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

Intraoperative neurophysiological monitoring in vestibular schwannoma surgery: advances and clinical implications

OBJECT

Intraoperative neurophysiological monitoring has become an integral part of vestibular schwannoma surgery. The aim of this article was to review the different techniques of intraoperative neurophysiological monitoring in vestibular schwannoma surgery, identify the clinical impact of certain pathognomonic patterns on postoperative outcomes of facial nerve function and hearing preservation, and highlight the role of postoperative medications in improving delayed cranial nerve dysfunction in the different reported series.

METHODS

The authors performed a review of the literature regarding intraoperative monitoring in acoustic/vestibular schwannoma surgery. The different clinical series representing different monitoring techniques were reviewed. All the data from clinical series were analyzed in a comprehensive and comparative model.

RESULTS

Intraoperative brainstem auditory evoked potential monitoring, direct cochlear nerve action potential monitoring, and facial nerve electromyography are the main tools used to assess the functional integrity of an anatomically intact cranial nerve. The identification of pathognomonic brainstem auditory evoked potential and electromyography patterns has been correlated with postoperative functional outcome. Recently, perioperative administration of intravenous hydroxyethyl starch and nimodipine as vasoactive and neuroprotective agents was shown to improve vestibular schwannoma functional outcome in few reported studies.

CONCLUSIONS

Recent advances in electrophysiological technology have considerably contributed to improvement in functional outcome of vestibular neuroma surgery in terms of hearing preservation and facial nerve paresis. Perioperative intravenous nimodipine and hydroxyethyl starch may be valuable additions to surgery.

Surgery for large vestibular schwannoma: residual tumor and outcome

OBJECTIVE

To evaluate clinical outcome with regard to the amount of residual tumor after surgery for large vestibular schwannoma.

PATIENTS

Between January 2000 and December 2005, 51 large vestibular schwannoma tumors with extrameatal diameter of 2.6 cm or greater (mean, 32 mm; median, 30 mm; range, 26-50 mm) were operated using the translabyrinthine approach. The extent of the resection was intraoperatively estimated as complete, near, and subtotal. The amount of residual tumor was measured, and the shape and localization was scored on gadolinium-enhanced magnetic resonance imaging (MRI). Correlation between intraoperative and MRI assessment was performed using the Fisher's exact test. Potential growth of residual tumor was documented with frequent MRI follow-up. Postoperative facial nerve function was classified according to the House-Brackmann classification.

RESULTS

Complete resection was performed in 26% of the patients, near-total resection in 58%, and subtotal resection in 16%. Magnetic resonance imaging showed residual tumor in 46% of patients (mean, 16.7 mm; SD, +/-8, range, 5-36 mm). Postoperative facial nerve function was House-Brackmann Grades I to II in 78% of the patients. The intraoperative assessment of near-total resection did not correlate with postoperative MRI (p = 0.25). Postoperative MRI showed either no residual tumor or residue that should actually have been classified as a subtotal resection. After a follow-up of 4 years (49 mo; mean, 48 mo), 94% of patients did not show changes on MRI.

CONCLUSION

Tumor control with good facial nerve function could be obtained in most patients. Intraoperative assessment did not correlate with the amount of residual tumor on postoperative MRI. Objective documentation with postoperative MRI to measure the extent of removal is therefore mandatory.

Diagnosis and therapy of vestibular schwannoma

MRI studies are of paramount importance for diagnosis and follow-up measurements during conservative and postinterventional management of vestibular schwannomas (VS). MRI findings that convey important information for hearing-preservation VS surgery are: length of tumor-cochlear nerve contact, involvement of the internal auditory canal, incomplete filling of internal auditory canal, tumor size less than 15 mm and the intralabyrinthine signal intensity on 3DFT-CISS gradient-echo images. Functional neuro-otologic studies of facial nerve function, hearing and vestibular/balance function provide a valuable means of assessment of the actual impairment of the functional status of the VS patient. Intraoperative monitoring of facial nerve function and hearing has been refined, resulting in improved final postoperative facial nerve and hearing outcomes in VS patients treated with microsurgery. Long-term results reported by teams practicing stereotactic radiosurgery or fractionated stereotactic radiotherapy have been very encouraging. On the other hand, conservative management appears to be a viable option for a select group of VS patients. The refinement of surgical technique has rendered surgery safer and less invasive, resulting in better functional outcomes. Steroid use is currently used postinterventionally to improve final hearing outcome, although with questionable effectiveness. Physical rehabilitation programs are applied to accelerate vestibular functional recovery postoperatively and there is weak evidence that early physical rehabilitation may improve the final facial nerve outcome. Quality-of-life measures have emerged as important determinants of final therapeutic decision-making. More studies with high levels of evidence are needed to support clinical decisions.

Vestibular schwannoma: surgery or gamma knife radiosurgery? A prospective, nonrandomized study

OBJECTIVE

To conduct a prospective, open, nonrandomized study of treatment-associated morbidity in patients undergoing microsurgery or gamma knife radiosurgery (GKRS) for vestibular schwannomas.

METHODS

Ninety-one patients with vestibular schwannomas with a maximum tumor diameter of 25 mm in the cerebellopontine angle were treated according to a prospective protocol either by GKRS (63 patients) or open microsurgery (28 patients) using the suboccipital approach. Primary end points included hearing function, according to the Gardner-Robertson scale, and facial nerve function, according to the House-Brackmann scale at 2 years. Clinical data included a balance platform test, score for tinnitus and vertigo using a visual analog scale, and working ability. Patients responded to the quality-of-life questionnaires Short-Form 36 and Glasgow Benefit Inventory.

RESULTS

Three elderly GKRS patients withdrew; all remaining patients were followed for 2 years. Both primary end points were highly significant in favor of GKRS (P < 0.001). Evidence of reduced facial nerve function (House-Brackmann grade 2 or poorer) at 2 years was found in 13 of 28 open microsurgery patients and 1 of 60 GKRS patients. Thirteen of 28 patients who underwent surgery had serviceable hearing (Gardner-Robertson grade A or B) preoperatively, but none had serviceable hearing postoperatively. Twenty-five of 60 GKRS patients had serviceable hearing before treatment, and 17 (68%) of them had serviceable hearing 2 years after treatment. The tinnitus and vertigo visual analog scale score, as well as balance platform tests, did not change significantly after treatment, and working status did not differ between the groups at 2 years. Quality of life was significantly better in the GKRS group at 2 years, based on the Glasgow Benefit Inventory questionnaire. One GKRS patient required operative treatment within the 2-year study period.

CONCLUSION

This is the second prospective study to demonstrate better facial nerve and hearing outcomes from GKRS than from open surgery for small- and medium-sized vestibular schwannomas.

Prognostic clinical and radiological parameters for immediate facial nerve function following vestibular schwannoma surgery

OBJECTIVE

The paper aims to define the parameters available before surgery which could predict immediate facial nerve function after excision of a vestibular schwannoma (VS).

METHODS

Ninety-nine patients with VS operated consecutively by a single surgeon using an identical surgical technique have been evaluated retrospectively. Data were collected regarding patients' sex, age at onset of symptoms and at surgery, initial symptoms, neurological status at presentation, early post-operative neurological status and complications. The main radiological parameters included in the study were tumour extension pattern, diameters, shape, and volume, as well as extent of bony changes of the internal auditory canal.

RESULTS

As the tumour stage and volume increase, facial nerve function is worse after surgery (p < 0.001 and p < 0.05, respectively). Concomitantly, larger extra-meatal tumour diameters in three dimensions (sagittal, coronal and axial) led to worse function (p < 0.01). Anterior and/or caudal tumour extension (p = 0.001 and p = 0.004, respectively) had more significant correlation than posterior and/or cranial extension (p = 0.022 and p = 0.353, respectively). Polycyclic VS had the worst prognosis, followed by the tumours with oval shape. The extent of intra-meatal tumour growth does not correlate with immediate facial nerve outcome. The different angles, lengths and diameters of the internal auditory channel showed no significant correlation with facial nerve outcome. Patients with headache as an initial symptom and those with gait instability and/or pre-operative poor facial nerve function had significantly worse immediate facial nerve outcome.

CONCLUSION

Our data suggests that the analysis of the radiological and neurological patient data prior to surgery could give reliable clues regarding the immediate post-operative facial nerve function.

Global assessment of outcomes after varying reinnervation techniques for patients with facial paralysis subsequent to acoustic neuroma excision

OBJECTIVE

To determine whether there are objective and/or subjective differences in facial function, tongue function and quality of life in patients who have undergone 1) direct facial-to-facial (Primary, 4 patients), 2) direct facial-to-hypoglossal (End-to-End, 7 patients), 3) end-to-side facial-to-hypoglossal nerve anastomoses with sural nerve/greater auricular nerve interposition (End-to-Side with Interposition Graft, 7 patients), and 4) end-to-side facial-to-hypoglossal nerve anastomoses (End-to-Side, 7 patients) after acoustic neuroma excision.

SETTING

Tertiary university referral center.

STUDY DESIGN

Case series.

METHODS

Twenty-five patients with complete facial paralysis after acoustic neuroma surgery who have also undergone 1 of 4 types of facial musculature reinnervation volunteered for the study. The mean duration of follow-up was 11.5 years (range, 1-25 yr). Each patient was globally assessed using the Sunnybrook Facial Grading scale (objective), Facial Disability Index (subjective), Oral-Pharyngeal Disability Index (subjective), Tongue Movement/Muscle symmetry (objective), and short-form SF-36 quality-of-life index (subjective).

RESULTS

Patients who underwent direct facial-to-hypoglossal anastomosis had generally poorer outcomes some of which were statistically significant (p < 0.05) in some components of the Oral-Pharyngeal Disability Index. All of these patients had reduced lateral tongue movement as well as ipsilateral tongue atrophy. There was no significant difference in the Sunnybrook Facial Grading scale scores in those patients in whom end-to-side interposition reinnervation surgery was performed compared with those in whom direct end-to-side anastomosis surgery was performed.

CONCLUSION

Complete sacrifice of the ipsilateral hypoglossal nerve does present with clinically and statistically significant morbidity in patients. Facial function is statistically similar in patients who underwent an end-to-side anastomosis with or without an interposition graft. These findings suggest thatin the setting of the posttranslabryinthine approach, the technicallyeasier interposition graft procedure is not acompromise.

Waterjet dissection of the vestibulocochlear nerve: an experimental study

Object

Waterjet dissection has been shown to protect intracerebral vessels, but no experience exists in applying this modality to the cranial nerves. To evaluate its potential, the authors examined waterjet dissection of the vestibulocochlear nerve in rats.

Methods

Lateral suboccipital craniectomy and microsurgical preparation of the vestibulocochlear nerve were performed in 42 rats. Water pressures of 2–10 bar were applied, and the effect was microscopically evaluated. Auditory brainstem responses (ABRs) were used to define nerve function compared with preoperative values and the healthy contralateral side. The final anatomical preparation documented the morphological and histological effects of waterjet pressure on the nerve.

Results

In using up to 6 bar, the cochlear nerve was preserved in all cases. Eight bar moderately damaged the nerve surface. A 10-bar jet markedly damaged or even completely dissected the nerve. Time course analysis of the ABR demonstrated complete functional nerve preservation up to 6 bar after 6 weeks in all rats. Waterjet dissection with 8 bar was associated with a 60% recovery of ABR. In the 10-bar group, no recovery was seen.

Conclusions

Microsurgical dissection of cranial nerves is possible using waterjet dissection while preserving both morphology and function. The aforementioned jet pressures are known to be effective in neurosurgical treatment of tumors. Thus, waterjet dissection may be useful in skull base surgery including dissection of cranial nerves from tumors. Further studies on this subject are encouraged.

Intracranial facial nerve grafting after removal of vestibular schwannoma

OBJECTIVE

The objectives of this study were to evaluate outcomes from facial nerve (FN) cable grafting in patients who experienced FN transection during vestibular schwannoma removal and to compare the FN outcomes of patients who underwent FN grafting by using fibrin glue with those of patients who underwent FN grafting by using microsuture.

MATERIAL AND METHODS

We retrospectively evaluated a series of 33 patients in whom FN grafting was achieved either by using microsuture (8 cases) or fibrin glue (25 cases). Immediate repair of the FN was performed in all cases at the time of initial resection. The patients FN function was assessed preoperatively, in the immediate postoperative period, and at 3, 6, 9, and 12 months or more postoperatively using the House-Brackmann grading system. All patients had at least 1-year follow-up.

RESULTS

At 12 months, a House-Brackmann grade III was achieved in 75% of those who underwent cable nerve graft interposition by using microsuture and in 76% of those who underwent cable nerve graft interposition by using fibrin glue. Analysis of final FN function outcomes demonstrated no statistically significant difference in FN outcomes between the 2 groups (P = .891, Mann-Whitney U test; P = .1, Fisher exact test).

CONCLUSIONS

The functional results after FN cable grafting by using fibrin glue exclusively were equivalent to those obtained with microsuture. However, the technique of FN repair by means of fibrin glue is technically simple, less time-consuming, and imparts less trauma on the nerve than does the traditional suture method.

Application accuracy of computed tomography-based, image-guided navigation of temporal bone

OBJECTIVE

Although frameless stereotactic techniques have become indispensable in neurosurgery, their technical complexity requires careful definition and evaluation. Navigation is of particular concern when it is applied to approach a complex, tight surgical area like the temporal bone, where every millimeter is important. Theoretically, the temporal bone is an ideal location in which to use image-guided navigation because its bony construct precludes pre- and intraoperative shift. In this context, the feasibility of using a navigational system is determined by the system's accuracy and by the spatial characteristics of the targets. Literature addressing the accuracy of image guidance techniques in temporal bone surgery is relatively sparse. Accuracy of these systems within the temporal bone is still under investigation. We investigated the application accuracy of computed tomography-based, frameless, image-guided navigation to identify various bony structures in the temporal bone via a retrosigmoid approach.

METHODS

In a total of 10 operations, we performed a retrosigmoid approach simulating operative conditions on either side of 5 whole, fresh cadaveric heads. Six titanium microscrews were implanted around the planned craniotomy site as permanent bone reference markers before the surgical procedure. High-resolution computed tomographic scans were obtained (slice thickness, 0.6-mm, contiguous non-overlapping slices; gantry setting, 0 degrees; scan window diameter, 225 mm; pixel size, >0.44 x 0.44). We used a Stryker navigation system (Stryker Instruments, Kalamazoo, MI) for intraoperative navigation. External and internal targets were selected for calculation of navigation accuracy.

RESULTS

The system calculated target registration error to be 0.48 +/- 0.21 mm, and the global accuracies (navigation accuracies) were calculated using external over-the-skull and internal targets within the temporal bone. Overall navigation accuracy was 0.91 +/- 0.28 mm; for reaching internal targets within temporal bone, accuracy was 0.94 +/- 0.22 mm; and for external targets, accuracy was 0.83 +/- 0.11 mm. Ninety-five percent of targets could be reached within 1.4 mm of their actual position.

CONCLUSION

Using high-resolution computed tomography and bone-implanted reference markers, frameless navigation can be as accurate as frame-based stereotaxy in providing a guide to maximize safe surgical approaches to the temporal bone. Although error-free navigation is not possible with the submillimetric accuracy required by direct anatomic contouring of tiny structures within temporal bone, it still provides a road map to maximize safe surgical exposure.

Analysis of causes for late presentation of Indian patients with vestibular schwannoma

OBJECTIVE

To determine the causes of delay in diagnosis and treatment of Indian patients with vestibular schwannomas.

METHODS

In a prospective study from 2003 to 2005, 50 patients with a confirmed diagnosis of vestibular schwannoma were interviewed to determine the causes for (1) the delay between the patient noting the initial symptom and the definitive diagnosis, and (2) the reasons for delayed diagnosis.

RESULTS

In 90 per cent of patients, the initial symptom was either hearing loss (62 per cent), vertigo (24 per cent) or tinnitus (4 per cent). However, most patients had been diagnosed and had presented for surgery only after neurological symptoms had became apparent. The delay between the initial medical consultation and the final diagnosis ranged from one month to 204 months (mean +/- standard deviation, 32.2 +/- 38.9 months). After the patient had noted symptoms, the diagnosis of vestibular schwannoma was delayed due to doctor-related causes in 80 per cent of cases, and due to patient-related causes in 20 per cent. Delay following diagnosis was minimal.

CONCLUSIONS

Delay in the diagnosis of vestibular schwannoma in Indian patients is due to both doctor- and patient-related factors.

Fat Implant is Superior to Muscle Implant in Vestibular Schwannoma Surgery for the Prevention of Cerebrospinal Fluid Fistulae

Objective:

Meticulous sealing of opened air cells in the petrous bone is necessary for the prevention of cerebrospinal fluid (CSF) fistulae after vestibular schwannoma surgery. We performed a retrospective analysis to determine whether muscle or fat tissue is superior for this purpose.

Methods:

Between January 2001 and December 2006, 420 patients underwent retrosigmoidal microsurgical removal by a standardized procedure. The opened air cells at the inner auditory canal and the mastoid bone were sealed with muscle in 283 patients and with fat tissue in 137 patients. Analysis was performed regarding the incidence of postoperative CSF fistulae and correlation with the patient's sex and tumor grade.

Results:

The rate of postoperative CSF leak after application of fat tissue was lower (2.2%) than after use of muscle (5.7%). Women had less postoperative CSF leakage (3.4%) than men (5.6%). There was an inverse correlation with tumor grade. Patients with smaller tumors seemed to have a higher rate of CSF leakage than those with large tumors without hydrocephalus. Only large tumors with severe dislocation of the brainstem causing hydrocephalus showed a higher incidence of CSF leaks.

Conclusion:

Fat implantation is superior to muscle implantation for the prevention of CSF leakage after vestibular schwannoma surgery and should, therefore, be used for the sealing of opened air cells in cranial base surgery.

The retrosigmoid intradural suprameatal approach to posterior cavernous sinus: microsurgical anatomy

OBJECTIVE

The retrosigmoid intradural suprameatal approach includes the standard retrosigmoid suboccipital route with drilling of the petrous bone above and anterior of the internal auditory meatus, allowing for exposure of the trigeminal nerve within the Meckel's cave and of the middle fossa. In this study, the authors analyzed the potential use of an extended variation of the suprameatal route to approach the posterior cavernous sinus for microsurgery of, e.g., petroclival meningiomas and trigeminal schwannomas.

METHODS

The microsurgical anatomy of the retrosigmoid suprameatal approach was examined by using 10 adult cadaveric specimens (20 sides), using 3-40x magnification. The exposure to the posterior cavernous sinus provided by this approach was focused.

RESULTS

After drilling the suprameatal tubercle toward the petrous apex, the Meckel's cave was exposed. The trochlear nerve was the landmark for opening the cavernous sinus by this approach. The dura located medially to the entry point of the trochlear nerve into the tentorium was resected, allowing exposure of the intracavernous carotid artery with its meningohypophyseal trunk.

CONCLUSION

The extended retrosigmoid intradural suprameatal approach allows exposure of the posterior cavernous sinus and may be used to remove lesions of the posterior fossa extending into the Meckel's cave and into the cavernous sinus.

Cystic acoustic neuromas: surgical outcome in a series of 58 patients

We aimed to analyze the clinical characteristics and surgical outcomes of surgically treated cystic acoustic neuromas, and to determine the prognostic significance of the presence of cystic components, by comparing surgical outcomes for solid and cystic tumors. A total of 58 patients (20.4%) with newly diagnosed cystic tumor were studied. The surgical outcome was analyzed in terms of extent of tumor removal, facial nerve preservation, morbidity and mortality; and was compared with that in patients with solid tumors. Facial nerve preservation rates were much better for solid tumors (82.7%) than for cystic tumors (67.9%). The extent of tumor removal was complete in 75.9% of patients with cystic tumors as compared with 90.2% for solid acoustic neuromas. Overall mortality was 8.6%. Cystic tumors differ from solid acoustic neuromas by having a rapid growth pattern, short clinical history and more frequent facial nerve involvement. They are associated with a poorer surgical outcome in terms of facial preservation and overall result.

Hypofractionated CyberKnife stereotactic radiosurgery for acoustic neuromas with and without association to neurofibromatosis Type 2

CyberKnife stereotactic radiosurgery (CKSRS) has been proved effective in treating intra-cranial lesions. To treat acoustic neuroma (AN) patients with or without neurofibromatosis Type 2 (NF2) associations, the functional preservation of hearing, trigeminal nerve, and facial nerve are important. Twenty-one patients were treated with hypofractionated CKSRS. Fourteen non-NF2 and seven NF2 patients were enrolled. Cranial nerve function, audiograms, and magnetic resonance images (MRI) were monitored. Mean follow-up was 15 month. Tumors with volumes ranging from 0.13 to 24.8 cm3 (mean 5.4 cm3) were irradiated with the marginal dose 1800-2000 cGy/3 fractions. Tumors were treated with an 80 to 89% isodose line (mean 83%) and mean 97.9% tumor coverage. Two patients experienced hearing deterioration (16.7%) in the non-NF2 group, and 3 patients (50%) in the NF2 group. No facial or trigeminal dysfunction, brain stem toxicity, or cerebellar edema occurred. Tumor regression was seen in 9 patients (43%) and stable in 12 patients (57%). 100% tumor control rate was achieved. Hypofractionated CKSRS was not only effective in tumor control but also excellent in hearing preservation for non-NF2 AN. But for NF2 patients, although the tumor control was remarkable, hearing preservation was modest as in non-NF2 patients.

Radiosurgery in patients with bilateral vestibular schwannomas

BACKGROUND

Patients with bilateral vestibular schwannomas offer a unique opportunity to determine the effectiveness of radiosurgery. By using the untreated tumor as an internal control, one can determine whether radiosurgery was able to interrupt the natural history of the treated tumor.

METHODS

From September 1998 to November 2004, 13 patients with neurofibromatosis type 2 had 14 tumors treated with radiosurgery at the University of Florida. A retrospective analysis was performed on these patients. Actuarial statistics were used to analyze local control in both the treated and untreated tumor.

RESULTS

The average follow-up length was 38 months. One patient failed to send a follow-up MRI. Actuarial local control in the treated tumors was 100% at 1 year and 92% at 2 and 5 years. Only 1 of the treated tumors continued to grow. In the untreated tumors, actuarial local control was 100% at 1 year, 78% at 2 years and 21% at 5 years. None of the untreated tumors decreased in size.

CONCLUSION

In all but 1 patient with follow-up data, radiosurgery successfully prevented or reversed tumor growth. Additionally, half of the untreated tumors continued to grow. This study shows that radiosurgery alters the natural history of vestibular schwannomas.

Cranial nerve preservation and outcomes after stereotactic radiosurgery for jugular foramen schwannomas

OBJECTIVE

Jugular foramen region schwannomas are rare intracranial tumors that usually present with multiple lower cranial nerve deficits. For some patients, complete surgical resection is possible but may be associated with significant morbidity. Stereotactic radiosurgery is a minimally invasive alternative or adjunct to microsurgery for such tumors. We reviewed our clinical and imaging outcomes after patients underwent gamma knife radiosurgery for management of jugular foramen schwannomas.

METHODS

Thirty-four patients with 35 tumors (one patient had bilateral tumors) underwent radiosurgery between May 1990 and December 2005. Twenty-two patients had previous microsurgical resection and all patients experienced various cranial neuropathies. A median of six isocenters were used. Median marginal and maximum doses were 14 and 28 Gy, respectively.

RESULTS

None of the patients were lost to evaluation and the mean duration of follow-up was 83 months. Tumors regressed in 17 patients, remained stable in 16, and progressed in two. Five- and 10-year actuarial control rates were 97 and 94%, respectively. Preexisting cranial neuropathies improved in 20% and remained stable in 77% after radiosurgery. One patient worsened. The function of all previous intact nerves was preserved after radiosurgery.

CONCLUSION

Stereotactic radiosurgery proved to be a safe and effective management for newly diagnosed or residual jugular foramen schwannomas. Long-term tumor control rates and stability or improvement in cranial nerve function was confirmed.

Hypoglossal-facial anastomosis

The aim of this paper was to report on further experience with a new technique for reanimation of the facial nerve. This procedure allows a straight end-to-side hypoglossal–facial anastomosis without interruption of the 12th cranial nerve or the need for graft interposition. It is technically demanding and time consuming but offers an effective, reliable, and extraordinarily quick means of reinnervating the facial muscles, including the orbicularis oculi muscle, thus avoiding the need for a gold weight in the eyelid or a fascial sling.

Preservation of function in vestibular schwannoma surgery

The management and surgical technique for microsurgical tumor removal of vestibular schwannomas (acoustic neuroma) with the suboccipital retrosigmoid approach and semi-sitting patient positioning is described. An emphasis is placed on the preservation of auditory and facial nerve function with a stepwise description of the technical and operative nuances, including presurgical evaluation, positioning, anesthesiological and neurophysiological aspects, approach, microsurgical techniques, and postsurgical care.

Long-Term Follow-up of Acoustic Schwannoma Radiosurgery With Marginal Tumor Doses of 12 to 13 Gy

PURPOSE

To define long-term tumor control and clinical outcomes of radiosurgery with marginal tumor doses of 12 to 13 Gy for unilateral acoustic schwannoma.

METHODS AND MATERIALS

A total of 216 patients with previously untreated unilateral acoustic schwannoma underwent Gamma Knife radiosurgery between 1992 and 2000 with marginal tumor doses of 12 to 13 Gy (median, 13 Gy). Median follow-up was 5.7 years (maximum, 12 years; 41 patients with >8 years). Treatment volumes were 0.08-37.5 cm(3) (median, 1.3 cm(3)).

RESULTS

The 10-year actuarial resection-free control rate was 98.3% +/- 1.0%. Three patients required tumor resection: 2 for tumor growth and 1 partial resection for an enlarging adjacent subarachnoid cyst. Among 121 hearing patients with >3 years of follow-up, crude hearing preservation rates were 71% for keeping the same Gardner-Robertson hearing level, 74% for serviceable hearing, and 95% for any testable hearing. For 25 of these patients with intracanalicular tumors, the respective rates for preserving the same Gardner-Robertson level, serviceable hearing, and testable hearing were 80%, 88%, and 96%. Ten-year actuarial rates for preserving the same Gardner-Robertson hearing levels, serviceable hearing, any testable hearing, and unchanged facial and trigeminal nerve function were 44.0% +/- 11.7%, 44.5% +/- 10.5%, 85.3% +/- 6.2%, 100%, and 94.9% +/- 1.8%, respectively.

CONCLUSIONS

Acoustic schwannoma radiosurgery with 12 to 13 Gy provides high rates of long-term tumor control and cranial nerve preservation after long-term follow-up.

The Influence of Prophylactic Vasoactive Treatment on Cochlear and Facial Nerve Functions after Vestibular Schwannoma Surgery

OBJECTIVE

Facial nerve paresis and hearing loss are common complications after vestibular schwannoma surgery. Experiments with facial nerves of the rat and retrospectively analyzed clinical studies showed a beneficial effect of vasoactive treatment on the preservation of facial and cochlear nerve functions. This prospective and open-label randomized pilot study is the first study of a prophylactic vasoactive treatment in vestibular schwannoma surgery.

METHODS

Thirty patients were randomized before surgery. One group (n = 14) received a vasoactive prophylaxis consisting of nimodipine and hydroxyethylstarch which was started the day before surgery and was continued until the seventh postoperative day. The other group (n = 16) did not receive preoperative medication. Intraoperative monitoring, including acoustic evoked potentials and continuous facial electromyelograms, was applied to all patients. However, when electrophysiological signs of a deterioration of facial or cochlear nerve function were detected in the group of patients without medication, vasoactive treatment was started immediately. Cochlear and facial nerve function were documented preoperatively, during the first 7 days postoperatively, and again after long-term observation.

RESULTS

Despite the limited number of patients, our results were significant using the Fisher's exact test (small no. of patients) for a better outcome after vestibular schwannoma surgery for both hearing (P = 0.041) and facial nerve (P = 0.045) preservation in the group of patients who received a prophylactic vasoactive treatment.

CONCLUSION

Prophylactic vasoactive treatment consisting of nimodipine and hydroxyethylstarch shows significantly better results concerning preservation of the facial and cochlear nerve function in vestibular schwannoma surgery. The prophylactic use is also superior to intraoperative vasoactive treatment.

News on the genetics, epidemiology, medical care and translational research of Schwannomas

Recent years have seen substantial news and updates in the genetics and diagnosis of schwannomas, even a new hereditary disease with schwannomas; Schwannomatosis has been defined. These developments have consequently led to better evaluation of the incidence of schwannomas. Although there has also been progress in the treatment of schwannomas especially in the field of radiation therapy, hereditary diseases with multiple tumours still represent a therapeutic dilemma. NF2 in particular still causes major morbidity and mortality owing to the neurological deficit of multiple tumour disease and deafness caused by vestibular nerve involvement. Thus there has been great enthusiasm about disease models in the hope that translational research will give rise to new therapies.

Treatment of vestibular schwannomas. Why, when and how?

Sporadic vestibular schwannoma (VS) causes unilateral hearing loss, tinnitus, vertigo and unsteadiness. In many cases, the tumour size may remain unchanged for many years following diagnosis, which is typically made by MRI. In the majority of cases the tumour is small, leaving the clinician and patient with the options of either serial scanning or active treatment by gamma knife radiosurgery (GKR) or microneurosurgery. Despite the vast number of published treatment reports, comparative studies are few, and evidence is no better than class III (May, 2006). The predominant clinical endpoints of VS treatment include tumour control, facial nerve function and hearing preservation. Less focus has been put on symptom relief and health-related quality of life (QOL). It is uncertain if treating a small tumour leaves the patient with a better chance of obtaining relief from future hearing loss, vertigo or tinnitus than by observing it without treatment. Recent data indicate that QOL is reduced in untreated VS patients, and may differ between patients who have been operated and patients treated with GKR. In the present paper we review the natural course and complaints of untreated VS patients, and the treatment alternatives and results. Furthermore, we review the literature concerning quality of life in patients with VS. Finally, we present our experience with a management strategy applied to more than 300 cases since 2001.

Ophthalmic Management of Facial Nerve Palsy: A Review

Facial nerve palsy affects individuals of all ages, races, and sexes. Psychological and functional implications of the paralysis present a devastating management problem to those afflicted, as well as the carriers. Since Sir Charles Bell's original description of facial palsy in 1821, our understanding and treatment options have expanded. It is essential that a multidisciplinary approach, encompassing ophthalmologists; Ear, Nose, and Throat surgeons; plastic surgeons; and psychologists work closely to optimize patient management in a staged approach. Although the etiology remains unknown, strong histological, cerebral spinal fluid, and radiological evidence suggests a possible association with herpes simplex virus in idiopathic facial nerve palsy (Bell's palsy). The use of steroids has been suggested as a means of limiting facial nerve damage in the acute phase. Unfortunately, no single randomized control trial has achieved an unquestionable benefit with the use of oral steroid therapy and thus remains controversial. In the acute phase, ophthalmologists play a pivotal role in preventing irreversible blindness from corneal exposure. This may be successfully achieved by using intensive lubrication, medical therapy (botulinum toxin), or surgery (upper lid weighting or tarsorraphy). Once the cornea is adequately protected and recovery deemed unlikely, longer term planning for eyelid and facial reanimation may take place in an individualized manner. Onset is sudden and management potentially lengthy. Physician empathy, knowledge, and experience are essential in averting long-term lifestyle and psychological discomfort for patients.

Cerebellopontine angle lesions in children

BACKGROUND

Cerebellopontine angle (CPA) lesions are more commonly found in adults in which they account for 5-10% of all intracranial tumors. However, they are uncommon in children, with an incidence of only 1%.

MATERIALS AND METHODS

This is a review of the management of CPA lesions in children admitted to the Hospital Nacional de Pediatría "Profesor Doctor Juan P. Garrahan" (Argentine National Pediatrics Hospital "Professor Juan P. Garrahan") between January 1988 and December 2003.

RESULTS

The series included 30 children with 33 CPA lesions, 20 arising from the subarachnoid space of the CPA and 13 from the vicinity and growing mainly into the CPA. Twenty-seven tumors were located in the left CPA (82%) and six (12%), on the right. Ten of the 30 patients developed hydrocephalus, but only three of these required treatment. All patients underwent retrosigmoid suboccipital craniotomy and microsurgical resection. Gross total removal was achieved in 12 cases, subtotal in 18, and fenestration of the cyst wall in the three arachnoid cysts. Ten patients have no sequelae, ten have mild deficit, three have severe deficits, and seven have died.

CONCLUSION

The CPA is a rare location for lesions in children, with clear predominance on the left side. Benign lesions are more frequent. Even though schwannoma is the most frequently found lesion, the histology varies widely.

Using an end-to-side interposed sural nerve graft for facial nerve reinforcement after vestibular schwannoma resection

✓ Increasing rates of facial and cochlear nerve preservation after vestibular schwannoma surgery have been achieved in the last 30 years. However, the management of a partially or completely damaged facial nerve remains an important issue. In such a case, several immediate or delayed repair techniques have been used.

On the basis of recent studies of successful end-to-side neurorrhaphy, the authors applied this technique in a patient with an anatomically preserved but partially injured facial nerve during vestibular schwannoma surgery. The authors interposed a sural nerve graft to reinforce the facial nerve whose partial anatomical continuity had been preserved. On follow-up examinations 18 months after surgery, satisfactory cosmetic results for facial nerve function were observed.

The end-to-side interposed nerve graft appears to be a reasonable alternative in cases of partial facial nerve injury, and might be a future therapeutic option for other cranial nerve injuries.

Split facial nerve course in vestibular schwannomas

Object

The facial nerve in vestibular schwannomas (VSs) is located on the ventral tumor surface in more than 90% of cases; other courses are rare. A split facial nerve course with two distinct bundles has thus far been described exclusively for medial extrameatal tumors.

Methods

Between 1996 and 2005, 16 consecutive cases of 241 surgically treated VSs were observed to have distinct splitting of the facial nerve. The mean tumor size measured 27 mm. In one third of the cases, intrameatal tumor extension with obliteration of the fundus was documented. All patients underwent extensive intraoperative neurophysiological monitoring using multichannel electromyography recordings. Patients were reevaluated 12 months after surgery.

In all 16 patients, distinct splitting of the facial nerve was demonstrated. The major portion of the facial nerve followed a typical course on the ventral tumor surface. The smaller nerve portion in all cases ran parallel to the brainstem up to the level of the trigeminal root exit zone and crossed on the cranial tumor pole to the internal auditory canal. The two nerve portions rejoined at the level of the porus acusticus. The smaller portion carried fibers exclusively to the orbicularis oris muscle, whereas the major portion supplied all three branches of the facial nerve.

Conclusions

In VSs, an aberrant course with distinct splitting of the facial nerve adds considerably to the surgical challenge. Long-term facial nerve results are excellent with extensive neurophysiological monitoring, which allows the differentiation and identification of aberrant facial nerve fibers and avoids additional risks to facial nerve preservation.

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.

Preservation of Facial Nerve Function after Postoperative Vasoactive Treatment in Vestibular Schwannoma Surgery

OBJECTIVE:

Facial nerve paresis and hearing loss are common complications after vestibular schwannoma surgery. Experimental and clinical studies point to a beneficial effect of nimodipine and hydroxyethyl starch for preservation of cochlear nerve function. A retrospective analysis was undertaken to evaluate the effect of vasoactive treatment on facial nerve outcome.

PATIENTS AND METHODS:

Forty-five patients with vestibular schwannoma removal, intraoperative electromyographic monitoring, and postoperative deterioration of facial nerve function were evaluated. Twenty-five patients underwent vasoactive treatment consisting of nimodipine and hydroxyethyl starch for improvement of hearing outcome. Twenty patients did not receive such treatment. Facial nerve function was evaluated before and after surgery, as well as 1 year after the surgical procedure. Patients were comparable regarding age, tumor size, and preoperative facial nerve function.

RESULTS:

Long-term results of facial nerve function were significantly improved in those patients who experienced severe postoperative deterioration of facial nerve function and received vasoactive treatment as compared with patients who did not receive nimodipine and hydroxyethyl starch after surgery. Treated patients showed a significantly higher rate of complete recovery compared with patients without treatment.

CONCLUSION:

The study points to a potential effect of vasoactive treatment for facial nerve function after vestibular schwannoma surgery. In particular, patients with postoperative disfiguring facial nerve palsy clearly benefit from intravenous hydroxyethyl starch and nimodipine with respect to a long-term socially acceptable facial nerve function.

Vestibular schwannoma management: What is the 'best' option?

There is an abundance of medical literature describing the management options for vestibular schwannomas. However, the lack of high quality clinical trials means that, for any individual patient, the decision is often based on the clinician's personal biases. The management options that are available are conservative treatment, surgery, single-dose stereotactic radiosurgery and fractionated radiotherapy. In this review, we set out what the aims of managing a vestibular schwannoma should be and compare how these different treatment modalities perform. The particular objectives of tumour control, cranial nerve preservation, prevention of malignancy, quality of life and cost-effectiveness are discussed. It remains difficult to differentiate between these methods when more than one is suitable; the literature confirms that they are all safe and effective, but the decision must be the patient's, based on their individual priorities. This review should equip the clinician to provide an informed overview of the options.

Facial nerve function after excision of large acoustic neuromas via the suboccipital retrosigmoid approach

We review our results for facial nerve preservation in 105 patients with large acoustic neuromas (diameter 4.0 cm or larger) undergoing excision via the suboccipital retrosigmoid approach. Microneurosurgical techniques and facial nerve monitoring were used. Complete tumor removal was achieved in 91 cases (86.7%) and subtotal removal in 14 (13.3%). There were two postoperative deaths (1.9%). The facial nerve was preserved anatomically in 83 (79.1%) patients. Using the House-Brackmann grading system, facial nerve function was assessed immediately after surgery, at the time of discharge and 1 year after surgery. Excellent function (Grades I and II) was present in 41.0%, 41.8%, and 56.7% of patients at each time interval, respectively, with acceptable function (Grade I-IV) in 78.5% (68/87 cases) at follow-up assessment at one year. The suboccipital retrosigmoid approach resulted in good anatomical and functional preservation of the facial nerve during excision of large acoustic neuromas, with minimal other morbidity and low mortality. We recommend this approach for excision of large acoustic neuromas.

Cystic acoustic neuroma

To define the clinical characteristics of cystic acoustic neuroma, we retrospectively analyzed 22 patients with cystic acoustic neuroma and reviewed the literature with regard to clinical manifestation, imaging features, diagnosis, surgical procedures and prognosis. An acoustic neuroma was defined as cystic according to the following criteria: the presence of hypodense/hypointense areas on CT or MRI, the identification of cystic elements at operation and histological verification. At the end of surgery, the facial nerve was anatomically intact in 86.4% of cystic acoustic neuromas. Complete removal of the tumor was achieved in 18 cases (81.8%). We conclude that patients with cystic acoustic neuroma need prompt surgery with special attention paid to the preservation of the facial nerve.

Nerve Regeneration through Nerve Autografts and Cold Preserved Allografts using Tacrolimus (FK506) in a Facial Paralysis Model: A Topographical and Neurophysiological Study in Monkeys

OBJECTIVE

Nerve regeneration through cold preserved nerve allografts is demonstrated, and treatment of nerve allografts with FK506 induces better regeneration than other immunosuppressants. We study nerve regeneration through cold preserved nerve allografts temporarily treated with FK506 and compare it with the regeneration obtained using classic nerve autografts in a facial paralysis model in monkeys.

METHODS

A trunk of the facial nerve on both sides was transected in eight monkeys and immediately repaired with a 3 to 4 cm nerve autograft or allograft. FK506 was administered to the animals of the allograft group for 2 months, and nerve allografts were cold preserved for 3 weeks. At periods of 3, 5, and 8 months after surgery, quantitative electrophysiological assessment and video recordings were performed. At the end of the study, quantitative analysis of neurons in the facial nucleus was carried out, and axons were stereologically counted.

RESULTS

After the regenerative period, neuronal density was higher in the autograft group. However, distal axonal counts were similar in both groups. Serial electrophysiological recordings and histology of nerve allografts showed that the grafts were partially rejected after cessation of the immunosuppressant.

CONCLUSION

The regeneration through nerve allografts temporarily treated with FK506 does not achieve the electrophysiological results and neuronal counts achieved with nerve autografts, but axonal collateralization in the allografts induces a similar activation of mimic muscles.

Long-term outcome of stereotactic radiosurgery (SRS) in patients with acoustic neuromas

PURPOSE

To evaluate the effectiveness and long-term outcome of stereotactic radiosurgery (SRS) for acoustic neuromas (AN).

PATIENTS AND METHODS

Between 1990 and 2001, we treated 26 patients with 27 AN with SRS. Two patients suffered from neurofibromatosis type 2. Before SRS, a subtotal or total resection had been performed in 3 and in 5 patients, respectively. For SRS, a median single dose of 13 Gy/80% isodose was applied.

RESULTS

The overall actuarial 5-year and 10-year tumor control probability in all patients was 91%. Two patients developed tumor progression after SRS at 36 and 48 months. Nineteen patients (73%) were at risk of treatment-related facial nerve toxicity; of these, 1 patient developed a complete facial nerve palsy after SRS (5%). A total of 93% of the lesions treated were at risk of radiation-induced trigeminal neuralgia. Two patients (8%) developed mild dysesthesia of the trigeminal nerve after SRS. The hearing preservation rate in patients with useful hearing before SRS was 55% at 9 years.

CONCLUSION

Stereotactic radiosurgery results in good local control rates of AN and the risk of cranial nerve toxicities is acceptable. As toxicity is lower with fractionated stereotactic radiotherapy, SRS should be reserved for smaller lesions.

Therapeutic strategy for large vestibular schwannomas

Management of large vestibular schwannoma (VS) remains a difficult problem for which the extent of tumor resection and the role of radiosurgery continue to be the subject of debate. To develop an optimal therapeutic strategy for large VS, various treatment options within the avenues of microsurgery and radiosurgery were evaluated and compared. The authors carefully reviewed the clinical data of 50 surgical cases of large VS, defined as tumors with an average diameter over 3 cm in magnetic resonance imaging (MRI). All patients underwent microsurgery as the primary treatment. Gross total removal (GTR) was achieved in nine patients (18%), near total removal (NTR) in 8 (16%), radical subtotal removal (R-STR) in 31 (62%), and subtotal removal (STR) in 2 (4%). Among the 33 patients with R-STR and STR, eight had undergone adjuvant radiosurgery for the residual mass. Average tumor volume and diameter were 26.8 cm(3) (13.5-55.1) and 36.4 mm (30.0-47.2), respectively. The mean follow-up duration was 113 months (58-167). The tumor control rate and facial nerve function according to the extent of removal were analyzed. The overall tumor control rate was 82%. Perfect tumor control was achieved after NTR and R-STR with adjuvant radiosurgery. However, 11% (1 of 9) of GTR patients and 32% (8 of 25) of R-STR-only and STR patients showed recurrence or regrowth. Overall favorable outcome of facial nerve function (H-B grade 1 or 2) was achieved in 78% of the patients. The facial nerve preservation rate was inversely proportional to the extent of tumor removal. NTR or R-STR with adjuvant radiosurgery might be acceptable therapeutic options for large VS in terms of achieving good tumor control and functional preservation of facial nerve.

Nausea and Dizziness after Vestibular Schwannoma Surgery: A Multivariate Analysis of Preoperative Symptoms

OBJECTIVE:

Nausea and dizziness are very discomforting for patients after vestibular schwannoma surgery and they impair recovery.

METHODS:

To identify preoperative symptoms and conditions that increase the risk of development of nausea after vestibular schwannoma surgery, a multivariate analysis was performed. One hundred fifteen patients with vestibular schwannoma had a microsurgical tumor removal in a standardized procedure in 2001 and 2002. Eighteen patients were excluded from the study because of previous surgery (recurrent tumors, 7 patients) or bilateral tumor occurrence (neurofibromatosis, 11 patients). Analysis was performed regarding postoperative amount of antiemetic medication, vomiting, and subjective feeling of the patient. Tumor grading, body mass index, sex, previous complaints, examination at admission, and side of the tumor were taken in consideration.

RESULTS:

Women had significant longer postoperative complaints (mean, 3.0 d; standard error, 0.47) and needed longer antiemetic therapy (mean, 3.3 d; standard error, 0.49) than men (mean, 1.72 d; standard error, 0.21). Patients developing no significant postoperative complaints were all in the higher tumor grading group, Grades 3a, 4a, and 4b. There was a significant difference in the duration of antiemetic therapy between tumors graded 1 and tumors graded 3 or 4. Patients with a positive stepping test preoperatively had a tendency to demand less antiemetic medication. Women with small tumors are most likely to develop significant complaints after vestibular schwannoma surgery.

CONCLUSION:

It is possible to identify patients with a higher risk of postoperative nausea and dizziness after vestibular schwannoma surgery. This allows one to inform these patients preoperatively and to initiate an early postoperative drug therapy to ease their symptoms.

Systematic review of the natural history of vestibular schwannoma

OBJECT

Magnetic resonance (MR) imaging now permits diagnosis of increasing numbers of small, minimally symptomatic vestibular schwannomas (VSs). Because VS growth patterns over time are very important in refining treatment strategies, these matters were systematically reviewed.

METHODS

An extensive MEDLINE search was performed to cull studies on VS growth according to sequential imaging. The percentages of growing and regressing tumors and lesions requiring treatment during follow-up periods were calculated. Factors associated with differences among studies were identified. Twenty-six studies including 1340 patients met all inclusion criteria. The overall frequency of VS growth during a mean follow-up period of 38 months was 46% (95% confidence interval [CI] 43-48%) and that of regression was 8% (95% CI 6-10%). The mean annual tumor growth rate was 1.2 mm/year. Furthermore, the percentage of cases requiring treatment during follow up was 18% (95% CI 16-21%). According to results of a sensitivity analysis, evaluation by serial MR imaging (39%, 95% CI 35-43%) and a prospective study design (29%, 95% CI 21-37%) were associated with less frequent reported tumor growth.

CONCLUSIONS

Although their applicability may be limited to relatively elderly patients with small tumors, data revealing a limited frequency of VS enlargement and an infrequent necessity for eventual therapy should assist decision-making in the treatment of small VSs causing minimal symptoms.

Facial Nerve Rerouting in Skull Base Surgery

Facial nerve rerouting techniques were developed to facilitate re-section of extensive tumors occupying the skull base. Facial nerve rerouting has its own limitations and risks, requiring microsurgical expertise, additional surgical time, and often some degree of facial nerve paresis. This article presents different degrees of anterior and posterior facial nerve rerouting, techniques of facial nerve rerouting, and a comprehensive review of outcomes. It then reviews anatomic and functional preservation of the facial nerve in acoustic neuroma resection, technical aspects of facial nerve dissection, intracranial facial nerve repair options, and outcomes for successful acoustic neuroma surgery.

Radiosurgery for vestibular schwannomas

BACKGROUND

Radiosurgery has been established as an important alternative to microsurgery. We report our experience with radiosurgery for tumor control and the complications of unilateral vestibular schwannomas.

METHODS

We reviewed our early experience regarding clinical presentation, management and outcomes in 45 patients with acoustic schwannomas who underwent gamma knife stereotactic radiosurgery. The median follow-up period was 25 months (range, 6-48 months). Thirteen patients had undergone 1 or more previous resections before radiosurgery; 32 underwent radiosurgery as the first procedure. Median tumor volume was 4.5 mL (range, 0.5-30.0), and median radiotherapy dose was 11.5 Gy (range, 10.5-14.0 Gy).

RESULTS

Tumor control was achieved in 43 patients (95.6%). Loss of central contrast enhancement was a characteristic change and was noted in 29 patients (64.4%). Reduction in tumor size was shown in 15 patients (33.3%). Thirteen patients (28.9%) had good or serviceable hearing preoperatively, and in all of these, the preoperative status was retained immediately after radiosurgery. At follow-up, however, 10 patients (76.9%) had preserved hearing and 3 (23.1%) had reduced hearing on the treated side. Hearing in 1 patient that was not serviceable preoperatively later improved to a serviceable level. No patients had delayed facial palsy or lower cranial nerve dysfunction, but one had delayed trigeminal sensory loss.

CONCLUSION

Radiosurgery achieved a high tumor control rate and a relatively low post-radiosurgical complication rate for acoustic neuromas.

Cranial nerve assessment in posterior fossa tumors with fast imaging employing steady-state acquisition (FIESTA)

Steady-state free precession is widely used for ultra-fast cardiac or abdominal imaging. The purpose of this work was to assess fast imaging employing steady-state acquisition (FIESTA) and to evaluate its efficacy for depiction of the cranial nerve affected by the tumor. Twenty-three consecutive patients with posterior fossa tumors underwent FIESTA sequence after contrast agent administration, and then displacement of the cranial nerve was evaluated. The 23 patients with posterior fossa tumor consisted of 12 schwannomas, eight meningiomas, and three cases of epidermoid. Except in the cases of epidermoid, intensity of all tumors increased on FIESTA imaging of the contrast enhancement. In the schwannoma cases, visualization of the nerve became poorer as the tumor increased in size. In cases of encapsulated meningioma, all the cranial nerves of the posterior fossa were depicted regardless of location. The ability to depict the nerves was also significantly higher in meningioma patients than in schwannoma patients (P<0.05). In cases of epidermoid, extension of the tumors was depicted clearly. Although the FIESTA sequence offers similar contrast to other heavily T2-weighted sequences, it facilitated a superior assessment of the effect of tumors on cranial nerve anatomy. FIESTA sequence was useful for preoperative simulations of posterior fossa tumors.

Evaluation of the Results of Endoscope-Assisted Acoustic Neuroma Surgery through Posterior Fossa Approach

The objective of this study was to evaluate the results of endoscope-assisted acoustic neuroma surgery in posterior fossa approach. Between 1996 and 2002, 60 consecutive patients with acoustic neuroma were operated via the retrosigmoid suboccipital approach. Standard 4-mm sinus endoscopes at different angles were used during the surgeries either for inspection or tumor endoscopic dissection. Clinical parameters and treatment outcome were evaluated retrospectively. Tumor sizes were small, medium and large in 46.6, 45 and 8.3% of the patients, respectively. The hearing preservation rate, which did not correlate with tumor size (p > 0.05), was 24.4%. The need for facial reanimation surgery, which was needed in 5% of patients, was significantly higher in the large tumors than in the small and medium tumors (p < 0.001). Cerebrospinal fluid fistula rate, which was not related to tumor size (p > 0.05), was 13.3%. Tumor recurrence or residual tumor was not encountered at all. In conclusion, endoscopes give accurate information about the relationship between the tumor and the adjacent structures and help control the fundus of the internal auditory canal to ensure complete tumor removal. It is also helpful in visually verifying the continuity of the facial and cochlear nerves. The use of endoscopes does not appear to increase the hearing preservation rate, but is very helpful in complete tumor removal in the posterior fossa approach.

Ophthalmic management of facial nerve palsy

The ophthalmologist plays a pivotal role in the evaluation and rehabilitation of patients with facial nerve palsy. It is crucial to recognize and treat the potentially life-threatening underlying causes. The immediate ophthalmic priority is to ensure adequate corneal protection. The medium to long-term management consists of treatment of epiphora, hyperkinetic disorders secondary to aberrant regeneration and poor cosmesis. Patients should be appropriately referred for general facial re-animation. This review aims to provide a guide to the management of this complex condition.

A Comparison of Surgical Techniques Used in Dynamic Reanimation of the Paralyzed Face

OBJECTIVES

To compare the outcomes of three surgical techniques used in the rehabilitation of the paralyzed face.

STUDY DESIGN

Retrospective study.

SETTING

University-based tertiary referral center.

PATIENTS

Between 1976 and 2000, rehabilitative facial nerve surgery was performed on 70 adult patients with varying underlying diseases.

INTERVENTION

Three methods of facial nerve rehabilitative surgery were performed: end-to-end anastomosis, cable nerve graft interposition, and classic faciohypoglossal transposition.

MAIN OUTCOME MEASURES

The House-Brackmann grade was scored at 6, 12, 24, and 36 months by the two senior authors. A favorable outcome was defined as House-Brackmann Grade </= III. Other parameters recorded were repair technique, age, nerve rerouting, whether the repair was immediate or delayed, and the anatomic position of the nerve defect in relation to the geniculate ganglion.

RESULTS

Data were available on 66 patients (94%), of whom 13 had an end-to-end anastomosis, 25 a cable nerve graft interposition, and 28 a classic faciohypoglossal transposition. At 24 months, a House-Brackmann Grade </= III was achieved in 84.6% of those who underwent end-to-end anastomosis, 56.0% of those who underwent cable nerve graft interposition, and 25.0% of those who underwent classical faciohypoglossal transposition. End-to-end anastomosis and cable nerve graft interposition were superior to classic faciohypoglossal transposition (log-rank test, p = 0.0013). Twenty-five percent of all cases demonstrated improvement in House-Brackmann grade after 24 months. Increasing age at the time of repair was associated with a poorer outcome (p = 0.03 on logistic regression).

CONCLUSION

End-to-end anastomosis confers the best facial function, followed by cable nerve graft interposition and then classic faciohypoglossal transposition. Contrary to some previous opinions, improvement in facial function can still occur 2 years after surgical repair, particularly with classic faciohypoglossal transposition.

Acoustic Neuromas after Failed Radiation Therapy: Challenges of Surgical Salvage

OBJECTIVES

As stereotactic radiation has emerged as a treatment option for acoustic neuromas, cases that require surgical salvage after unsuccessful radiation have emerged. We present a comparison of the technical challenges faced by the surgeons in the treatment of irradiated versus nonirradiated acoustic neuromas.

STUDY DESIGN

Matched case-control series.

METHODS

We identified nine patients with acoustic neuromas that required surgical resection after radiation therapy. Cases were performed with suboccipital and translabyrinthine approaches. Nine nonirradiated case-control subjects matched for age, sex, tumor size, and surgical approach were identified for purposes of general comparison. Operative findings and outcomes were compared for the two groups.

RESULTS

Surgical removal was found to be significantly more difficult after radiation therapy because of increased fibrosis and adhesion to adjacent nervous structures, particularly at the porus acousticus. Excessive scarring hindered identification of the facial nerve and added uncertainty as to the completeness of tumor removal. Decompression of the internal auditory canal (IAC) dura and resection of neoplasm in the IAC before cerebellopontine angle dissection was required for facial nerve identification. Operative time was significantly longer for irradiated cases, and facial nerve outcomes tended to be poorer, particularly when facial nerve dysfunction prompted the salvage procedure.

CONCLUSIONS

Surgical salvage of acoustic neuromas after radiation therapy is feasible, but it presents technical challenges beyond that associated with primary surgical therapy. Poorer outcomes of postoperative cranial nerve status were caused primarily by anatomic changes at the nerve/tumor interface. As surgical experience with the irradiated acoustic neuroma grows, operative observations should be incorporated into the counsel provided to patients with acoustic neuromas as they weigh different management options.

Acoustic neuroma radiosurgery with marginal tumor doses of 12 to 13 gy

PURPOSE

To define tumor control and clinical outcomes of radiosurgery to marginal tumor doses of 12-13 Gy for unilateral acoustic neuroma patients.

METHODS AND MATERIALS

Three hundred thirteen patients with previously untreated unilateral acoustic neuromas (vestibular schwannomas) underwent gamma knife radiosurgery between February 1991 and February 2001 with marginal tumor doses of 12-13 Gy (median, 13 Gy). Median follow-up was 24 months (maximum, 115 months; 36 patients with > or =60 months). Maximum doses were 20-26 Gy (median, 26 Gy), and treatment volumes were 0.04-21.4 mL (median, 1.1 mL).

RESULTS

The actuarial 6-year clinical tumor control rate (no requirement for surgical intervention) for the entire series was 98.6 +/- 1.1%. Two patients required tumor resection; one had a complete resection for solid tumor growth and one required partial resection for an enlarging adjacent subarachnoid cyst. Six-year actuarial rates for preservation of facial nerve function, normal trigeminal nerve function, unchanged hearing level, and useful hearing were 100%, 95.6 +/- 1.8%, 70.3 +/- 5.8%, and 78.6 +/- 5.1%, respectively. The risk of developing trigeminal neuropathy correlated with increasing tumor volume (p = 0.038).

CONCLUSIONS

Acoustic neuroma radiosurgery with doses of 12-13 Gy provides high rates of tumor control and cranial nerve preservation.

Preoperative Appearance of Facial Muscles on Magnetic Resonance Predicts Final Facial Function After Acoustic Neuroma Surgery

OBJECTIVE

Several previous studies have shown that muscle appearance on magnetic resonance is a sensitive indicator of muscle denervation. Previous attempts at determining preoperative indicators of final facial function after acoustic neuroma removal has been mostly unsuccessful. The goal of this study was to determine if the appearance of the facial muscles on preoperative imaging is predictive of final facial function after surgical removal of vestibular schwannomas.

STUDY DESIGN

We conducted a retrospective chart and magnetic resonance review.

SETTING

This study was conducted at a tertiary referral center.

PATIENTS

We included all patients who underwent vestibular schwannoma removal between January 1, 1997, and December 31, 2001, with available preoperative magnetic resonance images and a minimum of 12 months follow up.

INTERVENTIONS

We used translabyrinthine, middle fossa, and suboccipital approaches for tumor removal. A neuroradiologist, blinded to preoperative or final facial function after tumor removal, retrospectively reviewed preoperative magnetic resonance images.

MAIN OUTCOMES MEASURES

Facial muscles were evaluated on magnetic resonance and classified as symmetric or asymmetric. Facial function was graded using the House-Brackmann scale. Preoperative facial function was noted on the preoperative physical examination. Final function was determined at least 12 months postoperatively.

RESULTS

A total of 247 patients underwent tumor removal during the study period. One hundred thirty-two patients had adequate preoperative magnetic resonance images. Patients with preoperative facial muscle asymmetry seen on preoperative magnetic resonance indicating muscle atrophy had significantly worse final facial function, regardless of tumor size.

CONCLUSION

The preoperative appearance of facial muscles provides valuable insight into the physiology of the facial nerve in the presence of vestibular schwannomas. Patients with pre-operative facial muscle symmetry have significantly better facial function than those with atrophy.

Analysis of taste disturbance before and after surgery in patients with vestibular schwannoma

OBJECT

The frequency, nature, and history of subjective taste disturbance before and after vestibular schwannoma (VS) surgery was investigated.

METHODS

Personal interviews were conducted in 108 patients with unilateral VS. Abnormalities in taste perception, either a significant reduction or a change in character, were experienced by 31 patients (28.7%) before surgery and by 37 (34.3%) after tumor removal. Preoperative taste disturbance worsened after surgery in five (16.1%) of the 31 patients, remained unchanged in eight (25.8%), improved in two (6.5%), and became normal in 16 (51.6%). Taste disturbance occurred postoperatively in 22 (28.6%) of 77 patients who had experienced no preoperative taste disturbance. The mean onset of the abnormality after resection was 1.1 +/- 1.7 months. Postoperative taste disturbance resolved in 24 of the 37 patients (64.9%) within 1 year after onset.

CONCLUSIONS

Subjective taste disturbance was common before and after VS removal, and the natural history of this condition was very variable in the pre- and postoperative periods. All patients who undergo surgery for VS should receive appropriate counseling about the likelihood and course of postoperative complications, including dysfunction of the sensory component of the facial nerve.