Anatomical Limits of the Endoscopic Contralateral Transmaxillary Approach to the Petrous Apex and Petroclival Region.

Objectives This study aimed to establish the anatomical landmarks for performing a contralateral transmaxillary approach (CTM) to the petrous apex (PA) and petroclival region (PCR), and to compare CTM with a purely endoscopic endonasal approach (EEA). Design EEA and CTM to the PA and PCR were performed bilaterally in eight human anatomical specimens. Surgical techniques and anatomical landmarks were described, and EEA was compared with CTM with respect to ability to reach the contralateral internal acoustic canal (IAC). Computed tomographic scans of 25 cadaveric heads were analyzed and the "angle" and "reach" of CTM and EEA were measured. Results Entry to the PA via a medial approach was limited by (1) abducens nerve superiorly, (2) internal carotid artery (ICA) laterally, and (3) petroclival synchondrosis inferiorly (Gardner's triangle). With CTM, it was possible to reach the contralateral IAC bilaterally in all specimens dissected, without dissection of the ipsilateral ICAs, pterygopalatine fossae, and Eustachian tubes. Without CTM, reaching the contralateral IAC was possible only if: (1) angled endoscopes and instruments were employed or (2) the pterygopalatine fossa was dissected with mobilization of the ICA and resection of the Eustachian tube. The average "angle" and "reach" advantages for CTM were 25.6-degree greater angle of approach behind the petrous ICA and 1.4-cm more lateral reach. Conclusion The techniques and anatomical landmarks for CTM to the PA and PCR are described. Compared with a purely EEA, the CTM provides significant "angle" and "reach" advantages for the PA and PCR.

Lateral Transorbital Versus Endonasal Transpterygoid Approach to the Lateral Recess of the Sphenoid Sinus-A Comparative Anatomic Study.

BACKGROUND: The treatment of cerebrospinal fluid leaks of the lateral recess of the sphenoid sinus (LRSS) faces difficulties due to the deep location of the osseous defect. When treated with craniotomies, brain retraction is a concern. The endoscopic endonasal transpterygoid approach (EETA) is a direct and less invasive procedure; however, it may require transection of the vidian nerve (VN). OBJECTIVE: To investigate the feasibility of a lateral transorbital approach (LTOA) as an alternative pathway to the LRSS that avoids VN sacrifice. METHODS: Six embalmed heads with well-pneumatized LRSS were preselected by inspecting their computed tomography scans. One LTOA and one EETA were performed on 1 side of each specimen. The approaches were compared regarding working distance and neurovascular structures being sacrificed. The working area of the LTOA was also measured. RESULTS: The average working distances were 59.9 (±2.94) mm for the LTOA and 76.4 (±3.99) mm for the EETA (P < .001). The LTOA generated a working area with a diameter of 9 to 14 mm. The EETA demanded the sacrifice of VN and the sphenopalatine artery in all specimens to expose the LRSS. No neurovascular structures were found in the trajectory of the LTOA. CONCLUSION: The LTOA to the LRSS is feasible, with minimal risk of injuring neurovascular structures. It offers a shorter pathway when compared to the EETA. Although the LTOA provides no options for vascularized flap reconstruction, it allows immediate access to muscle grafts. The LTOA may serve as an alternative to treating cerebrospinal fluid leaks of the LRSS.

Supracerebellar Infratentorial and Occipital Transtentorial Approaches to the Pulvinar: Ipsilateral Versus Contralateral Corridors.

BACKGROUND: Due to the critical neurovascular structures that surround the pulvinar, deciding the best surgical approach can be challenging, with multiple options available. OBJECTIVE: To analyze and compare the ipsilateral vs the contralateral version of the 2 main approaches to the cisternal pulvinar surface: paramedian supracerebellar infratentorial (PSCI) and interhemispheric occipital transtentorial (IOT). METHODS: The PSCI and IOT approaches were performed on 7 formalin-fixed adult cadaveric heads to evaluate qualitatively and quantitatively the microsurgical exposure of relevant anatomic structures. We quantitatively measured the corridor distance to our target with each approach. RESULTS: The ipsilateral PSCI approach provided an easier access and a better exposure of the anteromedial portion of the cisternal pulvinar surface. The contralateral approach provided a wider and more accessible exposure of the posterolateral portion of the cisternal pulvinar surface. When protrusion of the posterior parahippocampal gyrus above the free edge of the tentorium was present, the contralateral PSCI approach provided an unobstructed view to both areas. The IOT approach provided a better view of the anteromedial portion of the cisternal pulvinar surface, especially with a contralateral approach. CONCLUSION: Multiple approaches to the pulvinar have been described, modified, and improved. Based on this anatomic study we believe that although the corridor distance with a contralateral approach is longer, the surgical view and access can be better. We recommend the use of a PSCI contralateral approach especially when a significant protrusion of the posterior parahippocampal gyrus is present.

Surgical Anatomy of the Subcallosal Artery: Implications for Transcranial and Endoscopic Endonasal Surgery in the Suprachiasmatic Region.

BACKGROUND: Suprachiasmatic subcallosal lesions may have an intimate relationship with the anterior communicating artery (AcomA); injury to AcomA branches can result in basal forebrain infarction and cognitive dysfunction. OBJECTIVE: To evaluate anatomic variations of the AcomA basal perforating branches, especially the subcallosal artery (ScA), for clinical implications when approaching the suprachiasmatic subcallosal region from endonasal and transcranial routes. METHODS: The origin, course, diameter, and branching pattern of the AcomA's perforating branches were studied in 33 specimens from transcranial and endonasal perspectives. RESULTS: The ScA was present in 79% of the specimens as a single dominant artery arising from the posterior/posterosuperior surface of the AcomA, along with hypothalamic arteries (55%), or as a single artery (24%). It coursed posteriorly towards the lamina terminalis region, curving superiorly to the subcallosal area. The ScA gave off many branches to provide the main blood supply to the subcallosal region. Importantly, it supplies the septal/subcallosal region bilaterally. The ScA can be found posterior, superior, or inferior to the AcomA when using a transylvian, interhemispheric, or endonasal approach, respectively. In specimens with no ScA (21%), the median callosal artery (MdCA) was the dominant artery arising from the AcomA. It followed an identical course to the ScA, providing supply to the same structures bilaterally, but its distal extension reached the body/splenium of the corpus callosum. The MdCA is a ScA variant. CONCLUSION: The ScA is a unique vessel because it supplies the septal/subcallosal region bilaterally; preservation of this vessel during surgery is crucial for successful outcomes.

The medial wall of the cavernous sinus. Part 2: Selective medial wall resection in 50 pituitary adenoma patients.

OBJECTIVE: Pituitary adenomas often invade the medial wall of the cavernous sinus (CS), but this structure is generally not surgically removed because of the risk of vascular and cranial nerve injury. The purpose of this study was to report the surgical outcomes in a large series of cases of invasive pituitary adenoma in which the medial wall of the CS was selectively removed following an anatomically based, stepwise surgical technique. METHODS: The authors' institutional database was reviewed to identify cases of pituitary adenoma with isolated invasion of the medial wall, based on an intraoperative evaluation, in which patients underwent an endoscopic endonasal approach with selective resection of the medial wall of the CS. Cases with CS invasion beyond the medial wall were excluded. Patient complications, resection, and remission rates were assessed. RESULTS: Fifty patients were eligible for this study, 15 (30%) with nonfunctional adenomas and 35 (70%) with functional adenomas, including 16 growth hormone-, 10 prolactin-, and 9 adrenocorticotropic hormone (ACTH)-secreting tumors. The average tumor size was 2.3 cm for nonfunctional and 1.3 cm for functional adenomas. Radiographically, 11 cases (22%) were Knosp grade 1, 23 (46%) Knosp grade 2, and 16 (32%) Knosp grade 3. Complete tumor resection, based on intraoperative impression and postoperative MRI, was achieved in all cases. The mean follow-up was 30 months (range 4-64 months) for patients with functional adenomas and 16 months (range 4-30 months) for those with nonfunctional adenomas. At last follow-up, complete biochemical remission (using current criteria) without adjuvant treatment was seen in 34 cases (97%) of functional adenoma. No imaging recurrences were seen in patients who had nonfunctional adenomas. A total of 57 medial walls were removed in 50 patients. Medial wall invasion was histologically confirmed in 93% of nonfunctional adenomas and 83% of functional adenomas. There were no deaths or internal carotid artery injuries, and the average blood loss was 378 ml. Four patients (8%) developed a new, transient cranial nerve palsy, and 2 of these patients required reoperation for blood clot evacuation and fat graft removal. There were no permanent cranial nerve palsies. CONCLUSIONS: The medial wall of the CS can be removed safely and effectively, with minimal morbidity and excellent resection and remission rates. Further follow-up is needed to determine the long-term results of this anatomically based technique, which should only be performed by very experienced endonasal skull base teams.

The medial wall of the cavernous sinus. Part 1: Surgical anatomy, ligaments, and surgical technique for its mobilization and/or resection.

OBJECTIVE: The medial wall of the cavernous sinus (CS) is often invaded by pituitary adenomas. Surgical mobilization and/or removal of the medial wall remains a challenge. METHODS: Endoscopic endonasal dissection was performed in 20 human cadaver heads. The configuration of the medial wall, its relationship to the internal carotid artery (ICA), and the ligamentous connections in between them were investigated in 40 CSs. RESULTS: The medial wall of the CS was confirmed to be an intact single layer of dura that is distinct from the capsule of the pituitary gland and the periosteal layer that forms the anterior wall of the CS. In 32.5% of hemispheres, the medial wall was indented by and/or well adhered to the cavernous ICA. The authors identified multiple ligamentous fibers that anchored the medial wall to other walls of the CS and/or to specific ICA segments. These parasellar ligaments were classified into 4 groups: 1) caroticoclinoid ligament, spanning from the medial wall and the middle clinoid toward the clinoid ICA segment and anterior clinoid process; 2) superior parasellar ligament, connecting the medial wall to the horizontal cavernous ICA and/or lateral wall of the CS; 3) inferior parasellar ligament, bridging the medial wall to the anterior wall of the CS or anterior surface of the short vertical segment of the cavernous ICA; and 4) posterior parasellar ligament, which anchors the medial wall to the short vertical segment of the cavernous ICA and/or the posterior carotid sulcus. The caroticoclinoid ligament and inferior parasellar ligament were present in most CSs (97.7% and 95%, respectively), while the superior and posterior parasellar ligaments were identified in approximately half of the CSs (57.5% and 45%, respectively). The caroticoclinoid ligament was the strongest and largest ligament, and it was typically assembled as a group of ligaments with a fan-like arrangement. The inferior parasellar ligament was the first to be encountered after opening the anterior wall of the CS during an interdural transcavernous approach. CONCLUSIONS: The authors introduce a classification of the parasellar ligaments and their role in anchoring the medial wall of the CS. These ligaments should be identified and transected to safely mobilize the medial wall away from the cavernous ICA during a transcavernous approach and for safe and complete resection of adenomas that selectively invade the medial wall.