Transcochlear Approach to Cerebellopontine Angle and Clivus Lesions: Indications, Results, and Complications

Microsurgical transcranial approaches to the posterior surface of petrosal portion of the temporal bone: quantitative analysis of surgical volumes and exposed areas

Different microsurgical transcranial approaches (MTAs) have been described to expose the posterior surface of the petrous bone (PPB). A quantitative, anatomical comparison of the most used MTAs, for specific areas of the PPB, is not available. Anatomical dissections were performed on five formalin-fixed, latex-injected cadaver heads (10 sides). Six MTAs were analyzed: Kawase approach (KWA), retrosigmoid approach (RSA), retrosigmoid approach with suprameatal extension (RSAS), retrolabyrinthine approach (RLA), translabyrinthine approach (TLA), and transcochlear approach (TCA). Surgical volumes and exposed areas of each approach were quantified with a dedicated neuronavigation system (ApproachViewer, part of GTx-Eyes II, University Health Network, Toronto, Canada) and adjuvant software (ITK-SNAP and Autodesk Meshmixer 3.5). Areas and volumes were compared using linear mixed models. TCA provided the best exposure of Trautmann's triangle and the retromeatal, suprameatal, meatal, and premeatal regions. RSAs provided the best exposure of the inframeatal region, with RSAS gaining significant exposure of the suprameatal region. KWA had the highest surgical volume, and RLA the lowest. Transpetrosal approaches offer the widest exposure of PPB proportionally to their invasiveness. Retrosigmoid approaches, which get to the studied region through a postero-lateral path, are paramount for the exposure of the inframeatal and suprameatal region and, given the adequate exposure of the remaining PPB, represent an effective approach for the cerebellopontine angle (CPA). These anatomical findings must be considered with approach-related morbidity and the pathological features in order to choose the most appropriate approach in clinical practice.

Predictors of hearing functional outcome following surgery for cerebellopontine angle meningioma

OBJECTIVE

Cerebellopontine angle (CPA) meningiomas can affect hearing function and require expeditious treatment to prevent permanent hearing loss. The authors sought to determine the factors associated with functional hearing outcome in CPA meningioma patients treated with surgery and/or radiation therapy in the form of either stereotactic radiosurgery or stereotactic radiation therapy.

METHODS

Consecutive patients with CPA meningiomas who had presented at our hospital from 2008 to 2018 were identified through retrospective chart review. Hearing function (as defined by pure tone average (PTA) and speech discrimination score (SDS) on Audiogram) was assessed before and after surgery for CPA meningioma. Audiograms with PTA > 50 dB and SDS < 69% were defined as poor hearing functional outcome. Multivariable Cox Proportional Hazards Regression Model was used to assess the associations between pre-operative hearing functional assessment and post-operative hearing functional outcomes.

RESULTS

The study cohort included 31 patients (80.6% females, with a mean age of 61.3 ± 15.2 years) with a median clinical follow-up of 5 months (range: 1 week-98 months). The mean pre-operative PTA and SDS were 23.8 ± 11.2 dB and 64.4 ± 22.2% respectively. At the last visit, there was significant hearing recovery, with an improvement of 29.7 ± 18.0 dB (p < 0.001) and 87.6 ± 17.8% (p < 0.001) in PTA and SDS respectively. After adjusting for age, gender, tumor volume, location, and tumor classification, Multivariable Cox Proportional Hazards Regression Model was conducted which revealed that patients undergoing surgery through retro sigmoid approach [Hazards Ratio (HR): 32.1, 95% Confidence Interval (CI): 2.11-491.0, p = 0.01] and gross total resection (GTR) (HR: 2.99, 95% CI: 1.09-9.32, p = 0.05) had significantly higher risk of poor hearing functional outcome compared to petrosal approach and near/subtotal resection. Moreover, patients with poor preoperative hearing had 85% higher chance of poor hearing functional outcome postoperatively (HR: 0.15, 95%CI: 0.03-0.59, p = 0.007).

CONCLUSION

Postoperative improvement in hearing is a reasonable expectation following surgery for CPA meningioma. Preoperative hearing, surgical approach and extent of surgical resection are predictive factors of postoperative hearing function outcome and can therefore aid in identification of patients at higher risk of hearing loss.

Risk Factors for Complications Following Lateral Skull Base Surgery and the Utility of ICU Monitoring

OBJECTIVE

To examine the role of intensive care unit (ICU) management following lateral skull base surgery for vestibular schwannoma and identify risk factors for complications warranting admission to the ICU.

STUDY DESIGN

Retrospective review.

SETTING

Tertiary referral center.

PATIENTS

Two hundred consecutive patients undergoing lateral skull base surgery for vestibular schwannomas.

INTERVENTION

Lateral skull base approach for resection of vestibular schwannoma and postoperative monitoring.

MAIN OUTCOME MEASURES

Patients were grouped if they sustained an ICU complication, a non-ICU complication, or no complication. Analysis was performed to determine patient or treatment factors that may be associated with ICU complications. Multivariate and three-way analysis of variance compared groups, and multivariate logistic regression determined adjusted odds ratios (aOR) for analyzed factors.

RESULTS

Seventeen of 200 patients sustained ICU complications (8.5%), most commonly hypertensive urgency (n = 15). Forty-six (23%) sustained non-ICU complications, and 137 (68.5%) had no complications. When controlling for age, sex, obesity, and other comorbidities, only hypertension (aOR 5.43, 95% confidence interval (CI) 1.35-21.73, p = 0.017) and tumor volume (aOR 3.29, 95% CI 1.09-9.96, p = 0.035) were independently associated with increased risk of ICU complications.

CONCLUSIONS

The necessity of intensive care following lateral skull base surgery is rare, with the primary ICU complication being hypertensive urgency. Preoperative hypertension and large tumor volume (>4500 mm3) were independently associated with increased risk for ICU complications. These findings may allow for risk stratification of patients appropriate for admission to stepdown units following resection of vestibular schwannomas. Further prospective, multi-center, randomized studies are necessary to validate these findings before systematic changes to current postoperative care practices.

Modified Translabyrinthine Approach for Massive Petrous Bone Cholesteatoma Removal and Cochlear Preservation Using Latent Spaces Anterior to the Cochlea

OBJECTIVE

Microsurgery is the reference standard treatment of petrous bone cholesteatoma (PBC). In most cases, radical removal of an extensive PBC can only be achieved at the cost of sacrificing the cochlea. Such treatment will result in the impossibility of future cochlear implantation for hearing rehabilitation purposes. To address this issue, a modification of the traditional translabyrinthine (TL) approach with endoscopic assistance has been developed for radical removal of extensive PBC with preservation of the cochlea.

METHODS

From June 2017 to December 2017, 3 patients with a massive PBC underwent surgical removal using the modified TL approach by the senior author in our department. We reviewed the patient characteristics and retrospectively studied the surgical outcomes and postoperative complications. In the present report, we have described our modified TL approach in detail.

RESULTS

Complete resection of the PBC and successful cochlea preservation were achieved in all 3 patients. No recurrence had developed during the follow-up period. However, various degrees of cochlear ossification were observed in 2 patients postoperatively.

CONCLUSIONS

This modified TL approach provides the possibility of fully exposing the whole petrous apex without removing the cochlea in selected cases. However, the development of long-term cochlear ossification requires further investigation to allow for successful cochlear implantation.

Posterior Petrosal Transotic Approach for Cerebellopontine Angle Hemangioblastoma: Technical Case Report

BACKGROUND AND IMPORTANCE

Although posterior petrosal approaches are utilized less frequently in many practices today, they continue to provide distinct surgical advantages in carefully selected cases. Here, we report a case of a recurrent cerebellopontine angle (CPA) hemangioblastoma that had failed a prior, more conservative, surgical approach. We provide cadaveric dissections of variations of posterior petrosal approaches to illustrate the advantages of the selected approach.

CLINICAL PRESENTATION

A 70-yr-old female presented with a growing left CPA hemangioblastoma. The lesion had undergone a prior subtotal resection from a retrosigmoid approach and subsequent adjuvant radiation treatment. The patient had worsening left facial strength, progressive balance difficulty, and absent left auditory function. Preoperative angiogram demonstrated arterial blood supply from the left anterior inferior cerebellar artery (AICA) that was deemed unsafe for embolization due to significant arteriovenous shunting. A posterior petrosal transotic approach was performed in order to optimize the working angle to the anterior brainstem and afford the ability to occlude the vascular supply from AICA prior to surgical resection of the lesion.

CONCLUSION

The posterior petrosal transotic approach offers an improved surgical working angle to the anterior brainstem compared to the translabyrinthine approach. This advantage can be particularly important with vascular tumors that receive blood supply anteriorly, as in this case from AICA, and can improve the safety of the resection.

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.

Endoscopic transorbital route to the petrous apex: a feasibility anatomic study

BACKGROUND

While the subtemporal approach represents the surgical module milestone designed to reach the petrous apex, a novel ventral route, which is the superior eyelid endoscopic transorbital approach, has been proposed to access the skull base. Accordingly, we aimed to evaluate the feasibility of this route to the petrous apex, providing a qualitative and quantitative analysis of this relatively novel pathway.

METHODS

Five human cadaveric heads were dissected at the Laboratory of Surgical NeuroAnatomy of the University of Barcelona. After proper dissection planning, anterior petrosectomy via the endoscopic transorbital route was performed. Specific quantitative analysis, as well as dedicated three-dimensional reconstruction, was done.

RESULTS

Using the endoscopic transorbital approach, it was possible to reach the petrous apex with an average volume bone removal of 1.33 ± 0.21 cm³. Three main intradural spaces were exposed: cerebellopontine angle, middle tentorial incisura, and ventral brainstem. The first one was bounded by the origin of the trigeminal nerve medially and the facial and vestibulocochlear nerves laterally, the second extended from the origin of the oculomotor nerve to the entrance of the trochlear nerve into the tentorium free edge while the ventral brainstem area was hardly accessible through the straight, ventral endoscopic transorbital trajectory.

CONCLUSION

This is the first qualitative and quantitative anatomic study concerning details of the lateral aspect of the incisura and ventrolateral posterior fossa reached via the transorbital window. This manuscript is intended as a feasibility anatomic study, and further clinical contributions are mandatory to confirm the effectiveness of this approach, defining its possible role in the neurosurgical armamentarium.

Transsphenoidal and infralabyrinthine approach of the petrous apex cholesterol granuloma

Space-demanding or destructive changes in the petrous bone are often challenging differential diagnosis. Cholesterol granulomas of the petrous apex can clinically present in a combination of hearing loss, vertigo, tinnitus, chronic cephalgia, impairment of facial nerve function, neuralgic pain of the nervus trigeminus, or manifest diplopia by the nerve palsy of the nervus abducens. CT-morphologically cholesterol granulomas appear as soft-tissue density masses, which may display a discrete rim after intravenous administration of a contrast agent. The MRI, T1 as well as T2-weighted images show a strong signal in the area of the lesion. Depending on the individual anatomical conditions, the surgical access must be carefully chosen between transsphenoidal, transtemporal, infracochlear/-labyrinthine, or translabyrinthine. Here, we present the transsphenoidal and translabyrinthine access for the excision of cholesterol granulomas of the petrous apex. The different accesses are compared using a neuro-navigation-supported surgical technique with respect to its complications, drainage possibilities, outcomes, and recurrence of symptoms.

The Tightrope Facial Nerve-An Unsupported Mastoid Segment After Resection of Recidivistic Cholesteatoma

OBJECTIVES/HYPOTHESIS

Cholesteatomas are epidermal inclusion cysts containing stratified squamous epithelium that arise in the middle ear and mastoid cavities resulting in a persistent inflammatory state. Complications include chronic otorrhea, granulation tissue, and bony erosion. Cholesteatoma growth patterns predict frequent involvement of the Fallopian canal of the facial nerve. Extensive disease may extend to the posterior and middle fossa dura, the otic capsule, the carotid artery, and the jugular bulb. Dehiscence of the Fallopian canal and direct involvement of the facial nerve epineurium by cholesteatoma are risk factors for intraoperative facial nerve injury during tympanomastoid surgery by exposing the facial nerve to mechanical trauma and inflammation during microdissection. We present two cases of recidivistic cholesteatoma with unusual medial involvement of the vertical segment of the facial nerve that resulted in an unsupported mastoid segment after resection. The outcomes from these two patients suggest that facial nerve function may be preserved despite circumferential exposure with appropriate preoperative planning and intra-operative techniques.

STUDY DESIGN

Case studies.

METHODS

Two patients undergoing revision tympanomastoidectomy for extensive recidivistic cholesteatoma with medial involvement of the facial nerve in the mastoid segment. In each case, the facial nerve was circumferentially exposed during the resection of the cholesteatoma.

RESULTS

Normal facial nerve function after surgery was confirmed in both patients at 18 months and 6 years, respectively.

CONCLUSIONS

Surgical resection of extensive cholesteatoma with medial involvement of the vertical segment of the facial nerve resulted in an unsupported mastoid segment in two patients with normal postoperative facial nerve function.

The Microsurgical Anatomy of the Modified Presigmoid Trans-Partial Bony Labyrinth Approach

OBJECTIVE

To investigate the surgical techniques of the modified presigmoid trans-partial bony labyrinth approach and the advantages in the exposure of the petroclival region and in the treatment of lesions in this area.

METHODS

Between April and October of 2012, a study on modification of the surgical approach was performed on 15 cadaveric heads. On the basis of the traditional presigmoid approach, semicircular canals, and the petrous apex were partially resected. The detailed conditions of the exposure of important structures of the petroclival region were recorded.

RESULTS

This approach provided a large operational space from the petroclival region to the posterior cavernous sinus. The range of presigmoid exposure (horizontal direction) was (19.41 ± 1.58)  mm, the exposure range of the inferior temporal (vertical direction) was (14.18 ± 1.88)  mm, the maximum exposure angle of the slope center depression was (60.54° ± 6.93°), and the depth of operation was (55.87 ± 4.34)  mm. The vertebral-basilar artery, anterior inferior cerebellar artery, superior cerebellar artery, ipsilateral III-X cranial nerves, contralateral VI cranial nerve, Meckel cave, and posterior cavernous sinus were well exposed.

CONCLUSION

The modified presigmoid trans-partial bony labyrinth approach was able to achieve excellent exposure of deep surfaces of the petroclival region and the posterior part of the cavernous sinus and showed advantages including a large range of exposure, multiple axes of visualization, preservation of hearing and facial nerve function, and early devascularization of tumors.

Maximizing the Petroclival Region Exposure Via a Suboccipital Retrosigmoid Approach: Where Is the Intrapetrous Internal Carotid Artery?

BACKGROUND

Recent reports have validated the use of retrosigmoid approach extensions to deal with petroclival lesions.

OBJECTIVE

To describe the topographic retrosigmoid anatomy of the intrapetrous internal carotid artery (IICA), providing guidelines for maximizing the petroclival region exposure via this route.

METHODS

The IICA was exposed bilaterally in 6 specimens via a retrosigmoid approach in the semisitting position. Its topographic relationship with pertinent posterolateral cranial base landmarks was quantified with neuronavigation.

RESULTS

Safe exposure of the IICA and the surrounding inframeatal/petroclival regions was accomplished in all specimens. On average, the IICA genu was 15.08 mm anterolateral to the XI nerve in the jugular foramen, 16.18 mm anteroinferolateral to the endolymphatic sac, and 10.63 mm anteroinferolateral to the internal acoustic meatus. On average, the IICA horizontal segment was 9.92 mm inferolateral to the Meckel cave, and its midpoint was 19.96 mm anterolateral to the XI nerve in the jugular foramen. The mean distance from the IICA genu to the cochlea was 1.96 mm. The genu and the midpoint of the horizontal segment of the IICA were exposed at a depth of approximately 14.50 mm from the posterior pyramidal wall with the use of different drilling angles (49.74° vs 39.54°, respectively).

CONCLUSION

Knowledge of the IICA general relationship with these landmarks (combined with a careful assessment of the preoperative imaging and with the use of intraoperative navigation and micro-Doppler) may help to enhance the inframeatal/petroclival region exposure via a retrosigmoid route, maximizing safe inframeatal and suprameatal petrous bone removal while minimizing neurovascular complications.

Facial nerve function after the extended translabyrinthine approach

Objective To evaluate facial nerve function after excision of petroclival/anterior cerebellopontine angle (CPA) meningiomas by the extended translabyrinthine (EXTL) approach and compare these with outcomes after the transcochlear and transotic approaches. Design Retrospective chart review. Setting/Participants A search of archived surgical cases at a single institution between January 1, 1995, and January 1, 2012. Main Outcome Measures Facial function measured on the House-Brackmann (HB) scale. Results A total of 16 patients underwent the EXTL approach for primary excision of petroclival meningiomas. Average tumor size was 4.6 cm, and six patients had gross total resection. Average length of follow-up was 36.4 months. Two patients required reoperation for tumor regrowth. Preoperative facial function was HB I or II in all patients with available examinations. Immediate postoperative facial nerve function ranged from HB I to HB VI. In patients with an intact facial nerve at surgery, all but one had long-term facial function of HB I or II. A robust response on intraoperative facial nerve monitoring was prognostic of favorable long-term facial function. Facial function declined in some patients after postoperative radiation or revision surgery. Conclusions The EXTL approach allows excellent exposure of petroclival/anterior CPA lesions and should be favored to improve facial outcomes.

Selection of surgical approaches based on semi-quantifying the skull-base invasion by petroclival meningiomas: a review of 66 cases

BACKGROUND

Petroclival meningiomas are still challenging for neurosurgeons. In the present study, we reviewed 66 petroclival meningiomas that underwent craniotomy to assess the surgical approaches for petroclival meningiomas based on semi-quantifying tumor extension to skull base and to evaluate the outcomes.

METHODS

According to invasion characteristics, skull base related to petroclival meningiomas was semi-quantitatively divided into five regions: upper, middle, and lower petroclival regions (region A, B, and C, respectively), cerebellopontine angle region (region D), and parasellar and cavernous sinus region (region E). Appropriate surgical approaches were adopted for petroclival meningiomas with varying degrees of invasion, including the subtemporal (11/66), retrosigmoid (15/66), presigmoid (32/66), combined retrosigmoid and far-lateral (2/66), supra-infratentorial (4/66), and extended middle cranial fossa (2/66) approaches.

RESULTS

The results showed that involvement of region A, B, and C was in 64, 50, and eight patients, respectively. Invasion to region D and E occurred in 13 and 39 cases, respectively. The ratio of single region involvement was only 7.6 %, whereas most petroclival meningiomas tended to invade more regions (39.4 % for two, 37.9 % for three, 12.1 % for four, and 3.0 % for five regions, respectively). Gross total resection was achieved in 29 cases (43.9 %), near total resection in 27 cases (40.9 %), and subtotal resection in ten cases (15.2 %). After a mean follow-up period of 32.21 months, obvious cranial nerve deficits existed in seven patients, and recurrence occurred in eight patients.

CONCLUSIONS

We introduced a simple and practicable method for classification of petroclival meningiomas, which could semi-quantify tumor invasion and help to select surgical approaches. With careful preoperative evaluation, a cautiously selected approach would improve the prognosis.

Retrosigmoid intradural inframeatal approach: indications and technique

BACKGROUND

Surgery of lesions of the petrous apex involving the inframeatal/infralabyrinthine area is challenging and related to a high risk of complications. Various extensive skull-base approaches have been used.

OBJECTIVE

To present and evaluate our experience with a new hearing-preserving extension of the retrosigmoid approach to the inframeatal/infralabyrinthine area.

METHODS

The approach was used in 3 patients harboring lesions in the petrous apex with variable extension in the inframeatal/infralabyrinthine region. The surgical accessibility of the lesions offered by the approach, the completeness of tumor removal, and the outcome, in particular, the functional outcome and complication rate, were assessed.

RESULTS

The tumor could be resected from the target area in all cases. No approach-related complications occurred. Serviceable hearing and normal facial nerve functions were preserved in all cases.

CONCLUSION

Our initial experience with the retrosigmoid inframeatal approach showed that it provides sufficient access to the area and offers the possibility of complete tumor removal. It allows for hearing and facial nerve functional preservation. The approach is safe and related to a very low complication rate.

The fallopian canal: a comprehensive review and proposal of a new classification

INTRODUCTION

The facial nerve follows a complex course through the skull base. Understanding its anatomy is crucial during standard skull base approaches and resection of certain skull base tumors closely related to the nerve, especially, tumors at the cerebellopontine angle.

METHODS

Herein, we review the fallopian canal and its implications in surgical approaches to the skull base. Furthermore, we suggest a new classification.

CONCLUSIONS

Based on the anatomy and literature, we propose that the meatal segment of the facial nerve be included as a component of the fallopian canal. A comprehensive knowledge of the course of the facial nerve is important to those who treat patients with pathology of or near this cranial nerve.