The transmastoid retrolabyrinthine approach in vestibular schwannoma surgery

Long-Term Hearing Stability at Different Frequencies after Lower Intact Bridge Tympanomastoidectomy and Possible Theoretical Basis

Objective: We aimed to review the long-term hearing outcomes of intact bridge tympanomastoidectomy (IBM) to discuss hearing preservation and combine the theory of "modified miniature lung," middle ear ventilation, and gas pressure balance theory to explore the possible reasons for long-term stable hearing. Study Design: We designed a collection of patients with chronic suppurative otitis media (CSOM) who underwent IBM and divided them into 2 groups to compare long-term and short-term hearing level. Setting: From April 2007 to July 2017, 102 patients received IBM for CSOM treatment in Eye & ENT Hospital of Fudan University. Methods: We divided the patients into 2 groups according to whether the follow-up period was longer than 6 months. We used the numerical value of the air-bone gap difference as an index to evaluate the degree of hearing recovery. Results: We found that 99/102 (97.1%) of the hearings were improved to more than 3 frequencies. There was no significant difference between long-term hearing level and short-term hearing level, which means IBM could get long-term hearing stability. Conclusion: Intact bridge tympanomastoidectomy could provide significant hearing recovery and long-term hearing stability.

Long-term hearing prognosis after vestibular schwannoma surgery with retrolabyrinthine approach

PURPOSE

The retrolabyrinthine approach is a surgical method designed to preserve hearing after surgery. When paired with intraoperative monitoring and an endoscope, this approach has demonstrated high rates of postoperative hearing preservation. However, the long-term prognosis of hearing preservation after utilizing this approach for vestibular schwannomas remains unexplored. This study aimed to examine the long-term outcomes of preserved hearing, providing insights into the suitability of the retrolabyrinthine approach for hearing preservation surgery.

METHODS

This study included 34 patients with preserved hearing after vestibular schwannoma surgery using the retrolabyrinthine approach at a single center. Long-term hearing prognosis and requirement for additional interventions were retrospectively examined.

RESULTS

Immediate after post-operative hearing preservation rate was 71.7%. Among the 34 patients with preserved hearing post-vestibular schwannoma surgery, four (11.8%) required additional interventions. Other patients experienced a gradual deterioration in their hearing status, with an approximate 10 dB decline during the 5-year follow-up; however, a serviceable hearing level persisted long after the surgery in these individuals.

CONCLUSIONS

This study indicated the rationale for the retrolabyrinthine approach as a hearing preservation surgery for vestibular schwannomas, emphasizing its long-term hearing prognosis.

The endoscopic transcanal approach to the internal auditory canal: an anatomic study

PURPOSE

The internal auditory canal (IAC) plays a key role in lateral skull base surgery. Although several approaches to the IAC have been proposed, endoscope-assisted transcanal corridors to the IAC have rarely been studied. We sought to provide a step-by-step description of the transcanal transpromontorial approach to the IAC and analyze anatomic relationships that might enhance predictability and safety of this approach.

METHODS

Ten cadaveric specimens were dissected and the extended transcanal transpromontorial approach to the IAC was established. Various morphometric measurements and anatomic landmarks were reviewed and analyzed.

RESULTS

The proposed technique proved feasible and safe in all specimens. There was no inadvertent injury to the jugular bulb or internal carotid artery. The chorda tympani, a key landmark for the mastoid segment of the facial nerve, was identified in all dissections. The spherical recess of the vestibule and middle turn of cochlea are important landmarks for identification of the labyrinthine segment of the facial nerve. Identification of all boundaries of the working area is also essential for safe access. Among various morphometric measurements, the modiolus-IAC angle (≈ 150°) proved particularly consistent; given its ease of use and low variability, we believe it could serve as a landmark for identification and subsequent dissection of the IAC.

CONCLUSIONS

The extended transcanal transpromontorial approach to the IAC is feasible and safe. Relying on anatomic landmarks to ensure preservation of the involved neurovascular structures is essential for a successful approach. The modiolus-IAC angle is a consistent, reproducible landmark for IAC identification and dissection.

Recent advances in Otology: Current landscape and future direction

Hearing is an essential sensation, and its deterioration leads to a significant decrease in the quality of life. Thus, great efforts have been made by otologists to preserve and recover hearing. Our knowledge regarding the field of otology has progressed with advances in technology, and otologists have sought to develop novel approaches in the field of otologic surgery to achieve higher hearing recovery or preservation rates. This requires knowledge regarding the anatomy of the temporal bone and the physiology of hearing. Basic research in the field of otology has progressed with advances in molecular biology and genetics. This review summarizes the current views and recent advances in the field of otology and otologic surgery, especially from the viewpoint of young Japanese clinician-scientists, and presents the perspectives and future directions for several topics in the field of otology. This review will aid next-generation researchers in understanding the recent advances and future challenges in the field of otology.

Hearing preservation surgery for vestibular schwannoma: a systematic review and meta-analysis

The aim of this systematic review is to analyse the role of hearing preservation surgery for vestibular schwannoma. The complications and hearing outcomes of the single surgical techniques were investigated and compared with those of less invasive strategies, such as stereotactic radiotherapy and wait and scan policy. This systematic review and meta-analysis was performed according to the PRISMA guidelines. All included studies were published in English between 2000 and 2022. Literature data show that hearing preservation is achieved in less than 25% of patients after surgery and in approximately half of cases after stereotactic radiotherapy, even if data on long-term preservation are currently not available.

Brazilian Society of Otology task force - Vestibular Schwannoma ‒ evaluation and treatment

OBJECTIVE

To review the literature on the diagnosis and treatment of vestibular schwannoma.

METHODS

Task force members were educated on knowledge synthesis methods, including electronic database search, review and selection of relevant citations, and critical appraisal of selected studies. Articles written in English or Portuguese on vestibular schwannoma were eligible for inclusion. The American College of Physicians' guideline grading system and the American Thyroid Association's guideline criteria were used for critical appraisal of evidence and recommendations for therapeutic interventions.

RESULTS

The topics were divided into 2 parts: (1) Diagnosis - audiologic, electrophysiologic tests, and imaging; (2) Treatment - wait and scan protocols, surgery, radiosurgery/radiotherapy, and systemic therapy.

CONCLUSIONS

Decision making in VS treatment has become more challenging. MRI can diagnose increasingly smaller tumors, which has disastrous consequences for the patients and their families. It is important to develop an individualized approach for each case, which highly depends on the experience of each surgical team.

Operational Analysis of Trautman's Triangle in Petroclival Region Approaches: Cone-Beam Computed Tomography Study

OBJECTIVE

This study was conducted to evaluate the anatomical and clinical features of Trautman's triangle (TT) and to better understand the possible surgical corridor for other surgical approaches involving the petroclival region, especially the presigmoid retrolabyrinthine approach.

METHODS

In this study, morphological analysis of structures related to TT was performed from cone beam computed tomography images of 134 female and 206 male individuals aged 18-65 years.

RESULTS

The TT area was observed as 5.6% (n = 19) type I, 63.2% (n = 215) type II, and 31.2% (n = 106) type III. It was determined that 87.6% of the sigmoid sinus (SS) was lateral to the posterior semicircular canal and 12.4% was medial. It was determined that the TT area showed a positive correlation with petrous slope and a negative correlation with mastoid aeration. In other words, as the TT area increased, the petrous inclination angle also increased, but the mastoid aeration decreased. It was also found that the TT area was associated with the location of the SS and the largest TT area (164.84 ± 42.29 mm2) was observed in the posteriorly located SS.

CONCLUSIONS

The relationship between TT and SS, petroclival angle, mastoid aeration, and subarcuate fossa has a very dynamic structure. Understanding the variations and clinical significance of these structures in the petroclival region is critical in determining the surgical approaches to be applied and understanding the etiology of vestibular system diseases.

Clinical correlation research of 3D reconstruction of retrolabyrinthine space based on HRCT of temporal bone

Background: The retrolabyrinthine approach helps clinicians perform complex surgeries such as vestibular neurectomy, resection of petrous apex cholesteatoma, or use this space to complete endoscopic combined with microscope surgical operations in a relatively safe buffer space. Some of our current studies using 3D reconstruction in the clinic have also helped us perform some complex surgical procedures.Objective: This study aims to reveal the relationship between important structures in retrolabyrinthine space through objective parameters. These measurement data help clinicians locate intraoperatively and provide a reference for clinical surgery. Also, we are intended to help improve surgical techniques and expand the operating space to increase reachable anatomic structure.Material and Methods: The inner structures of the temporal bone from HRCT (High-resolution computed tomography) images which were taken at the Eye & ENT Hospital of Fudan University were reconstructed. Precise measurement of the structures was accomplished by using the software 3D-Slicer (3D Slicer, https://www.slicer.org/; version 4.8.0, Massachusetts, USA).Results: 3D model of temporal bone structures, including the cochlea, semicircular canals (SCCs), the internal auditory canal (IAC), facial nerve (FN), jugular bulb(JB), and carotid artery was reconstructed. The combination of HRCT and 3D models is utilized to analyze the Quantitative data of the retrolabyrinthine space and its adjacent structures.Conclusions and Significance: 3D reconstruction of CT images clearly displayed the detailed structures of the temporal bone. Surgical adaptability of the retrolabyrinthine approach can be assessed preoperatively by image and other methods, and anatomical parameters play an important role in the retrolabyrinthine space. Therefore, this study helps to skeleton the bone as much as possible to expand the surgical space, so that the surgeon can contact the anatomical structure more diversified to expand the surgical indications.

Computed Tomography Assessment of the Retrolabyrinthine Approach

Introduction This study aimed to evaluate preoperative radiological assessments of the retrolabyrinthine approach to identify and describe anatomical constraints that may anticipate a more challenging situation for neurosurgeons and otolaryngologists specialized in skull base surgery. Materials and methods The study included 75 adult patients who underwent high-resolution computed tomography angiography scans of the head, with the aim of analyzing the side of the dominance of the sigmoid sinus (SS), the level of pneumatization of the mastoid portion of the temporal bone, and the height of the jugular bulb. Results The results showed that dominant SS and type 2 jugular bulbs were more common on the right side, while smaller type 1 bulbs were significantly more common on the left. Conclusions These findings provide valuable information for neurosurgeons and otolaryngologists in predicting the difficulty of the retrolabyrinthine approach based on preoperative radiological assessments.

Vestibular Schwannoma Surgery with Endoscope-Assisted Retrolabyrinthine Approach under Modified Reinforced Continuous Intraoperative Monitoring for Hearing Preservation: Experience of 33 Cases in a Single Center

Surgery for vestibular schwannoma includes various techniques such as the middle cranial fossa, suboccipital, translabyrinthine, and retrolabyrinthine approaches. The retrolabyrinthine approach does not impair the labyrinth and allows postoperative hearing preservation. Previously, we reported an endoscope-assisted retrolabyrinthine approach under reinforced continuous intraoperative monitoring for preservation of hearing and facial nerve function. However, the hearing preservation rate was relatively low in patients with long-wave V latency in the auditory brainstem response or poor otoacoustic emission response under this approach. Thus, the hearing preservation rate in such patients remains to be improved. To overcome this limitation, we modified the previous approach. In 26 of the 33 consecutive cases (79%) over the last three years, preservation of hearing equivalent to that before surgery or improved hearing was achieved. Postoperative deafness was observed in only two of the 33 cases (6%). According to previous reports, the rate of hearing preservation using the retrolabyrinthine approach is approximately 30-50%. Therefore, we have achieved a higher hearing preservation rate than that previously reported using the endoscopy-assisted retrolabyrinthine approach under reinforced continuous intraoperative monitoring. These improvements in our department are considered to be helpful for hearing preservation.

Novel Multiportal Approach to the Internal Auditory Canal for Hearing-Preserving Surgery: Feasibility Assessment in Dissections

OBJECTIVE

State-of-the-art, minimally invasive endoscopic transcanal surgery of the internal auditory canal (IAC) sacrifices the cochlea with complete hearing loss. With a combination of the transcanal infracochlear and transmastoid retrolabyrinthine approaches, we aim to preserve hearing and enable minimally invasive surgical treatment of vestibular schwannoma. In this study, we investigate the anatomical indications and the feasibility of both approaches in dissections, in human whole head specimens.

METHODS

We operated whole head anatomical specimens with a four-handed technique, using the retrolabyrinthine approach as the main surgical corridor and the infracochlear approach for endoscopic visualization. We tested 4 different powered surgical systems. We collected intraoperative data on the size of the access windows, the surgical freedom, and the exposed area of the IAC. Finally, we evaluated the outcome in postoperative computed tomography scans.

RESULTS

Six out of 14 sides were anatomically suitable and qualified for the surgery based on preoperative computed tomography. In all attempted sides, the IAC could be reached and opened, leaving the ossicular chain and the labyrinth intact. 51%-75% of the length and 22%-40% of the circumference of the IAC could be exposed. All tested instruments were beneficial at different stages of the surgery. The four-handed technique enabled good maneuverability of the instruments.

CONCLUSIONS

The combined multiportal approach to the IAC is feasible with a good surgical exposure and full anatomical preservation of hearing. State-of-the-art surgical instruments in specimens with suitable anatomy are sufficient to perform this approach.

Understanding the Molecular Mechanism of Vestibular Schwannoma for Hearing Preservation Surgery: Otologists’ Perspective from Bedside to Bench

Vestibular schwannoma is a clinically benign schwannoma that arises from the vestibulocochlear nerve that causes sensorineural hearing loss. This tumor is clinically and oncologically regarded as a benign tumor as it does not metastasize or invade surrounding tissues. Despite being a benign tumor, its management is difficult and controversial due to the potential serious complications, such as irreversible sensorineural hearing loss, of current interventions. Therefore, preventing hearing loss due to the natural course of the disease and complications of surgery is a challenging issue for an otologist. Improvements have been reported recently in the treatment of vestibular schwannomas. These include advances in intraoperative monitoring systems for vestibular schwannoma surgery where the risk of hearing loss as a complication is decreased. Precise genomic analysis of the tumor would be helpful in determining the characteristics of the tumor for each patient, leading to a better hearing prognosis. These procedures are expected to help improve the treatment of vestibular schwannomas. This review summarizes recent advances in vestibular schwannoma management and treatment, especially in hearing preservation. In addition, recent advances in the understanding of the molecular mechanisms underlying vestibular schwannomas and how these advances can be applied in clinical practice are outlined and discussed, respectively. Moreover, the future directions from the bedside to the bench side are presented from the perspective of otologists.

Hearing-Preserving Approaches to the Internal Auditory Canal: Feasibility Assessment from the Perspective of an Endoscope

OBJECTIVE

Minimally invasive transcanal transpromontorial endoscopic approaches to the internal auditory canal sacrifice the cochlea. Two hearing-preserving approaches, the exclusively endoscopic transcanal infracochlear approach and the endoscope-assisted transmastoid retrolabyrinthine approach, have been controversially discussed in the literature. In this study, we examine the feasibility of these 2 approaches by means of three-dimensional surface models, a population-based analysis of the available surgical space, and dissections in human whole-head specimens.

METHODS

We reconstructed three-dimensional surface models based on clinical high-resolution computed tomography scans of 53 adult temporal bones. For both approaches, we measured the maximal extensions and the area of the surgical access windows located between landmarks on the surrounding anatomic structures. We then identified the limiting extensions and derived the cumulative distribution to describe the available surgical space. Dissections were performed to validate the corridors and landmark selection.

RESULTS

The limiting extension for the infrachochlear approach is 7.0 ± 2.7 mm from the round window to the dome of the jugular bulb. The limiting extension for the retrolabyrinthine approach is 6.4 ± 1.5 mm from the dura of the posterior fossa to the facial nerve. The cumulative distribution shows that 80% of the cohort have access window extensions ≥3 mm for both approaches.

CONCLUSIONS

This study shows that in a high percentage of the measured cohort, the access windows are sufficiently large for endoscopic approaches to the internal auditory canal. With appropriate instrumentation, these hearing-preserving minimally invasive approaches may evolve into alternatives to surgical treatment.

Anatomic Assessment of the Limits of an Endoscopically Assisted Retrolabyrinthine Approach to the Internal Auditory Canal

Objective  Data regarding the surgical advantages and anatomic constraints of a hearing-preserving endoscopic-assisted retrolabyrinthine approach to the IAC are scarce. This study aimed to define the minimum amount of retrosigmoid dural exposure necessary for endoscopic exposure of the IAC and the surgical freedom of motion afforded by this approach. Methods  Presigmoid retrolabyrinthine approaches were performed on fresh cadaveric heads. The IAC was exposed under endoscopic guidance. The retrosigmoid posterior fossa dura was decompressed until the fundus of the IAC was exposed. Surgical freedom of motion at the fundus was calculated after both retrolabyrinthine and translabyrinthine approaches. Results  The IAC was entirely exposed in nine specimens with a median length of 12 mm (range: 10-13 mm). Complete IAC exposure could be achieved with 1 cm of retrosigmoid dural exposure in eight of nine mastoids. For the retrolabyrinthine approach, the median anterior-posterior surgical freedom was 13 degrees (range: 6-23 degrees) compared with 46 degrees (range: 36-53 degrees) for the translabyrinthine approach ( p  = 0.014). For the retrolabyrinthine approach, the median superior-inferior surgical freedom was 40 degrees (range 33-46 degrees) compared with 47 degrees (range: 42-51 degrees) for the translabyrinthine approach ( p  = 0.022). Conclusion  Using endoscopic assistance, the retrolabyrinthine approach can expose the entire IAC. We recommend at least 1.5 cm of retrosigmoid posterior fossa dura exposure for this approach. Although this strategy provides significantly less instrument freedom of motion in both the horizontal and vertical axes than the translabyrinthine approach, it may be appropriate for carefully selected patients with intact hearing and small-to-medium sized tumors involving the IAC.

Clinical Studies and Pre-clinical Animal Models on Facial Nerve Preservation, Reconstruction, and Regeneration Following Cerebellopontine Angle Tumor Surgery-A Systematic Review and Future Perspectives

Background and purpose: Tumorous lesions developing in the cerebellopontine angle (CPA) get into close contact with the 1st (cisternal) and 2nd (meatal) intra-arachnoidal portion of the facial nerve (FN). When surgical damage occurs, commonly known reconstruction strategies are often associated with poor functional recovery. This article aims to provide a systematic overview for translational research by establishing the current evidence on available clinical studies and experimental models reporting on intracranial FN injury.

Methods: A systematic literature search of several databases (PubMed, EMBASE, Medline) was performed prior to July 2020. Suitable articles were selected based on predefined eligibility criteria following the Preferred Reporting Items for Systematic Reviews and Meta Analyses (PRISMA) guidelines. Included clinical studies were reviewed and categorized according to the pathology and surgical resection strategy, and experimental studies according to the animal. For anatomical study purposes, perfusion-fixed adult New Zealand white rabbits were used for radiological high-resolution imaging and anatomical dissection of the CPA and periotic skull base.

Results: One hundred forty four out of 166 included publications were clinical studies reporting on FN outcomes after CPA-tumor surgery in 19,136 patients. During CPA-tumor surgery, the specific vulnerability of the intracranial FN to stretching and compression more likely leads to neurapraxia or axonotmesis than neurotmesis. Severe FN palsy was reported in 7 to 15 % after vestibular schwannoma surgery, and 6% following the resection of CPA-meningioma. Twenty-two papers reported on experimental studies, out of which only 6 specifically used intracranial FN injury in a rodent (n = 4) or non-rodent model (n = 2). Rats and rabbits offer a feasible model for manipulation of the FN in the CPA, the latter was further confirmed in our study covering the radiological and anatomical analysis of perfusion fixed periotic bones.

Conclusion: The particular anatomical and physiological features of the intracranial FN warrant a distinguishment of experimental models for intracranial FN injuries. New Zealand White rabbits might be a very cost-effective and valuable option to test new experimental approaches for intracranial FN regeneration. Flexible and bioactive biomaterials, commonly used in skull base surgery, endowed with trophic and topographical functions, should address the specific needs of intracranial FN injuries.

Transmastoid presigmoid retrolabyrinthine approach for removal of pontine cavernous malformation: how I do it

BACKGROUND

Bleeding of brainstem cavernous malformations (BSCM) cause high morbidity and should be treated surgically whenever possible.

METHOD

We present a 56-year-old man, who was diagnosed with a BSCM at right pons, which caused functional impairments of dorsal column, spinothalamic tract, cochlear nucleus, and middle cerebellar peduncle. A transmastoid presigmoid retorlabyrinthine approach via the lateral pontine zone (LPZ), with an assistance of imaging guidance and intraoperative neurophysiological monitoring, was performed to completely resect the BSCM. The patient recovered despite a transient worsening of cerebellar sign and hemiparesthesia for 1 week, without surgical complications.

CONCLUSIONS

A transmastoid presigmoid retrolabyrinthine approach through LPZ is safe and effective for lateral pontine BSCM resection.

Simultaneous supervision by microscope of endoscope-assisted microsurgery via presigmoid retrolabyrinthine approach: A pilot study

OBJECTIVE

To examine the impact of integrated hybrid operating rooms for endoscope-assisted microsurgery using the presigmoid retrolabyrinthine (RL) approach, and to determine the value of simultaneous supervision of skull base endoscopic procedures by microscope.

MATERIAL AND METHODS

We retrospectively reviewed endoscope-assisted surgery using the RL approach at our institution between September 2013 and January 2017. The simultaneous supervision of endoscopic procedures by microscope was realized using the integrated hybrid system. Intra- or postoperative complications and surgical outcomes were analyzed. All patients were followed for at least 1 year.

RESULTS

In total, 32 patients were studied: 4 vestibular schwannomas, 5 cholesteatomas, 8 hemifacial spasms, 5 glossopharyngeal neuralgias, and 10 Ménière's disease. In patients with vestibular schwannoma or cholesteatoma, complete removal was performed in all patients. In patients with Ménière's disease, hemifacial spasm or glossopharyngeal neuralgia, satisfactory symptom relief was achieved in all patients. Two (6.3%) patients had hearing loss after surgery which did not recover. One (3.1%) patient with vestibular schwannoma had mild facial palsy (HB III) at 2 weeks after the operation and recovered to near normal facial nerve function (HB II) at 1 year after surgery. No permanent or transient dysfunction of the trigeminal nerve or the lower cranial nerves was observed during follow-up. No complications such as cerebrospinal fluid (CSF) leakage or meningitis were observed.

CONCLUSION

The endoscope provided a clearer and larger view, which solved the limitations of surgery using the RL approach. Endoscopic surgery under simultaneous supervision by microscope was safe and efficient in hearing preservation as well as in preservation of facial nerve function. An integrated operation room provided better support and the ability to switch quickly between these various complex devices.

Endoscopically Assisted Drilling, Exposure of the Fundus through a Presigmoid Retrolabyrinthine Approach: A Cadaveric Feasibility Study

The presigmoid retrolabyrinthine approach to the cerebellopontine angle is traditionally described to not provide access to the internal auditory canal (IAC). We aimed to evaluate the extent of the IAC that could be exposed with endoscopically assisted drilling and to measure the percentage of the IAC that could be visualized with the microscope and various endoscopes after drilling had been completed. Presigmoid retrolabyrinthine approaches were performed bilaterally on 4 fresh cadaveric heads. We performed endoscopically assisted drilling to expose the fundus of the IAC, which resulted in exposure of the entire IAC in 8 of 8 temporal bone specimens. The microscope afforded a mean view of 83% (n = 8) of the IAC. The 0°, 30°, 45°, and 70° endoscope each afforded a view of 100% of the IAC in 8 of 8 temporal bone specimens. In conclusion, endoscopic drilling of the IAC of can provide an extradural means of exposing the entire length of the IAC while preserving the labyrinth.

Radiographic Assessment of the presigmoid retrolabyrinthine approach

Background:

Lesions of the petroclival fissure are difficult to access surgically. Both retrosigmoid and presigmoid retrolabyrinthine approaches have been described to successfully treat these complex tumors. The retrosigmoid approach offers quick and familiar access, whereas the presigmoid retrolabyrinthine approach reduces the operative distance and the need for cerebellar retraction. The presigmoid retrolabyrinthine approach, however, is constrained by anatomical limits that can be subject to patient variation. We sought to characterize the surgically relevant variation to guide preoperative assessment.

Methods:

One hundred and seventy-seven high-resolution computed tomography scans of the head (without preexisting pathology) were reviewed. Three hundred and fifty-four temporal bone scans were analyzed for level of aeration, size of Trautmann's triangle dura, and petrous slope. Petrous slope is the angle between the anterior sigmoid sinus and the petroclival fissure at the level of the internal acoustic canal.

Results:

Trautmann's triangle area had a mean of 185.15 mm² (range 71.4–426.7 mm²). Petrous slope had a mean value of 149° (range 106–178°). Increasing aeration was found to be correlated with decreasing petrous slope and decreasing Trautmann's triangle area.

Conclusion:

The presigmoid retrolabyrinthine approach is uniquely confined. Variations in temporal bone anatomy can have dramatic impacts on the operative time, risk profile, and final exposure. Preoperative assessment is critical in guiding the surgeon on the appropriateness of approach. Preoperative measurement of Trautmann's triangle, petrous slope, and aeration can help to reduce surgical morbidity.

The Retrolabyrinthine Presigmoid Approach to the Anterior Cerebellopontine Region: Expanding the Limits of Trautmann Triangle

OBJECTIVE

The anatomic area exposed through exposure of Trautmann triangle may not be sufficient. We studied the additional exposure provided by skeletonizing the sigmoid sinus (SS).

METHODS

In 5 human cadaveric heads, thin-cut computed tomography images of 2 sides of the temporal bone were obtained for a total of 10 sides. The estimated surgical working angle was calculated based on the relationship of the SS to the posterior semicircular canal (PSC), superior petrosal sinus, and jugular bulb on imaging. Mastoidectomy was performed, and heads with and without SS skeletonization were remeasured.

RESULTS

Working angle calculated on computed tomography was 56° ± 11.3. Skeletonization of the SS increased the distance between the PSC and SS by 5 mm (P = 0.01) and between the lateral semicircular canal and SS by 4 mm (P = 0.01). Skeletonization and retraction of the SS significantly increased the distance between the PSC and lateral semicircular canal to the SS. On images obtained after mastoidectomy, skeletonizing the SS helped improve anterior visibility on most samples that had an SS that was lateral to the PSC on axial imaging. In samples in which the SS was medial to the PSC or had only minimal lateral displacement, skeletonizing the SS did not markedly improve visibility of the retrolabyrinthine space.

CONCLUSIONS

Working area and visibility improved as the PSC and SS approached the same plane on axial imaging. Preoperative evaluation of the laterality of the SS to the PSC may assist a surgeon in determining the need for skeletonizing the SS and avoiding possible vascular injuries.

Predicting the presigmoid retrolabyrinthine space using a sigmoid sinus tomography classification: A cadaveric study

BACKGROUND

The presigmoid retrolabyrinthine space is characterized by a widely variable size. The main structure involved in this large variability is the sigmoid sinus. Few studies have attempted to establish a reliable classification of sigmoid sinus to predict the presigmoid retrolabyrinthine space. We used tomographic mapping of human cadaver temporal bones to classify the position of sigmoid sinus and performed a cadaveric study to assess the validity of a novel classification in predicting the presigmoid retrolabyrinthine space.

METHODS

Ten human cadaver temporal bones were randomly selected and subjected to fine-cut computed tomography scanning to classify the position of sigmoid sinus using a reference line. The specimens were classified into medial and lateral groups and each specimen was then subjected to mastoidectomy. The groups were compared using quantitative and qualitative analysis.

RESULTS

The medial group showed a larger distance between the sigmoid sinus and the external auditory canal and a shallower lateral semicircular canal. In the lateral group, the mastoidectomy was more demanding, and the Trautmann's triangle was typically narrower and often "hidden" medially to the sigmoid sinus.

CONCLUSIONS

The tomographic classification proposed in this study predicts, in a cadaveric model, the presigmoid retrolabyrinthine space. It may help the surgeon select the best approach to reach the petroclival region and lead to safer neurological and otological surgeries.

Microsurgery versus stereotactic radiation for small vestibular schwannomas: a meta-analysis of patients with more than 5 years' follow-up

OBJECTIVE

To compare the long-term outcome of hearing and tumor outcome of small vestibular schwannomas treated with stereotactic radiation and microsurgery.

DATA SOURCES

A thorough search for English-language publications and "in process" articles dating from 1948 to December 2011 was conducted using Ovid MEDLINE.

STUDY SELECTION

The principal criteria were patients having had microsurgery or radiation therapy as their sole treatment, with a follow-up of at least 5 years, and a useful hearing level at diagnosis.

DATA EXTRACTION

Sixteen studies met our criteria. Hearing preservation outcome (worse or preserved) and tumor outcome (failure, control) data, as well as all other significant observations, were collected from the articles. Stereotactic radiation was the only radiation therapy analyzed.

DATA SYNTHESIS

The Pearson χ test was our primary statistical analysis.

CONCLUSION

Stereotactic radiation showed significantly better long-term hearing preservation outcome rates than microsurgery (p < 0.001). However, long-term tumor outcome was not significantly different in stereotactic radiation as compared with microsurgery (p = 0.122). Although stereotactic radiation demonstrates a more favorable long-term hearing preservation outcome as compared with microsurgery, additional studies are required to provide the medical field with a better understanding of vestibular schwannoma treatment.

Microsurgical endoscopy-assisted presigmoid retrolabyrinthine approach as a minimally invasive surgical option for the treatment of medium to large vestibular schwannomas

BACKGROUND

Treatment of vestibular schwannomas presents many controversial aspects, from the indication to the selection of the best treatment option. In the era of stereotactic radiotherapy, microsurgery has to be competitive in terms of providing the best chances of functional preservation and complete tumor removal. The two most commonly used surgical approaches are the retrosigmoid suboccipital and the presigmoid translabyrinthine. We describe the endoscopy-assisted presigmoid retrolabyrinthine approach (EAPRA) aiming at combining the advantages of the retrosigmoid and translabyrinthine techniques.

METHODS

For 2 years (from May 2009 to June 2011), the EAPRA was used to remove medium to large sporadic vestibular schwannomas in ten patients.

RESULTS

Complete tumor removal was obtained in eight patients, postoperative transient facial nerve function impairment or worsening was observed in two, and one had hearing deterioration postoperatively. No threatening complications occurred after surgery, and the length of hospitalization was usually less than 10 days.

CONCLUSIONS

The EAPRA can provide direct access to the CPA along with labyrinthine complex conservation, allowing hearing function preservation and minimal cerebellar retraction. Endoscopic assistance is a crucial adjunct in the presigmoid retrolabyrinthine approach in order to address the limits imposed by labyrinthine complex preservation. It ensures complete visualization of the intracanalicular portion of the schwannoma, thus improving the rate of a radical tumor resection. The EAPRA could represent a valid surgical option in vestibular schwannoma surgery.

A brief history of mastoidectomy

AIM

 To describe to the new generation of otologists the origins of mastoidectomy as well as the difficulties our predecessors encountered and the solutions they devised to improve otologic surgery.

METHOD

 Retrospective literature review-based study.

RESULTS

 Before the mid-19th century, mastoidectomy was performed only sporadically and in most cases as a desperate attempt to save the lives of people suffering from complications of infectious otitis. The drainage of acute abscesses became a common procedure at the beginning of the 20th century, within the pre-antibiotic era. The first documented surgical incision to drain an infected ear was described by the French physician Ambroise Paré in the 16th century. The credit for performing the first mastoidectomy for the removal of purulent secretions went to Jean-Louis Petit. Mastoidectomies were normally performed to treat infections. However, mastoidectomies were also carried out for other purposes, particularly for the treatment of deafness and tinnitus, during various periods. Sir Charles Ballance credited Johannes Riolanus with recommending mastoidectomy for the treatment of tinnitus. William Wilde began the era of modern mastoidectomy with his introduction of the eponymous retroauricular incision.

CONCLUSION

 Mastoidectomy has evolved significantly throughout its history. Improvements in mastoidectomy have relied on the introduction of more elaborate surgical procedures, especially the advances in surgical equipment during the last century. Mastoidectomy continues to be a life-saving surgical procedure.

Vestibular schwannoma: 825 cases from a 25-year experience

INTRODUCTION

 Acoustic nerve tumors have been recognized as a clinico-pathologic entity for at least 200 years, and they represent 90% of cerebellopontine angle diseases. Histologically, the tumors are derived from Schwann cells of the myelin sheath, with smaller tumors consisting of elongated palisade cells, while in large tumors, cystic degeneration can be found in the central areas, possibly due to deficient vascularization. We retrospectively reviewed 825 cases of vestibular schwannomas, reported between January 1984 and August 2006, in which the patients underwent surgery to remove the tumor.

OBJECTIVE

 To evaluate signs, symptoms, aspects of clinical diagnosis, including the results of audiological and imaging studies, and surgical techniques and complications.

METHODS

 A retrospective chart review. The medical records of all patients undergoing surgical treatment for schwannoma during the period indicated were reviewed.

RESULTS AND CONCLUSION

 Hearing loss was the first symptom reported in almost all cases, and tumor size was not proportional to the impairment of the auditory threshold. The surgical techniques allowed safe preservation of facial function. In particular, the retrolabyrinthine route proved useful in small tumors, with 50% preservation of hearing.

Retrolabyrinthine approach for surgical placement of auditory brainstem implants in children

CONCLUSION

The extended retrolabyrinthine approach (RLA) is a safe and reliable approach for auditory brainstem placement in children. The surgical landmarks to reach cochlear nucleus are adequately exposed by this approach.

OBJECTIVE

To describe a new approach option for auditory brainstem implants (ABIs) in children, highlighting the anatomical landmarks to appropriately expose the foramen of Luschka.

METHODS

Three prelingually deafened children consecutively operated for ABIs via the RLA.

RESULTS

ABI placement via the RLA was successfully performed in all children without any further complications except multidirectional nystagmus in one child. The RLA we employed differed from that used for vestibular schwannoma only in the removal of the posterior semicircular canal. The lateral and superior semicircular canals and the vestibule remained intact, and there was no need to expose the dura of the internal auditory meatus. The jugular bulb was completely exposed to allow adequate visualization of the ninth cranial nerve and cerebellar flocculus.

Hearing preservation in the resection of vestibular schwannomas: patterns of hearing preservation and patient-assessed hearing function

Object

No extant literature documents the analysis of patient perceptions of hearing as a corollary to objective audiometric measures in patients with vestibular schwannoma (VS), or acoustic neuroma. Therefore, using objective audiometric data and patient perceptions of hearing function as outlined on a questionnaire, the authors evaluated the hearing of patients who underwent VS resection.

Methods

This investigation involved a retrospective review of 176 patients who had undergone VS resections in which hearing preservation was a goal. Both pre- and postoperative audiometry, expressed as a speech discrimination score (SDS) and pure tone threshold average (PTA), were performed, and the results were analyzed. Intraoperative auditory brainstem responses were also recorded. Eighty-seven of the patients (49.4%) completed a postoperative questionnaire designed to assess hearing function in a variety of social and auditory situations. Multiple linear regression analyses were completed to compare available audiometric results with questionnaire responses for each patient.

Results

One hundred forty-two patients (80.7%) had PTA and SDS audiometric data pertaining to the surgically treated ear; 94 of these patients (66.2%) had measurable postoperative hearing, as defined by a PTA < 120 dB or SD > 0%. Eighty-seven patients (49.4%) completed the retrospective questionnaire, and 74 of them had complete audiometric data and thus were included in a comparative analysis. Questionnaire data showed major postoperative subjective hearing decrements, even among patients with the same pre- and postoperative objective audiometric hearing status. Moreover, the subscore reflecting hearing while exposed to background noise, or the “cocktail party effect,” characterized the most significant patient-perceived hearing deficit following VS resection.

Conclusions

The authors' analysis of a patient-perceived hearing questionnaire showed that hearing during exposure to background noise, or the cocktail party effect, represents a significant postoperative hearing deficit and that patient perception of this deficit has a strong relation with audiometric data. Furthermore, questionnaire responses revealed a significant disparity between subjective hearing function and standard audiometrics such that even with similar levels of audiometric data, subjective measures of hearing, especially the cocktail party effect, decreased postoperatively. The authors posit that the incorporation of patient-perceived hearing function evaluation along with standard audiometry is an illustrative means of identifying subjective hearing deficits after VS resection and may ultimately aid in specific and subsequent treatment for these patients.

Beyond audiofacial morbidity after vestibular schwannoma surgery

Object

Outcomes following vestibular schwannoma (VS) surgery have been extensively described; however, complication rates reported in the literature vary markedly. In addition, the majority of reports have focused on outcomes related to cranial nerves (CNs) VII and VIII. The objective of this study was to analyze reported morbidity unrelated to CNs VII and VIII following the resection of VS.

Methods

The authors performed a comprehensive search of the English language literature, identifying and aggregating morbidity and death data from patients who had undergone microsurgical removal of VSs. A subgroup analysis based on surgical approach and tumor size was performed to compare rates of CSF leakage, vascular injury, neurological deficit, and postoperative infection.

Results

One hundred articles met the inclusion criteria, providing data for 32,870 patients. The overall mortality rate was 0.2% (95% CI 0.1–0.3%). Twenty-two percent of patients (95% CI 21–23%) experienced at least 1 surgically attributable complication unrelated to CNs VII or VIII. Cerebrospinal fluid leakage occurred in 8.5% of patients (95% CI 6.9–10.0%). This rate was markedly increased with the translabyrinthine approach but was not affected by tumor size. Vascular complications, such as ischemic injury or hemorrhage, occurred in 1% of patients (95% CI 0.75–1.2%). Neurological complications occurred in 8.6% of cases (95% CI 7.9–9.3%) and were less likely with the resection of smaller tumors (p < 0.0001) and the use of the translabyrinthine approach (p < 0.0001). Infections occurred in 3.8% of cases (95% CI 3.4–4.3%), and 78% of these infections were meningitis.

Conclusions

This study provides statistically powerful data for practitioners to advise patients about the published risks of surgery for VS unrelated to compromised CNs VII and VIII.

Transpetrosal approaches to the posterior fossa

Resection of the petrous temporal bone to various degrees provides different levels of access to lesions of the posterior fossa. Although their nomenclature can be confusing, the numerous variants of the transpetrosal approaches can be classified broadly into anterior and posterior groups. The posterior transpetrosal approaches include the retro-labyrinthine, translabyrinthine, and transcochlear, whereas the ones in the anterior group are extensions of the basic middle fossa approach. Both the anterior and posterior approaches have the potential of exposing the cerebellopontine angle and the petroclival region.

The posterior approaches are based on the standard mastoidectomy and involve resection of the petrous bone to various degrees. This results in progressively increased exposure anteriorly, but comes at the expense of hearing in the translabyrinthine approach and of hearing and facial strength in the transcochlear approach.

In contrast, the middle fossa approaches spare the lateral petrous bone and involve resection of the medial petrous bone to various degrees. All of the middle fossa approaches are designed to preserve hearing. Extensions of the middle fossa approaches involve resection of bone within the Kawase rhomboid and division of the tentorium to provide exposure of the posterior fossa.

B. Neto R, Bento RF, Ribas GC. Endoscopia do meato acústico interno pelo acesso retrolabiríntico

O acesso direto à região do ângulo pontocerebelar pela via retrolabiríntica é seguro, entretanto, não permite a visão direta de todo o meato acústico interno (MAI) pela otomicroscopia. Os endoscópios podem ser utilizados na exploração do MAI por esta via. OBJETIVO: Nosso objetivo é avaliar a capacidade de inspeção do MAI com endoscópios de diferentes angulações. FORMA DE ESTUDO: Estudo anatômico. MATERIAL E MÉTODO: Estudamos 40 ossos temporais humanos nos quais realizamos acessos retrolabirínticos. Nestes ossos, medimos as distâncias ocultas do MAI, em seus quatro quadrantes, utilizando o microscópio cirúrgico e os endoscópios de 0º, 30º e 70º. RESULTADOS: Observamos que as distâncias ocultas medidas foram diminuindo, com significância estatística, conforme o instrumento utilizado, nesta seqüência: microscópio, endoscópio de 0º, 30º e 70º. Somente o endoscópio de 70º permitiu a visão do fundo do MAI em todos os quadrantes, o que ocorreu em 27,5% dos casos. A visão parcial do fundo do MAI foi obtida em 67,5% dos ossos com o endoscópio de 70º e em 12,5% com o endoscópio de 30º, não tendo sido obtida em nenhum caso com o uso do endoscópio de 0º ou do microscópio. As médias de distâncias ocultas no quadrante ântero-superior, medidas com o microscópio e endoscópios de 0º, 30º e 70º foram respectivamente: 10,4mm, 7,3mm, 4,3mm e 1,1mm. CONCLUSÕES: O endoscópio de 70º demonstrou ser significativamente superior aos demais instrumentos na inspeção do MAI e sugerimos que ele seja considerado o instrumento de escolha na inspeção do MAI nos acessos retrolabirínticos.

Modified translabyrinthine approach and hearing preservation

OBJECTIVES/HYPOTHESIS

In 1991, the translabyrinthine approach was modified by sealing the vestibule with bone wax, which allowed preservation of the hearing function in one patient. The present study aimed specifically at evaluating the effectiveness of the modified translabyrinthine approach in preserving hearing function in a group of patients with vestibular schwannoma that involved the internal auditory canal.

STUDY DESIGN

Prospective study.

METHODS

The series consisted of 12 patients with vestibular schwannoma (average age, 49.7 y). The schwannoma was smaller than 2 cm in all patients who had surgery. The patients accepted for the study were required to have preserved hearing function.

RESULTS

None of the patients has shown signs of persistence or tumoral relapse on postoperative magnetic resonance imaging. Immediately after surgery, the entire group had excellent facial functionality. Six patients had maintained their hearing function (four in Class 1 and two in Class 2 according to the Gardner-Robertson scale) at the last follow-up after surgery. A patient during follow-up noted fluctuating hearing contemporarily with a tinnitus in the ear that had maintained its hearing, which was attributable to an endolymphatic hydrops. Three of the six patients with preserved hearing complained of persistent tinnitus. None of the patients had any of the complications or consequences of cerebellopontine surgery.

CONCLUSION

In our patients, Class 1 or 2 hearing was preserved in 50% of the patients, with no persistence or tumoral relapse. The follow-up has obviously been short, but the first results are encouraging and deserve to be studied further in a more comprehensive survey.