Supracerebellar infratentorial inverted subchoroidal approach to lateral ventricle lesions: Anatomical study and illustrative case

Background: This study provides an anatomical description of a novel supracerebellar infratentorial inverted subchoroidal (SIIS) approach to the lateral ventricle. An illustrative case is presented in which this approach was used to simultaneously resect two tumors residing in the posterior fossa and lateral ventricle. Methods: The SIIS approach was performed on five cadaveric heads using microsurgical and endoscopic techniques. Target points were defined in the lateral ventricle, and quantitative analysis was performed to assess limits of exposure within the lateral ventricle. Two coronal reference planes corresponding to the anterior and posterior margins of the lateral ventricle body were defined. Distances from target points to reference planes were measured, and an imaging-based predicting system was provided according to obtained measurements to guide preoperative approach selection. Results: Mean (standard deviation) distances between the predefined target points indicating the anterior limits and the anterior plane were 9 (7.0) mm, 11 (5.8) mm, and 7 (5.1) mm; posterior limits had distances of 8 (3.0) mm, 17 (9.2) mm, 15 (9.2) mm, and 9 (7.2) mm to the posterior plane. Limiting factors of the choroidal fissure dissection were the venous angle anteriorly and thalamocaudate vein posteriorly. The position of the venous angle had a high negative correlation with the anterior exposure limit ( = -0.87, \u3c 0.001; = -0.92, \u3c 0.001). Conclusion: A step-by-step anatomical description of a new SIIS approach is given, and a quantitative description of the limits of the exposure is provided to evaluate the application of this approach

Supracerebellar Infratentorial Approach for a Malignant Pineal Region Tumor Mimicking a Cavernous Malformation

A man in his early 20s presented with diplopia. Imaging revealed a pineal region hemorrhagic lesion, suggestive of cavernous malformation. The patient underwent an endoscopic third ventriculostomy and was transferred to our institution. In the sitting position, he underwent a supracerebellar infratentorial approach. Gross total resection was achieved without new neurological deficits. Pathologic diagnosis was consistent with a mixed germ cell tumor. The patient was referred to the radiation oncology department. Gravity retraction of the cerebellum was achieved with the supracerebellar infratentorial approach in the sitting position, torcular craniotomy exposed the major sinuses, and drainage of cerebrospinal fluid widened the surgical corridor and facilitated resection of this lesion (Video 1). Histopathological findings are critical to establish the correct diagnosis because magnetic resonance imaging findings can be misleading. The patient provided written informed consent for the procedure

Quantitative Anatomic Comparison of the Extreme Lateral Transodontoid vs Extreme Medial Endoscopic Endonasal Approaches to the Jugular Foramen and Craniovertebral Junction

BACKGROUND: Large, destructive intracranial and extracranial lesions at the jugular foramen (JF) and anterior craniovertebral junction (CVJ) are among the most challenging lesions to resect. OBJECTIVE: To compare the extreme lateral transodontoid approach (ELTOA) with the extreme medial endoscopic endonasal approach (EMEEA) to determine the most effective surgical approach to the JF and CVJ. METHODS: Seven formalin-fixed cadaveric heads were dissected. Using neuronavigation, we quantitatively measured and compared the exposure of the intracranial and extracranial neurovascular structures, the drilled area of the clivus and the C1 vertebra, and the area of exposure of the brainstem. RESULTS: The mean total drilled area of the clivus was greater with the EMEEA than with the ELTOA (1043.5 vs 909.4 mm 2 , P = .02). The EMEEA provided a longer exposure of the extracranial cranial nerves (CNs) IX, X, and XI compared with the ELTOA (cranial nerve [CN] IX: 18.8 vs 12.0 mm, P = .01; CN X: 19.2 vs 10.4 mm, P = .003; and CN XI, 18.1 vs 11.9 mm, P = .04). The EMEEA, compared with the ELTOA, provided a significantly greater area of exposure of the contralateral ventromedial medulla (289.5 vs 80.9 mm 2 , P \u3c .001) and pons (237.5 vs 86.2 mm 2 , P = .005) but less area of exposure of the ipsilateral dorsolateral medulla (51.5 vs 205.8 mm 2 , P = .008). CONCLUSION: The EMEEA and ELTOA provide optimal exposures to different aspects of the CVJ and JF. A combination of these approaches can compensate for their disadvantages and achieve significant exposure

Surgical Anatomy of the Middle Communicating Artery and Guidelines for Predicting the Feasibility of M2-M2 End-to-End Reimplantation

BACKGROUND: M2-M2 end-to-end reimplantation that creates a middle communicating artery has recently been proposed as a reconstruction technique to treat complex aneurysms of the middle cerebral artery that are not amenable to clipping. OBJECTIVE: To examine the surgical anatomy, define anatomic variables, and explore the feasibility of this bypass. METHODS: Sixteen cadaver heads were prepared for bypass simulation. After the middle cerebral artery bifurcation was approached, the proximal insular (M2) segments and perforators were explored. To define the maximal distance between the M2 segments that allows the bypass to be performed, the M2 segments were mobilized and reimplanted in an end-to-end fashion. RESULTS: Successful reimplantation was performed in all specimens. The mean maximal distance between the M2 segments to create the proposed reimplantation was 9.1 ± 3.2 mm. The mean vessel displacement was significantly greater for the superior (6.0 ± 2.3 mm) M2 segment than for the inferior (3.2 ± 1.4 mm) M2 segment (P \u3c .001). CONCLUSION: In this cadaveric study, the stumps of the M2 segments located at a distance of ≤9.1 mm could be approximated to create a feasible M2-M2 end-to-end anastomosis. Intraoperative inspection of the M2 segments and their perforators could allow further assessment of the feasibility of the procedure before final revascularization decisions are made

Comparative analysis of the combined petrosal and the pretemporal transcavernous anterior petrosal approach to the petroclival region

OBJECTIVE: The combined petrosal (CP) approach has been traditionally used to resect petroclival meningioma (PCM). The pretemporal transcavernous anterior petrosal (PTAP) approach has emerged as an alternative. A quantitative comparison of both approaches has not been made. This anatomical study compared the surgical corridors afforded by both approaches and identified key elements of the approach selection process. METHODS: Twelve cadaveric specimens were dissected, and 10 were used for morphometric analysis. Groups A and B (n = 5 in each) underwent the CP and PTAP approaches, respectively. The area of drilled clivus, lengths of cranial nerves (CNs) II-X, length of posterior circulation vessels, surgical area of exposure of the brainstem, and angles of attack anterior and posterior to a common target were measured and compared. RESULTS: The area of drilled clivus was significantly greater in group A than group B (mean ± SD 88.7 ± 17.1 mm2 vs 48.4 ± 17.9 mm2, p \u3c 0.01). Longer segments of ipsilateral CN IV (52.4 ± 2.33 mm vs 46.5 ± 3.71 mm, p \u3c 0.02), CN IX, and CN X (9.91 ± 3.21 mm vs 0.00 ± 0.00 mm, p \u3c 0.01) were exposed in group A than group B. Shorter portions of CN II (9.31 ± 1.28 mm vs 17.6 ± 6.89 mm, p \u3c 0.02) and V1 (26.9 ± 4.62 mm vs 32.4 ± 1.93 mm, p \u3c 0.03) were exposed in group A than group B. Longer segments of ipsilateral superior cerebellar artery (SCA) were exposed in group A than group B (36.0 ± 4.91 mm vs 25.8 ± 3.55 mm, p \u3c 0.02), but there was less exposure of contralateral SCA (0.00 ± 0.00 mm vs 7.95 ± 3.33 mm, p \u3c 0.01). There was no statistically significant difference between groups with regard to the combined area of the exposed cerebral peduncles and pons (p = 0.75). Although exposure of the medulla was limited, group A had significantly greater exposure of the medulla than group B (p \u3c 0.01). Finally, group A had a smaller anterior angle of attack than group B (24.1° ± 5.62° vs 34.8° ± 7.51°, p \u3c 0.03). CONCLUSIONS: This is the first study to quantitatively identify the advantages and limitations of the CP and PTAP approaches from an anatomical perspective. Understanding these data will aid in designing maximally effective yet minimally invasive approaches to PCM

Introduction of In Vivo Confocal Laser Endomicroscopy and Real-Time Telepathology for Remote Intraoperative Neurosurgery-Pathology Consultation

BACKGROUND: Precise communication between neurosurgeons and pathologists is crucial for optimizing patient care, especially for intraoperative diagnoses. Confocal laser endomicroscopy (CLE) combined with a telepathology software platform (TSP) provides a novel venue for neurosurgeons and pathologists to review CLE images and converse intraoperatively in real-time. OBJECTIVE: To describe the feasibility of integrating CLE and a TSP in the surgical workflow for real-time review of in vivo digital fluorescence tissue imaging in 3 patients with intracranial tumors. METHODS: Although the neurosurgeon used the CLE probe to generate fluorescence images of histoarchitecture within the operative field that were displayed on monitors in the operating room, the pathologist simultaneously remotely viewed the CLE images. The neurosurgeon and pathologist discussed in real-time the histological structures of intraoperative imaging locations. RESULTS: The neurosurgeon placed the CLE probe at various locations on and around the tumor, in the surgical resection bed, and on surrounding brain tissue with communication through the TSP. The neurosurgeon oriented the pathologist to the location of the CLE, and the pathologist and neurosurgeon discussed the CLE images in real-time. The TSP and CLE were integrated successfully and rapidly in the operating room in all 3 cases. No patient had perioperative complications. CONCLUSION: Two novel digital neurosurgical cellular imaging technologies were combined with intraoperative neurosurgeon-pathologist communication to guide the identification of abnormal histoarchitectural tissue features in real-time. CLE with the TSP may allow rapid decision-making during tumor resection that may hold significant advantages over the frozen section process and surgical workflow in general

A two-stage combined anterolateral and endoscopic endonasal approach to the petroclival region: an anatomical study and clinical application

OBJECT: The pretemporal transcavernous anterior petrosal (PTAP) approach and the combined petrosal (CP) approach have been used to resect petroclival meningiomas (PCMs). In this cadaveric anatomical study, a two-stage combined PTAP and endoscopic endonasal far medial (EEFM) approach (the PTAPE approach) was compared morphometrically to the CP approach. A case study provides a clinical example of using the PTAPE approach to treat a patient with a PCM. The key elements of the approach selection process are outlined. METHODS: Five cadaveric specimens underwent a CP approach and 5 underwent a PTAPE approach. The area of drilled clivus, length of multiple cranial nerves (CNs), and the area of brain stem exposure were measured, reported as means (standard deviations) by group, and compared. RESULTS: The total area of the clivus drilled in the PTAPE group (695.3 [121.7] mm) was greater than in the CP group (88.7 [17.06] mm, P \u3c 0.01). Longer segments of CN VI were exposed via the PTAPE than the CP approach (35.6 [9.07] vs. 16.3 [6.02] mm, P \u3c 0.01). CN XII (8.8 [1.06] mm) was exposed only in the PTAPE group. Above the pontomedullary sulcus, the total area of brain stem exposed was greater with the PTAPE than the CP approach (1003.4 [219.5] mm vs. 437.6 [83.7] mm, P \u3c 0.01). Similarly, the total exposure of the medulla was greater after the PTAPE than the CP exposure (240.2 [57.06] mm vs. 48.1 [19.9] mm, P \u3c 0.01). CONCLUSION: A combined open-endoscopic paradigm is proposed for managing large PCMs. This approach incorporates the EEFM approach to address the limitations of the PTAP and the CP approach in a systematic fashion. Understanding the anatomical findings of this study will aid in tailoring surgical approaches to patients with these complex lesions

Step-by-Step Dissection of the Extreme Lateral Transodontoid Approach to the Anterior Craniovertebral Junction: Surgical Anatomy and Technical Nuances

BACKGROUND: Multicompartmental lesions of the anterior craniovertebral junction require aggressive management. However, the lesions can be difficult to reach, and the surgical procedure is difficult to understand. The aim of this study was to create a procedural, stepwise microsurgical educational resource for junior trainees to learn the surgical anatomy of the extreme lateral transodontoid approach (ELTOA). METHODS: Ten formalin-fixed, latex-injected cadaveric heads were dissected under an operative microscope. Dissections were performed under the supervision of a skull base fellowship-trained neurosurgeon who has advanced skull base experience. Key steps of the procedure were documented with a professional camera and a high-definition video system. A relevant clinical case example was reviewed to highlight the principles of the selected approach and its application. The clinical case example also describes a rare complication: a pseudoaneurysm of the vertebral artery. RESULTS: Key steps of the ELTOA include patient positioning, skin incision, superficial and deep muscle dissection, vertebral artery dissection and transposition, craniotomy, clivus drilling, odontoidectomy, and final extradural and intradural exposure. CONCLUSIONS: The ELTOA is a challenging approach, but it allows for significant access to the anterior craniovertebral junction, which increases the likelihood of gross total lesion resection. Given the complexity of the approach, substantial training in the dissection laboratory is required to develop the necessary anatomic knowledge and to minimize approach-related morbidity

Comparative Anatomical Assessment of Full vs Limited Transcavernous Exposure of the Carotid-Oculomotor Window

BACKGROUND: Although the full transcavernous approach affords extensive mobilization of the oculomotor nerve (OMN) for exposure of the basilar apex and interpeduncular cistern region, this time-consuming procedure requires substantial dural dissection along the anterior middle cranial fossa. OBJECTIVE: To quantify the extent to which limited middle fossa dural elevation affects the carotid-oculomotor window (C-OMW) surgical area during transcavernous exposure after OMN mobilization. METHODS: Four cadaveric specimens were dissected bilaterally to study the C-OMW area afforded by the transcavernous exposure. Each specimen underwent full and limited transcavernous exposure and anterior clinoidectomy (1 procedure per side; 8 procedures). Limited exposure was defined as a dural elevation confined to the cavernous sinus. Full exposure included dural elevation over the gasserian ganglion, extending to the middle meningeal artery and lateral middle cranial fossa. RESULTS: The C-OMW area achieved with the limited transcavernous exposure, compared with full transcavernous exposure, provided significantly less total area with OMN mobilization (22 ± 6 mm2 vs 52 ± 26 mm2, P = .03) and a smaller relative increase in area after OMN mobilization (11 ± 5 mm2 vs 36 ± 13 mm2, P = .03). The increase after OMN mobilization in the C-OMW area after OMN mobilization was 136% ± 119% with a limited exposure vs 334% ± 216% with a full exposure. CONCLUSION: In this anatomical study, the full transcavernous exposure significantly improved OMN mobilization and C-OMW area compared with a limited transcavernous exposure. If a transcavernous exposure is pursued, the difference in the carotid-oculomotor operative corridor area achieved with a limited vs full exposure should be considered

Combined subtarsal contralateral transmaxillary retroeustachian and endoscopic endonasal approaches to the infrapetrous region

OBJECTIVE: The eustachian tube (ET) limits endoscopic endonasal access to the infrapetrous region. Transecting or mobilizing the ET may result in morbidities. This study presents a novel approach in which a subtarsal contralateral transmaxillary (ST-CTM) corridor is coupled with the standard endonasal approach to facilitate access behind the intact ET. METHODS: Eight cadaveric head specimens were dissected. Endoscopic endonasal approaches (EEAs) (i.e., transpterygoid and inferior transclival) were performed on one side, followed by ST-CTM and sublabial contralateral transmaxillary (SL-CTM) approaches on the opposite side, along with different ET mobilization techniques on the original side. Seven comparative groups were generated. The length of the cranial nerves, areas of exposure, and volume of surgical freedom (VSF) in the infrapetrous regions were measured and compared. RESULTS: Without ET mobilization, the combined ST-CTM/EEA approach provided greater exposure than EEA alone (mean ± SD 288.9 ± 40.66 mm2 vs 91.7 ± 49.9 mm2; p = 0.001). The VSFs at the ventral jugular foramen (JF), entrance to the petrous internal carotid artery (ICA), and lateral to the parapharyngeal ICA were also greater in ST-CTM/EEA than in EEA alone (p = 0.002, p = 0.002, and p \u3c 0.001, respectively). EEA alone, however, provided greater VSF at the hypoglossal canal (HGC) than did ST-CTM/EEA (p = 0.01). The SL-CTM approach did not increase the EEA exposure (p = 0.48). The ST-CTM/EEA approach provided greater exposure than EEA with extended inferolateral (EIL) or anterolateral (AL) ET mobilization (p = 0.001 and p = 0.02, respectively). The ST-CTM/EEA also increased the VSF lateral to the parapharyngeal ICA in comparison with EEA/EIL ET mobilization (p \u3c 0.001) but not with EEA/AL ET mobilization (p = 0.36). Finally, the VSFs at the HGC and JF were greater in EEA/AL ET mobilization than in ST-CTM/EEA without ET mobilization (p = 0.002 and p = 0.004, respectively). CONCLUSIONS: Combining the EEA with the more laterally and superiorly originating ST-CTM approach allows greater exposure of the infrapetrous and ventral JF regions while obviating the need for mobilizing the ET. The surgical freedom afforded by the combined approaches is greater than that obtained by EEA alone