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Objective While the transcondylar approach is technically challenging, it provides generous ventral and caudal exposure to the craniovertebral junction. This approach requires navigation around multiple eloquent neurovascular structures including the lower cranial nerves, vertebral artery and its branches, and the brainstem. Superficial exposure, including incision location and muscle dissection, can dramatically affect the surgical angle and maneuverability at depth. Methods We demonstrate the transcondylar approach in a step-by-step fashion in a formalin-embalmed, latex-injected cadaver head. Dissection within each layer of the suboccipital muscles was performed. A small cohort with an illustrative case is also included herein. Results The sternocleidomastoid (SCM) muscle was retracted anteriorly; the splenium capitis, semispinalis capitis, and longissimus capitis muscles were disconnected from the superior nuchal line and reflected inferomedially. The suboccipital muscle group was fully exposed. The superior and inferior oblique muscles were disconnected from the transverse process of C1. The superior oblique and the rectus capitis posterior major muscles were then dissected off the inferior nuchal line, and the suboccipital muscle group was retracted inferomedially en bloc. The greater auricular nerve was retracted laterally with the SCM, and the greater occipital nerve was retracted inferomedially with the suboccipital muscle group. Conclusions This technique avoids the obstructive muscle bulk that results from a myocutaneous approach while maximizing deep exposure. Understanding the detailed muscular anatomical relationship with the insertion location and suboccipital nerves is key to complete and safe extracranial dissection. Diligent dissection helps minimize postoperative pain and muscle spasm while optimizing the closure technique.

Objective The vidian nerve can be accessed in transcranial approaches in carefully selected patients to ensure its preservation and to serve as a landmark for sphenoid sinus entry. This report is to review a technique, evaluate it in laboratory settings, and present two illustrative cases. Design The study involves cadaveric dissection and illustrative cases. Setting The study conducted in a cadaveric dissection laboratory. Participants The object of the study is one cadaveric head and two illustrative clinical cases. Main Outcome Measures Two cases using this approach were illustrated, and a cadaver dissection was performed in a step-by-step fashion. Results: The vidian canal can be accessed by drilling the anterolateral triangle. Two illustrated cases were presented; in one, the vidian nerve was used as part of a corridor to access the sphenoid sinus for tumor delivery, and in the other, the technique was used to find and preserve the vidian nerve during transcranial resection. Conclusion Careful identification of the vidian canal in transcranial surgery is a beneficial technique in carefully selected cases which allows identification of the nerve both for its preservation in selected cases and to create the vidian–maxillary corridor for tumor resection. Knowing the anatomy and pneumatization variants is important in the surgical approach.

Background: The genetic underpinning of meningiomas remains incompletely understood, despite their prevalence in adults. We prospectively analyzed the genetic profiles of a large cohort of skull base meningiomas and assessed relevant pathological and clinical variables. Methods: Copy-number alterations were analyzed on resected skull base meningiomas using array-based comparative genomic hybridization. Pathologic features and clinical factors associated with outcome were also assessed. Results: A total of 83 skull base meningiomas from 80 patients (49F/31M; mean age, 55 years; range, 22–90 years) were profiled following surgical resection. The majority of tumors were de novo, undergoing primary resection, 27 tumors were recurrent, and 7 patients harbored multiple intracranial meningiomas. Overall, 19 tumors had prior radiation exposure, 3 being radiation induced, and 15 patients received postoperative adjuvant radiation. The most common tumor locations were petroclival/petrosal (26), sphenoid wing (13), parasagittal/falcine (12), planum sphenoidale/olfactory groove (9), and tuberculum/clinoid (8), followed by intraventricular, middle fossa, tentorial, torcular, cavernous sinus, and foramen magnum locations. Among the tumors, 59 were WHO grade I (28 meningothelial, 11 fibroblastic, 10 transitional, 4 secretory, 4 angiomatous, and 2 psammomatous); 18 were grade II (17 atypical and 1 clear cell); and 6 were grade III (five anaplastic and one rhabdoid). Overall, 8 tumors were observed to exhibit brain invasion and 19 cases had intratumoral necrosis. Across all tumors, monosomy 22 was the most frequent copy number alteration, occurring in 47% of all samples (29% of grade I tumors, 89% of grade II tumors, and 100% of grade III meningiomas). The following alterations were frequently observed, particularly in anaplastic tumors: loss of chromosome 1p (all: 30%, grade I: 10%, grade II: 78%, and grade III: 83%); 6q (all: 22%, grade I: 5%, grade II: 50%, and grade III: 100%); 7p (all: 13%, grade I: 0%, grade II: 33%, and grade III: 83%); 10q (all: 8%, grade I: 2%, grade II: 22%, and grade III: 33%); and 18q (all: 16%, grade I: 3%, grade II: 33%, and grade III: 83%). The incidence of chromosomal loss varied significantly by location. Paravenous meningiomas, involving the sagittal sinus, torcula, and cavernous sinus, harbored an especially high rate of chromosomal loss (1p-: 65%; 6q-: 29%; 18q-: 29%; and monosomy 22: 76%). Petrosal/petroclival (1p-: 32%; 6q-: 23%; 18q-: 14%; and monosomy 22: 59%) and sphenoid (1p-: 23%; 6q-: 15%; 18q-: 8%; and monosomy 22: 31%) meningiomas also expressed higher chromosomal losses than planum sphenoidale/olfactory (1p-: 0%; 6q-: 0%; 18q-: 11%; and monosomy 22: 0%) and tuberculum/clinoid (1p-: 0%; 6q-: 0%; 18q-: 0%; and monosomy 22: 0%) meningiomas, which featured fewer copy number alterations. Polysomy involving multiple chromosomes was a marked feature of angiomatous meningiomas. Furthermore, patterns of intratumoral heterogeneity emerged from an illustrative case. Conclusion: Traditional histopathologic classifications fail to fully account for the natural history and growth patterns of intracranial meningiomas. Systematic genomic characterization of a large series of skull base meningiomas reveals distinct subsets of tumors, which may be further correlated with clinical outcomes.