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

Ophthalmic Complications Following Acoustic Neuroma Resection

BACKGROUND

Past studies have shown high rates of ocular complications with the need for ophthalmic surgery following acoustic neuroma resection (ANR).

OBJECTIVE

To determine the rates of ophthalmic complications, referrals, and surgery following ANR, and the factors associated with poor outcomes.

METHODS

A retrospective study of ophthalmic outcomes in patients who underwent ANR was conducted, following institutional review board approval. Surgical approach, tumor size, tumor characteristics, completeness of resection, postoperative House-Brackmann grades, ocular complications, referrals to ophthalmology, and ophthalmic treatments were recorded.

RESULTS

Between 2007 and 2012, 174 patients underwent ANR. There were 3 surgical groups: retrosigmoid (n = 97), translabyrinthine (n = 59), and combined retrosigmoid and translabyrinthine (n = 18). Median tumor size was 2.2 cm. Postoperatively, 30% of patients had facial nerve dysfunction (House-Brackmann ≥3), which recovered to 19% by 1 mo and 8.6% by 1 yr following ANR. Fifty-six (32.9%) patients experienced ocular complications postoperatively, with lagophthalmos, dry eye, and blurry vision as the most common complications. Thirty-six (67.9%) of the patients who required ophthalmic treatment were managed nonsurgically, with just 13 (7.6%) patients requiring referral to an ophthalmologist. In total, only 9 (5.3%) patients received an ophthalmic procedure. Patients with tumors >2 cm, those undergoing combined retrosigmoid and translabyrinthine resection, and those with severe facial nerve dysfunction which did not improve in the first month following surgery were more likely to have poor ophthalmic outcomes.

CONCLUSION

We present lower rates of ophthalmic complications following ANR than previously reported. Improved surgical technique, better postoperative eye care, and facial nerve monitoring most likely accounted for the improved ocular outcomes.

Relationship of the sinus anatomy to surface landmarks is a function of the sinus size difference between the right and left side: Anatomical study based on CT angiography

BACKGROUND

Several cadaveric studies demonstrate reliable localization of the transverse sinus and the transverse sigmoid junction (TSJ). These studies use the line drawn from the inion to the posterior root of the zygoma (IZ) and the asterion, respectively. We investigated how the size difference between the right and left transverse sinuses (TS) and sigmoid sinuses (SS) affected the accuracy of their respective superficial landmarks, particularly with regards to where this relationship may result in unsafe and/or complicated surgical access.

METHODS

We utilized Vitrea software to render three-dimensional images based on computed tomographic angiography (CTA). We measured the relationship between the TS and SS to their respective superficial landmarks.

RESULTS

We analyzed 50 patients in this study. The distal TS was found caudal to the inion-to-zygoma (IZ) line on average by 5.0 ± 4.3 mm on the right and 6.4 ± 9.3 mm on the left. The mid TS was found cranial on average 3.5 ± 5.7 mm on the right and 3.2 ± 6.0 mm cranial on the left to the superior nuchal line (SNL). The distance from the asterion to the SS was 11.5 ± 2.4 mm medial on the right and 12.1 ± 4.4 mm medial on the left. The average distance was greater on the left than the right when using the IZ landmark. This was directly proportional to the size difference of the sinuses (r2 = 0.15, P = 0.03).

CONCLUSIONS

Statistically significant differences between the right and left TS and SS were seen in terms of size. This appeared to correlate nicely to the differences observed between the locations of the TSs' and their respective superficial landmarks.

Surgical technique and results of cable graft interpositioning of the facial nerve in lateral skull base surgeries: experience with 213 consecutive cases

OBJECTIVE The aim in this study was to review the technique and outcomes of cable graft interpositioning of the facial nerve (FN) in lateral skull base surgeries. METHODS The authors retrospectively evaluated data from patients who had undergone cable graft interpositioning after nerve sacrifice during skull base tumor removal between June 1987 and May 2015. All patients had undergone lateral skull base approaches to remove tumors at a quaternary referral center in Italy. Facial nerve function was evaluated before and after surgery using the House-Brackmann (HB) grading system. RESULTS Two hundred thirteen patients were eligible for study. The mean follow-up was 44.3 months. The most common pathology was vestibular schwannoma (83 cases [39%]), followed by FN tumor (67 cases [31%]). Facial nerve tumors had the highest incidence of nerve interruption (67 [66%] of 102 cases). Preoperative FN function was normal (HB Grade I) in 105 patients (49.3%) and mild (HB Grade II) in 19 (8.9%). At the last postoperative follow-up, 108 (50.7%) of the 213 patients had recovered to Grade III nerve function. Preoperative HB grading of the FN was found to have a significant effect on outcome (p = 0.002). CONCLUSIONS Cable graft interpositioning is a convenient and well-accepted procedure for immediate restoration of the FN. The study results, over a large number of patients, showed that the stitch-less fibrin glue-aided coaptation technique yields good results. The best possible postoperative result achieved was an HB Grade III. The chances of a good postoperative result increase when FN function is normal preoperatively. Slow-growing tumors of the cerebellopontine angle had a favorable outcome after grafting.

Functional outcome and complications after the microsurgical removal of giant vestibular schwannomas via the retrosigmoid approach: a retrospective review of 16-year experience in a single hospital

BACKGROUND

Intracranial vestibular schwannoma still remain to be difficulty for its unique microsurgical technique and preservation of neuro-function, as well as reducing common complications that may arise in surgery.

METHODS

We consecutively enrolled 657 unilateral giant (>4 cm diameter) vestibular schwannoma patients treated in Huashan Hospital via the suboccipital retrosigmoid approach in the past 16 years. The extension of tumor removal, surgical mortality, facial nerve function, hearing, and the other main short and long-term complications were the studied parameters.

RESULTS

Gross total resection was performed in 556 patients (84.6%); near-total resection was achieved in 99 patients (15.1%). The mortality rate is 0.6%. The main short-term complications included 'new' deafness (47.6%), intracranial infection (7.6%), lower cranial nerve defects (7.5%) and pneumonia (6.2%). The facial nerve was preserved anatomically in 589 cases (89.7%). Good facial nerve functional outcome (House-Brackmann Grades I and II) postoperatively was achieved in 216 patients (32.9%). Other 308 cases (46.9%) were House-Brackmann grade III, and 133 patients (20.2%) were House-Brackmann grade IV-VI. Follow-up data were available for 566 of the 657 patients (86.1%). The common long-term complications were hearing loss (85.2%), facial paralysis (HB grade IV-VI, 24.4%) and facial numbness (15.7%).

CONCLUSIONS

Trends in the data lead the authors to suggest that the microsurgical technique, intraoperative nerve monitoring, and multidisciplinary cooperation, were the keys to improving prognostic outcomes in giant intracranial vestibular schwannoma patients.

Gamma Knife radiosurgery for treatment of growing vestibular schwannomas in patients with neurofibromatosis Type 2: a matched cohort study with sporadic vestibular schwannomas

OBJECTIVE Neurofibromatosis Type 2 (NF2) is a tumor syndrome characterized by an autosomal dominant pattern of inheritance. The hallmark of NF2 is the development of bilateral vestibular schwannomas (VSs), generally by 30 years of age. One of the first-line treatment options for small to medium-large VSs is radiosurgery. Although radiosurgery shows excellent results in sporadic VS, its use in NF2-related VS is still a topic of dispute. The aim of this study was to evaluate long-term tumor control, hearing preservation rates, and factors influencing outcome of optimally dosed, contemporary Gamma Knife radiosurgery (GKRS) for growing VSs in patients with NF2 and compare the findings to data obtained in patients with sporadic VS also treated by means of GKRS. METHODS The authors performed a retrospective analysis of 47 growing VSs in 34 NF2 patients who underwent GKRS treatment performed with either the Model C or Perfexion Leksell Gamma Knife, with a median margin dose of 11 Gy. Actuarial tumor control rates were estimated using the Kaplan-Meier method. For patient- and treatment-related factors, a Cox proportional hazards model was used to identify predictors of outcome. Trigeminal, facial, and vestibulocochlear nerve function were assessed before and after treatment. NF2-related VS patients were matched 1:1 with sporadic VS patients who were treated in the same institute, and the same indications for treatment, definitions, and dosimetry were used in order to compare outcomes. RESULTS Actuarial tumor control rates in NF2 patients after 1, 3, 5, and 8 years were 98%, 89%, 87%, and 87%, respectively. Phenotype and tumor volume had significant hazard rates of 0.086 and 22.99, respectively, showing that Feiling-Gardner phenotype and a tumor volume not exceeding 6 cm³ both were associated with significantly better outcome. Actuarial rates of serviceable hearing preservation after 1, 3, 5, and 7 years were 95%, 82%, 59%, and 33%, respectively. None of the patients experienced worsening of trigeminal nerve function. Facial nerve function worsened in 1 patient (2.5%). No significant differences in tumor control, hearing preservation, or complications were found in comparing the results of GKRS for NF2-related VS versus GKRS for sporadic VS. CONCLUSIONS With modern GKRS, the use of low margin doses for treating growing VSs in patients with NF2 demonstrates good long-term tumor control rates. Feiling-Gardner phenotype and tumor volume smaller than 6 cm³ seem to be independently associated with prolonged progression-free survival, highlighting the clinical importance of phenotype assessment before GKRS treatment. In addition, no significant differences in tumor control rates or complications were found in the matched-control cohort analysis comparing GKRS for VS in patients with NF2 and GKRS for sporadic VS. These results show that GKRS is a valid treatment option for NF2-related VS, in addition to being a good option for sporadic VS, particularly in patients with the Feiling-Gardner phenotype and/or tumors that are small to medium in size. Larger tumors in patients with the Wishart phenotype appear to respond poorly to radiosurgery, and other treatment modalities should therefore be considered in such cases.

[Surgical treatment of acoustic neuromas (vestibular schwannomas)]

Clinical guidelines are topical systematically developed provisions designed to help the doctor make a decision about a treatment approach in certain clinical situations; they provide information on conducting diagnostic and screening tests, the amount of medical and surgical care, and other aspects of clinical practice. Vestibular schwannomas account for 8% of all intracranial lesions, up to 30% of posterior cranial fossa tumors, and 85% of cerebellopontine angle tumors. The incidence rate of acoustic neuromas is approximately 1 case per 100000 population per year. The paper addresses the issues of classification, diagnosis, and treatment of acoustic neuromas. The guidelines discuss in detail the key aspects of formulation of clinical diagnosis, classification features, definition of the indications for surgical or radiation treatment, and principles of expectant treatment in vestibular schwannomas. The article pays particular attention to surgical treatment of acoustic neuromas and describes the criteria for choosing a surgical approach, use of modern surgical equipment, and stages of tumor resection. On the basis of the accepted clinical classification, we propose the algorithms of action depending on the disease stage, pathological process dynamics, patient's age, and clinical manifestations. The key points of the clinical guidelines rely on evidence-based criteria. The work is intended for neurosurgery practitioners.

Complications and Management of Large Intracranial Vestibular Schwannomas Via the Retrosigmoid Approach

OBJECTIVE

To investigate the common complications from the microsurgical treatment of large intracranial vestibular schwannoma (VS) via suboccipital retrosigmoid approach and to propose strategies for minimizing such complications.

METHODS

We selected all patients with large unilateral VS from the collected database (1999-2013) who underwent microsurgical resection as their initial treatment for histopathologically confirmed VS. Tumors larger than 30 × 20 mm were defined as large.

RESULTS

A total of 1167 patients with VS were included. Gross total tumor resection was achieved in 1006 patients (86.2%). The mortality rate is 0.77%. The facial nerve was preserved anatomically in 1083 cases (92.8%), and the functional valuation of the facial nerve according to postoperative House-Brackmann scale showed 423 patients (36.2%) in grades I-II, 534 cases (45.8%) in grade III, and 210 patients (18.0%) in grade IV-VI. The main short-term postoperative complication included new hearing loss (American Institute of Otolaryngology-Head and Neck Surgery grade D) in 634 cases (54.3%), disequilibrium in 250 cases (21.4%), labial herpes in 127 cases (10.9%), meningitis in 115 (9.85%) and lower cranial nerve deficit in 77 cases (6.59%). Follow-up data were available for 978 of the 1167 patients (83.8%). Long-term complications include hearing loss (American Institute of Otolaryngology-Head and Neck Surgery grade D) (75.8%), permanent facial paralysis (11.9%), facial numbness (10.9%), tinnitus (2.96%), chronic headache (2.25%), and taste disturbance (1.43%).

CONCLUSIONS

The key factors for reducing surgical complications include careful assessment of the functions of acoustic and facial nerves as well as a thorough understanding of anatomy via the retrosigmoid approach before operation, skillful microsurgical technique, and monitoring of multiple cranial nerves during resection.

Facial nerve repair after operative injury: Impact of timing on hypoglossal-facial nerve graft outcomes

PURPOSE

Reanimation of facial paralysis is a complex problem with multiple treatment options. One option is hypoglossal-facial nerve grafting, which can be performed in the immediate postoperative period after nerve transection, or in a delayed setting after skull base surgery when the nerve is anatomically intact but function is poor. The purpose of this study is to investigate the effect of timing of hypoglossal-facial grafting on functional outcome.

MATERIALS AND METHODS

A retrospective case series from a single tertiary otologic referral center was performed identifying 60 patients with facial nerve injury following cerebellopontine angle tumor extirpation. Patients underwent hypoglossal-facial nerve anastomosis following facial nerve injury. Facial nerve function was measured using the House-Brackmann facial nerve grading system at a median follow-up interval of 18months. Multivariate logistic regression analysis was used determine how time to hypoglossal-facial nerve grafting affected odds of achieving House-Brackmann grade of ≤3.

RESULTS

Patients who underwent acute hypoglossal-facial anastomotic repair (0-14days from injury) were more likely to achieve House-Brackmann grade ≤3 compared to those that had delayed repair (OR 4.97, 95% CI 1.5-16.9, p=0.01).

CONCLUSIONS

Early hypoglossal-facial anastomotic repair after acute facial nerve injury is associated with better long-term facial function outcomes and should be considered in the management algorithm.

[Vestibular schwannoma - management and microsurgical results]

BACKGROUND

The experience of the medical team, interdisciplinarity, quality of the physician-patient relationship, sensible use of modern technology, and a sound knowledge about the long-term results of observation and interventions all influence treatment quality in patients with vestibular schwannomas.

OBJECTIVES

Compilation of findings regarding the results of observation and microsurgical treatment of patients with these tumors. Deduction of strategies for the medical management from these data.

MATERIALS AND METHODS

Review of the pertinent literature concerning the course of the disease with observational management and microsurgical treatment with respect to tumor growth and symptoms.

RESULTS

Reported annual growth rates of vestibular schwannoma vary between 0.3 and 4.8 mm. Vertigo is the symptom that is most influential on quality of life regardless of the medical management strategy. Up to 75 % of patients are treated within 5 years of the primary diagnosis. Independent of the approach, reported resection rates are higher than 95 %, even with preservation of function as the primary goal. Recurrence rates after subtotal removal are three times higher than after complete removal. Facial nerve preservation is accomplished in more than 90 % of cases. With functional hearing before surgery and small tumors, the chance of hearing preservation exceeds 50 %.

CONCLUSIONS

Quality of life is primarily defined by symptoms caused by the tumor itself and only secondarily by the medical interventions. Treatment should be directed towards the preservation of the patient's quality of life from the beginning. Results of medical treatment should be superior to the natural course of the disease.

In vivo visualization of the facial nerve in patients with acoustic neuroma using diffusion tensor imaging–based fiber tracking

OBJECTIVE

Preoperative determination of the facial nerve (FN) course is essential to preserving its function. Neither regular preoperative imaging examination nor intraoperative electrophysiological monitoring is able to determine the exact position of the FN. The diffusion tensor imaging–based fiber tracking (DTI-FT) technique has been widely used for the preoperative noninvasive visualization of the neural fasciculus in the white matter of brain. However, further studies are required to establish its role in the preoperative visualization of the FN in acoustic neuroma surgery. The object of this study is to evaluate the feasibility of using DTI-FT to visualize the FN.

METHODS

Data from 15 patients with acoustic neuromas were collected using 3-T MRI. The visualized FN course and its position relative to the tumors were determined using DTI-FT with 3D Slicer software. The preoperative visualization results of FN tracking were verified using microscopic observation and electrophysiological monitoring during microsurgery.

RESULTS

Preoperative visualization of the FN using DTI-FT was observed in 93.3% of the patients. However, in 92.9% of the patients, the FN visualization results were consistent with the actual surgery.

CONCLUSIONS

DTI-FT, in combination with intraoperative FN electrophysiological monitoring, demonstrated improved FN preservation in patients with acoustic neuroma. FN visualization mainly included the facial-vestibular nerve complex of the FN and vestibular nerve.

Routine early CT scanning after craniotomy: is it effective for the early detection of postoperative intracranial hematoma?

BACKGROUND

Postoperative intracranial hematoma (POIH) is a frequent sequela secondary to cranial surgery. The role of routine early postoperative computed tomography (CT) scanning in the detection of POIH remains controversial. The study was aimed at analyzing the effect of routine early CT scanning after craniotomy for the early detection of POIH.

METHODS

Routine early postoperative CT scanning was performed at our institute, and a retrospective study was conducted to analyze the data. POIH was defined as an intracranial hematoma requiring surgical management.

RESULTS

A total of 1,148 patients undergoing craniotomy were included in this study; 28 of these patients developed POIH. The majority of POIH cases (15/28, 54 %) were detected during the first 6 h following craniotomy. A routine CT scan was performed on all included patients but two; however, CT scans detected only 16 POIH cases. During the first 6 h, the rate at which CT scans detected POIH was 1.9 % (15/786); subsequently, the rate decreased to only 0.3 % (1/360; p < 0.05, compared with the rate during the first 6 h). Among patients without clinical manifestations, the rate at which the routine post-craniotomy CT scan detected POIH was only 0.7 % (5/721) (p < 0.05, compared with the incidence of POIH). Finally, among high-risk POIH patients, the POIH-positive rate of routine CT scanning was elevated.

CONCLUSIONS

It appears that routine early CT scan is ineffective for the detection of POIH in patients undergoing craniotomy. However, if the strategy for routine scanning can be improved, its effect may be beneficial.

Surgical management of skull base tumors

AIM

To present a review of the contemporary surgical management of skull base tumors.

BACKGROUND

Over the last two decades, the treatment of skull base tumors has evolved from observation, to partial resection combined with other therapy modalities, to gross total resection and no adjuvant treatment with good surgical results and excellent clinical outcomes.

MATERIALS AND METHODS

The literature review of current surgical strategies and management of skull base tumors was performed and complemented with the experience of Barrow Neurological Institute.

RESULTS

Skull base tumors include meningiomas, pituitary tumors, sellar/parasellar tumors, vestibular and trigeminal schwannomas, esthesioneuroblastomas, chordomas, chondrosarcomas, and metastases. Surgical approaches include the modified orbitozygomatic, pterional, middle fossa, retrosigmoid, far lateral craniotomy, midline suboccipital craniotomy, and a combination of these approaches. The selection of an appropriate surgical approach depends on the characteristics of the patient and the tumor, as well as the experience of the neurosurgeon.

CONCLUSION

Modern microsurgical techniques, diagnostic imaging, intraoperative neuronavigation, and endoscopic technology have remarkably changed the concept of skull base surgery. These refinements have extended the boundaries of tumor resection with minimal morbidity.

Surgical outcome in cystic vestibular schwannomas

Background:

Cystic vestibular schwannomas (VS) form a rare subgroup that differs from the solid variant clinically, radiologically, and histopathologically. These tumors also vary in their surgical outcome and carry a different risk of post-operative complications. We analyzed our series of 64 patients with cystic VS and discuss the technical difficulties related to total excision of these tumors and focus on complication avoidance.

Materials and Methods:

A retrospective review of cystic VS surgically managed over a span of 11 years. The case records were evaluated to record the clinical symptoms and signs, imaging findings, surgical procedure, complications, and follow-up data. Post-operative facial nerve palsy was analyzed with respect to tumor size and tumor type.

Results:

Progressive hearing impairment was the most common initial symptom (76.6%). Atypical initial symptoms were present in 15 patients (23.4%). Preoperatively, 78% patients had good facial nerve function (HB grade 1, 2) and 22% had intermediate (HB grade 3, 4) to poor (HB grade 5 and 6) function. Mean tumor size was 4.1 cm. Complete tumor removal was achieved in 53 patients (83%). The facial nerve was anatomically intact but thinned out after tumor excision in 38 patients (59.4%). Ninety percent patients had either intermediate or poor facial nerve function at follow-up. Poor facial nerve outcome was associated with giant tumors and peripherally located, thin-walled cystic tumors.

Conclusion:

Resection of cystic VS is complicated by peritumoral adhesions of the capsule to the nerve. Extensive manipulation of the nerve in order to dissect the tumor–nerve barrier results in worse facial nerve outcome. The outcome is worse in peripherally located, thin-walled cystic VS as compared to centrally located, thick-walled cystic tumors. Subtotal excision may be justified, especially in tumors with dense adhesion of the cyst wall to the facial nerve in order to preserve nerve integrity.

Total Facial Paralysis after Vestibular Schwannoma Surgery: Probability of Regaining Normal Function

The aim of the present study was to ascertain the precise fraction of vestibular schwannoma cases that recover to normal function after postoperative total facial nerve paralysis and to compare our results with those presented in the literature. This was a retrospective case review of 631 cases. Among the 132 cases with immediate postoperative facial nerve palsy (House Brackmann [HB] grade VI), only 2 (1.5%) recovered to normal function (HB grade I). In an attempt to compare our results with those of other series in the literature, we found a large variation in the incidence of recovery of this group of patients to grade I, ranging from 0% to 50%. Our analysis of the reported data revealed widely varying methods of data collection and presentation, making a scientifically valid comparison particularly difficult. According to our data, complete (HB grade I) or near-complete (HB grade II) facial nerve function recovery from an immediate postoperative grade VI palsy is extremely rare.

Early Nerve Grafting for Facial Paralysis After Cerebellopontine Angle Tumor Resection With Preserved Facial Nerve Continuity

IMPORTANCE

Preserving facial nerve function is a primary goal and a key decision factor in the comprehensive management of vestibular schwannoma and other cerebellopontine angle (CPA) tumors.

OBJECTIVE

To evaluate the use of the pattern of facial paralysis recovery in the early postoperative months as a sole predictor in selecting patients for facial nerve grafting after CPA tumor resection when cranial nerve VII is uninterrupted.

DESIGN, SETTING, AND PARTICIPANTS

Sixty-two patients with facial paralysis and uninterrupted cranial nerve VII who developed facial paralysis after CPA tumor resection at The Johns Hopkins Hospital were followed up prospectively to assess for spontaneous recovery and to determine candidacy for facial reanimation surgery. The study dates and dates of analysis were January 1, 2009, to March 31, 2015.

INTERVENTIONS

After a minimum of 6 months of clinical follow-up and no signs of clinical recovery, patients underwent facial nerve exploration and a masseteric or hypoglossal nerve transfer. Intraoperative direct nerve stimulation was performed to assess for the presence of subclinical reinnervation. Patients were followed up for a minimum of 18 months after surgery to evaluate outcomes.

MAIN OUTCOMES AND MEASURES

Facial function and recovery were studied objectively with a Smile Recovery Scale, Facial Asymmetry Index, and House-Brackmann (HB) grading system. Other outcome measures included the duration of paralysis, time to recovery, and evidence of synkinesis.

RESULTS

Sixty-two patients (33 men, 29 women; mean age 51.8 years) with uninterrupted facial nerves after CPA tumor resection developed HB grade IV, V, or VI facial paralysis. Ten patients underwent nerve grafting by 12 months, 9 patients received grafting after 12 months, and 8 patients had no intervention. Thirty-five patients spontaneously recovered. In all patients who underwent nerve grafting, there were no detectable facial muscle movements or electromyographic response to direct facial nerve stimulation suggestive of occult reinnervation. Overall, early facial reanimation surgery resulted in a shorter total duration of paralysis. Masseteric nerve grafting resulted in earlier recovery compared with hypoglossal nerve grafting (5.6 vs 10.8 months, P = .005). Patients who showed no signs of recovery by 6 months after CPA surgery but declined facial reanimation surgery demonstrated at best HB grade V recovery after 18 months of observation.

CONCLUSIONS AND RELEVANCE

The recovery pattern in the early postoperative period among patients who develop facial paralysis after CPA tumor resection is a useful clinical tool in selecting patients for facial reanimation surgery. Patients can be counseled for facial reanimation surgery as early as 6 months after surgery because satisfactory facial functional recovery is unlikely to occur when there is no clinical evidence of spontaneous nerve regeneration in the first 6 months.

LEVEL OF EVIDENCE

3.

[Rehabilitation of facial palsy and vertigo in patients with vestibular schwannoma]

BACKGROUND

Facial palsy and vertigo, as symptoms of vestibular schwannoma (VS) or consequences of its therapy, have a significant impact on patients' quality of life.

OBJECTIVE

This review analyzed current literature on the topic and deduced recommendations for rehabilitation of facial palsy and vertigo.

METHODS

The present review describes a PubMed-based search of the literature of the past 10 years.

RESULTS

There is no evidence-based drug therapy for the treatment of acute facial palsy after VS surgery. Several surgical procedures for facial nerve reconstruction, muscle transfer, and static techniques have been established. Physiotherapeutic movement therapy, optimally with biofeedback, seems to improve facial function in patients with post-paralytic syndrome. Botulinum toxin injections are the method of choice for synkinesis treatment. For treatment of acute and chronic vertigo in patients with VS, the same antivertiginous drugs as for other vertigo patients are used. If the patient shows retained vestibular stimulation function, preoperative intratympanic gentamycin therapy followed by compensation training is a promising approach to decreasing postoperative vertigo. Good vestibular rehabilitation comprises intensive and regular movement training, preferably with real-time feedback and therapy control.

CONCLUSION

There are several conservative, surgical, or combined conservative-surgical treatment options for individualized facial nerve rehabilitation of VS patients, as confirmed by clinical studies. In cases of acute vertigo, standard antivertiginous pharmacotherapy is indicated. In cases of acute and also of chronic vertigo, intensive balance and movement training relieves complaints.

Surgery for sporadic vestibular schwannoma. Part I: General outcome and risk of tumor recurrence

BACKGROUND

Vestibular schwannomas are slow growing, benign tumors. There are three possible management options: surgery, radiation treatment or active surveillance. The aim of this study was to assess the general outcome and risk of tumor recurrence.

MATERIALS AND METHODS

The study included 220 consecutive patients (134 women, 86 men; the age ranged from 18 to 74) operated with the retrosigmoid transmeatal approach. The largest extrameatal diameter of the tumor ranged from 8 to 72mm (mean 30mm). According to the Samii grading scale, the tumors were classified as follows: T2-12 (6%), T3-51 (23%) and T4-157 (71%). Gross total resection was performed in 217 patients and neartotal in 3.

RESULTS

Two hundred and eighteen (99.1%) patients were discharged home in a satisfactory neurological condition (GR or MD in GOS). One (0.5%) patient died due to brainstem infarction. One (0.5%) patient had unchanged severe cerebellar syndrome in comparison to the preoperative period (SD in GOS). In long-term follow-up, one patient went blind within a few months after surgery. Including the results of further neurosurgical procedures for CSF leak, shunt implantation, tumor regrowth and facial nerve reanimation, 98.6% of the patients were fully independent but with different neurological deficits. Tumor recurrence was observed in 5 (2.3%) patients during the follow-up period (mean term: 6.4 years). The average time to recurrence diagnosis was 8.8 years. All those patients were operated on again without any adjuvant therapy and there was no further re-growth at mean follow-up of 5.2 years.

CONCLUSIONS

Complete removal of VS is usually curative and poses very low risks of severe disability (if audio-facial sequels are not included), mortality and long-term recurrence. For recurrent tumors, carefully tailored revision surgery without irradiation offers a high efficacy with low risk of complications.

Predictors of Trigeminal Neuropathy After Radiosurgery for Vestibular Schwannomas

PURPOSE

To analyze the relationship between dosimetric characteristics and symptoms related to trigeminal neuropathy (TN) observed after radiosurgery (RS) for vestibular schwannomas (VS); to propose guidelines to optimize planification in VS RS regarding TN preservation; and to detail the mechanism of TN impairment after VS RS.

METHODS AND MATERIALS

One hundred seventy-nine patients treated between 2011 and 2013 for VS RS and without trigeminal impairment before RS were included in a retrospective study. Univariate and multivariate analyses were performed to determine predictors of TN among characteristics of the patients, the dosimetry, and the VS.

RESULTS

There were 20 Koos grade 1, 99 grade 2, 57 grade 3, and 3 grade 4. Fourteen patients (7.8%) presented a transitory or permanent TN. Between the patients with and without TN after VS RS, there was no significant difference regarding dosimetry or VS volume itself. Significant differences (univariate analysis P<.05, Mann-Whitney test) were found for parameters related to the cisternal portion of the trigeminal nerve: total integrated dose, maximum dose, mean dose, volume of the Vth nerve (Volv), and volume of the Vth nerve receiving at least 11 Gy (VolVcist>11Gy), but also for maximal dose to the Vth nerve nucleus and intra-axial portion (Dose maxVax). After multivariate analysis, the best model predicting TN included VolVcist>11Gy (P=.0045), Dose maxVax (P=.0006), and Volv (P=.0058). The negative predictive value of this model was 97%.

CONCLUSIONS

The parameters VolVcist>11Gy, Dose maxVax, and Volv should be checked when designing dosimetry for VS RS.

Microsurgical management of vestibular schwannoma after failed previous surgery

OBJECTIVE Microsurgical treatment of recurrent vestibular schwannoma (VS) is difficult and poses specific challenges. The authors report their experience with 53 cases of surgically treated recurrent VS. Outcome of these tumors was compared to that of primarily operated on VS. Special attention was given to the facial nerve functional outcome. METHODS A retrospective analysis was performed of the patients who underwent surgery for recurrent VS at one institution from 2000 to 2013. The preoperative data, intraoperative findings, and outcome in terms of facial nerve function and improvement of the preoperative symptoms were analyzed and compared with those in a control group of 30 randomly selected patients with primarily operated on VS. A multivariate regression analysis was performed to test the factors that could affect the facial nerve outcome in each group. RESULTS Fifty-three consecutive patients underwent surgery for recurrent VS. Seventeen patients were previously operated on and received postoperative radiosurgery (Group A). Thirty-six patients were previously operated on but did not receive postoperative radiosurgery (Group B). The overall postoperative facial nerve function was significantly worse in Groups A and B in comparison with the control group (Group C). Interestingly, there was no significant difference in the facial nerve outcome among the 3 groups in patients who had good preoperative facial nerve function. The tumor size and the preoperative facial nerve function are variables that significantly affect the facial nerve outcome. Most of the patients showed improvement of the preoperative symptoms, such as trigeminal hypesthesia, gait disturbance, and headache. CONCLUSIONS Complete microsurgical tumor removal is the optimal management for patients with recurrent or regrowing VS. The procedure is safe, associated with favorable facial nerve outcome, and may also improve existing neurological symptoms.

A Systematic Analysis of the Reliability of Diffusion Tensor Imaging Tractography for Facial Nerve Imaging in Patients with Vestibular Schwannoma

Surgeons need to visualize the facial nerve reliably in relation to the vestibular schwannoma (VS) in surgical planning. Diffusion tensor imaging (DTI) tractography has enabled unprecedented in vivo preoperative visualization. We collected data to measure the accuracy of DTI for an accurate location of the nerve in preoperative VS resection planning. A PubMed search for relevant studies was conducted. Inclusion criteria were gross total resection of VS, preoperative DTI identification of the facial nerve, and intraoperative cranial nerve localization by the surgeon. Exclusion criteria were tumors other than VS and unsuccessful preoperative location of the cranial nerve. Accuracy rate was calculated by comparing the intraoperative and preoperative locations detailed by DTI. The query identified 38 cases of VS that fit our inclusion criteria. Overall, 89% had surgical findings that agreed with the DTI location of the facial nerve. Of these cases, 32 patients had a postoperative House-Brackmann grade I or II. Our findings suggest that DTI is a reliable method for facial nerve imaging. Implementation of this technique may help decrease facial nerve injury during surgery. Limitations and further studies are needed to better understand what factors correlate with successful location of the facial nerve and DTI in patients with VS.

Improved Postoperative Facial Nerve and Hearing Function in Retrosigmoid Vestibular Schwannoma Surgery Significantly Associated with Semisitting Position

OBJECTIVE

The pros and cons of semisitting positioning (SSP) versus lateral, horizontal positioning (LP) during retrosigmoid vestibular schwannoma (VS) surgery, especially concerning postoperative cranial nerve and brain stem preservation, are under continuous discussion.

METHODS

In a single-center retrospective cohort study, 30 VSs operated on in SSP compared with 30 operated on in LP with comparable demography were analyzed. During SSP surgery, transesophageal echocardiographic monitoring for venous air embolism was used continuously. Electrophysiologic cranial nerve monitoring was used in both groups.

RESULTS

Length of surgery was significantly different between both groups: 183 minutes mean in SSP surgery versus 365 minutes mean in LP surgery (P = 0.0001). Postoperative rates of facial palsy and hearing loss were also significantly different. Six months postoperatively, 63% had normal facial nerve function after SSP surgery, whereas in LP surgery, 40% had no facial palsy (P = 0.02). Hearing preservation rate was also significantly different: 44% in SSP surgery compared with 14% in LP surgery who had preserved hearing (P = 0.006). Because of cerebrospinal fluid leaks, there were 3 operative revisions in the LP group (10%) and 1 (3.3%) in the SSP group. A clinically insignificant venous air embolism rate was found in 3.3% of patients (1/30) during SSP surgery. The neurologic outcome after 6 months was 1.2 on the Rankin Scale in the LP group and 1.0 in the SSP group, with zero mortality.

CONCLUSIONS

SSP compared with LP surgery was associated with significantly shorter operation time and better facial and cochlear nerve function in VS surgery postoperatively, without differences in complication rates.

Strategies and Pitfalls of Motor-Evoked Potential Monitoring during Supratentorial Aneurysm Surgery

BACKGROUND

The aims of this study were to reveal the strategies and pitfalls of motor-evoked potential (MEP) monitoring methods during supratentorial aneurysm surgery, and to discuss the drawbacks and advantages of each method by reviewing our experiences.

METHODS

Intraoperative MEP monitoring was performed in 250 patients. Results from 4 monitoring techniques using combinations of 2 stimulation sites and 2 recording sites were analyzed retrospectively.

RESULTS

MEP was recorded successfully in 243 patients (97.2%). Direct cortical stimulation (DCS)-spinal recorded MEP (sMEP) was used in 134 patients, DCS-muscle recorded MEP (mMEP) in 97, transcranial electrical stimulation (TES)-mMEP in 11 and TES-sMEP in 1. TES-mMEP during closure of the skull was used in 21 patients. DCS-mMEP was able to detect waveforms from upper and/or lower limb muscles. Alternatively, DCS-sMEP (direct [D]-wave) could accurately estimate amplitude changes. A novel "early warning sign" indicating ischemia was found in 21 patients, which started with a transiently increased amplitude of D-wave and then decreased after proximal interruption of major arteries. False-negative findings in MEP monitoring in 2 patients were caused by a blood insufficiency in the lenticulostriate artery and by a TES-sMEP recording, respectively.

CONCLUSIONS

The results of this study suggest that to perform accurate MEP monitoring, DCS-mMEP or DCS-sMEP recording should be used as the situation demands, with combined use of TES-mMEP recording during closure of the skull. DCS-sMEP is recommended for accurate analysis of waveforms. We also propose a novel "early warning sign" of blood insufficiency in the D-wave.

Surgery for sporadic vestibular schwannoma. Part IV. Predictive factors influencing facial nerve function after surgery

OBJECTIVE

To analyze the impact of various clinical, radiological and perioperative factors that could influence the facial nerve intraoperative disruption risk (CNVII-IDR) and its long-term function (CNVII-LTF) after vestibular schwannoma (VS) surgery.

MATERIAL AND METHODS

The study included 212 patients operated on for sporadic VS with no history of previous treatment for VS or CNVII palsy. The mean size of the tumor was 30 mm. Gross (210) or near-total (2) resections were carried out using the retrosigmoid (210) or translabyrinthine (2) approach. Correlation studies and multivariate regression analysis (RA) were performed.

RESULTS

In correlation studies, the CNVII-IDR was increased by: headaches and cerebellar ataxia if one of them was the first symptom of the tumor (33% and 29%, respectively, p=0.008); preoperative hydrocephalus (40% vs. 9%, p=0.01), tumor size >3 cm (18% vs. 5%, p<0.01), tumor volume >10 cm(3) (19% vs. 4%, p<0.01), right-sided location 15% vs. 6%, p=0.047), lateral "park-bench" position (19% vs. 5% for supine position, p<0.01) and the procedure order (16% for the first 106 procedures vs. 6% for the last 106 procedures, p<0.05). In RA the tumor volume (p=0.012), side of the tumor (p=0.028) and patient's position during surgery (p=0.016) independently affected the CNVII-IDR. The following factors correlated significantly with satisfactory CNVII-LTF (HB grades I-III): tumor stage <T4 (p=0.000), tumor size ≤3 cm (p=0.000), tumor volume ≤10 cm(3) (p=0.001), and left-sided location (p=0.048). Additional factors correlated significantly with very good CNVII-LTF (HB grades I-II): anterior CNVII displacement (p=0.044), nimodipine use (p=0.016), the absence of postoperative complications (p=0.019), CNVII responsive on final intraoperative EMG stimulation (p=0.000) and supine position during surgery (p=0.018). However, an independent impact on very good CNVII-LTF proved to be the tumor size (p=0.0000), side (p=0.0175), and nimodipine use (p=0.0349).

CONCLUSIONS

In our series, the factors related to size and side of the tumor confirmed an independent impact on CNVII-IDR and CNVIILTF. The significance of patient positioning may reflect the impact of learning curve as only the first 91 patients were operated on using the lateral "park-bench" position. An independent impact on CNVII-LTF was exerted by the perioperative use of nimodipine.

Communicating Hydrocephalus Associated with Intracranial Schwannoma Treated by Gamma Knife Radiosurgery

OBJECTIVE

Gamma knife radiosurgery (GKRS) has been established as an effective and safe treatment for intracranial schwannoma. However, serious complications can occur after GKRS, including hydrocephalus. The pathophysiology and risk factors of this disorder are not yet fully understood. The objective of the study was to assess potential risk factors for hydrocephalus after GKRS.

METHODS

We retrospectively reviewed the medical radiosurgical records of 244 patients who underwent GKRS to treat intracranial schwannoma. The following parameters were analyzed as potential risk factors for hydrocephalus after GKRS: age, sex, target volume, irradiation dose, prior tumor resection, treatment technique, and tumor enhancement pattern. The tumor enhancement pattern was divided into 2 groups: group A (homogeneous enhancement) and group B (heterogeneous or rim enhancement).

RESULTS

Of the 244 patients, 14 of them (5.7%) developed communicating hydrocephalus. Communicating hydrocephalus occurred within 2 years after GKRS in most patients (92.8%). No significant association was observed between any of the parameters investigated and the development of hydrocephalus, with the exception of tumor enhancement pattern. Group B exhibited a statistically significant difference by univariate analysis (P = 0.002); this difference was also significant by multivariate analysis (P = 0.006).

CONCLUSION

Because hydrocephalus is curable, patients should be closely monitored for the development of this disorder after GKRS. In particular, patients with intracranial schwannomas with irregular enhancement patterns or cysts should be meticulously observed.

Surgery for sporadic vestibular schwannoma. Part III: Facial and auditory nerve function

OBJECTIVE

The aim of this analysis was to assess short-term and long-term outcomes with respect to the preservation of facial and auditory nerve function following surgery for sporadic vestibular schwannomas.

MATERIAL AND METHODS

The study included 220 consecutive patients operated on with the retrosigmoid (217) or translabyrinthine (3) approach. The mean extrameatal diameter of the tumor was 30mm. In 217 patients, gross total resection was performed and near-total in 3. Before surgery, the facial nerve (CNVII) weakness was found in 18% of patients and only 20% had serviceable hearing. Intraoperative neurophysiological CNVII monitoring was routinely used (the last 211 procedures). Intraoperative monitoring of the cochlear nerve function was used when the preservation of hearing was attempted (45 procedures).

RESULTS

The rate of CNVII continuity loss during surgery was 11%, however, this decreased to 6% in the second half of the series. Facial nerve function deteriorated, in 88% of the patients shortly after surgery. However, it improved in 87% in follow-up. Delayed CNVII palsy was found in 5% of the patients and had a good prognosis in 88%. Final satisfactory CNVII function (CNVII-SF, HB grades I-III) was achieved in 76% of the patients when excluding the anastomosis results, and 87% when including them. In recent years, the rate of CNVII-SF has risen to 94%. Non-serviceable hearing was preserved in 49% of the patients, on whom it was attempted.

CONCLUSION

Considering the size of the tumors and extent of the resections, the preservation of CNVII function is currently very high. A close surveillance of CNVII function evolution following surgery is mandatory, as 2/3 of the patients discharged with deep paresis will need different face reanimation procedures. The preservation of useful hearing is still problematic, especially in patients with large tumors.

Temporomandibular disorder or not? A case report

OBJECTIVES

The purpose of this case study is to show the need for a good differential diagnosis of suspected temporomandibular disorder (TMD) with otologic symptoms.

METHODS/RESULTS

This study is a clinical case referring to a patient seeking treatment for pain in the right maxilla. The usual Medical History for diagnosis of a TMD was applied. Anamnesis revealed the patient had had a right maxillary pain for one month, a slight hearing loss and dizziness for the past five to six months, and two implants placed in the upper jaw two years previously. Clinical examination showed right temporomandibular joint (TMJ) clicking and tenderness in the lateral pterygoid muscles and in the right masseter muscle. Temporomandibular disorder and orofacial pain were diagnosed, and the appropriate treatment was initiated. In addition, a cranial magnetic resonance imaging (MRI) evaluation was requested and revealed acoustic neuroma.

CONCLUSION

The coexistence of TMD with otovestibular symptoms suggests the need for a cranial MRI evaluation, especially if the dental or TMD treatment has not been positive.

Strategy for the surgical treatment of vestibular schwannomas in patients with neurofibromatosis type 2

OBJECTIVE

Guidelines for appropriate management of vestibular schwannomas in NF2 patients are controversial. In this paper we reviewed our experience with patients with NF2 for the results of surgical treatment with particular reference to hearing and facial nerve preservation.

METHODS

We included in the study 30 patients (16 women and 14 men) with the diagnosis of NF2 treated in our department between 1998 and 2014 who underwent surgery for vestibular schwannoma removal with a follow-up for at least 1 year. In 3 cases, the vestibular schwannomas were unilateral. Six patients with bilateral vestibular schwannomas underwent unilateral procedure. Therefore, 51 acoustic tumors were studied in 30 patients.

RESULTS

No operative death we noted. Significant deterioration to the non-functional level occurred in 19 out of 22 cases with well-preserved preoperative hearing. Only three ears maintained their preoperative good hearing. Hearing was preserved in cases of small schwannoma not exceeding 2 cm. Among 21 patients who underwent bilateral operations hearing was preserved in 3 out of 7 cases when smaller tumor or better hearing level side was attempted at first surgery. In contrary none of the 14 patients retained hearing when the first operation concerned the worse-hearing ear. Among 14 tumors up to 2 cm there was only one case of moderately severe facial nerve dysfunction (House-Brackmann Grade IV) in the long follow-up.

CONCLUSION

Early surgical intervention for vestibular schwannoma in NF2 patient is a viable management strategy to maintain hearing function and preserve facial nerve function.

Identification of cranial nerves near large vestibular schwannomas using superselective diffusion tensor tractography: experience with 23 cases

BACKGROUND

The preservation of the facial nerve (FN) and acoustic function in large vestibular schwannoma (VS) surgery is challenging because of nerve course uncertainties and morphological deviations. Preoperative diffusion tensor tractography (DTT) has been proposed to predict the FN location. This study was conducted to evaluate the effectiveness of this technique for identifying the FN, cochlear nerve (CN) and trigeminal nerve (TN) in large VSs.

METHODS

The study included 23 consecutive patients with VS of Hannover classification T3b to T4b from November 2013 through May 2014. Diffusion tensor images and anatomical images were acquired. The DTT images of the cranial nerves were extracted before surgery for each patient to determine the relationships of these nerves with the tumor. The results were then validated during the tumorectomy.

RESULTS

In 21 (91.30%) patients, the location of the FN on the DTT images agreed with the intraoperative findings, including in 2 patients in whom the FN passed through the interface between the parenchyma and the cystic changes and in 3 patients with a membranoid FN. The CN or fibers of unclear function were observed on DTT images in four patients with functional hearing. One penetrating fiber of unknown function was effectively constructed. The TN was accurately detected on the DTT images for all patients.

CONCLUSIONS

DTT effectively revealed the location of the FN, including cases in which the FN was membranoid or passed through the interface between an area exhibiting cystic changes and the tumor nodule. Fibers aside from the FN and the TN were revealed by DTT in patients who retained functional hearing. Penetrating fibers were also found using DTT. This technique can be useful during VS resection.

Facial and Cochlear Nerve Complications following Microsurgical Resection of Vestibular Schwannomas in a Series of 221 Cases

Background

Despite improvements in microsurgical technique and the use of intraoperative electrophysiological monitoring, the potential for facial and cochlear nerve injury remains a possibility in the resection of vestibular schwannomas (VS). We reviewed a series of 221 cases of VS resected via a retrosigmoid approach at our institution from October 2008 to April 2014 and determined the incidence of postoperative facial and cochlear deficits.

Material/Methods

A total of 221 patients – 105 (47.5%) male and 116 (52.5%) female – with a mean age of 46.1 years (range 29–73 years), with VS ≥3 cm (n=183, 82.8%) and <3 cm (n=38, 17.2%) underwent surgical resection via a retrosigmoid approach and were evaluated for postoperative facial and cochlear nerve deficits.

Results

Near-total resection (>95% removal) was achieved in 199 cases (90%) and subtotal resection (>90% removal) in 22 cases (10%). At 6 month follow-up, House-Brackmann grades I–III were observed in 183 cases (82.8%), grade IV in 16 cases (7.2%), and grade V in 22 cases (10%). Of the 10 patients that had preoperative functional hearing, 3 (33%) retained hearing postoperatively. Cerebrospinal fluid leakage occurred in 6 patients (2.7%), lower cranial nerve palsies in 9 patients (4.1%), and intracranial hematomas 3 cases (1.4%).

Conclusions

The observed incidence of persistent postoperative nerve deficits is very low. Meticulous microsurgical dissection of and around the facial and cochlear nerves with the aid of intraoperative electrophysiological nerve monitoring in the retrosigmoid approach allows for near-total resection of medium and large VS with the possibility of preservation of facial and cochlear nerve function.

Facial Nerve Outcome after Vestibular Schwannoma Resection: A Comparative Meta-Analysis of Endoscopic versus Open Retrosigmoid Approach

The minimal access retrosigmoid endoscopic approach to vestibular schwannoma (VS) resection has been used with promising results. However, it has not been compared with the standard open approach in the literature. We performed a meta-analysis review for all articles describing both approaches for VS from 1996 to 2011. We found 1861 articles. After review and discussion, we narrowed our study to 25 articles, 4 endoscopic and 21 open. The total number of patients was 3026 for open and 790 for endoscopic. The mean tumor sizes in the open and endoscopic series were 2.5 cm and 2.7 cm, respectively. Good facial nerve outcome was achieved in 67% of the open series patients and in 94% of the endoscopic series patients. Other outcomes in the open and endoscopic series were the following: gross total resection, 91% versus 97%; functional hearing, 22.6% versus 46%; wound infection, 1.3% versus 2.6%; and recurrence, 5.4% versus 2.2%. We acknowledge the limitations of our study, but we can state that the endoscopic approach is not inferior to the standard open approach. In expert hands the endoscopic approach can offer as good a result as the open, with potential benefits such as less pain and a shorter length of stay in the hospital. There is a need for more controlled studies for a definitive comparison.

Evidence of polyclonality in neurofibromatosis type 2-associated multilobulated vestibular schwannomas

BACKGROUND

Neurofibromatosis type 2 (NF2) is a tumor syndrome that results from mutation of the NF2 tumor suppressor gene. The hallmark of NF2 is the presence of bilateral vestibular schwannoma (VS). Though NF2-associated and sporadic VS share identical histopathologic findings and cytogenetic alterations, NF2-associated VS often appears multilobulated, is less responsive to radiosurgery, and has worse surgical outcomes. Temporal bone autopsy specimens and MRI of the inner ear performed on NF2 patients suggest that multiple discrete tumors may be present within the labyrinth and cerebellopontine angle.

METHODS

Treatment-naïve ears in patients enrolled in a prospective NF2 natural history study (NIH#08-N-0044) were included for MRI analysis. T2-weighted and postcontrast T1-weighted MRIs were evaluated for the presence of multiple discrete tumors or a multilobulated mass. Peripheral blood (germline) and regional samples of tumor tissue were procured from consecutive patients enrolled in this study undergoing resection of a multilobulated VS (MVS). Histopathologic evaluation and genetic analysis (single nucleotide polymorphism array analysis, NF2 sequencing) were performed on each specimen.

RESULTS

Over half of NF2 ears harbored either an MVS (60/139 ears) or multiple discrete masses (19/139 ears). For 4 successive MVSs, genetic analysis revealed an admixture of cell populations, each with its own somatic NF2 mutation or deletion.

CONCLUSIONS

These findings suggest that the majority of NF2-associated VSs are polyclonal, such that the tumor mass represents a collision of multiple, distinct tumor clones. This explains the characteristic lobulated gross appearance of NF2-associated VS, and may also explain the substantially different treatment outcomes compared with sporadic VS.

Comparison of outcomes following complex posterior fossa surgery performed in the sitting versus lateral position

The sitting position during surgery is thought to provide important advantages, yet it remains controversial. We compared surgical and neurological outcomes for patients operated on in the sitting versus lateral position. Technically difficult procedures performed from the years 2001-2008 for complex lesions in the posterior fossa (vestibular schwannomas, other cerebellopontine angle tumors, foramen magnum meningiomas, brainstem cavernomas, pineal region tumors) were included. Outcomes in the two surgical positions were compared for all 243 patients (93 sitting, 38.3%; 150 lateral, 61.7%) and for 130/243 patients with vestibular schwannomas (50 sitting, 38.5%; 80 lateral, 61.5%). Sitting and lateral patient subgroups were clinically comparable. There were no surgical mortalities. The extent of removal and surgical and neurological outcomes were comparable. We found no advantage in surgical or neurological outcomes for use of the sitting or lateral surgical positions in technically difficult posterior fossa procedures. In vestibular schwannoma surgeries facial nerve preservation (House-Brackmann score 1-2) was related to extent of resection but not to surgical position. The choice of operative position should be based on lesion characteristics and the patient's preoperative medical status as well as the experience and preferences of the surgeons performing the procedure.

Improved preservation of function during acoustic neuroma surgery

OBJECT

Restoration of cranial nerve functions during acoustic neuroma (AN) surgery is crucial for good outcome. The effects of minimizing the injury period and maximizing the recuperation period were investigated in 89 patients who consecutively underwent retrosigmoid unilateral AN surgery.

METHODS

Cochlear nerve and facial nerve functions were evaluated during AN surgery by use of continuous auditory evoked dorsal cochlear nucleus action potential monitoring and facial nerve root exit zone-elicited compound muscle action potential monitoring, respectively. Factors affecting preservation of function at the same (preoperative) grade were analyzed.

RESULTS

A total of 23 patients underwent standard treatment and investigation of the monitoring threshold for preservation of function; another 66 patients underwent extended recuperation treatment and assessment of its effect on recovery of nerve function. Both types of final action potential monitoring response and extended recuperation treatment were associated with preservation of function at the same grade.

CONCLUSIONS

Preservation of function was significantly better for patients who received extended recuperation treatment.

Stereotactic radiotherapy for vestibular schwannoma

BACKGROUND

Vestibular schwannomas (acoustic neuromas) are common benign tumours that arise from the Schwann cells of the vestibular nerve. Management options include observation with neuroradiological follow-up, microsurgical resection and stereotactic radiotherapy.

OBJECTIVES

To assess the effect of stereotactic radiotherapy compared to observation, microsurgical resection, any other treatment modality, or a combination of two or more of the above approaches for vestibular schwannoma.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials; PubMed; EMBASE; CINAHL; Web of Science; CAB Abstracts; ISRCTN and additional sources for published and unpublished trials. The date of the search was 24 July 2014.

SELECTION CRITERIA

Randomised controlled trials (RCTs) exploring the efficacy of stereotactic radiotherapy compared with observation alone, microsurgical resection or any other possible treatment or combination of treatments in patients with a cerebellopontine angle tumour up to 3 cm in diameter, presumed to be a vestibular schwannoma.

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures expected by The Cochrane Collaboration.

MAIN RESULTS

No studies met the inclusion criteria for this review.

AUTHORS' CONCLUSIONS

There is no high quality evidence in the literature from RCTs to determine whether stereotactic radiotherapy is better than microsurgical resection or observation alone for patients with a vestibular schwannoma. In the absence of such evidence, the treatment method should be chosen on an individual basis, taking into consideration the patient's preferences, clinician experience and the availability of radiotherapeutic equipment. With the growing availability of radiotherapeutic equipment, randomised controlled trials should be undertaken to evaluate the role of stereotactic radiotherapy in comparison with other treatment options.

The extracisternal approach in vestibular schwannoma surgery and facial nerve preservation

The classical surgical technique for the resection of vestibular schwannomas (VS) has emphasized the microsurgical anatomy of cranial nerves. We believe that the focus on preservation of the arachnoid membrane may serve as a safe guide for tumor removal. Method The extracisternal approach is described in detail. We reviewed charts from 120 patients treated with this technique between 2006 and 2012. Surgical results were evaluated based on the extension of resection, tumor relapse, and facial nerve function. Results Overall gross total resection was achieved in 81% of the patients. The overall postoperative facial nerve function House-Brackmann grades I-II at one year was 93%. There was no recurrence in 4.2 years mean follow up. Conclusion The extracisternal technique differs from other surgical descriptions on the treatment of VS by not requiring the identification of the facial nerve, as long as we preserve the arachnoid envelope in the total circumference of the tumor.

Tumour resection volumes and facial nerve outcomes for vestibular schwannomas

The objective of this study is to correlate tumour volume relationship with surgical outcomes in subtotal resections and accepted nomenclature through a retrospective study at Charing Cross Hospital, London, a tertiary referral centre. The participants were 16 patients with vestibular schwannoma managed with subtotal resection between 2002 and 2011. The main outcome measures were surgical technique; tumour volume; recurrence and post-operative facial nerve function. Mean pre-operative and post-operative volumes for all patients were 14.7 and 3.7 cm(3) respectively. Tumour volumes do not correlate with diameter (p < 0.05). Mean reduction in volume of these subtotal resections was 75 %. Long term facial nerve outcome was good in the majority of patients: House-Brackmann Grade I/II in 12 (75 %), Grade III/IV in 2 (12.5 %) and Grade V/VI in 2 patients (12.5 %). Notably, two patients with Grade I/II House-Brackmann grading later developed Grade V/VI palsy following adjunctive radiotherapy. Seven of the 16 subtotal resections had subsequent radiotherapy or microsurgery. Mean follow up was 26.5 months. In conclusion, subtotal resections lead to good facial nerve outcomes but may require further treatments. Radiation treatment can worsen facial nerve function. There is no standardised use of tumour volumes or accepted guidelines for resection terminology. We propose the use of tumour volumes to define this further.

Medial acoustic neuromas: clinical and surgical implications

OBJECT

Medial acoustic neuroma is a rare entity that confers a distinct clinical syndrome. It is scarcely discussed in the literature and is associated with adverse features. This study evaluates the clinical and imaging features, pertinent surgical challenges, and treatment outcome in a large series of this variant. The authors postulate that the particular pathological anatomy with its arachnoidal rearrangement has a profound implication on the surgical technique and outcome.

METHODS

The authors conducted a retrospective analysis of 52 cases involving 33 women and 19 men who underwent resection of medial acoustic neuromas performed by the senior author (O.A.) over a 20-year period (1993-2013). Clinical, radiological, and operative records were reviewed, with a specific focus on the neurological outcomes and facial nerve function and hearing preservation. Intraoperative findings were analyzed with respect to the effect of arachnoidal arrangement on the surgeon's ability to resect the lesion and the impact on postoperative function.

RESULTS

The average tumor size was 34.5 mm (maximum diameter), with over 90% of tumors being 25 mm or larger and 71% being cystic. Cerebellar, trigeminal nerve, and facial nerve dysfunction were common preoperative findings. Hydrocephalus was present in 11 patients. Distinguishing intraoperative findings included marked tumor adherence to the brainstem and frequent hypervascularity, which prompted intracapsular dissection resulting in enhancement on postoperative MRI in 18 cases, with only 3 demonstrating growth on follow-up. There was no mortality or major postoperative neurological deficit. Cerebrospinal fluid leak was encountered in 7 patients, with 4 requiring surgical repair. Among 45 patients who had intact preoperative facial function, only 1 had permanent facial nerve paralysis on extended follow-up. Of the patients with preoperative Grade I-II facial function, 87% continued to have Grade I-II function on follow-up. Of 10 patients who had Class A hearing preoperatively, 5 continued to have Class A or B hearing after surgery.

CONCLUSIONS

Medial acoustic neuromas represent a rare subgroup whose site of origin and growth patterns produce a distinct clinical presentation and present specific operative challenges. They reach giant size and are frequently cystic and hypervascular. Their origin and growth pattern lead to arachnoidal rearrangement with marked adherence against the brainstem, which is critical in the surgical management. Excellent surgical outcome is achievable with a high rate of facial nerve function and attainable hearing preservation. These results suggest that similar or better results may be achieved in less complex tumors.

The intracranial facial nerve as seen through different surgical windows: an extensive anatomosurgical study

BACKGROUND

The facial nerve has a short intracranial course but crosses critical and frequently accessed surgical structures during cranial base surgery. When performing approaches to complex intracranial regions, it is essential to understand the nerve's conventional and topographic anatomy from different surgical perspectives as well as its relationship with surrounding structures.

OBJECTIVE

To describe the entire intracranial course of the facial nerve as observed via different neurosurgical approaches and to provide an analytical evaluation of the degree of nerve exposure achieved with each approach.

METHODS

Anterior petrosectomies (middle fossa, extended middle fossa), posterior petrosectomies (translabyrinthine, retrolabyrinthine, transcochlear), a retrosigmoid, a far lateral, and anterior transfacial (extended maxillectomy, mandibular swing) approaches were performed on 10 adult cadaveric heads (20 sides). The degree of facial nerve exposure achieved per segment for each approach was assessed and graded independently by 3 surgeons.

RESULTS

The anterior petrosal approaches offered good visualization of the nerve in the cerebellopontine angle and intracanalicular portion superiorly, whereas the posterior petrosectomies provided more direct visualization without the need for cerebellar retraction. The far lateral approach exposed part of the posterior and the entire inferior quadrants, whereas the retrosigmoid approach exposed parts of the superior and inferior quadrants and the entire posterior quadrant. Anterior and anteroinferior exposure of the facial nerve was achieved via the transfacial approaches.

CONCLUSION

The surgical route used must rely on the size, nature, and general location of the lesion, as well as on the capability of the particular approach to better expose the appropriate segment of the facial nerve.