Driscoll, Colin L. W.

Abstract Epidermoid cysts are rare, benign lesions that result from inclusion of ectodermal elements during neural tube closure. 1 Cysts are composed of desquamated epithelial cells and restrict diffusion on magnetic resonance imaging (MRI). 2,3 Symptoms are attributable to anatomic location. 4,5 In this video, we illustrate the surgical treatment of an epidermoid cyst located in the right cerebellopontine angle, petrous apex, and Meckel's cave. The patient, a 33-yr-old female with right-sided V1 trigeminal hypoesthesia, underwent surveillance imaging for 2 yr. However, she developed progressive V1 and V2 trigeminal hypoesthesia and imaging revealed enlargement of the lesion. Therefore, surgical resection was pursued. The patient consented to the procedure. The patient underwent a right middle fossa craniotomy and anterior petrosectomy. After identifying the greater superficial petrosal nerve and cutting the middle meningeal artery as it exited foramen spinosum, Kawase's triangle was drilled, and the dura over Meckel's cave and the subtemporal dura were opened. The lesion was resected, taking care to preserve the trigeminal nerve and the basilar artery. A retrosigmoid craniotomy was then fashioned. The cyst and its capsule were dissected off the brainstem and cranial nerves utilizing natural corridors between the trigeminal and vestibulocochlear nerves as well as between the facial and lower cranial nerves. Gross total resection was confirmed on postoperative MRI, and she was discharged home on postoperative day 5. Three months after surgery, she underwent formal pinprick testing, which revealed 95% loss of sensation in V1, 20% loss in V2, and normal sensation in V3. Three-month postoperative MRI showed no residual tumor.

Abstract Objective Cerebrovascular complications (CVC) are rare consequences of vestibular schwannoma (VS) surgery. Our objective was to assess incidences of findings suggestive of postoperative CVC in a large single surgeon cohort, as well as potential risk factors, and implications. Study Design A cohort of 591 patients was retrospectively reviewed. Postoperative magnetic resonance images were screened for findings suggestive of stroke, T2 hyperintensity in the cerebellopontine angle structures or new encephalomalacia. Clinical records were queried for findings consistent with postoperative CVC. Results In total, 61 patients had radiographic findings consistent with possible postoperative CVC (10%); of them, eight had documented intraoperative vascular injury (1.4%), and four had postoperative clinical exam changes indicative of CVC (0.7%). Clinically manifest intraoperative vascular injuries occurred in four patients and involved the petrosal venous complex (n = 3, 5%) or anterior inferior cerebellar artery (n = 1, 2%); clinical deficits included hemiparesis (n = 1, 2%), facial anesthesia (n = 2, 4%), dysphagia (n = 2, 2%), and unfavorable facial nerve function in two (50%). Three out of four patients in this group required out-of-home placement (75%). Clinical CVCs (n = 4) were not significantly associated with tumor size, tumor cyst, gross total resection, or length of stay. Patients with clinical CVC were significantly more likely to require posthospitalization rehabilitation (19 vs. 75%, p = 0.02; 14 vs. 100%, p = 0.0002). Conclusion Although radiographic findings suggestive of CVC were unexpectedly common in this cohort, intraoperative vascular injury and postoperative clinical CVC were exceedingly rare. The association between unfavorable facial nerve outcome and clinical CVC is likely a marker for more difficult operations, predisposing to higher risk of complications.

Abstract BACKGROUND Vestibular schwannomas (VS) have a peak incidence in the sixth and seventh decades of life. Stereotactic radiosurgery is often the preferred treatment for VS among patients of advanced age. The fraction of elderly patients potentially requiring consideration for surgical treatment is anticipated to expand, mandating an update to management paradigms in this population. OBJECTIVE To describe our experience with surgical management of VS in patients aged 75 yr and older. METHODS Cohort study of all patients aged ≥75 yr with sporadic VS requiring surgical treatment at our institution between 1999 and 2020. Data included preoperative baseline characteristics and outcome data including extent of resection, facial nerve and hearing status, functional outcome, length of stay, and complications. RESULTS A total of 24 patients were included, spanning an age range of 75 to 90 yr. Average tumor size was 2.76 ± 1.04 cm, and average baseline Modified 5-item Frailty Index (mFI-5) score was 1.08 ± 0.93. Extent of resection was gross total in 5 (20.8%), near total in 3 (12.5%), and sub-total resection in the remaining 16 (66.7%). One patient died in the postoperative period because of an acute sub-dural hematoma. Favorable facial nerve function (HB1-2) was preserved in 12 patients (75%) between 75 and 79 yr and 2 patients (28.6%) aged ≥ 80 yr. No cerebrospinal fluid leak or surgical site infection was observed; 3 patients developed hydrocephalus requiring ventriculo-peritoneal shunt placement. Nine patients required out-of-home disposition; all patients eventually returned to independent living. CONCLUSION Microsurgical resection of VS can be safely undertaken in patients greater than 75 y/o but may carry an increased risk of poor facial function.

Background Jugular paragangliomas represent a surgical challenge due to their vascularity and proximity to vital neurovascular structures. Preoperative embolization aids in reducing intraoperative blood loss, transfusion requirements, and improves surgical visualization. Several embolization agents have been used. Objective The aim of this study is to evaluate the safety and efficacy of PVA in pre-operative embolization of jugular paragangliomas. Methods A retrospective review of all patients who underwent jugular paraganglioma resection with pre-operative embolization between 2000 and 2020 was performed. Pre-operative data including baseline patient and tumor characteristics were documented. Outcomes of preoperative embolization including extent of devascularization and post-embolization complications were recorded. Early and long-term postoperative outcomes were reported. Results Twenty-nine patients met study criteria with a median age of 38 years. Average tumor size was 3.4±1.8 cm. The most commonly encountered arterial feeder was the ascending pharyngeal artery followed by the posterior auricular artery. More than 50% reduction in tumor blush was achieved in 25 patients (86.2%). None of the patients experienced new or worsening cranial neuropathy following embolization. Gross total or Near total resection was achieved in 13 patients (44.8%). A STR or NTR was chosen in these patients to preserve cranial nerve function or large vessel integrity. Average intraoperative estimated blood loss was 888 ml, 9 patients (31%) required intra-operative transfusion of blood products. Extent of resection and post-operative complications did not correlate with extent of devascularization. Conclusion Pre-operative embolization of jugular paraganglioma tumors with PVA particles is an effective strategy with a high safety profile.

Abstract Trigeminal nerve schwannomas (TNSs) are rare lesions that typically present with symptoms of trigeminal neuropathy or other cranial nerve palsies. These lesions classically have a dumbbell shape, with an anterior component within Meckel's cave and posterior component extending into the posterior fossa through the porus trigeminus. Surgical resection of TNSs can often be achieved via an extradural subtemporal approach to Meckel's cave without an anterior petrousectomy, even for tumors with a significant posterior fossa component, as the tumor often erodes a portion of the petrous apex. 1 We present the case of a 53-yr-old female presenting to our institution with complete trigeminal neuropathy secondary to a right-sided, previously resected and radiated TNS. Serial imaging demonstrated an interval growth of significant residual tumor despite multiple adjuvant therapies, and, thus, the patient was recommended to undergo additional surgical resection. The lesion was approached through a right-sided subtemporal approach to Meckel's cave, 2 with a plan to utilize an anterior petrousectomy only if difficulty resecting the posterior fossa component of the tumor was encountered. Intraoperatively, the posterior fossa component was found to be densely adherent to the adjacent brainstem, likely secondary to prior surgery and radiation therapy, and, thus, an anterior petrousectomy was performed. Postoperatively, the patient had stable trigeminal neuropathy without any new neurological deficits and a magnetic resonance imaging (MRI) confirmed a gross total resection. In the accompanying video, we hope to demonstrate the steps and nuances of both the subtemporal approach to accessing Meckel's cave and anterior petrousectomy when employed for the resection of TNSs. The patient in question provided formal consent for the making of this video.

Abstract Introduction The middle fossa (MF) approaches encompass a group of versatile surgical accesses to pathologies in the MF, internal auditory canal (IAC), and superomedial aspect of the posterior fossa. Although many descriptions of the MF approaches have been published, a practical surgical guide that allows an easy understanding for Skull Base trainees is needed. Methods Three formalin-fixed, colored-injected specimens were dissected under microscopic magnification (six sides). A MF craniotomy followed by IAC drilling was performed on three sides, and anterior petrosectomy (AP) was performed in the remaining three sides. The anatomical dissection was documented in stepwise three-dimensional photographic images. Following dissection, representative case applications were reviewed. Results The MF approach provides direct access to the MF structures and IAC. The AP provides excellent access to the superomedial aspect of the posterior fossa. Key common steps include: positioning and skin incision; scalp and muscle flaps; burr holes; craniotomy flap elevation; dural dissection along the petrous ridge; division of the middle meningeal artery; and exposure of the greater superficial petrosal nerve, tegmen tympani, and V3. Then, to approach the IAC: superior IAC drilling, and longitudinal dura opening. The area drilled in the AP approach forms a pentagon limited by the petrous internal carotid artery, cochlea, IAC, petrous ridge, and lateral border of V3. Conclusion The MF approaches are challenging. Operatively oriented skull base dissections provide a crucial foundation for learning these techniques. We describe comprehensive step-by-step approaches intended to develop familiarity in the cadaver laboratory and facilitate understanding of their potential for skull base disorders. Basic surgical principles are described to help in the operating room as well as illustrative cases.

Abstract PurposeTo clarify the need for post-operative radiation treatment in skull base chondrosarcomas (SBCs).MethodsA retrospective analysis of patients with grade I or II SBC. Patients were divided according to post-surgical treatment strategies: (A) planned upfront radiotherapy and (B) watchful waiting. Tumor control and survival were compared between the treatment groups. The median follow-up after resection was 105 months (range, 9-376).ResultsThirty-two patients (Grade 1, n = 16; Grade 2, n = 16) were included. The most frequent location was petroclival (21, 64%). A gross total resection (GTR) was achieved in 11 patients (34%). Fourteen (44%) underwent upfront radiotherapy (group A) whereas 18 (56%) were followed with serial MRI alone (group B). The tumor control rate for the entire group was 77% and 69% at 10- and 15-year, respectively. Upfront radiotherapy (P = 0.25), extent of resection (P = 0.11) or tumor grade (P = 0.83) did not affect tumor control. The majority of Group B patients with recurrent tumors (5/7) obtained tumor control with repeat resection (n = 2), salvage radiotherapy (n = 2), or a combination of both (n = 1). The 10-year disease-specific survival was 95% with no difference between the group A and B (P = 0.50). ConclusionFor patients with grade I/II SBC, a reasonable strategy is deferral of radiotherapy after maximum safe resection until tumor progression or recurrence. At that time, most patients can be successfully managed with salvage radiotherapy or surgery. Late recurrences may occur, and life-long follow-up is advisable.