Midline and off-midline infratentorial supracerebellar approaches to the pineal gland

Optimizing the selection of the endoscopically assisted supracerebellar transtentorial approach to the medial temporo-occipital region: Clinical application of one novel grid coordinate system

The endoscopically assisted supracerebellar transtentorial (eSCTT) approach is advocated for managing pathologies of the medial temporo-occipital region, but quantitative analysis is currently lacking. The aims of this study were to establish a grid coordinate system on the tentorium to model the anatomical relationship between medial temporo-occipital region pathology and the slope of the tentorium, and then to compare the paramedian eSCTT and extreme-lateral eSCTT approaches quantitatively. Bilateral paramedian and extreme-lateral eSCTT approaches were used to dissect three adult cadaveric heads anatomically. A grid coordinate system was established on the tentorium, and the angles of attack and depth of the surgical corridor of each coordinate point were obtained so that the two eSCTT approaches could be compared statistically. The measurements were then analyzed to determine the condition for selecting each eSCTT approach, and its clinical feasibility was assessed in three patients with large tumors in the medial temporo-occipital region. For coordinate points where the X-coordinate on the grid coordinate system was 1 cm outside the apex of the tentorium, the paramedian eSCTT approach had a significantly wider angle of attack and shorter depth of surgical corridor than the extreme-lateral eSCTT approach. In contrast, the extreme-lateral eSCTT approach was better for coordinate points where the Y-coordinate on the grid coordinate system was 1 cm in front of the apex of the tentorium. The long axis of each patient's tumor was projected on to the tentorium and its corresponding coordinate points were used to match the more appropriate eSCTT approach. Preliminary results for three patients treated with the eSCTT approach for large tumors in the medial temporo-occipital region were encouraging. When the eSCTT approach is applied to manage a large tumor of the medial temporo-occipital region, assessment of the long axis of the tumor and knowledge of the selective condition for each eSCTT approach can help in clinical decision-making.

Endoscopic-assisted paramedian supracerebellar infratentorial approach to the posterior portion of the third ventricle: anatomical study and surgical cases

BACKGROUND

To date, morphometrical data providing a systematic quantification of accessibility and operability parameters to the boundaries of the posterior portion of the third ventricle (PTV) when applying an endoscopic-assisted paramedian supracerebellar infratentorial approach (EPSIA) are lacking. We performed an anatomical study and complemented our findings with surgical cases.

METHODS

Eight EPSIAs towards the PTV were performed in cadaveric specimens. Optimal approach angles (OA), surgical freedom (SF) and operability indexes (Oi) to the PTV boundaries were assessed. Additionally, a 54-year-old man and 33-year-old woman were operated on PTV tumors applying the EPSIA.

RESULTS

Sagittal OA to ventricle's roof and floor was 36±1.4° and 25.5±3.5° respectively, axial OA to the ipsilateral and contralateral ventricle's wall were 9.5±1.3° and 28.5±1.6°. SF was maximal on the contralateral wall (121.2±19.3mm2), followed by the roof (112.7±18.8mm2), floor (106.6±19.2mm2) and ipsilateral wall (94.1±15.7mm2). SF was significantly lower along the ipsilateral compared the contralateral wall (P<0.01) and roof (P<0.05). Facilitated surgical maneuvers with multiangled exposure were possible up to 8.5±1.07mm anterior to ventricle's entrance, whereas surgical maneuvers were possible but difficult up to 15.25±3.7mm. Visualization of more anterior was possible up to a distance of 27±2.9mm, but surgical maneuvers were barely feasible. EPSIA enabled successful resection of both PTV tumors and postoperative course was uneventful.

CONCLUSIONS

EPSIA can be effective for approaching the PTV, enabling surgery along all boundaries, but especially on its roof and contralateral wall. In the not-enlarged ventricle, surgical maneuvers are feasible up to the level of the Monro foramen, becoming more limited anteriorly.

Quantitative analysis of exposure and surgical maneuverability of three purely endoscopic keyhole approaches to the floor of the third ventricle

BACKGROUND

The quantitative anatomic analysis of comprehensively endoscopic approaches to the third ventricle is scarce at present. The objective of the study is to quantitatively assess and compare the exposure and microsurgical maneuverability of three absolutely endoscopic keyhole approaches, including interhemispheric transcallosal transchoroidal (TCTC), frontal transforminal transchoroidal (TFTC) and supraorbital subfrontal translamina terminalis (SFTL) approaches.

METHODS

Anatomical dissections and exposure of the important structures of the third ventricle were performed using six formalin-fixed cadaveric human heads (twelve sides) under endoscope. Tubular retractor system was used in the TFTC approach. Quantitative anatomical relationship between the important landmarks were obtained. Moreover, the exposure and surgical operability of three approaches were evaluated through applying the rating scale and accomplishing the quantitative anatomic analysis, area of surgical freedom and angle of attack.

RESULTS

The mediolateral, anteroposterior (AM: between aqueduct and mammillary body; IM: between infundibular recess and mammillary body) and superoinferior distance of TCTC, TFTC and SFTL approaches were 4.0±1.0, 4.2±0.4, 4.1±1.1 mm; 17.3±1.4, 17.6±0.5, 12.8±3.3 mm (AM); 7.7±0.3, 7.8±0.5 mm, not measured (IM); and 5.6±0.3, 7.8±0.8, 7.8±1.5 mm, respectively. Similar to TFTC, the exposed landmarks of TCTC were almost scored a "4" by three neurosurgeons except the infundibular recess scored a "3" according to the rating scale. During the SFTL approach, apart from the roof, the majority of the landmarks were scored a "4" except for the infundibular recess, which was scored a "3." The mean area of surgical freedom of TCTC (0° endoscope: 220±47; 30°: 247±56 mm2) was not significantly different from that of TFTC approach (0° endoscope: 216±49; 30°: 245±53 mm2) under same endoscope, P>0.05. Mean angle of attack of TCTC (0° endoscope: 21±4°; 30°: 26±4°) was significantly larger than that of TFTC approach (0° endoscope: 16±3°; 30°: 19±3°), P<0.05.

CONCLUSIONS

Purely endoscopic TCTC and TFTC approaches offer brilliant exposure of the anterior, middle and posterior third ventricle. TCTC approach may have better surgical maneuverability than TFTC approach. Despite the long working distance, the whole third ventricle are exposed well except for the roof in the SFTL approach, and surgical manipulation can be accomplished smoothly.

Anatomy of the posterior Fossa: a comprehensive description for pediatric brain tumors

Posterior fossa tumors are the most common pediatric brain tumors, and present unique challenges in terms of their location and surgical management. The posterior fossa comprehends complex anatomy and represents the smallest and deepest of the three cranial base fossae. An in-depth understanding of posterior fossa anatomy is crucial when it comes to the surgical resection of pediatric brain tumors. Mastering the knowledge of posterior fossa anatomy helps the neurosurgeon in achieving a maximal and safe volumetric resection, that impacts in both overall and progression free survival. With the advancements in microsurgery, the telovelar approach has emerged as the workhorse technique for the resection of posterior fossa tumors in pediatric patients. This approach involves meticulously dissecting of the natural clefts present in the cerebellomedullary fissure, making a comprehensive understanding of the underlying anatomy key for its success.

Purely Endoscopic Supracerebellar Infratentorial Approach to the Pineal Region in Pediatric Population

Pineal lesions represent less than 1% of all brain tumors (Villani et al., Clin Neurol Neurosurg 109:1-6, 2007). The abysmal location and critical neurovascular structures remain a surgical challenge, despite the advent of microneurosurgery. The classical wide surgical suboccipital craniotomy with the supracerebellar infratentorial approach, described by Sir Victor Horsley (Victor, Proc R Soc Med 3:77-78, 1910), is infamous for its considerable surgical morbidity and mortality. This was later upgraded microneurosurgically by Stein to improve surgical outcomes (Stein, J Neurosurg 35:197-202, 1971).Ruge et al. reported the first purely endoscopic fenestration of quadrigeminal arachnoid cysts via this corridor (Ruge et al., Neurosurgery 38:830-7, 1996). A cadaver-based anatomical study by Cardia et al. demonstrated the viability for endoscope-assisted techniques (Cardia et al., J Neurosurg 2006;104(6 Suppl):409-14). However, the first purely endoscopic supracerebellar infratentorial (eSCIT) approach to a pineal cyst was performed in 2008 by Gore et al. (Gore PA et al., Neurosurgery 62:108-9, 2008).Unlike transventricular endoscopy, eSCIT approach poses no mechanical risk to the fornices and can be utilized irrespective of ventricular size. More vascular control and resultant reduction in uncontrolled hemorrhage improve the feasibility of attaining complete resection, especially around corners (Zaidi et al,, World Neurosurg 84, 2015). Gravity-dependent positioning and cerebrospinal fluid (CSF) diversion aid cerebellar relaxation, creating the ideal anatomical pathway. Also, angle of the straight sinus, tentorium, and tectal adherence can often influence the choice of approach; thus direct endoscopic visualization not only counteracts access to the engorged Galenic complex but also encourages sharp dissection of the arachnoid (Cardia et al., J Neurosurg 104:409-14, 2006). These tactics help provide excellent illumination with magnification, making it less fatiguing for the surgeon (Broggi et al., Neurosurgery 67:159-65, 2010).The purely endoscopic approach thwarts the dreaded risk of air embolisms, via simple copious irrigation from a small burr hole (Shahinian and Ra, J Neurol Surg B Skull Base 74:114-7, 2013). The tiny opening and closure are rapid to create, and the smaller wound decreases postoperative pain and morbidity. Recent literature supports its numerous advantages and favorable outcomes, making it a tough contender to traditional open methods.

Endoscopic far-lateral supracerebellar infratentorial approach for resection of dumbbell-shaped trigeminal schwannoma: surgical techniques and preliminary results

BACKGROUND

Trigeminal schwannomas (TSs) are mostly benign tumors. However, dumbbell-shaped TSs are most challenging for surgeons and pose a high surgical risk.

OBJECTIVE

We describe the technique of the purely endoscopic far-lateral supracerebellar infratentorial approach (EFL-SCITA) for removing dumbbell-shaped TSs and further discuss the feasibility of this approach and our experience.

METHODS

EFL-SCITA was performed for resection of 5 TSs between January 2020 and March 2023. The entire procedure was performed endoscopically with the goal of total tumor resection. During the operation, the tumor was exposed in close proximity and multiple angles under the endoscope, and the peri-tumor nerves were carefully identified and protected, especially the normal trigeminal fiber bundles around the tumor.

RESULTS

All the tumors of 5 patients involved the middle and posterior cranial fossa, of which total removal was achieved in 2 patients and near-total removal in 3 patients. The most common preoperative symptoms were relieved after surgery. Two patients had postoperative mild facial paralysis (House-Brackmann grade II), and 1 patient had abducens palsy; both recovered during the follow-up period. Two patients experienced new postoperative facial hypesthesia, and 1 experienced mastication weakness, which did not recover. There was no tumor recurrence or residual tumor growth during the follow-up period in any of the patients.

CONCLUSION

EFL-SCITA is a new and effective alternative for the surgical treatment of TSs. For dumbbell-shaped TSs, this approach provides sufficient surgical field exposure and freedom of operation.

Combined cone-beam CT imaging and microsurgical dissection of cadaver specimens to study cerebral venous anatomy: a technical note

PURPOSE

Cadaver dissections and X-ray based 3D angiography are considered gold standards for studying neurovascular anatomy. We sought to develop a model that utilize the combination of both these techniques to improve current tools for anatomical research, teaching and preoperative surgical planning, particularly addressing the venous system of the brain.

MATERIALS AND METHODS

Seven ethanol-fixed human cadaveric heads and one arm were injected with a latex-barium mixture into the internal jugular veins and the brachial artery. After the ethanol-based fixation, specimens were scanned by high-resolution cone-beam CT and images were post-processed on a 3D-workstation. Subsequent, microsurgical dissections were performed by an experienced neurosurgeon and venous anatomy was compared with relevant 3D venograms.

RESULTS

Latex-barium mixtures resulted in a homogenous cast with filling of the cerebral venous structures down to 150 μm in diameter. The ethanol-based preparation of the cadaveric brains allowed for near-realistic microsurgical maneuverability during dissection. The model improves assessment of the venous system for anatomical education and hands-on surgical training.

CONCLUSION

To our knowledge we describe the first preparation method which combines near-realistic microsurgical dissection of human heads with high-resolution 3D imaging of the cerebral venous system in the same specimens.

Dynamic Lateral Semisitting Position for Supracerebellar Approaches: Technical Note and Case Series

BACKGROUND

It has always been a matter of debate which position is ideal for the supracerebellar approach. The risk of venous air embolism (VAE) is the major deterrent for surgeons and anesthesiologists, despite the fact that sitting and semisitting positions are commonly used in these operations.

OBJECTIVE

To demonstrate a reduction on the risk of VAE and tension pneumocephalus throughout the operation period while taking advantages of the semisitting position.

METHODS

In this study, 11 patients with various diagnoses were operated in our department using the supracerebellar approach in the dynamic lateral semisitting position. We used end-tidal carbon dioxide and arterial blood pressure monitoring to detect venous air embolism.

RESULTS

None of the patients had clinically significant VAE in this study. No tension pneumocephalus or major complications were observed. All the patients were extubated safely after surgery.

CONCLUSION

The ideal position, with which to apply the supracerebellar approach, is still a challenge. In our study, we presented an alternative position that has advantages of the sitting and semisitting positions with a lower risk of venous air embolism.

Pure endoscopic resection of pineal region tumors through supracerebellar infratentorial approach with 'head-up' park-bench position

OBJECTIVE

Neuroendoscopic resection via supracerebellar infratentorial (SCIT) approach is adequate for some indicated pineal region tumors with the natural infratentorial corridor. We described this full endoscopic approach through a modified 'head-up' park-bench position to facilitate the procedure.

METHODS

We reviewed the clinical and radiological data of four patients with pineal region lesions who underwent pure endoscopic tumor resection through the SCIT approach with this modified position. The related literature concerning fully endoscopic pineal region tumor resection was also reviewed.

RESULTS

This cohort included four patients with pineal region tumors. External ventricular drainage (Ommaya reservoir) was performed in three patients with hydrocephalus in advance. The average tumor volume was 19.2 ± 17.2 cm³. Pathological examination confirmed two mixed germinomas, one glioblastoma multiforme, and one hemangioblastoma. Gross total resection (GTR) was achieved in all patients, and all patients recovered well without neurological deficits or surgical complications. Hydrocephalus was relieved among all patients.

CONCLUSIONS

The pure endoscopic SCIT approach could enable safe and effective resection of pineal region tumors, even for relatively large lesions. The endoscope could provide a panoramic view and illumination of the deep-seated structures. Compared with the sitting position, this modified ergonomic position could be implemented easily.

The parietooccipital interhemispheric transtentorial approach for pineal tumors

Access to the pineal region has always been a challenge for neurosurgeons. The parietooccipital interhemispheric transtentorial approach is a slight variation of the traditional occipital transtentorial approach that provides adequate exposure to the lesions of the pineal region without introducing additional risks. In this study, the modified parietooccipital interhemispheric transtentorial approach is discussed including step-by-step anatomical cadaveric dissections and operative images. 27 adult patients (age > 18) who were operated over a 30-year period (1992-2022) by the senior author (M.N.P.) at two clinics, Marmara University, Department of Neurosurgery, Istanbul, Turkey and Acibadem Mehmet Ali Aydinlar University, Department of Neurosurgery, Istanbul, Turkey were analyzed. Only pineal region tumors were included in the analysis. Falcotentorial meningiomas and vascular lesions including cavernomas were excluded. 5 cadaveric specimens were dissected step by step following the surgical approach. Each step was documented using a Canon EOS 5D Mark II camera with Canon 100 mm Macro Lens. Step by step images of the dissections were presented including comparison with surgical images. Additional illustrations were used to describe the surgical corridor. The surgical corridor is maintained anterior to the parietooccipital sulcus along the medial of the precuneus. No retraction to the calcarine sulcus resulted in no postoperative hemianopsia. The neurovascular structures along the surgical corridor along with the nuances of the tentorium incision and splenium resection are discussed. The parietooccipital interhemispheric transtentorial approach provides a wide and safe corridor for surgical resection of pineal tumors.

Endoscopically assisted presigmoid retrolabyrinthine approach to the lateral mesencephalic sulcus: a cadaveric study with comparison to the variant supracerebellar infratentorial approaches

The supracerebellar infratentorial (SCIT) approach is commonly used to gain access to the lateral mesencephalic sulcus (LMS), which has been established as a safe entry point into the posterolateral midbrain. This study describes a lateral variant of the SCIT approach, the supreme-lateral SCIT approach, for accessing the LMS through the presigmoid retrolabyrinthine craniectomy and quantitatively compares this approach with the paramedian and extreme-lateral SCIT approaches. Anatomical dissections were performed in four cadaveric heads. In each head, the supreme-lateral SCIT approach was established on one side, following a detailed description of each step, whereas the paramedian and supreme-lateral SCIT approaches were established on the other side. Quantitative measurements of the exposed posterolateral midbrain, the angles of LMS entry, and the depth of surgical corridors were recorded and compared between the three SCIT approach variants. The supreme-lateral (67.70 ± 23.14 mm²) and extreme-lateral (70.83 ± 24.99 mm²) SCIT approaches resulted in larger areas of exposure anterior to the LMS than the paramedian SCIT approach (38.61 ± 9.84 mm²); the supreme-lateral SCIT approach resulted in a significantly smaller area of exposure posterior to the LMS (65.24 ± 6.81 mm²) than the other two variants (paramedian = 162.75 ± 31.98 mm²; extreme-lateral = 143.10 ± 23.26 mm²; both P < .001). Moreover, the supreme-lateral SCIT approach resulted in a surgical corridor with a shallower depth and a smaller angle relative to the horizontal plane than the other two variants. The supreme-lateral SCIT approach is a more lateral approach than the extreme-lateral SCIT approach, providing a subtemporal approach with direct LMS visualization. The supreme-lateral SCIT offers the benefits of both subtemporal and SCIT approaches and represents a suitable option for the management of selected midbrain pathologies.

Comparison Between the Supracerebellar Infratentorial and Precuneal Interhemispheric, Transtentorial Approaches to the Cerebellomesencephalic Fissure: An Anatomoradiological Study and Illustrative Cases

BACKGROUND

The dorsal brainstem and cerebellomesencephalic fissure are challenging surgical targets. To afford a preferentially craniocaudal trajectory to this region, the precuneal interhemispheric transtentorial approach (PCIT) has been proposed.

OBJECTIVE

To didactically describe and compare exposures and anatomic indications of the supracerebellar infratentorial approach (SCIT) and PCIT to the cerebellomesencephalic fissure.

METHODS

Nine formalin-fixed, latex-injected cadaveric head specimens were used to perform a midline SCIT and bilateral PCITs and measure the distance of each approach. Twenty-four formalin-fixed specimens were used to measure the distance from the most posterior cortical bridging vein entering the superior sagittal sinus to the calcarine sulcus and the torcula. Fifty-one magnetic resonance images were reviewed to calculate the angle of each approach. Three illustrative surgical cases were described.

RESULTS

Mean distances from the brain or cerebellar surface to the operative target of the PCIT and SCIT were 7.1 cm (range: 5-7.7 cm) and 5.5 cm (range: 3.8-6.2 cm), respectively. The SCIT provided direct access to structures of the quadrigeminal cistern bilaterally. The PCIT provided access from the ipsilateral inferior colliculus to the ipsilateral infratrochlear zone. The PCIT's benefit was the direct access it provided to the cerebellomesencephalic fissure because of its superior to inferior trajectory.

CONCLUSION

The PCIT is indicated for unilateral lesions of the cerebellomesencephalic fissure and dorsal brainstem that harbor a craniocaudal long axis and do not have a superior extension beyond the superior colliculi. The SCIT is beneficial for lesions that extend bilaterally, have an anteroposterior long axis, or involve the Galenic complex.

Supracerebellar Infratentorial Approach, Indications, and Technical Pitfalls

Posterior tentorial incisura not infrequently requires to be exposed for tumors of pineal gland, pulvinar, midbrain and cerebellum, aneurysms, arteriovenous malformations. Residing almost at the center of the brain, this area is almost equal distance to any point on the calvarium behind coronal sutures enabling alternative routes to encounter. Compared to supratentorial routes either subtemporal or suboccipital approach, infratentorial supracerebellar route has several advantages as providing shortest, most direct approach to the lesions of this area without encountering any important arteries and veins. Since its initial description at the early twentieth century, a wide range of complications arising from cerebellar infarction, air embolism, and neural tissue damage have been encountered. Working in a deep, narrow corridor without enough illumination and visibility under very limited anesthesiology support hindered popularization of this approach. In the contemporary era of neurosurgery, advanced diagnostic tools and surgical microscopes with state-of-the-art microsurgery techniques coupled with modern anesthesiology have eliminated almost all drawbacks of infratentorial supracerebellar approach.

Benign and Malignant Tumors of the Pineal Region

Pineal region tumors fall into five broad categories: benign pineal region tumors, glial tumors, papillary tumors, pineal parenchymal tumors, and germ cell tumors. Genetic and transcriptional studies have identified key chromosomal alterations in germinomas (RUNDC3A, ASAH1, LPL) and in pineocytomas/pineoblastomas (DROSHA/DICER1, RB1). Pineal region tumors generally present with symptoms of hydrocephalus including nausea, vomiting, papilledema, and the classical Parinaud's triad of upgaze paralysis, convergence-retraction nystagmus, and light-near pupillary dissociation. Workup requires neuroimaging and tissue diagnosis via biopsy. In germinoma cases, diagnosis may be made based on serum or CSF studies for alpha-fetoprotein or beta-HCG making the preferred treatment radiosurgery, thereby preventing the need for unnecessary surgeries. Treatment generally involves three steps: CSF diversion in cases of hydrocephalus, biopsy through endoscopic or stereotactic methods, and open surgical resection. Multiple surgical approaches are possible for approach to the pineal region. The original approach to the pineal region was the interhemispheric transcallosal first described by Dandy. The most common approach is the supracerebellar infratentorial approach as it utilizes a natural anatomic corridor for access to the pineal region. The paramedian or lateral supracerebellar infratentorial approach is another improvement that uses a similar anatomic corridor but allows for preservation of midline bridging veins; this minimizes the chance for brainstem or cerebellar venous infarction. Determination of the optimal approach relies on tumor characteristics, namely location of deep venous structures to the tumor along with the lateral eccentricity of the tumor. The immediate post-operative period is important as hemorrhage or swelling can cause obstructive hydrocephalus and lead to rapid deterioration. Adjuvant therapy, whether chemotherapy or radiation, is based on tumor pathology. Improvements within pineal surgery will require improved technology for access to the pineal region along with targeted therapies that can effectively treat and prevent recurrence of malignant pineal region tumors.

Surgical Approaches to the Third Ventricle: An Update

The third ventricle is located in the deepest part of the brain and is delimited by both telencephalic and diencephalic structures. Its location makes every surgical procedure inside or around it quite challenging, due to the distance from the surface to the fragility of the neurovascular structures that is necessary to dissect before entering its cavity and to the narrow surgical corridors through which it is necessary to work. Its geometric localization inside the cranial cavity and the anatomical relationship with the interhemispheric fissure offers nevertheless to the surgeon an impressive variety of surgical approaches, which allow to reach every millimeter of the third ventricle lumen. Mastering properly all these approaches requires an impressive anatomical knowledge, the best available technology, and most refined technical skills, making the surgery of the third ventricle a point of excellence in the evolution of each neurosurgeon. The development of neuronavigation and neuroendoscopy has been a revolution in neurosurgery in the last 20 years and offered special advantages for the surgery of the third ventricle. In fact, the narrow corridors of approach make the precision of the neuronavigation and the enlightenment and magnification of the neuroendoscopy especially useful to reach the third ventricle cavity and working inside or around it. This chapter reviews the history of the surgery of the third ventricle and offers an update of the variety of surgical corridors identified and of the technology now available to properly work through them and inside the third ventricle cavity.

Three underdogs among galenic veins: anatomical analysis and literature review of surgical relevant veins in the quadrigeminal cistern

Recent studies (Alaou-Ismaili et al. 2020; Kilic et al. Eur J Radiol 56:212-219, 2005) among experienced sub-specialized neurosurgeons described divergent perceptions of surgical risk for venous sacrifice in posterior fossa surgery. Three galenic veins stood out as controversial in venous risk assessment and underexplored in the literature: the internal occipital vein (IOV), the precentral cerebellar vein (PCV), and the superior vermian vein (SVV). We have conducted a narrative review based on a systematic literature search to analyze terminology and anatomic descriptions and to suggest a coherent synthesis of published data on these veins. A systematic PubMed literature search was carried out using the keywords: "posterior fossa," "venous anatomy," and "radiology." Relevant radiological, microsurgical, and anatomical articles were selected if they described the anatomy of the three veins. Anatomical descriptions were analyzed with hermeneutic methodology alongside the articles' radiological and anatomical dissection pictures. New illustrations were created to depict the synthesized image of the venous anatomy. A total of 13 articles described the anatomy and terminology of the relevant veins. The descriptions of the IOV included smaller non-occipital vessels that confused the identification of the vessel. IOV is analyzed to be the vein draining the primary visual cortex, which drains into the vein of Galen (VG). The PCV and SVV enter the VG from below and are fused in almost half of all studied patients, creating a third vessel by the name of the superior cerebellar vein. A conscientious narrative review and hermeneutic analysis produced a synthesized, uniform picture of terminology and anatomy. Consensus on anatomical descriptions and definitions are indispensable for validation of anatomy, research into anatomical variation, for surgical planning and documentation.

Endoscopic Far-Lateral Supracerebellar Infratentorial Approach for Petroclival Region Meningioma: Surgical Technique and Clinical Experience

BACKGROUND

The management of petroclival region meningioma remains the ultimate achievement in neurosurgery, because of the formidable technical challenges involved.

OBJECTIVE

To describe the technique and feasibility of the purely endoscopic far-lateral supracerebellar infratentorial approach (EF-SCITA) for the treatment of petroclival region meningiomas.

METHODS

We reviewed the clinical data of 10 consecutive cases of petroclival region meningiomas treated with the EF-SCITA from August 2018 to August 2020. The clinical outcomes were analyzed. The patient was placed in the lateral position, and then, a "C" shaped incision and craniotomy with exposed sigmoid and transverse sinuses were performed. With the endoscopic holder, endoscopic procedures were performed using standard 2-hand microsurgical techniques. Whether the tentorium or Meckel cave was handled depended on the tumor extension.

RESULTS

The mean diameter was 45 × 25 mm. Dizziness and headache were the main symptoms. All 10 patients achieved gross total or subtotal resection (Petroclival Meningioma Grade I-III) with good neurological outcomes. The EF-SCITA provides satisfactory, direct exposure to the petroclival region. Cranial nerve deficits are the main postoperative complications. Two patients had a trochlear nerve injury, 3 patients had transient facial paralysis, and 2 patients had oculomotor paralysis (1 total and 1 incomplete), but both of them recovered during the follow-up period. One patient experienced an ipsilateral superior cerebellar artery infarction, and another patient had transient hemiparesis.

CONCLUSION

The EF-SCITA is effective for most petroclival region meningiomas, except for the cavernous sinus type. This approach simplifies craniotomy procedures, omits burdensome petrosectomy, and avoids crossing posterior neurovascular structures.

Pineal region tumours in the sitting position: how I do it

Background

Pineal region tumours remain challenging neurosurgical pathologies.

Methods

Detailed anatomical knowledge of the posterior incisural space and its variations is critical. An opaque arachnoidal membrane seals the internal cerebral and basal veins, leading to thalamic, basal ganglia, mesencephalic/pontine infarctions if injured. Medium-size tumours can be removed en-bloc with all traction/manipulation applied on the tumour side, virtually without contact of ependymal surfaces of the pulvinars or third ventricle. Sacrifice of the cerebello-mesencephalic fissure vein may be required.

Conclusions

The sitting position offers superior anatomical orientation and remains safe with experienced teams. Meticulous microsurgical techniques and detailed anatomical knowledge are likely to secure safe outcomes.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00701-021-04821-3.

Visualization and Maneuverability Features of a Robotic Arm Three-Dimensional Exoscope and Operating Microscope for Clipping an Unruptured Intracranial Aneurysm: Video Comparison and Technical Evaluation

BACKGROUND

In recent years, three-dimensional (3D) digital exoscope systems have been developed and reported to form an adequate alternative to the conventional operating microscope.

OBJECTIVE

To illustrate essential and practical features in a surgical video comparing a robotic arm 3D digital exoscope and a conventional operating microscope to clip a middle cerebral artery aneurysm.

METHODS

We used a mouth switch-controlled operating microscope (OPMI PENTERO 900; Carl Zeiss Meditec AG) and robotic arm-controlled 3D digital Aeos exoscope (Aesculap Inc). We assessed the following visualization and optical features: overall visualization quality, color and contrast quality, range and quality of magnification, and adjustment of focus. In addition, we assessed maneuverability for changing surgical site within and viewing angle of the surgical field.

RESULTS

We found that both modalities are suitable for this surgery and offer distinct qualities. The microscope enables faster magnification adjustment and continuous mouth switch-controlled focus adjustments. The advantages of the exoscope include the adaptation of color and contrast settings, and the surgeon can keep both hands in the surgical field while the camera pivots around its working field.

CONCLUSION

The exoscope and operating microscope offer a similar high-quality visualization of, and smooth maneuvering within, the surgical field. The method of visualization and maneuvering is, however, very distinct. Therefore, a surgeon's acquaintance and experience with the specific features and how to optimally use them in surgery are of utmost importance. Further analyses of both systems are needed to evolve these tools.

Pleomorphic xanthoastrocytoma at the pineal region: rare case report with successful surgical management

Background

Pineal region tumors are commonly present in the pediatric age group. However, pleomorphic xanthoastrocytoma (PXA) is very rare at this region, and only few case reports have been reported till now in literature.

Case presentation

Here, we report a rare case of pineal region, juxta-thalamic, pleomorphic xanthoastrocytoma (PXA) in an 11-year-old male child. The child presented with severe headache after which MRI was done. It was suggestive of pineal region low-grade tumor. The patient was operated in Parkbench position with SCIT (supracerebellar approach) in a retractor-free manner. Gross total resection was done. However, the patient developed postoperative left-sided hemiparesis. It got improved in 1 month, and the patient became ambulatory. Histopathology came out as pleomorphic xanthoastrocytoma.

Conclusion

Surgical management should include careful resection near the internal capsule to avoid postoperative hemiparesis. Also, shunt should be delayed in the cystic cavity created by resection of tumor.

Occipital posterior interhemispheric supratentorial approach for resection of midbrain cavernous malformation

Approaches to the pineal region are various, and each has its advantages and disadvantages. The authors present a case of a 50-year-old woman who presented with progressive hemiparesis and vertical gaze palsy; she was diagnosed with a midbrain cavernous malformation. The patient underwent an occipital posterior interhemispheric supratentorial transpineal approach with gross-total resection. On long-term follow-up, her symptoms significantly improved. The authors review the regional anatomy and present the operative video. They also discuss the various approaches with their indications, advantages, and disadvantages.

The video can be found here: https://stream.cadmore.media/r10.3171/2021.4.FOCVID2133.

Anatomic, qualitative, and quantitative evaluation of the variants of the infratentorial supracerebellar approach to the posteroinferior thalamus

The posteroinferior region of the thalamus is formed by the pulvinar, and it is surgically accessed through the infratentorial supracerebellar approach, between the midline and the retromastoid region. This study aimed to compare the paramedian, lateral, extreme lateral, and contralateral paramedian corridors with the posteroinferior thalamus through a suboccipital craniotomy and an infratentorial supracerebellar access. Ten cadavers were studied, and the microsurgical dissections were accompanied by the measurement of the variables using a neuronavigation system. Statistical analysis was performed using analysis of variance (ANOVA). The distance between the access midpoint at the cranial surface and pulvinar varied between 53.3 and 53.9 mm, the contralateral access being an exception (59.9 mm). The vertical angle ranged from 20.6° in the contralateral access to 23.5° in the lateral access. There was a gradual increase in the horizontal angle between the paramedian (17.4°), lateral (31.3°), and extreme lateral (43.7°) accesses. But, this angle in the contralateral access was 14.6°, similar to that of the paramedian access. The exposed area of the thalamus was 125.1 mm² in the paramedian access, 141.8 mm² in the lateral access, and 165.9 mm² in the extreme lateral access, which was similar to that of the contralateral access (164.9 mm²). The horizontal view angle increased with lateralization of the access, which facilitated microscopic visualization. With regard to the exposure of the microsurgical anatomy, the extreme lateral and contralateral accesses circumvent the neural and vascular obstacles at the midline, allowing a larger area of anatomical exposure.

Management of pineal region tumors in a pediatric case series

Pineal region tumors commonly present with non-communicating hydrocephalus. These heterogeneous histological entities require different therapeutic regimens. We evaluated our surgical experience concerning procurance of a histological diagnosis, management of hydrocephalus, and choice of antitumoral treatment. We analyzed the efficacy of neuroendoscopic biopsy and endoscopic third ventriculocisternostomy (ETV) in patients with pineal region tumors between 2006 and 2019 in a single-center retrospective cross-sectional study with regard to diagnostic yield, hydrocephalus treatment, as well as impact on further antitumoral management. Out of 28 identified patients, 23 patients presented with untreated hydrocephalus and 25 without histological diagnosis. One patient underwent open biopsy, and 24 received a neuroendoscopic biopsy with concomitant hydrocephalus treatment if necessary. Eighteen primary ETVs, 2 secondary ETVs, and 2 ventriculoperitoneal shunts (VPSs) were performed. Endoscopic biopsy had a diagnostic yield of 95.8% (23/24) and complication rates of 12.5% (transient) and 4.2% (permanent), respectively. ETV for hydrocephalus management was successful in 89.5% (17/19) with a median follow-up of more than 3 years. Following histological diagnosis, 8 patients (28.6%) underwent primary resection of their tumor. Another 9 patients underwent later-stage resection after either adjuvant treatment (n = 5) or for progressive disease during observation (n = 4). Eventually, 20 patients received adjuvant treatment and 7 were observed after primary management. One patient was lost to follow-up. Heterogeneity of pineal region tumor requires histological confirmation. Primary biopsy of pineal lesions should precede surgical resection since less than a third of patients needed primary surgical resection according to the German pediatric brain tumor protocols. Interdisciplinary decision making upfront any treatment is warranted in order to adequately guide treatment.

Safe handling of veins in the pineal region-a mixed method study

Surgical experience in pineal surgery is largely confined to a few experienced surgeons and may be lost when they stop their practice. The objective of this study is to systematically preserve and analyze valuable practical knowledge of pineal region surgical venous anatomy. A survey was constructed to obtain experienced surgeons' perception of estimated risks and individual experience following occlusion of veins during pineal surgery. Data were qualitative and analyzed with a mixed methods approach. Of the 126 invited neurosurgeons, 40 submitted completed questionnaires. General agreement existed of which veins were associated with high and low risks following occlusion. The risk of death was estimated to be high with sacrifice of the vein of Galen (83%), both internal cerebral veins (69%) and the basal veins (58%). The risk of death was estimated to be lower with the sacrifice of both superior vermian veins (13%) and one internal occipital vein (10%). Importantly, a sub-group of experienced surgeons reported substantial risk of death and consequences with the sacrifice of cerebellar bridging veins (8-13%). Our findings provide a coherent picture of surgical risk with venous sacrifice, which can inform the surgical community of systematically gathered views from aggregated surgeries of a very large cohort of patients. Extensive presurgical radiological workup and anatomical studies seemed to correlate more cautious risk estimations. Our findings increase available knowledge of risks of venous complications.

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.

Supracerebellar Infratentorial Endoscopic and Endoscopic-Assisted Approaches to Pineal Lesions: Technical Report and Review of the Literature

The pineal gland has a deep central location, making it a surgeon's no man's land. Surgical pathology within this territory presents a unique challenge and an opportunity for employment of various surgical techniques. In modern times, the microsurgical technique has been competing with the endoscope for achieving superior surgical results. We describe two cases utilizing a purely endoscopic and an endoscopic-assisted supracerebellar infratentorial approach in accessing lesions of the pineal gland. We also discuss our early learning experience with these approaches.