Retrolabyrinthine approach to the lateral skull base: the value of preoperative temporal bone CT analysis

PURPOSE

The most used neurosurgical approach to reach cerebellar-pontine angle is the retrosigmoid route. This article describes the presigmoid approach which requires excellent knowledge of the labyrinthine block together with quantitative analysis of temporal bone CT.

METHODS

CT-based quantitative measurements were obtained in patients undergoing vestibular neurectomy with a presigmoid approach. Eighteen patients were enrolled, and five measures were taken: Trautmann's area, the petro-clival angle, presigmoid dura length and its angle. The relationship between these measurements and hospitalization days, operating times, and complications was explored.

RESULTS

The posterior semicircilar canal (PSC)-sigmoid sinus (SS) distance, presigmoid dura- internal auditory canal (IAC)-PSC angle, and duration of surgery are predictors of complications. Specifically, a PSC-sigmoid sinus distance <11 mm, a dura presig-IAC-PSC angle <14 are associated with the highest risk of complications.

CONCLUSION

Preoperative temporal bone CT scan can guide the surgeon through the narrowest areas of the surgical approach. Trautmann's triangle area and petro-clival angle reduction are challenging and can be faced with combined microscopic-endoscopic technique, and with optics angulation-rotation. The retrolabyrinthine approach can enable hearing preservation and minimal cerebellar retraction.

Combined petrosal approach: a systematic review and meta-analysis of surgical complications

Transpetrosal approaches are known to be associated with a significant risk of complications, including CSF leak, facial palsy, hearing impairment, venous injury, and/or temporal lobe injury. We aimed to evaluate the morbidity of the standard combined petrosal approach (CPA), defined as a combination of the posterior (retrolabyrinthine) and the anterior petrosal approach. We performed a systematic review and meta-analysis of articles reporting on clinical series of patients operated on for petroclival meningiomas through CPA. Studies that used the terminology "combined petrosal approach" without matching the aforementioned definition were excluded as well as clinical series that included less than 5 patients. A total of 8 studies were included involving 160 patients. The pooled complication rates were 3% (95% CI, 0.5-5.6) for CSF leak, 8.6% (95% CI, 4.1-13.2%) for facial palsy, 8.2% (95% CI, 3.9-12.6%) for hearing impairment, 2.8% (95% CI, 0.9-6.5%) for venous complications, and finally 4.8% (95%, 1.2-8.4%) for temporal lobe injury. Contrary to the general belief, CPA is associated with an acceptable rate of complications, especially when compared to alternative approaches to the petroclival area. In view of the major advantages like shorter trajectory, multiple angles of surgical attack, and early tumor devascularization, CPA remains an important tool in the armamentarium of the skull base surgeon.

Combined Petrosal Approach for Resection of a Large Trigeminal Schwannoma With Meckel's Cave Involvement-Part II: Microsurgical Approach and Tumor Resection: 2-Dimensional Operative Video

This video is the second part of a 2-part video presentation demonstrating the microsurgical technique of a combined petrosal approach for resection of a large trigeminal schwannoma in a 54-yr-old woman involving multiple cranial fossae extending anteriorly into Meckel's cave. The patient presented with long-standing worsening headache and facial tingling and numbness. After discussing the benefits and risks of the surgery as well as the alternative management strategies, the patient decided to proceed with surgery and informed consent was obtained. The surgery was performed in a single stage. The technical nuances of anterior and posterior (retrolabyrinthine) petrosectomy are demonstrated and discussed. Microsurgical resection of the tumor is also demonstrated emphasizing the important steps of dural opening, arachnoid dissection, identification and preservation of cranial nerves, and exploration of Meckel's cave. Use of endoscopic-assistance for visualization of the cerebellopontine angle and neurovascular structures is also demonstrated.  Table in video reprinted by permission from Copyright Clearance Center: Springer Nature, Acta Neurochirurgica, Frontotemporal epidural approach to trigeminal neurinomas, Dolenc VV, Copyright 1994.

Combined Petrosal Approach for Resection of a Large Trigeminal Schwannoma With Meckel's Cave Involvement-Part I: Anatomic Rationale and Analysis: 2-Dimensional Operative Video

Resection of large trigeminal schwannomas involving both posterior and middle cranial fossae is challenging. The depth of the surgical target in the superomedial corner of the cerebellopontine angle and the petrous apex makes for a difficult lesion to favorably access, expose, and safely resect. Judicious planning of a skull base approach is therefore the most crucial step in successful management of these formidable tumors. When properly chosen, planned, and executed, the combined petrosal approach sets the stage for an optimal exposure of such tumors that involve both posterior and middle cranial fossae. The present video is the first of a 2-part video presentation that explains the anatomic rationale of selecting a combined petrosal approach (anterior petrosectomy and retrolabyrinthine petrosectomy) for the resection of a large trigeminal schwannoma involving the posterior and middle cranial fossae with an extension into Meckel's cave in a 54-yr-old female presenting with 5-yr history of increasing headaches, left-sided face numbness, and disequilibrium. The benefits, risks, and alternatives of the surgical procedure were discussed in detail with the patient and she consented to proceed with surgery. Part I also discusses the important nuances of positioning the patient, as well as planning and execution of the skin incision, including pericranial flap harvesting.  Of note, the patient consented to the publication of images obtained from her.

The presigmoid retrolabyrinthine approach: Technical note

BACKGROUND

The retrolabyrinthine approach is classified among the posterior petrosectomies. Its goal is to achieve an enlarged mastoidectomy while sparing the intrapetrous neurotologic structures in order to offer maximal exposure of the posterior cerebellopontine angle compound.

METHODS

The stages of the procedure are subsequently the skeletonization of the sigmoid sinus, wide opening of the mastoid antrum and exposure of the semicircular canals. We present herein the technique, indications and limitations of the retrolabyrinthine approach.

CONCLUSION

The retrolabyrinthine approach is a demanding technique. Nowadays the retrolabyrinthine approach is routinely combined to additional resections of the petrous bone, so-called "combined petrosectomies", to target the jugular foramen or the petroclival area.

How I do it: the combined petrosectomy

BACKGROUND

Petroclival and ventral brain stem tumors require a complex approach.

METHOD

The combined petrosectomy is an epidural transtentorial-transpetrosal otoneurosurgical approach to achieve a retrolabyrinthine presigmoidal approach and an anterior petrosectomy in one single procedure. The different steps of this approach are described and illustrated by figures and a video. The indications and limitations of the technique are presented.

CONCLUSION

The combined petrosectomy offers multiple corridors to the petroclival region and ventral brainstem while preserving the intrapetrous neurotological structures. Meticulous stepwise bony resection optimizing the dural opening and preservation of veins contributes to reducing the risk inherent to this technique.

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.