Evaluation of Surgical Approaches to Endoscopic Auditory Brainstem Implantation

Objectives: This study investigates the use of endoscopy for the placement of an auditory brainstem implant by translabyrinthine, retrosigmoid (suboccipital), and middle cranial fossa approaches. Study Design: Cadaver dissection and endoscope-assisted placement of the auditory brainstem implant. Methods: Translabyrinthine, retrosigmoid, and middle cranial fossa dissections were performed bilaterally in five cadaveric heads. An auditory brainstem implant was placed within the lateral recess of the fourth ventricle under endoscopic visualization. The implantation was performed with all approaches and documented by digital image capture followed by production of dye-sublimation photographic prints. Results: The lateral recess was visualized with the endoscope in all three approaches to the brainstem. The 30° endoscope provided the best visualization by translabyrinthine and retrosigmoid dissection and was essential for the middle cranial fossa approach. Refinement of implant position was readily achieved, as even the deepest portion of the recess could be seen with all three approaches. Conclusions: This study finds that endoscopy provides superior visualization of the lateral recess of the fourth ventricle than the operating microscope with all approaches. The retrosigmoid approach is recommended, as it provides the best view of the implantation site and the easiest angle for placement of the prosthesis. The use of the endoscope may allow for a smaller craniotomy than with conventional microscopic techniques, depending on tumor size. The translabyrinthine approach provides a good view of the lateral recess but had no advantage over other approaches. The middle cranial fossa approach is only possible with angled endoscopes; however, it is technically the most difficult and places the facial nerve at greatest risk.     

Residual and recurrent acoustic neuromas

A retrospective study was conducted on all 23 patients who underwent operation for residual or recurrent acoustic neuromas during the 10-year period January 1976 through December 1985. The most common symptoms at the time of reoperation were ataxia (16 patients), facial paresthesias (13 patients), and headaches (9 patients). Primary procedures had consisted of suboccipital posterior fossa approaches in 22 patients and a middle fossa approach in one. Reoperation for recurrent or residual tumor consisted of a retrosigmoid approach in 17 patients and a translabyrinthine or translaby-rinthine/retrosigmoid approach in six patients. This study confirms that residual or recurrent acoustic tumors are not common. It also suggests that long-term follow-up, for at least 7 to 8 years, is indicated.     

Facial function in hearing preservation acoustic neuroma surgery

OBJECTIVE: To determine if facial function is worse after hearing preservation acoustic neuroma surgery (retrosigmoid and middle fossa) than in translabyrinthine surgery. DESIGN: Retrospective medical record review. SETTING: Private neuro-otology subspecialty practice of patients operated on in a tertiary care hospital. PATIENTS: This study evaluated 315 consecutive acoustic neuroma surgical procedures between April 1989 and July 1998. A total of 209 translabyrinthine procedures and 106 hearing preservation surgical procedures were performed. The hearing preservation procedures were equally divided between retrosigmoid (n = 48) and middle fossa (n = 58) procedures. METHODS: Medical records were reviewed and tabulated for tumor size, surgical approach, and House-Brackmann facial function grade at short-, intermediate-, and long-term intervals. RESULTS: Postoperative facial function in hearing preservation surgical procedures at short- and long-term follow-up was not worse than facial function after translabyrinthine surgical procedures in comparably sized tumors. CONCLUSION: Concern about postoperative facial function should not be the deciding factor in selecting hearing preservation vs nonhearing preservation acoustic neuroma surgery.     

Endoscope-assisted vestibular neurectomy

Objective/Hypothesis: In some instances endoscopes offer better visualization than the microscope and frequently allow less invasive surgery. This study was undertaken to determine whether endoscopy is safe and effective during neurectomy of the vestibular nerve. Method: Ten patients with intractable unilateral Meniere's disease underwent a retrosigmoid craniotomy for neurectomy of the vestibular nerve. Endoscopy with a Hopkins telescope was used during each procedure to study posterior fossa anatomic relationships and to assist the neurectomy. Preoperative and postoperative audiometric evaluation was performed in all patients undergoing vestibular neurectomy. Nine of these patients had preoperative electronystagmography, and four patients completed postoperative electronystagmography. The 1995 American Academy of Otolaryngology—Head and Neck Surgery's Committee on Hearing and Equilibrium guidelines for the diagnosis and evaluation of therapy in Meniere's disease were used. Results: Complete neurectomy was achieved in all 10 patients. Endoscopy allowed improved identification of the nervus intermedius and the facial, cochlear, and vestibular nerves and adjacent neurovascular relationships without the need for significant retraction of the cerebellum or brainstem. In addition, endoscopic identification of the cleavage plane between the cochlear and vestibular nerves medial to or within the internal auditory canal (n = 3) was not made with the 0-degree endoscope; however, identification was made with the 30- or 70-degree endoscope in all cases. In all patients with Meniere's disease, elimination of the recurrent episodes of vertigo (n = 10) or otolithic crisis of Tumarkin (n = 1) was achieved. Conclusions: Posterior fossa endoscopy can be performed safely. Endoscope-assisted neurectomy of the vestibular nerve may offer some advantages over standard microsurgery including increased visualization, more complete neurectomy, minimal cerebellar retraction, and a lowered risk of cerebrospinal fluid leakage.     

Surgical exposure of the fundus of the internal auditory canal: Anatomic limits of the middle fossa versus the retrosigmoid transcanal approach

Objective: To define the anatomic limitations and advantages of the middle cranial fossa and the retrosigmoid transcanal approaches in the exposure of the fundus of the internal auditory canal (IAC). Study Design: A series of 15 cadaver temporal bone specimens were dissected and the measurements of the lateral recess of the IAC were made with a millimeter rule and rounded to the nearest quarter millimeter. Methods: Retrospective case review, surgical observation, review, and measurements recorded from magnetic resonance scans. Surgical observations and measurements recorded from cadaver specimens. Results: These results were compared with historical studies of the retrosigmoid transcanal approach. The results utilizing a combination of these approaches to remove acoustic neuromas at a tertiary referral center during the preceding 11 years are also presented. Previous studies have shown that for the retrosigmoid transcanal approach, it is impossible to expose 3 to 4 mm of the lateral recess of the IAC without violating the vestibule and/or the endolymphatic duct. This has led some authors to advocate the middle cranial fossa approach to the IAC when hearing preservation is a consideration. The current study shows that the falciform crest obscures the inferior half of the fundus. This creates a pocket that cannot be visualized, which on average is 1.82 × 2.33 mm. Conclusion: The fundus of the IAC cannot be completely exposed without violating the labyrinth through either the posterior fossa or middle fossa approach. The clinical implications of these studies are unknown at this time. Low recurrence rates are achieved with both approaches. The anatomic limitations of both approaches must still be considered when planning or performing these approaches, to minimize the risk of recurrence.     

Endolymphatic duct status during middle fossa dissection of the internal auditory canal: a human temporal bone radiographic study

OBJECTIVE: Successful hearing preservation after acoustic neuroma resection is sometimes complicated by delayed hearing deterioration. The middle fossa approach appears to offer superior long-term hearing results when compared to the retrosigmoid surgical approach. The goal of this study is to investigate the hypothesis that internal auditory canal (IAC) drilling during middle fossa acoustic neuroma removal is associated with a lower incidence of endolymphatic duct (ELD) injury, a potential cause of delayed hearing loss (HL) known to accompany retrosigmoid hearing preservation dissection techniques. STUDY DESIGN: A human temporal bone anatomic and radiographic study complemented with a literature review. METHODS: Twenty human temporal bones were analyzed with high-resolution multislice computed tomography (HRMCT) and subjected to standard extended middle fossa IAC dissection with labyrinthine preservation and follow-up HRMCT for analyses of the ELD. RESULTS: Zero of 20 (0%) temporal bones were found to have violation of the ELD with preservation of the labyrinthine structures and the endolymphatic sac. Reviews of human and animal studies indicate that injury to the ELD may create endolymphatic hydrops, a known cause of hearing deterioration. CONCLUSION: The ELD is not vulnerable to injury during IAC dissection using the middle fossa approach. A previous radiographic study has shown that the ELD is violated in 24% of temporal bones during retrosigmoid dissection of the IAC. These findings support and may help explain other outcome studies that show that long-term hearing results are superior with the use of the middle fossa approach when compared to results following retrosigmoid dissection.     

扩大迷路径路切除经枕下径路手术后复发的听神经瘤

目的：探讨听神经瘤经枕下径路手术后复发、后经扩大迷路径路再次切除肿瘤的方法及效果。方法：对5例复发的听神经瘤患者，采用扩大迷路径路手术，在经典迷路径路的基础上，通过充分切除岩骨骨质扩大手术视野，将复发的肿瘤组织完全切除。结果：5例听神经瘤直径为2．5～4．0cm，均全部切除，无死亡病例，未发生颅内感染及脑脊液漏；面神经功能与术前一致；术后CT和MRI复查均显示无肿瘤残存，小脑、脑干位置恢复正常。经0．5～2年7个月的随访，至今未见复发，患者已恢复正常生活和工作。结论：枕下径路手术容易残留内听道内的肿瘤，再次手术采用扩大迷路径路可直接暴露肿瘤并到达脑干，既可避免瘢痕粘连区，方便定位面神经，又能全部切除复发的肿瘤，且具有创伤小、面神经功能保存完好等优点。     

内窥镜技术在乙状窦后径路听神经瘤切除术中的应用

目的：探讨乙状窦后径路听神经瘤切除术中应用内窥镜的方法及其在减少残瘤发生率中的价值。方法：常规乙状窦后径路切除听神经瘤（常规手术组）15例，乙状窦后径路加内窥镜检查切除听神经瘤（结合窥镜组）11例，比较其疗效。结果：常规手术组术后3例有残留肿瘤，而结合窥镜组均为阴性；术后听功能，前庭功能障碍发生率及面神经麻痹发生率两组之间差异均无显著性意义。结论：乙状窦后径路听神经瘤切除术，术中使用内窥镜操作方便，安全，未出现由此引起的并发症，并可防止或减少残留病灶及肿瘤复发的发生率，有临床推广应用价值。     

Comparison of postoperative facial nerve outcomes between translabyrinthine and retrosigmoid approaches in matched-pair patients

OBJECTIVES/HYPOTHESIS: The objective was to assess whether the translabyrinthine approach for acoustic tumor removal offers better postoperative facial nerve function compared with the retrosigmoid approach. STUDY DESIGN: Retrospective case review from a tertiary otology referral center. METHODS: Patients who had undergone either retrosigmoid or translabyrinthine approach for removal of acoustic neuroma from January 1, 1980, to December 31, 1999, were included in the study. Two groups of patients were created, one containing retrosigmoid cases and the other, translabyrinthine. Attempts were made to match each retrosigmoid case to a translabyrinthine case with regard to tumor size, patient age, and date of operation. This matching served to eliminate these variables from influencing postoperative facial nerve outcomes. From an initial pool of 450 patients, 35 pairs of patients were matched for the study. Facial nerve functions were reported at immediate, 3-month, and 1-year postoperative periods. RESULTS: Patient demographics demonstrated that matched patients had almost identical tumor size, patient age, and date of operation. Comparisons of postoperative facial nerve functions between the matched groups revealed that retrosigmoid approach carried 2.86 times higher risk of facial nerve dysfunction during the immediate postoperative period. However, by 1 year, the facial nerve outcomes were similar between the two groups. CONCLUSION: Compared with the translabyrinthine approach, retrosigmoid approach carries a higher risk of postoperative facial nerve dysfunction during the immediate postoperative period. However, long-term facial nerve outcomes are identical between the two approaches.     

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.     

经迷路进路听神经瘤术后脑脊液漏的预防及处理

目的　探讨经迷路进路听神经瘤切除术后脑脊液漏发生的影响因素及处理方法。方法1999年以来采用迷路进路或扩大迷路进路听神经瘤切除术 85例 ,前 4 1例采用传统关闭术腔技术 ,后4 4例对关闭技术进行改良 ,分析其脑脊液漏的发生率。发生脑脊液漏者行保守或手术治疗。结果传统关闭技术组中脑脊液漏的发生率为 19 5 % ( 8 4 1) ,改良关闭技术组中脑脊液漏的发生率为 2 3%( 1 4 4 ) ,两组差异有显著性意义 (P =0 0 13)。传统关闭技术组中脑脊液漏多数发生在大型听神经瘤中 ,其发生率随肿瘤增大有上升的趋势。 9例脑脊液漏的患者中 ,3例经保守治疗 ;6例经手术修补成功 ,其中 5例 1次修补成功。结论　改良关闭术腔技术可显著降低经迷路进路听神经瘤切除术后脑脊液漏的发生率 ,手术修补为终止脑脊液漏的有效措施     

Cochlear schwannoma removed through the external auditory canal by a transcanal exclusive endoscopic technique

Surgical approaches to the inner ear and internal auditory canal (IAC) are widely known and extensively recorded. The most popular can be classified as retrosigmoid, transmastoid‐translabyrinthine, and middle cranial fossa approaches. For the first time, an exclusive endoscopic approach to the IAC is described here, used to remove a cochlear schwannoma involving both the IAC and labyrinth. The operation provided a direct transcochlear intradural approach from lateral to medial and from external to internal auditory canal, without any external incision. The pathology was totally removed, and the postoperative outcome of the facial nerve was grade II (House‐Brackmann grading system) at 3‐month follow‐up. Laryngoscope, 123:2862–2867, 2013     

Conservative management of acoustic neuroma in the elderly patient

A subtotal resection through the translabyrinthine approach should be used in the treatment of large symptomatic acoustic neuromas in patients over the age of 65. This approach will consistently relieve the patient's symptoms of brain stem compression, reduce postoperative morbidity and complications, and preserve facial nerve function. In the elderly, after subtotal resection, the remaining tumor in 80% of cases appears to remain dormant during the average six year follow-up (1-16 year range). Eighty percent of acoustic neuromas not operated upon, appear to grow at a slow rate (0.2 cm/yr) while 20% grow at a fast rate (1 cm/yr). Patients over the age of 65 with small acoustic neuromas do not need surgical intervention. Yearly CT scanning is recommended to determine the growth rate of the acoustic neuroma. A conservative approach should be used in the treatment of all acoustic neuromas in the elderly.     

Complications of the translabyrinthine approach for the removal of acoustic neuromas.

OBJECTIVE: To report the complications that occurred during a large series of surgical procedures for the removal of acoustic neuromas using the translabyrinthine approach. DESIGN: Retrospective analysis. SETTING: Neuro-otology practice with academic affiliation. Procedures were performed at either a university medical center or a community hospital in conjunction with a neurosurgery team. PATIENTS: A total of 258 patients (142 men, 116 women; mean age, 51 years) underwent the translabyrinthine approach during a 14-year period. All patients had a histologically proven diagnosis of acoustic neuroma. RESULTS: There were no deaths. There were 3 cases (1.1%) of neurovascular compromise. There were 20 cases (7.8%) of cerebrospinal fluid leak, 16 (80%) of which presented as rhinorrhea and 4 (20%) as incisional leaks. The leaks at the incision responded to conservative management, while rhinorrhea usually required more aggressive means of closure. Four patients (1.6%) were diagnosed as having bacterial meningitis. Complete gross tumor removal was not achieved in 4 patients (1.6%). Facial nerve function, as measured by the House-Brackmann system, was recorded in all patients at 1 year: 76% had a score of I or II; 18%, a score of III or IV; and 6%, a score of V or VI. Other complications included 3 cases of pneumonia, 1 case of severe gastric hemorrhage, and 1 case of wound infection. CONCLUSIONS: The results of this series generally agree with those of other large series and demonstrate the safety and effectiveness of the translabyrinthine approach in excising acoustic neuromas.     

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。     

经迷路进路听神经瘤术后脑脊液漏的预防及处理

目的 探讨经迷路进路听神经瘤切除术后脑脊液漏发生的影响因素及处理方法。方法1999年以来采用迷路进路或扩大迷路进路听神经瘤切除术85例，前41例采用传统关闭术腔技术，后44例对关闭技术进行改良，分析其脑脊液漏的发生率。发生脑脊液漏者行保守或手术治疗。结果 传统关闭技术组中脑脊液漏的发生率为19．5％(8／41)，改良关闭技术组中脑脊液漏的发生率为2．3％(1／44)，两组差异有显著性意义(P=0．013)。传统关闭技术组中脑脊液漏多数发生在大型听神经瘤中，其发生率随肿瘤增大有上升的趋势。9例脑脊液漏的患者中，3例经保守治疗；6例经手术修补成功，其中5例1次修补成功。结论 改良关闭术腔技术可显著降低经迷路进路听神经瘤切除术后脑脊液漏的发生率，手术修补为终止脑脊液漏的有效措施。     

Experiences at the Timone Hospital, Marseille in acoustic neuroma surgery

The authors report their experiences after operating on 279 patients with unilateral acoustic neuromas between 1976 and 1988, with 258 cases managed by the translabyrinthine approach and 21 cases by the middle fossa approach. The authors emphasize the necessity for total removal in order to avoid recurrences.     

Cerebrospinal fluid leak following acoustic neuroma removal

Cerebrospinal fluid (CSF) leak has been a constant and unresolved complication of acoustic tumor surgery. This study retrospectively reviews 381 primary acoustic tumor surgeries performed by a single, senior, neurotologist and neurosurgeon team from 1979 through 1991. There were 68 cerebrospinal fluid leaks in 66 patients (66/381; 17%). There was no significant difference in the incidence of CSF leak between the translabyrinthine group (21%) and the retrosigmoid transmeatal group (16%). Translabyrinthine leaks were evenly divided between rhinorrhea and the postauricular wound while retrosigmoid transmeatal leaks were predominantly rhinorrhea. Eleven of 14 translabyrinthine wound leaks responded to pressure dressing and suture. The remaining 3 ceased with continuous lumbar cerebrospinal fluid drainage. Ten of 14 cases of translabyrinthine rhinorrhea responded to continuous lumbar cerebrospinal fluid drainage, and those in whom it failed were cured with revision of the mastoidectomy/labyrinthectomy cavity. Twenty-one of 28 cases of retrosigmoid transmeatal rhinorrhea responded to continuous lumbar cerebrospinal fluid drainage, and those in whom it failed were cured with extracranial, transmastoid revision. The incidence of cerebrospinal fluid leak was not influenced by age, sex, size of tumor, postoperative hydrocephalus, or the intraoperative use of autologous fibrin glue. Meningitis was an unusual complication, occurring in 3% of all patients.     

并发慢性中耳乳突炎的大听神经瘤经扩大迷路进路二期手术切除

目的：探讨经扩大迷路进路摘除伴发慢性中耳乳突炎的大听神经瘤的手术方法。方法：先一期手术彻底清除鼓室乳突病灶，术毕封闭中耳乳突腔；2周后行二期手术，经一期径路进行听神经瘤切除术。结果：2例并发慢性中耳炎的大听神经瘤均得到全切，术后面神经功能正常，切口一期愈合。随访半年以上无感染发生。结论：并发慢性中耳乳突炎的大听神经瘤同样可经扩大迷路进路进行手术切除。     

Hearing preservation in acoustic neuroma surgery: middle fossa versus retrosigmoid approach

OBJECTIVE: To compare the results of the middle fossa approach with those of the retrosigmoid approach in acoustic neuroma hearing preservation surgery. STUDY DESIGN: Retrospective review. SETTING: Tertiary care facility. PATIENTS: Patients of the otology service with acoustic neuromas and useful hearing. Fifteen intracanalicular tumors were removed via a middle fossa approach and matched with 15 intracanalicular tumors removed via the retrosigmoid approach. Four additional patients with larger tumors were operated on via the middle fossa approach and matched with patients having similar tumors removed via the retrosigmoid approach. MAIN OUTCOME MEASURES: The 1994 Committee on Hearing and Equilibrium guidelines for the evaluation of hearing preservation in acoustic neuroma were applied. Facial nerve results were graded according to the House-Brackmann grading scale 3 months postoperatively. RESULTS: In the group operated on by the middle fossa approach, the average preoperative pure-tone threshold average (PTA) was 23 dB with a word recognition score (WRS) of 79%, and the postoperative PTA averaged 49 dB with a mean WRS of 56%. In the group operated on by the retrosigmoid approach, the mean preoperative PTA was 16 dB with a WRS of 95% and a postoperative PTA value of 62 dB and WRS of 51% (hearing preservation rate of 47%). The middle fossa patients had an average change in PTA of 19 dB and an average change in WRS of 20% (hearing preservation rate of 57%). Overall, the retrosigmoid patients had an average change in PTA of 42 dB and an average change in WRS of 40%. The average change in PTA for larger tumors removed via the middle fossa approach was 32 dB, whereas all matched retrosigmoid patients lost all hearing. The rate of cerebrospinal fluid leak and facial nerve outcomes were similar between the two groups. The retrosigmoid group had a higher rate of postoperative headache. CONCLUSIONS: Compared with the retrosigmoid approach, the middle fossa approach for hearing preservation surgery yields better hearing results for intracanalicular tumors and also has a lower incidence of postoperative headache.