Microsatellite analysis of recurrent vestibular schwannoma (acoustic neuroma) following stereotactic radiosurgery.

HYPOTHESIS: Genetic and immunohistochemical studies may provide insight into the mechanisms of vestibular schwannoma (VS) recurrence following radiation therapy. BACKGROUND: Stereotactic radiation therapy is an increasingly common alternative to microsurgical resection for the primary management of sporadic VS. The molecular mechanisms associated with recurrent vestibular schwannoma (VS) following radiation therapy are not known. METHODS: Primary or irradiated VS tumors were fresh-frozen at the time of surgical resection and microdissected to undergo DNA extraction. Lymphocytic control DNA was isolated from blood obtained by venipuncture. Paired normal and tumor DNA specimens were analyzed for allelic loss by PCR amplification of polymorphic dinucleotide repeat sequences. Immunohistochemical studies were performed on paraffin-embedded, irradiated surgical specimens. RESULTS: Using 16 polymorphic microsatellite markers, 20 of 26 non-irradiated VS demonstrated loss of heterozygosity (LOH) in at least one locus of chromosome 22q. In contrast, none of the four irradiated recurrent VS demonstrated LOH on chromosome 22q (p = 0.008). No allelic loss was seen in either the primary or irradiated VS utilizing markers mapping to chromosome 10. Deletions on chromosome 10 are seen in both benign and higher-grade meningiomas and intracranial malignancies associated with radiotherapy. Immunohistochemical studies were performed to detect the protein product of the NF2 gene, merlin, in the four irradiated VS. NF2 staining was not observed. CONCLUSION: This study represents the first microsatellite and immunohistochemical analysis of recurrent VS following radiation therapy. Our preliminary observations suggest an alternative mechanism of NF2 inactivation that may correlate with radioresistance in VS.     

Acoustic neuroma (vestibular schwannoma) revision

The authors present their experience of more than 25 years, now in excess of 1200 patients, with cerebellopontine angle tumors. This article focuses on the management of planned subtotal resection of acoustic tumors in five subjects, and unexpected "residual" discovered by MRI scanning in 10 cases, which represents, to the best of the authors' knowledge, a residual rate of 1% of operated patients. The rate of residual tumor is as high as 19% in some series and, in part, depends on the surgical approach. For the purpose of this article, the authors did not include their cases of neurofibromatosis, because these tumors behave differently than unilateral sporadic schwannomas.     

听神经瘤手术并发症的处理

目的探讨听神经瘤手术并发症及其处理。方法对105例（110例次）听神经瘤手术的并发症进行回顾性研究，总结手术期问出现的各种并发症及其影响因素。结果105例（110例次）听神经瘤手术，并发症中，全聋86．4％（95／110），面瘫63．6％（70／110），其他并发症的发生依次是脑脊液漏12．7％（14／110）、颅内血肿5．5％（6／110）、颅神经麻痹4．5％（5／110）、脑膜炎3．6％（4／110）、肢体活动障碍3．6％（4／110）、平衡障碍1．8％（2／110）、偏瘫失语0．9％（1／110）；术中彻底止血、术后控制血压、术后24h内有效的镇静方式是防止术后颅内血肿的重要步骤，术后48h为出血期，发生颅内血肿应尽早手术处理；术后脑脊液耳鼻漏的主要原因乳突气房开放后封闭不严，脑脊液切口漏的原因是切口缝合不严、加压包扎不够；经再次治疗均痊愈；术前脑室引流术是高颅压患者减少其他并发症的重要步骤。结论听神经瘤手术严重并发症的发生率很低，其相关因素有肿瘤大小及手术方式；手术医生组的经验和技巧是避免出现并发症的关键因素。     

Acoustic neuroma (vestibular schwannoma) therapy from an oto-rhino-laryngological perspective

Acoustic neuroma/vestibular schwannoma treatment has changed considerably since the 1990s, when surgical treatment was recommended in all cases of schwannoma, whereas nowadays a more differentiated approach is taken. The three classical approaches (translabyrinthine, transtemporal, and suboccipital) still have their surgical value; however, greater importance is apportioned to radiotherapy (radiosurgery, gamma- and cyber-knife). Magnetic resonance imaging in particular has changed diagnostics and how tumor growth is followed. Electrophysiological monitoring of facial and auditory nerves has helped lower postoperative morbidity. New issues have been raised regarding quality of life. Neuropsychological investigations for cognitive and mnestic performance following procedures in the cerebellopontine angle have highlighted problem areas receiving hitherto little attention. Finally, the therapy of this benign lesion should be planned individually, taking the patient's age as well as their professional and personal status into consideration.     

Acoustic neuroma (schwannoma) surgery 1978-1990

A series of 151 patients with 154 acoustic schwannomas have been operated upon in Manchester Royal Infirmary by a joint Otological and Neurosurgical team, employing either the translabyrinthine or the suboccipital approach. The perioperative mortality rate was 3 per cent. Anatomical preservation of the facial nerve was achieved in 89 per cent of tumour removals and a good to normal functional result in 79 per cent of cases. Attempts at hearing preservation have been unsuccessful, largely because of the small number of patients in the series in whom useful hearing was present preoperatively. Complications included major brain stem ischaemia (1.2 per cent), CSF fistula (5 per cent) and facial dysaesthesia (7 per cent). The incidence of mortality and morbidity is directly related to tumour size and to the experience of the surgeons. A number of patients experienced an unusual type of post-operative dreamlike state which appeared to be a form of hypnagogic hallucination, and the possible neurophysiological mechanism responsible for this phenomenon is discussed. The continuing failure to attain the ideal of early diagnosis is lamented, and the importance of a flexible bidisciplinary surgical approach emphasized.     

Complications in acoustic neuroma surgery.

There has been a continuous lowering of mortality and morbidity rates in the 20th century, thanks to increasing experience and newer technology. Despite this, the readership should be aware of the hazards involved in this challenging field. Complications occur, and their incidence, mechanism, management, and prevention have been outlined here so physicians performing these procedures will be better prepared to manage them. We have found that the occurrence of complications can be greatly reduced through a team approach using the combined talents of a neurotologist, neurosurgeon, and frequently an internist. It is apparent from this article that the morbidity of removing larger tumors is significantly greater than the morbidity of removing small tumors. The recent introduction of MRI to the diagnostic armamentarium of the neurotologist may permit earlier detection and a further reduction of morbidity and mortality rates. Only continued study of prevention of complications will assure the improved quality of our results for patients undergoing microsurgical removal of acoustic neuromas.     

Management of surgical complications and failures in acoustic neuroma surgery

Acoustic neuromas (ANs) are the most common tumors of the cerebellopontine angle. Although numerous advances have occurred in the operative management of AN and perioperative care leading to a significant decrease in associated morbidity and mortality, there are several characteristic complications that accompany microsurgical resection of AN. Understanding the types and rates of complications in association with the various approaches is essential in patient counseling, establishing patient expectations, and ensuring the best patient outcome. In this article, the justification for incomplete surgical resection is discussed. Also, the most common complications of AN microsurgery and the associated management are reviewed.     

Acoustic neuroma (vestibular schwannoma). Treatment from a neurosurgical perspective

During the last century microsurgical approaches laid emphasis in descending order on preservation of life, total tumor excision and function. Today, the priority of microsurgery has changed to functional preservation. The management of vestibular schwannomas consists of observation, surgical resection, or radiation therapy. In recent years, there has been an increase in observation-only management for small tumors, or radiotherapy in the case of tumor progression. The number of surgical procedures is in decline, with surgery being reserved mainly for large tumors.     

Hearing preservation in acoustic neuroma surgery.

This article reviews the Montreal experience of hearing preservation in acoustic neuroma surgery. The medical records since 1995 of 36 patients who underwent acoustic neuroma extirpation with the intent to preserve hearing were examined. Intraoperative monitoring was conducted using auditory brainstem response measurement with electrocochleography via a transtympanic electrode. The role of intraoperative monitoring in guiding surgical technique and its correlation with postoperative hearing outcome are discussed. A review of the literature regarding hearing preservation in acoustic neuroma surgery is included.     

Hearing preservation in acoustic neuroma surgery.

With advances in imaging, intracanalicular acoustic neuromas are identified readily in patients including, oftentimes, those with serviceable hearing. Fourteen patients were operated on in an attempt to preserve hearing. Hearing was retained in 10 (71%) of the 14. Serviceable hearing was present in 7 (50%), borderline serviceable hearing in 2 (14%), and nonserviceable hearing in 1 (7%). The problems, advantages, and disadvantages of the differing approaches are discussed.     

The learning curve in vestibular schwannoma surgery.

OBJECTIVE: This study aimed to examine the effect of surgical team experience on facial nerve function and complication rate in vestibular schwannoma surgery. STUDY DESIGN: The study design was a retrospective analysis of a case series. SETTING: The study was conducted at a tertiary referral center. PATIENTS: One hundred sixty consecutive patients undergoing vestibular schwannoma excision participated. INTERVENTION: Surgical excision of vestibular schwannoma via a translabyrinthine, middle cranial fossa, suboccipital, or combined approach was performed. MAIN OUTCOME MEASURES: Facial nerve function (House-Brackmann score) and complication rates including cerebrospinal fluid leak and meningitis compared by groups of 20 patients were measured. RESULTS: There was a statistically significant improvement in the number of patients achieving a House-Brackmann grade I result between the first 20 patients (35% House-Brackmann grade 1) and the ensuing 7 groups of 20 patients (74% House-Brackmann grade 1) by chi2 analysis. When considering House grades I and II together, there was no statistically significant difference in facial nerve function in the first 20 patients (80%) compared to the last 7 groups of 20 patients (88%) by Tukey's pairwise comparisons (p = 0.245). Mean tumor size was not significantly different in the groups studied (p = 0.54). The total cost of patient care declined over the study period; however, the wide case-to-case variance made it so that this trend was not statistically significant (p = 0.448). CONCLUSIONS: A learning curve of 20 patients was demonstrated by this study to have been necessary for attaining acceptable standards in the surgical removal of vestibular schwannomas by a new surgical team. The findings of this study may have implications for patient care and surgeon training.     

Cranioplasty in acoustic neuroma surgery

OBJECTIVES: To measure the incidence of postoperative headaches after retrosigmoid resections of acoustic neuromas and to evaluate the impact of cranioplasty on the prevention and management of these headaches. STUDY DESIGN: A prospective evaluation was performed on 30 consecutive patients who underwent a cranioplasty after retrosigmoid excision of their acoustic neuroma. The results were compared with 30 historical control patients who underwent the same procedure but did not have reconstruction with a cranioplasty. The patients were evaluated by review of office records and via telephone questionnaire. METHODS: One group of patients (30 patients) had no cranioplasty, and the other group of 30 patients had primary reconstruction with a titanium mesh-acrylic cranioplasty. All 60 patients were asked to report on the duration and severity of their headaches by means of a standard questionnaire, grading their symptoms on a scale of 1 to 4. The data were subjected to chi2 and Student t test statistical analyses. RESULTS: New-onset, postoperative headaches occurred in 27% of patients, 23% in the cranioplasty group compared with 30% in the group without cranioplasty (a difference that was not statistically significant [P = .158]). However, there was a statistically significant difference in the severity of the headaches (P<.03). The headaches in the cranioplasty group were less severe and were not disabling. There were no complications, infections, or extrusions related to the cranioplasty. CONCLUSIONS: Cranioplasty has not been able to eliminate postoperative headaches. However, the use of cranioplasty has significantly decreased the severity of postoperative headaches after retrosigmoid excision of acoustic neuromas.     

Facial nerve outcome in acoustic neuroma surgery.

Patients consider facial paralysis the most concerning sequelae following acoustic tumor resection. Surgical and anesthetic refinements have lowered operative mortality to allow the surgeon to focus on preserving facial nerve function. Tumor size, microsurgical technique, and intraoperative monitoring are the most important factors that define the risk of postoperative facial paralysis. A protocol for uniform surgical reporting is proposed.     

Hearing preservation surgery in vestibular schwannoma

OBJECTIVES: To study the effect of pre-operative hearing level and tumour size on the hearing outcome of hearing preservation surgery for vestibular schwannoma. STUDY DESIGN AND SETTING: A review of literature conducted at Gruppo Otologico, a tertiary referral centre for neurotology and skull base surgery. RESULTS: A total of 1993 patients in 16 publications addressing the topic of hearing preservation surgery in vestibular schwannoma were analysed. The American Academy of Otolaryngology-Head and Neck Surgery hearing classification system was the classification upon which we based our analysis. CONCLUSION: Defining hearing preservation as class-A hearing, there was a strong inverse relationship between pre-operative hearing and post-operative hearing levels and between tumour size and post-operative hearing levels.     

Balance impairment after acoustic neuroma surgery.

OBJECTIVE: The aim of this study was to assess the incidence of balance problems after acoustic neuroma surgery, evaluating whether disequilibrium is disabling. STUDY DESIGN: Retrospective observational study. SETTING: Rehabilitation center. PATIENTS: A group of 386 patients who underwent acoustic neuroma surgery. INTERVENTIONS: Patients were selected from a population of 459 subjects who had undergone surgery for acoustic neuroma. MEAN OUTCOME MEASURES: The Dizziness Handicap Inventory, The Activities-specific Balance Confidence Scale (ABC), and a specific questionnaire on oscillopsia. RESULTS: The specific questionnaire emphasized that 39 patients (10.10%) perceived disequilibrium as disabling, and the oscillopsia handicap score result was moderate in 73.32% of the sample, mild in 21.50%, and severe in 5.18% of patients. The Dizziness Handicap Inventory and ABC scales revealed the presence of handicap and disability due to disequilibrium and the influence of some variables such as sex and a higher oscillopsia handicap score. Dizziness Handicap Inventory and ABC scores were higher in symptomatic patients. CONCLUSION: Disequilibrium influences handicap and disability after acoustic neuroma surgery. This symptom is also present after several years since surgery, and some patients perceived disequilibrium as disabling.