or VI results on final follow-up. Six (8%) patients developed cerebrospinal fluid leaks.

CONCLUSION

By achieving excellent exposure and using meticulous microsurgical technique, it is possible to resect small vestibular schwannomas via the middle fossa approach, with preservation of hearing at excellent or preoperative levels in the majority of patients, with excellent or satisfactory facial nerve outcomes in 96% of patients.

Clinical outcome of continuous facial nerve monitoring during primary parotidectomy

OBJECTIVES

To assess whether continuous facial nerve monitoring during parotidectomy is associated with a lower incidence of facial nerve paresis or paralysis compared with parotidectomy without monitoring and to assess the cost of such monitoring.

DESIGN

A retrospective analysis of outcomes for patients who underwent parotidectomy with or without continuous facial nerve monitoring.

SETTING

University medical center.

PATIENTS

Fifty-six patients undergoing parotidectomy in whom continuous electromyographic monitoring was used and 61 patients in whom it was not used.

MAIN OUTCOME MEASURES

(1) The incidence of early and persistent facial nerve paresis or paralysis and (2) the cost associated with facial nerve monitoring.

RESULTS

Early, unintentional facial weakness was significantly lower in the group monitored by electromyograpy (43.6%) than in the unmonitored group (62.3%) (P=.04). In the subgroup of patients without comorbid conditions or surgeries, early weakness in the monitored group (33.3%) remained statistically lower than the rate of early weakness in the unmonitored group (57.5%) (P=.03). There was no statistical difference in the final facial nerve function or incidence of permanent nerve injury between the groups or subgroups. After multivariate analysis, nonmonitored status (odds ratio [OR], 3.22), advancing age (OR, 1.47 per 10 years), and longer operative times (OR, 1.3 per hour) were the only significant independent predictive variables significantly associated with early postoperative facial weakness. The incremental cost of facial nerve monitoring was $379.

CONCLUSIONS

The results suggest that continuous electromyographic monitoring of facial muscle during primary parotidectomy reduces the incidence of short-term postoperative facial paresis. Advantages and disadvantages of this technique need to be considered together with the additional costs in deciding whether routine use of continuous monitoring is a useful, cost-effective adjunct to parotid surgery.

Train time as a quantitative electromyographic parameter for facial nerve function in patients undergoing surgery for vestibular schwannoma

Object

The authors describe a quantitative electromyographic (EMG) parameter for intraoperative monitoring of facial nerve function during vestibular schwannoma removal. This parameter is based on the automated detection of A trains, an EMG pattern that is known to be associated with postoperative facial nerve paresis.

Methods

For this study, 40 patients were examined. During the entire operative procedure, free-running EMG signals were recorded in muscles targeted by the facial nerve. A software program specifically designed for this purpose was used to analyze these continuous recordings offline. By automatically adding up time intervals during which A trains occurred, a quantitative parameter was calculated, which was named “train time.”

A strong correlation between the length of train time (measured in seconds) and deterioration of postoperative facial nerve function was demonstrated. Certain consecutive safety thresholds at 0.5 and 10 seconds were defined. Their transgression reliably indicated postoperative facial nerve paresis. At less than a 10-second train time, discrete worsening, and at more than 10 seconds, profound deterioration of facial nerve function can be anticipated.

Conclusions

Train time as a quantitative parameter was shown to be a reliable indicator of facial nerve paresis after surgery for vestibular schwannoma.

Recurrent pleomorphic adenoma of the parotid gland

BACKGROUND

Surgery of recurrent pleomorphic adenoma presents an increased risk of facial nerve injury and a considerable re-recurrence rate.

METHODS

A series of 33 patients with first recurrence of pleomorphic adenoma of the parotid gland was analyzed. The data were derived from medical records as well as from interviews and clinical examinations of all living patients. Histologic material of the initial and recurrent tumor were reviewed.

RESULTS

Multifocal recurrence and carcinoma in pleomorphic adenoma were observed in 73% and 9% of patients, respectively. The incidence of permanent partial facial nerve injury after surgery was 23% in patients with initial enucleation and 14% in those with initial superficial parotidectomy (including 1 patient with facial nerve resection and 1 patient with a partial facial paresis before recurrence surgery). A subsequent recurrence occurred in 6 patients, all with initial enucleation after a mean time interval of 9 years.

CONCLUSIONS

The preservation of the facial nerve was possible in all but 1 patient treated for the first recurrence with a relatively low rate of permanent partial facial paresis because of the use of the operating microscope and facial nerve monitor. To evaluate the re-recurrence rate, a follow-up of at least 10 years is necessary.

Facial nerve monitoring during acoustic neuroma removal

As the surgeon's ability to perform total acoustic tumor removal without major neurologic deficit has reached a pinnacle, preservation of facial nerve function has assumed a higher priority. Satisfactory postoperative facial function depends upon an anatomically and physiologically intact facial nerve. Precise localization of the facial nerve is the first step toward preservation of function. Intraoperative facial nerve (FN) stimulation allows the surgeon to safely locate the facial nerve. Monitoring evoked electromyographic activity with an audio speaker provides direct, ongoing information regarding trauma to the nerve during dissection. Intraoperative FN monitoring was used in 18 consecutive translabyrinthine acoustic tumor removals. Seventeen patients had an excellent facial nerve result (Grade I or II using the House 6-point scale). The authors conclude that intraoperative FN stimulation and monitoring during acoustic tumor removal is a safe and reliable method of locating and protecting the facial nerve during cerebellopontine angle surgery.

Continuous Facial Nerve Monitoring during Pleomorphic Adenoma Recurrence Surgery

OBJECTIVES

Surgery of recurrent pleomorphic adenoma (RPA) is known to lead to a high facial nerve complication rate. The efficacy of the continuous facial nerve monitoring (CFNM) technique remains to be proven in RPA surgery. The goal was thus to evaluate facial nerve palsy rates and the recovery period after parotidectomy for RPA using CFNM by way of continuous electromyography and to compare these rates and the operation time with those of patients who had undergone surgery without facial nerve monitoring.

DESIGN

Cohort study.

PATIENTS

Forty-seven patients were referred for RPA (1981-2003). Among them, 32 (18 unmonitored and 14 monitored) patients displayed no preoperative facial palsy, and histologic analyses revealed evidence of recurrence. The operation time and the extent and duration of postoperative facial nerve palsy were examined in both groups (monitored vs. unmonitored). Both groups had a similar clinical appearance distribution.

RESULTS

Facial nerve paralysis was estimated using the House-Brackmann grading scale. CFNM reduced the intensity of facial nerve paralysis independently of the kind of surgery performed. The complete deficit rates were 0% for the monitored group and 5.6% for the unmonitored group. Postoperative facial nerve paralysis was significantly lower (P = .01) in the monitored group than in the unmonitored group. CFNM improved the duration of facial paralysis (P = .001) in the monitored group. The operation time was significantly lower in the monitored group than in the unmonitored group (P = .001).

CONCLUSIONS

Routine use of CFNM during RPA surgery improves the surgical outcome. The facial nerve deficit can be reduced, and the recovery of facial nerve function is faster.

Temporoparietal fascia flaps and superficial musculoaponeurotic system plication in parotid surgery reduces Frey's syndrome

PURPOSE

The purpose of this retrospective study was to evaluate the incidence of Frey's syndrome after parotid gland surgery with elevation of a skin flap versus the interposition of musculoaponeurotic tissue between the skin and the facial nerve.

MATERIALS AND METHODS

The standard skin flap was used in 122 patients (1981 to 1989), whereas interposition of temporoparietal galea or superficial musculoaponeurotic system was performed in 146 consecutive patients (1989 to 1998).

RESULTS

The incidence of Frey's syndrome was reduced from 33% to 4% with the use of a musculoaponeurotic layer, and the mean duration of postoperative facial nerve paresis decreased from 3 months to 6 weeks.

CONCLUSIONS

Consideration should be given to the use of an interpositional layer of tissue between the facial nerve and the skin flap to reduce the incidence of Frey's syndrome after parotid gland surgery.

The long-term growth rate of residual acoustic neurinomas

The growth rate of 19 residual acoustic neurinomas was examined in a long-term follow-up study (median, 10 years; range, 5 to 17 years) following intracapsular removal. Of these, 10 (53%) had regrowth, three (16%) showed regression, and six (32%) were unchanged. The 10 acoustic neurinomas showing regrowth were divided into two categories, either solid or cystic, according to computed tomographic findings. Five acoustic neurinomas with cyst formation showed rapid regrowth, with the tumour doubling time ranging from 0.15 to 5.0 years (median, 4.5 years), and required re-operation. Five solid tumours showed slow regrowth, with the tumour doubling time ranging from 9 to 34 years (median, 15 years). Although cyst formation is a major factor in rapid regrowth, residual acoustic neurinomas without cyst formation have a slower growth potential. In this study, 74% of the residual acoustic neurinomas have never required re-operation. It is advisable to choose intracapsular removal if there is major risk of neurological deficits.

Anterior clinoidectomy and opening of the internal auditory canal using an ultrasonic bone curette

OBJECTIVE

During cranial base surgery, use of a high-speed drill for osteotomy has become common. We performed anterior clinoidectomy and opening of the internal auditory canal using an ultrasonic bone curette, and we report the advantages and clinical applications of this method.

DESCRIPTION OF INSTRUMENTATION

The ultrasonic surgical equipment comprises a power supply unit, footswitch, and handpiece (weight, 110 g; diameter, 20 mm; length, 140 mm from tip to angled section). The handpiece tip is 2 mm wide, and the amplitude of longitudinal vibration can be varied from 120 to 365 microm at an ultrasonic frequency of 25 kHz. Cool-controlled irrigation fluid emerges near the tip, through the sheath.

EXPERIENCE AND RESULTS

We performed anterior clinoidectomy in eight cases of paraclinoid aneurysm and opening of the internal auditory canal in six cases of acoustic neuroma without damage to the dura mater or nearby structures such as brain tissue, blood vessels, and cranial nerves. In addition, no damage to the facial nerve or labyrinthine organ resulted from heat or vibration caused by the ultrasonic bone curette.

CONCLUSION

Ultrasonic bone curettage represents safe instrumentation for performance of anterior clinoidectomy and opening of the internal auditory canal without damage to surrounding structures. This technique allows surgeons to perform procedures on deep areas without incurring psychomotor stress.

Landmarks of the facial nerve: implications for parotidectomy

Facial nerve paralysis is a daunting potential complication of parotid surgery and is widely reported. Knowledge of the key landmarks of the facial nerve trunk is essential for safe and effective surgical intervention in the region of the parotid gland. In current practice, wide ranges of landmarks are used to identify the facial nerve trunk, however, there is much debate in the literature about the safety and reliability of each of these landmarks. The aim of this study, therefore, was to evaluate the relation of the surrounding anatomical structures and surgical landmarks to the facial nerve trunk. The anatomical relationship of the facial nerve trunk to the surrounding structures was determined after micro-dissection on 40 adult cadavers. The shortest distances between the facial nerve and the "tragal pointer", attachment of the posterior belly of digastric muscle, tympanomastoid suture, external auditory canal, transverse process of the axis, angle of the mandible and the styloid process were measured. In addition, these distances were compared in the right and left sides, males and females and edentulous and non-edentulous mandibles. The distance of the facial nerve trunk from each of the surrounding landmarks ranged from (mm): tragal pointer, 24.3 to 49.2 (mean 34); posterior belly of digastric, 9.7 to 24.3 (mean 14.6); external auditory canal, 7.3 to 21.9 (mean 13.4); tympanomastoid suture, 4.9 to 18.6 (mean 10.0); styloid process, 4.3 to 18.6 (mean 9.8); transverse process of the axis, 9.7 to 36.8 (mean 16.9); angle of the mandible, 25.3 to 48.69 (mean 38.1). The length of the facial nerve trunk from its point of exit from the stylomastoid foramen to its bifurcation into upper and lower divisions ranged from (mm) 8.6 to 22.8 (mean 14.0). The results demonstrated that the posterior belly of digastric, tragal pointer and transverse process of the axis are consistent landmarks to the facial nerve trunk. However, it should be noted that the tragal pointer is cartilaginous, mobile, asymmetrical and has a blunt, irregular tip. This study advocates the use of the transverse process of the axis as it is easily palpated, does not require a complex dissection and ensures minimum risk of injury to the facial nerve trunk.

Continuous intraoperative electromyographic monitoring of cranial nerves during resection of fourth ventricular tumors in children

The authors reviewed the results of continuous intraoperative electromyographic (EMG) monitoring of muscles innervated by cranial nerves in 17 children whose preoperative imaging studies showed compression or infiltration of the fourth ventricular floor by tumor to determine how intraoperative EMG activity correlated with postoperative cranial nerve morbidity. Bilateral lateral rectus (sixth) and facial (seventh) nerve musculatures were monitored in all children. Cranial nerve function was documented immediately postoperatively and at 1 year. Of the 68 nerves monitored, nine new neuropathies occurred in six children (sixth nerve in four children and seventh nerve in five). In five new neuropathies, intraoperative EMG activity could be correlated in one of four sixth nerve injuries and four of five seventh nerve injuries. Electromyographic activity could not be correlated in four children with new neuropathies. Of 59 cranial nerves monitored that remained unchanged, 47 had no EMG activity. Twelve cranial nerves (three sixth nerves and nine seventh nerves) had EMG activity but no deficit. Of four children with lateral rectus EMG activity, three had new seventh nerve injuries. Lateral rectus EMG activity did not predict postoperative abducens injury. The absence of lateral rectus EMG activity did not assure preserved abducens function postoperatively. Likely because of the close apposition of the intrapontine facial nerve to the abducens nucleus, lateral rectus EMG activity was highly predictive of seventh nerve injury. Although facial muscle EMG activity was not an absolute predictor of postoperative facial nerve dysfunction, the presence of facial muscle EMG activity was associated statistically with postoperative facial paresis. The absence of facial muscle EMG activity was rarely associated with facial nerve injury. The authors speculate that EMG activity in the facial muscles may have provided important intraoperative information to the surgeon so as to avoid facial nerve injury.

Factors which influence the facial nerve outcome in vestibular schwannoma surgery

A series of 276 patients with a unilateral vestibular schwannoma has been analysed with respect to the factors affecting post-operative facial nerve outcome. Age, tumour size, operative approach and the use of intra-operative facial nerve monitoring have been examined. The tumours were removed via either a translabyrinthine or a retrosigmoid approach. In this series increasing age and increasing tumour size were associated with a worse facial nerve outcome. The use of intra-operative facial nerve monitoring and the retrosigmoid approach were both associated with a better facial nerve outcome. Those patients having a retrosigmoid approach had a facial nerve result that was over one House grade better than those having translabyrinthine tumour removal.

Modified transotic approach to the cerebellopontile angle

A modification of the transotic approach to the cerebellopontile angle involves complete removal of the otic capsule bone, obliteration of the middle ear cleft, and removal of the posterior external auditory canal wall, while leaving the fallopian canal intact. The major advantage of this technique is that it allows more direct visualization of the most vulnerable portion of the facial nerve medial to the anterior wall of the internal auditory canal during acoustic tumor removal.

Continuous intraoperative facial nerve monitoring in predicting postoperative injury during parotidectomy

OBJECTIVES/HYPOTHESIS

To assess whether the use of continuous intraoperative facial nerve monitoring correlates to postoperative facial nerve injury during parotidectomy.

STUDY DESIGN

A retrospective analysis.

METHODS

Forty-five consecutive parotidectomies were performed using an electromyograph (EMG)-based intraoperative facial nerve monitor. Of those, 37 had complete data for analysis. Intraoperative findings and final interpretation of the EMGs were analyzed by a senior neurologist and neurophysiologist. All patients were analyzed, including those with preoperative weakness and facial nerve sacrifice.

RESULTS

The overall incidence of facial paralysis (House-Brackmann scale > 1) was 43% for temporary and 22% for permanent deficits. This includes an 11% incidence of preoperative weakness and 14% with intraoperative sacrifice. An abnormal EMG occurred in only 16% of cases and was not significantly associated with permanent or temporary facial nerve paralysis (chi, P < 1.0; Fisher's exact P < .68). Of the eight patients with permanent paralysis, only two had abnormalities on the facial nerve monitor. Also, only one of five patients with intraoperative sacrifice of the facial nerve had an abnormal EMG. Factors significantly associated with the incidence of facial paralysis include malignancy, advanced age, extent of parotidectomy, and dissection beyond the parotid gland (chi and Fisher's, P < .05).

CONCLUSIONS

The results suggest that abnormalities on the intraoperative continuous facial nerve monitor during parotidectomy do not predict facial nerve injury. The incidence of permanent and temporary facial nerve paralysis compare favorably with the literature given that this study includes patients with revision surgery, intraoperative sacrifice, and preoperative paralysis. Standard of care implications will be discussed.

Nimodipine-induced improved survival rate of facial motor neurons following intracranial transection of the facial nerve in the adult rat

OBJECT

Neuronal survival is an important factor in the achievement of functional restitution after peripheral nerve injuries. Intracranial tumors or trauma may cause patients to exhibit a temporary or permanent facial nerve palsy. Nimodipine, which acts as an antagonist to L-type voltage-gated calcium channels, has been shown to be neuroprotective in various lesion models of the central and peripheral nervous systems. The aim of the present study was to evaluate the effect of nimodipine on motor neuron survival in the facial motor nucleus following intracranial transection of the adult rat facial nerve.

METHODS

The facial nerve was cut intracranially in the posterior cranial fossa. Nimodipine was administered orally preoperatively for 3 days and postoperatively for up to 1 month, after which the number of neuronal profiles was quantified. The glial reaction was studied in the facial nucleus for up to 1 month by using immunocytochemical analysis. There was a significantly larger proportion of surviving motor neurons 1 month postinjury in animals treated with nimodipine (61+/-6.7%) in comparison with untreated animals (26.8+/-11.3%). Immunocytochemical analysis showed an increase in the amount of OX42 (microglia), ED1 (macrophages), and anti-glial fibrillary acidic protein (astrocytes) ipsilateral to the nerve injury; however, there was no difference between the two experimental groups of animals 2 to 28 days after surgery.

CONCLUSIONS

The authors propose a neuroprotective role for nimodipine, which may be useful as a "cranial nerve protective agent" following insults such as head injury or skull base surgery.