Outcome on hearing and facial nerve function in microsurgical treatment of small vestibular schwannoma via the middle cranial fossa approach

Temporal lobe injury with middle fossa approach to intracanalicular vestibular schwannomas: a systematic review

There are several surgical approaches for vestibular schwannoma (VS) resection. However, management has gradually shifted from microsurgical resection, toward surveillance and radiosurgery. One of the arguments against microsurgery via the middle fossa approach (MFA) is the risk of temporal lobe retraction injury or sequelae. Here, we sought to evaluate the incidence of temporal lobe retraction injury or sequela from a MFA via a systematic review of the existing literature. This systematic review was conducted according to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines. Relevant studies reporting temporal lobe injury or sequela during MFA for VS were identified. Data was aggregated and subsequently analyzed to evaluate the incidence of temporal lobe injury. 22 studies were included for statistical analysis, encompassing 1522 patients that underwent VS resection via MFA. The overall rate of temporal lobe sequelae from this approach was 0.7%. The rate of CSF leak was 5.9%. The rate of wound infection was 0.6%. Meningitis occurred in 1.6% of patients. With the MFA, 92% of patients had good facial outcomes, and 54.9% had hearing preservation. Our series and literature review support that temporal lobe retraction injury or sequelae is an infrequent complication from an MFA for intracanalicular VS resection.

Clinical practice guideline on the management of vestibular schwannoma

INTRODUCTION

Vestibular schwannoma (VS) is the most common tumour of the cerebellopontine angle. The greater accessibility to radiological tests has increased its diagnosis. Taking into account the characteristics of the tumour, the symptoms and the age of the patient, three therapeutic strategies have been proposed: observation, surgery or radiotherapy. Choosing the most appropriate for each patient is a frequent source of controversy.

MATERIAL AND METHODS

This paper includes an exhaustive literature review of issues related to VS that can serve as a clinical guide in the management of patients with these lesions. The presentation has been oriented in the form of questions that the clinician usually asks himself and the answers have been written and/or reviewed by a panel of national and international experts consulted by the Otology Commission of the SEORL-CCC.

RESULTS

A list has been compiled containing the 13 most controversial thematic blocks on the management of VS in the form of 50 questions, and answers to all of them have been sought through a systematic literature review (articles published on PubMed and Cochrane Library between 1992 and 2023 related to each thematic area). Thirty-three experts, led by the Otology Committee of SEORL-CCC, have analyzed and discussed all the answers. In Annex 1, 14 additional questions divided into 4 thematic areas can be found.

CONCLUSIONS

This clinical practice guideline on the management of VS offers agreed answers to the most common questions that are asked about this tumour. The absence of sufficient prospective studies means that the levels of evidence on the subject are generally medium or low. This fact increases the interest of this type of clinical practice guidelines prepared by experts.

Variants of the Anterior Subtemporal Approach to the Gasserian Ganglion and Related Structures: An Anatomical Study With Relevant Implications for Keyhole Surgery

BACKGROUND

The advantages and limitations of different craniotomy positions and approach trajectories to the gasserian ganglion (GG) and related structures using an anterior subtemporal approach have not been studied systematically. Knowledge of these features is of importance when planning keyhole anterior subtemporal (kAST) approaches to the GG to optimize access and minimize risks.

METHODS

Eight formalin-fixed heads were used bilaterally to assess temporal lobe retraction (TLR), trigeminal exposure, and relevant anatomical aspects of extra- and transdural classic anterior subtemporal (CLAST) approaches compared with slightly dorsally and ventrally allocated corridors.

RESULTS

TLR to the GG and foramen ovale was found to be lower via the CLAST approach (P < 0.001). Using the ventral variant, TLR to access the foramen rotundum was minimized (P < 0.001). The overall TLR was maximal using the dorsal variant (P < 0.001) owing to interposition of the arcuate eminence. An extradural CLAST approach required wide exposure of the greater petrosal nerve (GPN) and middle meningeal artery (MMA) sacrifice. Both maneuvers were spared using a transdural approach. Using CLAST, medial dissection >39 mm can enter the Parkinson triangle, jeopardizing the intracavernous internal carotid artery. The ventral variant enabled access to the anterior portion of the GG and foramen ovale without the need for MMA sacrifice or GPN dissection.

CONCLUSIONS

The CLAST approach provides high versatility to approach the trigeminal plexus, minimizing TLR. However, an extradural approach jeopardizes the GPN and requires MMA sacrifice. The risk of cavernous sinus violation exists when progressing medially beyond 4 cm. The ventral variant has some advantages to access the ventral structures and avoid MMA and GPN manipulation. In contrast, the usefulness of the dorsal variant is rather limited owing to the greater TLR required.

Introducing an Evidence-Based Approach to Wait-And-Scan Management of Sporadic Vestibular Schwannoma

The advent of MRI has led to more sporadic vestibular schwannomas diagnosed today than ever before. Despite the average patient being diagnosed in their sixth decade of life with a small tumor and minimal symptoms, population-based data demonstrate that more tumors per capita are treated today than ever before. Emerging natural history data justify either an upfront treatment approach or the "Size Threshold Surveillance" approach. Specifically, if the patient elects to pursue observation, then existing data support the tolerance of some growth during observation in appropriately selected patients up until a specific size threshold range (about 15 mm of CPA extension). The current article discusses the rationale behind a shift in the existing observation management approach, where initial detection of growth typically begets treatment, and outlines the application of a more flexible and nuanced approach based on existing evidence.

Auditory Brain Stem Response Predictors of Hearing Outcomes after Middle Fossa Resection of Vestibular Schwannomas

Objectives To analyze the relationship between preoperative and intraoperative auditory brain stem response (ABR) characteristics and hearing outcomes in patients with vestibular schwannomas (VS) undergoing hearing preservation (HP) surgery via a middle cranial fossa (MCF) approach.

Design Prospective study.

Setting Academic tertiary skull base referral center.

Methods Pre- and postoperative pure-tone average (PTA) and word recognition score (WRS) were examined. Intraoperative ABR wave III latency, wave V latency, and amplitude were recorded. HP was defined as postoperative WRS ≥50%.

Participants Adult patients with VS and WRS ≥50% who underwent MCF tumor resection between November 2017 and September 2019.

Main Outcome Measures Postoperative hearing outcomes.

Results Sixty patients were included. Mean tumor size was 9.2 mm (range, 3–17). HP rates were 56.7% for the cohort and 69.7% for tumors <10 mm. A complete loss of wave V was associated with an 82.9% increase in postoperative PTA (p < 0.001) and 97.2% decrease in WRS (p < 0.001), whereas a diminished wave V was correlated with 62.7% increase in PTA (p < 0.001) and 55.7% decrease in WRS (p = 0.006). A diminished or absent wave V, but not increased wave III/V latency or decreased wave V amplitude, was correlated with a decline in postoperative hearing class (r = 0.735, p < 0.001). Receiver-operating characteristic analysis demonstrated that a stable wave V has the highest accuracy in predicting HP (sensitivity of 82.6%, specificity of 84.8%).

Conclusion Of the examined preoperative and intraoperative ABR characteristics, a stable wave V intraoperatively was the strongest predictor of HP after MCF resection of VS.

Level of Evidence Level III.

Progression of Hearing Loss in Observed Non-Growing Vestibular Schwannoma

OBJECTIVE

To assess hearing outcomes in observed vestibular schwannoma (VS) with focus on non-growing tumors.

STUDY DESIGN

Retrospective review.

SETTING

Two tertiary neurotology centers.

PATIENTS AND INTERVENTIONS

Patients with sporadic VS undergoing at least 3 years' observation.

MAIN OUTCOME MEASURES

Changes in pure tone averages (PTA) and word recognition scores (WRS) normalized to the contralateral ear.

RESULTS

During the study period, 39 of 105 included patients (37.1%) had tumor growth. Patients with tumor growth had a mean normalized increase in PTA of 8.0 dB HL (p = 0.008) corresponding to a normalized average worsening of their PTA of 1.8 dB per year. Patients with non-growing tumors less than 5 mm in maximal dimension did not have significant ongoing normalized hearing loss (p > 0.05). Patients with non-growing tumors more than or equal to 5 mm had a mean normalized increase in PTA of 7.4 dB HL (p = 0.001) corresponding to an average of 2.0 dB HL per year, which was similar to the loss observed in growing tumors regardless of size (p > 0.05). Normalized decline in PTA of at least 5 dB HL was seen in 72% of patients with growing tumors, 53% of patients with nongrowing tumors more than or equal to 5 mm, and 38% of patients with non-growing tumors less than 5 mm.

CONCLUSIONS

A long-term analysis of hearing outcomes in observed vestibular schwannoma is presented. With observation, VS more than or equal to 5 mm is associated with continued hearing loss even without tumor growth, while non-growing tumors less than 5 mm are not associated with continuing hearing loss. These data inform expectations for observed VS for providers and patients.

Neuromonitoring of the cochlear nerve during vestibular schwannoma resection and simultaneous cochlear implantation

Vestibular schwannomas (VS) are benign tumors that originate from the nerve sheath of one of the two vestibular nerves. VS can have a severe impact on everyday life of the patient and may lead to symptoms such as vertigo, hearing loss (e.g., as sudden deafness), deafness, and tinnitus. Treatment concepts include observational waiting with regular imaging control ("wait and scan"), radiotherapy, or surgical resection. Depending on the size of the tumor and status of functional hearing, the surgical approach may be retrosigmoidal, transtemporal, retrolabyrinthine, or translabyrinthine. The translabyrinthine approach always results in complete deafness due to opening of the bony labyrinth. If the nerve structure of the cochlear nerve is preserved, hearing rehabilitation with a cochlear implant (CI) may be successful. In this article the surgical technique for microsurgical resection of VS using a translabyrinthine approach with simultaneous cochlear implantation under intraoperative monitoring of the cochlear nerve by electrical stimulation is presented.

[Neuromonitoring of the cochlear nerve during vestibular schwannoma resection and simultaneous cochlear implantation. German version]

Vestibular schwannomas (VS) are benign tumors that originate from the nerve sheath of one of the two vestibular nerves. VS can have a severe impact on everyday life of the patient and may lead to symptoms such as vertigo, hearing loss (e.g., as sudden deafness), deafness, and tinnitus. Treatment concepts include observational waiting with regular imaging control ("wait and scan"), radiotherapy, or surgical resection. Depending on the size of the tumor and status of functional hearing, the surgical approach may be retrosigmoidal, transtemporal, retrolabyrinthine, or translabyrinthine. The translabyrinthine approach always results in complete deafness due to opening of the bony labyrinth. If the nerve structure of the cochlear nerve is preserved, hearing rehabilitation with a cochlear implant (CI) may be successful. In this article the surgical technique for microsurgical resection of VS using a translabyrinthine approach with simultaneous cochlear implantation under intraoperative monitoring of the cochlear nerve by electrical stimulation is presented.

Outcomes after mini-craniotomy middle fossa approach combined with mastoidectomy for lateral skull base defects

PURPOSE

Controversy exists regarding the ideal approach for repair of lateral skull base defects. Our goal is to report the outcomes following middle cranial fossa (MCF) mini-craniotomy combined with mastoidectomy for patients with superior semicircular canal dehiscence (SSCD), spontaneous cerebrospinal fluid (CSF) leak, and cholesteatoma.

MATERIALS AND METHODS

A retrospective database from chart review was formed consisting of 97 patients who met surgical criteria: SSCD, spontaneous CSF leak, and cholesteatoma. Mini-craniotomy MCF approach (<4 × 2 cm in size) combined with mastoidectomy was performed. All patients were admitted directly to the ICU postoperatively. Multiple factors were assessed, including need for revision surgery, duration of surgery, length of post-operative stay, and hospital readmission.

RESULTS

Average surgery time was 110 min with no intraoperative complications. The average length of hospitalization was 2 days with an average ICU stay of 1 day. There were no neurologic complications; however, there were 3 inpatient complications (3%) which included 1 patient (1%) that had wound breakdown and 2 patients (2%) that had severe post-operative vertigo. A total of 8 patients (8%) required revision surgery and these were primarily for SSCD. The 30-day readmission rate was 3%.

CONCLUSION

In the current series, all patients that underwent mini-craniotomy MCF surgery combined with mastoidectomy had minimal complications, short surgical time, limited hospital stay, low revision surgery rate and few hospital readmissions. This combined approach offers superior visualization of lateral skull base defects without the morbidity and risk typically associated with traditional, extensive MCF surgery.

Facial Nerve Outcomes After Vestibular Schwannoma Microsurgical Resection in Neurofibromatosis Type 2

OBJECTIVE

The aim of this study is to investigate facial nerve outcomes after microsurgical resection in neurofibromatosis type 2 (NF2) compared to sporadic tumors.

STUDY DESIGN

Single institutional retrospective chart review.

SETTING

Tertiary referral center.

METHODS

All adult patients with NF2 vestibular schwannoma (VS) or sporadic VS who underwent microsurgical resection from 2008 to 2019 with preoperative magnetic resonance imaging (MRI) and 1 year of postsurgical follow-up were included. The primary outcome measure was postoperative House-Brackmann (HB) facial nerve score measured at first postoperative visit and after at least 10 months.

RESULTS

In total, 161 sporadic VSs and 14 NF2 VSs met inclusion criteria. Both median tumor diameter (NF2, 33.5 mm vs sporadic, 24 mm, P = .0011) and median tumor volume (NF2, 12.4 cm³ vs sporadic, 2.9 cm³, P = .0005) were significantly greater in patients with NF2. The median follow-up was 24.9 months (range, 12-130.1). Median facial nerve function after 1 year for patients with NF2 was HB 3 (range, 1-6) compared to HB 1 (range, 1-6) for sporadic VS (P = .001). With multivariate logistic regression, NF2 tumors (odds ratio [OR] = 13.9, P = .001) and tumor volume ≥3 cm³ (OR = 3.6, P = .025) were significantly associated with HB ≥3 when controlling for age, sex, extent of tumor resection, translabyrinthine approach, and prior radiation.

CONCLUSION

Tumor volume >3 cm³ and NF2 tumors are associated with poorer facial nerve outcomes 1 year following microsurgical resection.

Postoperative Hearing Preservation in Patients Undergoing Retrosigmoid Craniotomy for Resection of Vestibular Schwannomas: A Systematic Review of 2034 Patients

BACKGROUND

Vestibular schwannomas (VS) are benign tumors derived from Schwann cells ensheathing the vestibulocochlear nerve. The retrosigmoid (RS) surgical approach is useful to resect tumors of multiple sizes while affording the possibility of preserving postoperative hearing.

OBJECTIVE

To conduct a systematic review of published literature investigating hearing preservation rates in patients who underwent the RS approach for VS treatment.

METHODS

The PubMed, Scopus, and Embase databases were surveyed for studies that reported preoperative and postoperative hearing grades on VS patients who underwent RS treatment. Hearing preservation rates were calculated, and additional patient demographic data were extracted. Tumor size data were stratified to compare hearing preservation rates after surgery for intracanalicular, small (0-20 mm), and large (>20 mm) tumors.

RESULTS

Of 383 deduplicated articles, 26 studies (6.8%) met eligibility criteria for a total of 2034 patients with serviceable preoperative hearing, for whom postoperative hearing status was evaluated. Aggregate hearing preservation was 31% and 35% under a fixed and random effects model, respectively. A mixed effects model was used to determine hearing preservation rates depending on tumor size, which were determined to be 57%, 37%, and 12% for intracanalicular, small, and large tumors, respectively. Significant cross-study heterogeneity was found (I2 = 93%, τ2 = .964, P < .01; Q = 287.80, P = < .001), with rates of hearing preservation ranging from 0% to 100%.

CONCLUSION

Tumor size may have an effect on hearing preservation rates, but multiple factors should be considered. Discussion of a patient's expectations for hearing preservation is critical when deciding on VS treatment plans.

Cochlear Patency after Translabyrinthine and Retrosigmoid Vestibular Schwannoma Surgery

OBJECTIVES

To assess the incidence and onset of cochlear obliteration after translabyrinthine and retrosigmoid vestibular schwannoma surgery.

MATERIALS AND METHODS

We retrospectively identified a consecutive series of eighty ears in eighty vestibular schwannoma patients who were treated via a translabyrinthine or retrosigmoid approach by a single neuro-otological surgical team in a tertiary referral center from May 2011 to January 2018. Postoperative, high- resolution T2-weighted turbo spin echo three-dimensional magnetic resonance (MR) images of the posterior fossa were evaluated at the level of the membranous labyrinth and internal auditory canal. Perilymphatic patency of the vestibule, basal, and apical cochlear turns were scored and classified as patent, hypointense, partially obliterated, or completely obliterated.

RESULTS

Twenty-five vestibular schwannomas were treated with surgery via a translabyrinthine approach, and fifty-five were treated using a retrosigmoid approach; of these, 8% and 65%, respectively, showed no signs of perilymphatic alterations in the basal or apical turns, while 84% and 20%, respectively, showed partial or complete obliteration in the basal or apical turns with a mean postoperative interval of 127 and 140 days, respectively. All the patients who underwent multiple MR scans and had a completely patent perilymphatic system on the first postoperative scan remained patent during subsequent scans; 16% of the patients showed worsened perilymphatic appearance. The onset of cochlear obliteration occurred within 2-7 months in most translabyrinthine patients.

CONCLUSION

These findings may support the need for simultaneous cochlear electrode or dummy implantation in translabyrinthine surgery. Second-stage implantation could be feasible in cases where a retrosigmoid approach is used; however, the implantation should be considered within the initial months to avoid cochlear obliteration. Findings on the first postoperative MR could indicate the need for intensified MR follow-up and may even predict the occurrence of cochlear obliteration.

Surgery of the lateral skull base: a 50-year endeavour

Disregarding the widely used division of skull base into anterior and lateral, since the skull base should be conceived as a single anatomic structure, it was to our convenience to group all those approaches that run from the antero-lateral, pure lateral and postero-lateral side of the skull base as “Surgery of the lateral skull base”. “50 years of endeavour” points to the great effort which has been made over the last decades, when more and more difficult surgeries were performed by reducing morbidity. The principle of lateral skull base surgery, “remove skull base bone to approach the base itself and the adjacent sites of the endo-esocranium”, was then combined with function preservation and with tailoring surgery to the pathology. The concept that histology dictates the extent of resection, balancing the intrinsic morbidity of each approach was the object of the first section of the present report. The main surgical approaches were described in the second section and were conceived not as a step-by-step description of technique, but as the highlighthening of the surgical principles. The third section was centered on open issues related to the tumor and its treatment. The topic of vestibular schwannoma was investigated with the current debate on observation, hearing preservation surgery, hearing rehabilitation, radiotherapy and the recent efforts to detect biological markers able to predict tumor growth. Jugular foramen paragangliomas were treated in the frame of radical or partial surgery, radiotherapy, partial “tailored” surgery and observation. Surgery on meningioma was debated from the point of view of the neurosurgeon and of the otologist. Endolymphatic sac tumors and malignant tumors of the external auditory canal were also treated, as well as chordomas, chondrosarcomas and petrous bone cholesteatomas. Finally, the fourth section focused on free-choice topics which were assigned to aknowledged experts. The aim of this work was attempting to report the state of the art of the lateral skull base surgery after 50 years of hard work and, above all, to raise questions on those issues which still need an answer, as to allow progress in knowledge through sharing of various experiences. At the end of the reading, if more doubts remain rather than certainties, the aim of this work will probably be achieved.

[The efficacy of botulinum therapy in treatment of delayed facial palsy after resection of vestibular schwannoma]

Delayed facial palsy is a complication developing 3 or more days after surgery. The etiology and pathogenesis of this condition has not been fully explored, and there are no treatment standards for it. As in the case of Bell's paralysis, glucocorticosteroids (GCSs) are currently used to treat delayed facial palsy. However, patients with contraindications to GCSs need new therapy modalities.

AIM

We aimed to evaluate the efficacy and safety of botulinum therapy in patients with delayed facial palsy after neurosurgical interventions.

MATERIAL AND METHODS

We examined 33 patients with delayed facial palsy developed 3 or more days after resection of vestibular schwannoma. The main group included 18 patients with contraindications to GCSs who received injections of botulinum toxin A (BTA) into the facial muscles of the healthy side for muscle relaxation. The comparison group consisted of 15 patients who received a course of prednisolone (1 mg/kg/day) for 5-7 days. The efficacy of treatment was assessed using the House-Brackmann scale and Clinical Global Impression Scale. The follow-up period after therapy was 3 months.

RESULTS

Delayed facial palsy was more common in the following cases: the facial nerve was located near the antero-inferior tumor pole; the tumor was adherent to the facial nerve; the tumor extended in the oral direction; the tumor had with unclear borders and was 11 to 30 mm in size. In most patients of both groups, facial muscle palsy developed more than 11 days after surgery. Treatment both in the main and control groups resulted in a significant improvement: complete regression of the facial asymmetry in patients of the main group and comparison groups 3 months after treatment onset was 83.3 and 93.3% (House-Brackmann scale), respectively.

CONCLUSION

Botulinum therapy may be recommended for patients with delayed facial palsy developed after vestibular schwannoma resection, who have contraindications to GCSs.

Translabyrinthine microsurgical resection of small vestibular schwannomas

OBJECTIVE

Translabyrinthine resection is one of a number of treatment options available to patients with vestibular schwannomas. Though this procedure is hearing destructive, the authors have noted excellent clinical outcomes for patients with small tumors. The authors review their experience at a tertiary acoustic neuroma referral center in using the translabyrinthine approach to resect small vestibular schwannomas. All operations were performed by a surgical team consisting of a single neurosurgeon and 1 of 7 neurotologists.

METHODS

Data from a prospectively maintained clinical database were extracted and reviewed. Consecutive patients with a preoperative diagnosis of vestibular schwannoma that had less than 1 cm of extension into the cerebellopontine angle, operated on between 2008 and 2013, were included. Patents with neurofibromatosis Type 2, previous treatment, or preexisting facial weakness were excluded. In total, 107 patients were identified, 74.7% of whom had poor hearing preoperatively.

RESULTS

Pathologically, 6.5% of patients were found to have a tumor other than vestibular schwannoma. Excluding two malignancies, the tumor control rates were 98.7%, as defined by absence of radiographic disease, and 99.0%, as defined by no need for additional treatment. Facial nerve outcome was normal (House-Brackmann Grade I) in 97.2% of patients and good (House-Brackmann Grade I–II) in 99.1%. Complications were cerebrospinal fluid leak (4.7%) and sigmoid sinus thrombosis (0.9%), none of which led to long-term sequelae.

CONCLUSIONS

Translabyrinthine resection of small vestibular schwannomas provides excellent results in terms of complication avoidance, tumor control, and facial nerve outcomes. This is a hearing-destructive operation that is advocated for selected patients.

Middle Fossa Approach for Resection of Vestibular Schwannomas: A Decade of Experience

BACKGROUND

The middle cranial fossa (MCF) approach is a challenging surgical technique for the resection of small and intermediate sized, primarily intracanalicular, vestibular schwannomas (VS), with the goal of hearing preservation (HP).

OBJECTIVE

To describe a decade-long, single institutional experience with the MCF approach for resection of VS.

METHODS

This is a retrospective cohort study of 63 patients who underwent the MCF approach for resection of VS from 2006 to 2016. Audiometric data included pure-tone average (PTA), low-tone pure-tone average (LtPTA), word recognition score, and American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) hearing classification at presentation and follow-up. Patients with postoperative serviceable (AAO-HNS class A-B) and/or useful (AAO-HNS class A-C) hearing were compared to those without HP. Facial nerve function was assessed using the House–Brackmann scale.

RESULTS

The mean age and duration of follow-up were 50 ± 13 yr and 21 ± 21 mo, respectively. The mean tumor size was 10 ± 4 mm. The serviceable and usable HP rates were 54% and 50%, respectively. Some residual hearing was preserved in 71% of patients. Large tumor size (P = .05), volume (P = .03), and extrameatal tumor extension (P = .03) were associated with poor audiometric outcomes. The presence of a fundal fluid cap (P = .01) was a favorable finding. At definitive testing, LtPTA was significantly better preserved than traditional PTA (P = .01). Facial nerve outcomes, tumor control rates, and durability of audiometric outcomes were excellent. 47% of patients pursued aural rehabilitation.

CONCLUSION

In our series, the MCF approach for VS provided excellent rates of tumor and facial nerve function, with durable serviceable HP.

Surgical outcomes of middle fossa approach in intracanalicular vestibular schwannoma

CONCLUSION

Middle fossa approach (MFA) shows a hearing preservation rate of 86% and facial nerve function was preserved with HB grade I or II in 93%. MFA is a good treatment option for intra-canalicular vestibular schwannomas when surgical excision is needed.

BACKGROUND

Surgical outcomes of vestibular schwannoma have progressively improved with the advancement of microsurgical instruments. MFA is known to have better chances to preserve hearing, while it has limited access to the posterior fossa, limitation of tumor size, and higher risk of post-operative facial nerve weakness.

OBJECTIVES

To investigate surgical outcomes and clinical efficiency of MFA in vestibular schwannoma.

METHODS

A retrospective study was done in 14 patients who underwent MFA for vestibular schwannoma in Asan Medical Center.

RESULTS

The median age at diagnosis was 46.3 years. At initial presentation, 57% of the patients had vertigo, 43% hearing disturbance, and 64% tinnitus. The mean tumor size was 9.7 mm. The tumors were completely resected in 86% of the patients. Hearing was post-operatively preserved in 12 patients and two patients lost their hearing following surgery. Facial nerve function post-operatively remained unchanged in 12 patients (86%).

Is less always better? Keyhole and standard subtemporal approaches: evaluation of temporal lobe retraction and surgical volume with and without zygomatic osteotomy in a cadaveric model

OBJECTIVE The subtemporal approach is one of the surgical routes used to reach the interpeduncular fossa. Keyhole subtemporal approaches and zygomatic arch osteotomy have been proposed in an effort to decrease the amount of temporal lobe retraction. However, the effects of these modified subtemporal approaches on temporal lobe retraction have never been objectively validated. METHODS A keyhole and a classic subtemporal craniotomy were executed in 4 fresh-frozen silicone-injected cadaver heads. The target was defined as the area bordered by the superior cerebellar artery, the anterior clinoid process, supraclinoid internal carotid artery, and the posterior cerebral artery. Once the target was fully visualized, the authors evaluated the amount of temporal lobe retraction by measuring the distance between the base of the middle fossa and the temporal lobe. In addition, the volume of the surgical and anatomical corridors was assessed as well as the surgical maneuverability using navigation and 3D moldings. The same evaluation was conducted after a zygomatic osteotomy was added to the two approaches. RESULTS Temporal lobe retraction was the same in the two approaches evaluated while the surgical corridor and the maneuverability were all greater in the classic subtemporal approach. CONCLUSIONS The zygomatic arch osteotomy facilitates the maneuverability and the surgical volume in both approaches, but the temporal lobe retraction benefit is confined to the lateral part of the middle fossa skull base and does not result in the retraction necessary to expose the selected target.

Impact of Elevation of Temporal Lobe During Middle Fossa Acoustic Neuroma Surgery on Contralateral Speech Discrimination

AIM

For middle fossa acoustic neuroma approach, retractors are needed to elevate the temporal lobe to be able to access the internal auditory meatus. The temporal lobe hosts the primary and secondary auditory fields. The question arises regarding whether this elevation affects the functionality of the auditory cortex.

MATERIAL AND METHODS

In patients, who underwent acoustic neuroma surgery, contralateral speech discrimination was tested pre- and postsurgery using different speech discrimination tests. Results of patients with a middle fossa approach were compared with patients with a translabyrinthine approach.

RESULTS

No major differences between the translabyrinthine and the middle fossa approach could be detected.

CONCLUSION

Elevation of the temporal lobe during middle fossa approach for acoustic neuroma surgery does not lead to short-term impaired contralateral speech discrimination compared with translabyrinthine approach.

Small Vestibular Schwannomas: Does Surgery Remain a Viable Treatment Option?

Background Surgery for small vestibular schwannomas (Koos grade I and II) has been increasingly rejected as the optimal primary treatment, instead favoring radiosurgery and observation that offer lower morbidity and potentially equal efficacy. Our study assesses the outcomes of contemporary surgical strategies including tumor control, functional preservation, and implications of pathologic findings. Design Retrospective review. Setting/Participants Eighty consecutive patients (45 women, 35 men; mean: 47 years of age). Main Outcomes Measures Approaches included retrosigmoid approach (52%), translabyrinthine (40%), and middle fossa (8%). Operated on by the same surgical team, we analyzed presentation, radiographic imaging, surgical data, and outcomes. Results At last follow-up (mean: 34 months), 95% had good facial nerve function (House-Brackmann grade I or II); 36% who presented with serviceable hearing retained it; and 93% who presented with vestibular dysfunction reported resolution. Pathology identified two grade I meningiomas. Conclusions As one of the largest contemporary surgical series of small vestibular schwannomas, we discuss some nuances to help refine treatment algorithms. Although observation and radiosurgery have established roles, our results reinforce microsurgery as a viable, safe option for a subgroup of patients.

VIIIth nerve cavernous hemangioma mimicking a stage 1 acoustic schwannoma

OBJECTIVE

To report a case of VIIIth nerve cavernous hemangioma, a very rare differential diagnosis among the various pathologies presenting as small enhancing entities into the internal auditory canal. It is one of the most challenging when imaging is not able to differentiate it from an intrameatal vestibular schwannoma.

METHODS AND RESULTS

We report a cavernous hemangioma extruding from the internal auditory canal, diagnosed after a left translabyrinthine resection in a 45-year-old man complaining of profound sensorineural hearing loss, with no facial paresis or dizziness. The preoperative differential diagnosis of a vestibular schwannoma was impossible, due to the absence of calcifications that usually characterize temporal bone hemangiomas. Clinical presentation, radiological features and treatment considerations are discussed along with up-to-date review of pertinent literature.

CONCLUSIONS

When considering an apparent small intra-auditory canal schwannoma, otoneurologists should be aware of the rare possibility of a cavernous hemangioma. Early diagnosis and surgical treatment may improve the functional outcome, possibly preserving neural integrity.