Driscoll, Colin L. W.

Objectives This video was aimed to describe the relevant anatomy and key surgical steps of retrosigmoid approach for gross total resection of a medium-sized vestibular schwannoma (VS). Design The procedure is described in a surgical instructional video. Setting The surgery took place at a tertiary skull base referral center. Participant Patient is a 63-year-old woman who reported with nonserviceable hearing (Pure Tone Average 60 dB Hearing level, Word Recognition Score 45%), occasional tinnitus, and a VS in the left cerebellopontine angle (CPA), extending into internal auditory canal (IAC), measuring 1.7 cm parallel to the petrous temporal bone. Main Outcome Measures The VS was resected by retrosigmoid approach. Results The surgery results gross total resection of the VS with postoperative House–Brackmann grade 1 facial nerve function and no postoperative complications. Conclusion The retrosigmoid approach is a good strategy to remove VS involving the CPA and the IAC.The link to the video can be found at: https://youtu.be/B6K_UkrKitg.

Purpose: To examine the etiology, clinical course, and management of recurrent peripheral facial nerve paralysis. Methods: Retrospective review at a single tertiary academic center and systematic review of the literature. Clinical presentation, laboratory and imaging findings, treatment and outcome for all cases of recurrent ipsilateral, recurrent contralateral, and bilateral simultaneous cases of facial paralysis are reviewed. Results: Between 2000 and 2017, 53 patients [41.5% men, 29 median age of onset (range 2.5 wk–75 yr)] were evaluated for recurrent facial nerve paralysis at the authors’ institution. Twenty-two (41.5%) cases presented with ipsilateral recurrences only, while the remaining 31 patients (58.5%) had at least 1 episode of contralateral recurrent paralysis. No cases of bilateral simultaneous facial nerve paralysis were observed. The median number of paretic events for all patients was 3 (range 2–20). The median nadir House–Brackmann score was 4, with a median recovery to House–Brackmann grade 1.5 over a mean recovery time of 61.8 days (range 1–420 d). Diagnostic evaluation confirmed Melkersson–Rosenthal syndrome in four (7.5%) cases, neurosarcoidosis in two (3.7%), traumatic neuroma in one (1.9%), Ramsay Hunt syndrome in one (1.9%), granulomatosis with polyangiitis in one (1.9%), and neoplastic causes in three (5.7%) cases [facial nerve schwannoma (n = 2; 3.7%), metastatic squamous cell carcinoma to the deep lobe of the parotid gland (n = 1; 1.9%)]; ultimately, 77.4% (41) of cases were deemed idiopathic. Facial nerve decompression via a middle cranial fossa approach was performed in three (5.7%) cases without subsequent episodes of paralysis. Conclusion: Recurrent facial nerve paralysis is uncommon and few studies have evaluated this unique population. Recurrent ipsilateral and contralateral episodes are most commonly attributed to idiopathic facial nerve paralysis (i.e., Bell's palsy); however, a subset harbor neoplastic causes or local manifestations of underlying systemic disease. A comprehensive diagnostic evaluation is warranted in patients presenting with recurrent facial nerve paralysis and therapeutic considerations including facial nerve decompression can be considered in select cases.

Objectives This video was aimed to describe the surgical indications, relevant anatomy, and surgical steps of retrosigmoid approach for resection of a large cystic vestibular schwannoma (VS). Design The operative steps are described in a surgical instructional video. Setting The surgery took place at a tertiary skull base referral center. Participant Patient is a 62-year-old man who reported with right sided profound hearing loss with no word recognition, progressive dizziness and tinnitus, excruciating burning pain in the V2 distribution of right trigeminal nerve, wide-based gait, and a right cerebellopontine angle (CPA) cystic VS measuring 3.3 cm. Main Outcome Measures The large cystic VS was resected through retrosigmoid approach. Results The surgery resulted in removal of the large cystic VS with initial delayed facial weakness that completely resolved (House Brackmann grade 1) by 3 month follow-up. The patient had no other postoperative complications and is convalescing well from the procedure. Conclusion Cystic VS presents some unique challenges compared with their solid counterparts. The cystic tumor capsule may be very adherent to the adjacent structures, and distinguishing thin cyst walls from the arachnoid of the CPA, can be quite challenging. The retrosigmoid approach provides adequate surgical exposure for VS tumor resection.The link to the video can be found at: https://youtu.be/sFNvRWG465Q.

Glioblastoma (GBM) of the internal auditory canal (IAC) is exceedingly rare, with only 3 prior cases reported in the literature. The authors present the fourth case of cerebellopontine angle (CPA) and IAC GBM, and the first in which the lesion mimicked a vestibular schwannoma (VS) early in its natural history. A 55-year-old man presented with tinnitus, hearing loss, and imbalance. MRI identified a left IAC/CPA lesion measuring 8 mm, most consistent with a benign VS. Over the subsequent 4 months he developed facial weakness. The tumor grew remarkably to 24 mm and surgery was recommended; the main preoperative diagnosis was malignant peripheral nerve sheath tumor (MPNST). Resection proceeded via a translabyrinthine approach with resection of cranial nerves VII and VIII, followed by facial-hypoglossal nerve anastomosis. Intraoperative frozen section suggested malignant spindle cell neoplasm, but final histopathological and molecular testing confirmed the lesion to be a GBM. The authors report the first case in which absence of any brainstem interface effectively excluded a primary parenchymal tumor, in particular GBM, from the differential diagnosis. Given the dramatic differences in treatment and prognoses between malignant glioma and MPNST, this case emphasizes the importance of surgical intervention on an aggressively growing lesion, which provides both the best probability of local control and the critical tissue diagnosis.

Abstract Selected upper cerebellopontine angle (CPA)/petroclival region lesions can be visualized and resected through a middle fossa approach with anterior petrosectomy. This approach is particularly well suited for tumors that extend from the CPA into Meckel's cave or the middle cranial fossa. We present the case of a 55-yr-old man who presented with sudden left-sided hearing loss, with complete recovery after medical treatment. MRI demonstrated a left 1.8 cm contrast-enhancing upper CPA lesion with extension into Meckel's cave most consistent with a trigeminal schwannoma. The patient initially opted for observation. MRI 11 mo later showed notable enlargement in the tumor, and the patient started to experience left-sided neuralgic face pain. The decision was made to perform surgery. Documented and verified informed consent was obtained A step-by-step surgical video with surgical anatomy images highlights the 5 steps followed by the authors to perform an anterior petrosectomy. The dura mater was opened parallel to the superior petrosal sinus both in the infratentorial and supratentorial spaces in order to clip and coagulate the superior petrosal sinus and divide the tentorium. The lesion was fully visualized and the trigeminal nerve was clearly identified displaced inferiorly but not splayed by the tumor, making the diagnosis of trigeminal schwannoma unlikely. The lesion was debulked and dissected off the brainstem as well as the trigeminal nerve with the final view of intact nerve fascicles entering the posterior aspect of Meckel's cave. Pathology returned as a WHO grade 1 meningioma. The patient recovered well with only mild facial hypesthesia and complete tumor resection on follow-up imaging.

OBJECTIVEMiddle fossa surgery is challenging, and reliable surgical landmarks are essential to perform accurate and safe surgery. Although many descriptions of the middle fossa components have been published, a clinically practical description of this very complex anatomical region is lacking. Small structure arrangements in this area are often not well visualized or accurately demarcated with neuronavigation systems. The objective is to describe a “roadmap” of key surgical reference points and landmarks during middle fossa surgery to help the surgeon predict where critical structures will be located.METHODSThe authors studied 40 dry skulls (80 sides) obtained from the anatomical board at their institution. Measurements of anatomical structures in the middle fossa were made with a digital caliper and a protractor, taking as reference the middle point of the external auditory canal (MEAC). The results were statistically analyzed.RESULTSThe petrous part of the temporal bone was found at a mean of 16 mm anterior and 24 mm posterior to the MEAC. In 87% and 99% of the sides, the foramen ovale and foramen spinosum, respectively, were encountered deep to the zygomatic root. The posterior aspect of the greater superficial petrosal nerve (GSPN) groove was a mean of 6 mm anterior and 25 mm medial to the MEAC, nearly parallel to the petrous ridge. The main axis of the IAC projected to the root of the zygoma in all cases. The internal auditory canal (IAC) porus was found 5.5 mm lateral and 4.5 mm deep to the lateral aspect of the trigeminal impression along the petrous ridge (mean measurement values). A projection from this point to the middle aspect of the root of the zygoma, being posterior to the GSPN groove, could estimate the orientation of the IAC.CONCLUSIONSIn middle fossa approaches, the external acoustic canal is a reliable reference before skin incision, whereas the zygomatic root becomes important after the skin incision. Deep structures can be related to these 2 anatomical structures. An easy method to predict the location of the IAC in surgery is described. Careful study of the preoperative imaging is essential to adapt this knowledge to the individual anatomy of the patient.

Introduction Although numerous anatomical and operative atlases have been published, those that have focused on the skull base either have provided views that are quite difficult to achieve in the operating room to better depict surgical anatomy or are written at the level of an audience with considerable knowledge and experience. Methods Five sides of three formalin-fixed latex-injected specimens were dissected under microscopic magnification. A posterior petrosectomy approach was performed by three neurosurgical residents at different training levels with limited previous experience in anatomical dissection mentored by the senior authors (C. L. W. D. and M. J. L.) and a clinical skull base fellow with additional anatomical dissection experience (M. P. C.). Anatomical dissections were performed until the expected level of dissection quality was achieved to demonstrate each important step of the surgical approach that would be understandable to all trainees of all levels. Following dissection education, representative case applications were reviewed. Results The posterior petrosectomy (also known as presigmoid retrolabyrinthine approach) affords excellent access to cranial nerves III to XI and a diverse array of pathologies. Key steps include positioning and skin incision, scalp and muscle flaps, burr holes, craniotomy flap elevation, superficial mastoidectomy, otic capsule exposure and presigmoid dura decompression, primary presigmoid durotomy, inferior temporal durotomy, superior petrosal sinus ligation, tentorium sectioning, and final exposure. Conclusion The posterior petrosectomy is a challenging approach; thorough operative-style laboratory dissection is essential to provide trainees with a suitable guide. We describe a comprehensive approach to learning this technique, intended to be understandable and usable by a resident audience.