Alexander, A. Yohan

BACKGROUND AND OBJECTIVES: Endoscopic transnasal surgery offers a minimally invasive alternative to transcranial approaches for accessing midline skull base lesions involving the petrous apex and petroclival region. However, lateral access, particularly behind the petrous internal carotid artery (ICA), remains limited. The contralateral transmaxillary (CTM) approach provides a more direct surgical trajectory, more parallel to the petrous ICA. Yet, lateral access through this approach can be restricted by anatomic barriers, including the pterygoid process and lateral buttress of the maxillary sinus. We aimed to evaluate the contralateral transmaxillary-transpterygoid (CTMP) approach, with and without the lateral buttress removal (CTMP-LBR), to determine whether these modifications could enhance surgical access to the petroclival region. METHODS: Ten sides from 5 formalin-fixed, latex-injected cadaveric specimens were dissected to compare CTM, CTMP, and CTMP-LBR approaches. Petrous bone drilling was directed posterolaterally behind the petrous ICA toward the region medial to the cochlea. In addition, 30 sides from computed tomography angiography scans were analyzed to obtain radiographic measurements for each approach. RESULTS: Compared with CTM, both CTMP and CTMP-LBR significantly increased access for retrocarotid petrous bone drilling ( P < .001) and yielded a wider surgical angle relative to midline ( P < .001), in both cadaveric and radiographic analyses. In dissections, 20% of sides required CTM only, 50% benefited from CTMP, and 30% required CTMP-LBR to achieve adequate lateral access. Radiographic analysis revealed that CTMP required a median of 4 mm of pterygoid drilling, whereas CTMP-LBR required 9 mm and enabled a trajectory parallel to the petrous ICA with only 11 mm of soft tissue displacement. Patients with smaller angles between the petrous ICA and the horizontal plane were significantly more likely to benefit from CTMP over CTM ( P = .005). CONCLUSION: Modification of the CTM approach with pterygoid drilling and optional LBR improves retrocarotid access. Preoperative evaluation of the petrous ICA angle may help optimize patient-specific planning in endoscopic petroclival surgery.

OBJECTIVE Craniopharyngiomas are challenging lesions, and aggressive resections may cause significant postoperative morbidity and mortality. To mitigate morbidity, a potential strategy of subtotal resection (STR) and adjuvant radiation therapy (RT) has been used, but its impact on survival when compared to gross-total resection (GTR) has been under-investigated. Thus, the objective of this study was to analyze short-term mortality between patients undergoing STR ± RT and GTR, and differences in overall survival (OS) between patients undergoing STR, STR + RT, and GTR in a large, nationally representative database. METHODS The authors queried the National Cancer Database for patients diagnosed with craniopharyngioma between 2004 and 2017. Tumor characteristics, treatment strategies, and extent of resection were analyzed. Endpoints were 3-month mortality rate and OS, which were compared between treatment modalities. Firth’s logistic regression was used to analyze 3-month mortality and was adjusted for age, sex, Charlson Comorbidity Index score, histopathological diagnosis, income quartile, insurance payor, and maximal tumor diameter. Differences in survival between treatment modalities were compared with log time-to-event analyses after excluding deaths occurring within 3 months to control for immortal time bias. RESULTS A total of 1460 adult and 390 pediatric patients were included. Adults undergoing STR ± RT had a lower rate of 3-month mortality compared to those undergoing GTR in adjusted analysis (2.8% vs 4.6%, odds ratio 0.42; p = 0.03). Survival curves for the STR + RT and GTR cohorts did not significantly differ (p = 0.198). A strategy of STR alone showed worse OS compared with GTR and STR + RT (p < 0.01). The average follow-up length for adults was 65.5 months. For pediatric patients, 3-month mortality for those undergoing GTR and STR ± RT was similar (0% vs 1%, respectively; p = 0.33). Additionally, compared to GTR, there were no significant differences in OS between STR + RT (p = 0.41) and STR alone (p = 0.44). The average follow-up length for the pediatric cohort was 79 months. CONCLUSIONS STR + RT was associated with a favorable perioperative mortality profile when compared with GTR and provided similar long-term survival outcomes. Therefore, STR + RT may be considered when GTR carries significant risks.

BACKGROUND AND OBJECTIVES: Contralateral transfalcine approaches are widely used for interhemispheric/mesial cortical pathologies, even those extending beyond 2 cm lateral from the midline. Nevertheless, the superior limit of contralateral exposure through this approach is not defined. This anatomic study aims to characterize the maximal superior and lateral limits of contralateral exposure using a contralateral transfalcine approach. METHODS: Interhemispheric approaches in the anterior, middle, and posterior-thirds of the interhemispheric fissure were performed in 10 cadaveric head specimens. Rectangular falcine incisions were made and carried maximally superiorly. The contralateral hemisphere was maximally laterally resected from the superior point of visualization down to the level of the corpus callosum. Distances between the most superior point of visualization of the contralateral hemisphere and the superficial point of its cortex and between the midline and the most lateral point of visualization at the level of the corpus callosum were measured and are reported as averages. RESULTS: At the anterior-third of the interhemispheric fissure, the superior point of visualization was 4.8 mm inferior to the cortex. The lateral distance of visualization at the genu of the corpus callosum was 22.9 mm. At the middle-third, the superior point of visualization was 9.7 mm inferior to the cortex. The lateral distance visualized at the body of the corpus callosum was 22.4 mm. At the posterior-third, the superior point visualization of the mesial contralateral hemisphere was 12.6 mm inferior to the cortex. The lateral distance visualized at the splenium of the corpus callosum was 21.3 mm. CONCLUSION: Using the contralateral transfalcine approach, the superior limit of contralateral exposure progressively decreases more posteriorly along the interhemispheric corridor—ranging from 4.8 mm inferior to the cortex in the anterior-third to 12.6 mm inferior to the cortex in the posterior-third. The contralateral optimal view of exposure increases deeper along the interhemispheric corridor.

BACKGROUND AND OBJECTIVES: Contemporary skull base surgeons must understand transcranial and endoscopic endonasal approaches to the petrous apex (PA). We provide an anatomic overview and comparison of main approaches to the PA through illustrative anatomic dissections. METHODS: On 10 sides of 5 specimens, transcranial approaches to the PA including the anterior petrosal, transcochlear, and retrosigmoid with suprameatal extension were performed. For endoscopic endonasal approaches, the transclival approach was performed in the midline of 5 specimens and its contralateral transmaxillary extension was performed on 10 sides. RESULTS: The anterior petrosal approach offers an anterolateral view of the PA bounded by petrous ridge posteromedially, internal auditory canal posterolaterally, greater superficial petrosal nerve anterolaterally, and lateral boundary of cranial nerve V, the Gasserian ganglion, and V3 anteromedially; it exposes the middle fossa and, once the PA is removed, the superomedial cerebellopontine angle. The transcochlear approach affords a lateral view of the PA defined medially and inferiorly by inferior petrosal sinus, posteriorly by posterior fossa dura, anteriorly by the petrous internal carotid artery, and superiorly by the superior petrosal sinus and middle fossa dura. Through a retrosigmoid approach, the PA is bounded by the superior petrosal sinus superiorly, the sagittal plane of cranial nerve VI medially, and the axial and sagittal plane of the internal auditory canal porus inferiorly and laterally, respectively. It affords a panoramic view of the posterior fossa and access to Meckel's cave after PA drilling. Endoscopic endonasal approaches target the anteromedial PA, and it is demarcated by a triangle consisting of cranial nerve VI posterolaterally, the paraclival segment of the internal carotid artery anteriorly, and the petroclival synchondrosis inferiorly and medially. The addition of the contralateral transmaxillary approach enhances lateral access up to the internal auditory canal. CONCLUSION: We provide a comprehensive overview of the main approaches to the PA through illustrative anatomic dissections and representative cases.