Abstract Proper patient positioning is critical in neurosurgery to optimize surgical access and minimize complications. The park bench (PB) position is frequently employed for posterior fossa procedures due to its neurosurgical advantages but carries risks of hemodynamic changes and pressure-related injuries. We report an uncommon perioperative complication in an elderly man undergoing cerebellopontine angle tumor excision in the PB position. Following a 13-h procedure, the patient developed a hematoma over the right mid-axillary region, which progressively enlarged postoperatively despite stable hemodynamic parameters and normal coagulation profiles. On the seventh postoperative day, imaging revealed a fusiform aneurysm of the right axillary artery without active bleeding or arteriovenous fistula. Conservative management was chosen due to the patient’s clinical stability and lack of distal ischemia. The hematoma subsequently resolved, and the patient was discharged without neurological deficits. This case highlights the potential for rare but significant vascular complications associated with the PB position. Prolonged mechanical compression and arm extension may have contributed to aneurysm formation or exacerbation, possibly unmasking a preexisting vascular lesion. Preventive measures, such as adequate padding, careful arm positioning, and frequent intraoperative pressure point checks, are essential to reduce the risk of neurovascular compromise. Although axillary artery aneurysms are rare, especially in the perioperative setting, clinicians should maintain a high index of suspicion in the presence of progressive hematoma. Early imaging and multidisciplinary input are crucial for timely diagnosis and safe management. This case underscores the importance of vigilant perioperative positioning and monitoring practices in complex neurosurgical procedures.

The lateral suboccipital approach is a fundamental surgical method for accessing the cerebellopontine angle. This article outlines critical aspects, including anatomical landmarks, surgical positioning, and techniques for craniotomy and dural opening, based on practices at our institution. Important landmarks include the mastoid process, asterion, and suboccipital triangle, which contains critical structures such as the vertebral artery. Preoperative three-dimensional computed tomography imaging significantly aids surgical planning through visualizing bone landmarks and venous sinus positioning. Optimal patient positioning, involving careful head flexion and rotation in the park-bench position, is essential to minimize complications such as airway edema. Accurate muscle dissection and careful handling of the mastoid emissary vein are detailed to prevent venous sinus occlusion. Significant complications associated with this procedure include cerebrospinal fluid (CSF) leakage, vertebral artery injury, and venous sinus injury. Strategies for preventing CSF leakage include meticulous dural closure using artificial dura and fat grafts. While rare, vertebral artery injury demands precise handling to prevent severe ischemic complications. Overall, careful anatomical understanding, rigorous preoperative planning, and a meticulous surgical technique are paramount to minimize complications associated with the lateral suboccipital approach.

Suboccipital craniotomy in the park bench position is linked to considerable physiological alterations. Effective fluid management in this context is a challenge to anesthesiologists. No published data exist on pulse pressure variation and central venous pressure guidance in patients undergoing tumor resection in the park bench posture. We undertake a study to evaluate the concept that two approaches of goal-directed fluid treatment enhance optimal fluid management and improve hemodynamic stability. We established the fluid management protocol for this process. This is a prospective randomized double-blinded study of adult patients undergoing suboccipital craniotomy to remove tumors in the park bench position. The comparison of pulse pressure variation and central venous pressure for fluid management regarding mean intraoperative fluid administration as the primary outcome. A sample size of 54 will yield over 80% power to identify a mean fluid difference of at least 500 ml between two specified methods. The secondary outcomes are data pertinent to fluid administered during and after surgery, including the lowest systolic blood pressure, serum lactate levels, vasopressor utilization, and duration of ICU stay. The statistical analysis will be validated based on the data distribution and types of data. This is the first study to examine two goal-directed fluid therapies, pulse pressure variation and central venous pressure, in patients with posterior fossa tumors and undergoing surgery in the park bench position. Researchers want to contribute novel information to the domain of fluid optimization in neurosurgery. ClinicalTrials.gov NCT06595667.

IntroductionSuboccipital craniotomy in the park bench position is linked to considerable physiological alterations. Effective fluid management in this context is a challenge to anesthesiologists. No published data exist on pulse pressure variation and central venous pressure guidance in patients undergoing tumor resection in the park bench posture. We undertake a study to evaluate the concept that two approaches of goal-directed fluid treatment enhance optimal fluid management and improve hemodynamic stability. We established the fluid management protocol for this process.Methods and analysisThis is a prospective randomized double-blinded study of adult patients undergoing suboccipital craniotomy to remove tumors in the park bench position. The comparison of pulse pressure variation and central venous pressure for fluid management regarding mean intraoperative fluid administration as the primary outcome. A sample size of 54 will yield over 80% power to identify a mean fluid difference of at least 500 ml between two specified methods. The secondary outcomes are data pertinent to fluid administered during and after surgery, including the lowest systolic blood pressure, serum lactate levels, vasopressor utilization, and duration of ICU stay. The statistical analysis will be validated based on the data distribution and types of data. This is the first study to examine two goal-directed fluid therapies, pulse pressure variation and central venous pressure, in patients with posterior fossa tumors and undergoing surgery in the park bench position. Researchers want to contribute novel information to the domain of fluid optimization in neurosurgery.Trial registrationClinicalTrials.gov NCT06595667.

The choice of the optimal surgical position in the treatment of posterior fossa lesions still remains a controversial and debated issue. Morphometric data on the different perspective of vision offered by different surgical position are scarce. This article investigated the differences due to the vision perspectives provided by the sitting and park bench positions. The study was conducted using 4 fixed cadaver heads. A standardized retrosigmoid approach was performed on each side of each head. Three operators collected anatomic observation and 2 separate measurements each, for all the sides and diagonals of the projections of 2 areas delimited by the cranial nerves in the cerebellopontine angle (defined as working windows ABCD and ABEF). The collection of the measurements was repeated for each side of each head, both in the sitting and in the park bench positions. The average areas of the working windows were calculated for each position and then compared by statistical analysis. The park bench position is associated to larger areas for both working windows ( P = .0013 for ABCD; P < .001 for ABEF) compared with the sitting position. These measures allow to quantify the differences of the working windows that are an indirect expression of the different angle of vision of each position. Our cadaveric study shows that there is a better vision perspective offered by the park bench position for lesions that do not modify the course of the cranial nerves in the cerebellopontine angle. However, different positioning of patients presents different advantages and limitations for surgeon based on size of the tumor and lesion location. In our opinion, choice of patient positioning could be tailored to lesion's peculiarities more than on surgical habits.

Background/Objectives: Patient positioning during surgery can influence intra- and postoperative complications. Therefore, we assessed the impact of the sitting and park-bench positions on anesthetic parameters and complications in neurosurgical patients. Methods and Patients: For this retrospective study, 314 adults who underwent neurosurgical procedures for posterior fossa pathologies were divided into two groups: sitting (n = 231) and park-bench (n = 83). The following data were collected, monitored, recorded, and compared: age, sex, tumor type, surgical approach, cardiovascular and respiratory complications, and postoperative surgical complications. The association of hypotension with the position was further investigated through multivariate logistic regression models by adjusting for CO2 decrease, desaturation, and documented gas embolism. Results: The average age was significantly lower in the sitting group (55 years, interquartile range (IQR) = 43-63; female proportion = 59.74%) than in the park-bench group (62 years, IQR = 45-74; female proportion = 57.83%) (p < 0.001). Cerebellopontine angle tumors were detected in 37.23% of the patients who underwent an operation in the sitting position and in 7.26% who underwent an operation in the park-bench position (p < 0.001). Patients in the sitting position had significantly greater anesthetic complication (91.77% vs. 71.08%, p < 0.001), hypotension (61.9% vs. 16.87%), and >2 mmHg CO2 decrease (35.06% vs. 15.66%, p < 0.001) incidences. Hypoxemia and death occurred more frequently in the park-bench group (8.43% vs. 1.73% and 6.03% vs. 1.3%, respectively). Conclusions: Compared with the park-bench position, the sitting position was associated with a greater specific anesthetic complication incidence and lower postoperative mortality rate, indicating a need for careful risk-benefit assessment when selecting each individual patient's surgical position.

Abstract BACKGROUND Petroclival meningiomas pose a surgical challenge due to their complex regional anatomy, with proximity to vital neurovascular structures and involvement of deep, narrow surgical corridors. Until 1970, they were generally considered unresectable due to high operative morbidity. However since the introduction of advanced microscopic surgery with neuronavigation and intraoperative neurophysiological monitoring, surgical outcomes have improved. Sadly, this technology is not available in most low income countries. We report a case of successful resection of a left petroclival meningioma in Mbarara Regional Referral Hospital in Uganda, despite the lack of advanced technology. CASE REPORT A 36 year old female presented with a 1 year history of intermittent vomiting and convulsions, worsening over 2 weeks. Neurological examination was normal except a Grade 2 left facial palsy. CT head was performed locally but a 7 hour journey was required for MRI brain; this confirmed a left petroclival meningioma. She returned for tumour resection 2 weeks later due to theatre capacity; neuronavigation, auditory brainstem response testing, sensory/motor evoked potentials and cranial nerve monitoring were not available. A left frontal EVD was initially inserted to control intracranial pressure, before placement in a right park bench position and head secured in a Mayfield clamp. Left retrosigmoid approach was used, with the meningioma visible on reflection of the dura. Under basic microscopic vision, gross total resection was performed with Simpson Grade 2 outcome. The EVD was replaced with an Ommaya reservoir. Postoperative CT head showed no tumour residual, with resolution of the facial palsy and all symptoms. Complications included CSF leak from the nose and Ommaya site, which resolved with conservative management, and DVT treated with anticoagulation. She was discharged at 3 weeks, is fully functioning and working in the community, with Modified Rankin Score 1. Neuropathology results reported meningothelial meningioma WHO Grade 1. CONCLUSION Lack of advanced technology in low income countries results in more difficulty locating lesions, increased risk of injury to neurovascular structures and longer operative time. Reduced availability of MRI delays diagnosis, whilst the low resourced hospital wards, together with reliance on patients’ families to fund medication and investigations, results in a challenging perioperative period. Despite this, we report the successful gross total resection of a petroclival meningioma in Uganda. We rely on an in depth understanding of skull base neuroanatomy, three dimensional mental imagery, detailed clinical examination and thorough review of preoperative imaging. We aspire to adopt more advanced technology and collaborate with higher income countries, but hope this case will inspire other low income countries who face similar challenges.

The purpose of this study is to analyze the sitting position and the park-bench position for intra-anesthesia complications in pediatric patients undergoing neurosurgery for posterior fossa lesions. Our goal is to highlight the risks associated with each of these positions under general anesthesia to aid in clinical decision making for optimal patient outcomes with regard to postoperative complications. We retrospectively reviewed 41 pediatric patients (1 to 18 years old) undergoing posterior fossae surgery in the sitting (32) and park-bench (9) positions between January 2015 and December 2021. The majority of patients (15) who underwent surgery in the sitting position had fourth ventricular tumors (28.12%) and cerebellopontine tumors (18.76%) that required the sitting position. Of 32 patients operated on in the sitting position, 23 (71.78%) developed anesthetic complications, compared to 8 patients in the park-bench group (88.89%). Venous air embolism occurred in only 6.25% of patients in the sitting group. Compared to the sitting position, no cases of gas embolism were documented in the park-bench position. However, transient episodes of gas embolism cannot be excluded due to the higher incidence of hemodynamic instability (44.44%), need for additional fluid therapy (44.44%) and vasopressor support (11.11%), decreased CO2 (22.22%) and oxygen desaturation (22.22%). Patients who underwent surgery in the sitting position had a longer duration of surgery [247.5 min IQR (172.75 - 325.25)] and a longer duration of anesthesia [331 min IQR (237.5 - 423.25)]. Pneumocephalus (4, 12.5%) and postoperative hematoma (3, 9.38%) were the most common postoperative complications in patients who underwent surgery in the sitting position. In the park-bench group, three patients had postoperative complications, including postoperative hematoma (2, 25%) and hydrocephalus (1, 12.5%). The incidence of anesthetic complications is lower in the sitting position compared to the park-bench position. Although there was no documented gas embolism in the park-bench position, the lower rate of venous air embolism in the sitting position may suggest a better control or a lower risk in this position. However, the sitting position has a less frequent occurrence of hemodynamic instability than the park-bench position.

The modified park bench position enhances surgical exposure while minimizing brainstem manipulation but poses significant anesthetic challenges. This case report aimed to describe the author’s anesthesia management in a modified park bench position for neurosurgery. A 39-year-old woman presented with intermittent headaches, nausea, and vomiting for three months, alongside vision deterioration. She denied loss of consciousness, seizures, weight loss, or trauma. Examination revealed typical vital signs, neurological function, and musculoskeletal integrity. Supporting tests showed elevated SGOT levels and a primary malignant brain tumor with suspected hemorrhage and surrounding vasogenic edema. She underwent craniotomy after fasting and standard anesthesia preparation. An arterial line, premedication, and intubation were administered, followed by five-hour surgery in the modified park bench position. Postoperatively, pain was managed with fentanyl, paracetamol, and ibuprofen. She was monitored in the ICU for seven days and discharged on the eighth postoperative day. In summary, managing primary malignant brain tumors like glioblastoma requires thorough preoperative assessment, precise anesthesia planning, and vigilant intraoperative monitoring for patient safety and successful outcomes. The collaborative effort of neurosurgery and anesthesia teams and postoperative care is vital for patient recovery and underscores the importance of comprehensive perioperative management.

Background In neurosurgical procedures where the park bench position is employed, the risk of perioperative pressure injuries is elevated due to the limited contact surface area, with the head and part of the upper torso extending beyond the surgical table. This study aimed to examine the effects of preventative measures against such injuries, proposing a potential standard for postural fixation in these surgeries. Methods Conducted at a medical center, from January 2017 to March 2023, this prospective cohort study involved participants aged 20 and above who underwent neurosurgical procedures in the park bench position under general anesthesia. The focus was on comparing the incidence of pressure injuries between intervention and control groups. The study adhered to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines. Results Out of 65 patients enrolled, 28 were assigned to each of the intervention and control groups. The control group experienced 17 instances of postoperative pressure injuries and skin disorders in areas prone to pressure, such as the axillary and greater trochanter regions. Conversely, the intervention group reported no such incidents, underscoring the efficacy of meticulous surgical positioning and management of bodily pressure, temperature, humidity, and microclimate. Conclusion Implementing preventive measures in neurosurgical park bench procedures significantly reduces the incidence of postoperative pressure injuries and skin disorders. These findings advocate for the adoption of standardized postural fixation protocols in such surgeries, potentially influencing global clinical practices in neurosurgery.

The cranial nerve (CN) V and adjacent neurovascular structures are crucial landmarks in microvascular decompression (MVD). MVD of CN V is the most effective treatment for patients with drug-resistant trigeminal neuralgia (TN) diagnosis. The endoscope-assisted retrosigmoid approach (RSA) provides better exposure and less cerebellar retraction in the corridor towards the cerebellopontine angle (CPA). Five adult cadaver heads (10 sides) underwent dissection of the MVD in park bench position. MVD was simulated using microsurgical RSA, and the anatomical landmarks were defined. Microsurgical dissections were additionally performed along the endoscopic surgical path. Additionally, we present an illustrative case with TN caused by anterior inferior cerebellar artery (AICA) compression. The CN V and its close relationships were demonstrated. Endoscopic and microscopic three-dimensional pictures were obtained. This study increases the anatomical and surgical orientation for CN V and surrounding structures. The CN V arises from the lateral part of the pons and runs obliquely upward toward the petrous apex. It has motor roots that leave from pons antero-supero-medial direction to the sensory root. The endoscopic instruments provide perfect visualization with minimal cerebellar retraction during MVD. MVD surgically targets the offending vessel(s) leading to TN and aims to create a disconnected area. The combination of preoperative radiographic assessment with and anatomical correlation provides safe and effective application while facilitating selection of the most appropriate approach. The RSA allows satisfactory visualization for CN V. Endoscope-assisted microsurgery through the CPA is a challenge, it should be performed with advanced anatomical knowledge.

Abstract Background: Intraoperative MRI (iMRI) is an important modality in brain tumor surgery to identify residual tumors, however, it is problematic due to patient positional limitations. In this study, we investigated the usefulness of iMRI for posterior fossa lesions. Materials and Methods: Of 320 cases of brain tumors removed using iMRI from June 2016 to April 2023, 24 cases of posterior fossa lesions were included. Tumor type, approach method, imaging availability, tumor removal rate, and complications were examined retrospectively. Results: Tumor types included 8 gliomas, 5 epidermoid cysts, 4 meningiomas, 3 metastatic brain tumors, 1 schwannoma, and 3 others. Eleven patients underwent midline suboccipital approach in the supine position, 8 patients underwent lateral suboccipital approach, 2 patients underwent occipital transtentorial approach, and 2 patients underwent anterior transpetrosal approach in the supine position. transpetrosal approach in 2 cases and subtemporal approach in 1 case. iMRI showed residual lesion in 14 of 24 patients. More than half of the gliomas and epidermoid cysts had intraoperative residual disease, whereas only one meningioma did. Total resection was achieved except for one case of intentional residual schwannoma and two cases of glioma. Discussion: iMRI requires the upper body to fit within a gantry, and it is difficult to image in the park bench position. However, various approaches is possible by using a supine-lateral or semi-prone position. In the concorde position, where the fourth ventricle and upper cerebellum are approached, it is useful to insert a mat in the anterior thoracic and raise the upper body. For tumors in the dorsal brainstem and upper cerebellum, the occipital transtentorial approach was used. iMRI is effective in the removal of all tumors, including gliomas in intramedullary tumors and epidermoid cysts in extramedullary tumors. Conclusion: iMRI can be used in posterior cranial fossa lesions.

The Park‐Bench Position (PBP) is associated with a high incidence rate of intraoperatively acquired pressure injuries (IAPIs). Preventive measures must be established to prevent the development of IAPIs. We investigated the risk factors for PBP by applying a soft silicone multilayered foam dressing (SMD) under core temperature management to prevent IAPIs. We conducted a prospective, single‐centre, open‐label observational study of patients undergoing elective neurosurgery operations using PBP in a university hospital in Japan. The incidence rate of IAPIs in this study was compared with that in our two previous studies, in which a film dressing was applied and core temperature management was not performed. IAPIs developed in 90 patients (6.7%); in the lateral thoracic region in five patients and the iliac crest region in one patient. The operative time (every 1 h: p = 0.0001, OR: odds ratio 3.62, 95% CI: confidence interval 1.73–11.42) was significantly associated with the incidence of IAPIs. In our two previous studies, the incidence rate of IAPIs was 11.0% and 24.1%, respectively, when film dressing was used. SMD may weaken the involvement of risk factors in IAPIs.

The pineal region tumors are challenging for neurosurgeons and can lead to secondary hydrocephalus. The introduction of the exoscope has provided clinical interventions with high image quality and an ergonomic system for pineal region tumor operations. In this study, the authors describe the exoscopic approach used to facilitate the surgical resection of pineal region tumors and relieve hydrocephalus. In this retrospective cohort study, we consecutively reviewed the clinical and radiological data of 25 patients with pineal region lesions who underwent three-dimensional exoscopic tumor resection at a single center. The patient cohort consisted of 16 males and 9 females, with an average age of 34.6 years (range, 6-62 years; 8 cases aged ≤18). Pathological examination confirmed eight pineal gland tumors, four gliomas, nine germ cell neoplasms, two ependymomas, and two metastatic tumors. Preoperative hydrocephalus was present in 23 patients. Prior to tumor resection, external ventricular drainage (EVD) with Ommaya reservoir implantation was performed in 17 patients. Two patients received preoperative endoscopic third ventriculostomy (ETV), and five patients received a ventriculoperitoneal (VP) shunt, including one who received both procedures. Gross total resection was achieved in 19 patients (76%) in the 'head-up' park bench position using the exoscope. Eight patients (31.6%) with third ventricle invasion received subtotal resection, mainly in glioma cases, which was higher than those without invasion (0%), but not statistically significant ( P =0.278, Fisher's exact test). No new neurological dysfunction was observed after surgery. Two patients (8%) developed intracranial and pulmonary infections, and two patients (8%) suffered from pneumothorax. Hydrocephalus was significantly relieved in all patients postoperatively, and four patients with relapse hydrocephalus were cured during the long-term follow-up. Postoperative adjuvant management was recommended for indicated patients, and a mean follow-up of 24.8±14.3 months showed a satisfied outcome. The exoscope is a useful tool for pineal region tumor resection and hydrocephalus relief, particularly with posterior third ventricle invasion, as total resection could be achieved without obvious complication. The special superiority of the exoscope for the indicated pineal region tumors should be highlighted.

Abstract Von Hippel–Lindau (VHL) disease is a rare genetic disorder associated with the central nervous system and visceral organs. Pheochromocytomas occur in 10% of VHL patients, while cerebellar tumors are common tumors in VHL syndrome, with an incidence of 60%. The most common position for posterior fossa operations is the park bench or lateral decubitus position. These positions have primarily replaced the sitting position. However, the advantages of the supine position cannot be overlooked. The coexistence of pheochromocytoma and the cerebellar tumor may require modification in surgical position and anesthesia management in line with possible pathophysiological changes. We present the anesthesia management in posterior fossa surgery in patients with postponed pheochromocytoma surgery. The present case highlights the importance of a multidisciplinary team approach and anesthetic management.

Cavernous Malformations: What They Have Taught Us.

ABSTRACT 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.

パークベンチ体位での右側頭葉腫瘍摘出術術後に，左顎下腺と舌の腫脹をきたしたまれな症例を経験した．症例は23歳女性で，手術終了後に全身麻酔からの覚醒が十分であるのを確認し抜管した．術後5時間から左頚部腫脹が出現し，術後13時間には左顎下腺と舌の腫脹による気道閉塞をきたし気管切開を施行した．頚部屈曲や気管チューブ留置により顎下腺管や動静脈が圧迫されることで顎下腺や周囲組織が腫脹し，これにより舌静脈の還流が障害され舌が腫脹したと考えられた．術後合併症として顎下腺や舌の腫脹が起こりうるため，頚部腫脹の徴候を十分に観察し気道狭窄が進行する前に気管挿管を行うべきである．

Superior semicircular canal dehiscence (SCD) repair through the middle cranial fossa approach is typically performed on a patient in the supine position and the patient's head is turned to the contralateral side and secured with surgical pinions or supported on a headrest. However, traditional supine positioning method may place strain on the patient's neck, limit the surgeon's visualization of the dehiscence due to inadequate head rotation, and compromise the ergonomic positioning of the surgeon. Here, we present a novel positioning method for middle fossa SCD repair that allows for optimal head rotation in a semi‐supine position, requires less set‐up and patient manipulation than the park bench position, and does not require the use of surgical pins. Laryngoscope, 133:1218–1221, 2023

(1) Background: Superior cerebellar peduncle (SCP) lesions are sparsely reported in the literature. The surgical approaches to the cerebello-mesencephalic region remain challenging. In this article, we present the extreme lateral supracerebellar infratentorial (ELSI) approach to treat a large hemorrhagic pilocytic astrocytoma of the SCP. (2) Methods: An 11-year-old boy, known for neurofibromatosis Type I, presented to the emergency department of our institution with symptoms and signs of intracranial hypertension. The cerebral magnetic resonance imaging (MRI) revealed a large hemorrhagic lesion centered on the SCP provoking obstructive hydrocephalus. Following an emergency endoscopic third ventriculocisternostomy (ETV), he underwent a tumor resection via an endoscope-assisted ELSI approach. (3) Results: ELSI approach allows for a wide exposure with direct access to lesions of the SCP. The post-operative course was uneventful, and the patient was discharged home on post-operative day 5. Post-operative MRI revealed a near total resection with a small residual tumor within the mesencephalon. (4) Conclusion: ELSI approach offers an excellent exposure with the surgical angles necessary for median and paramedian lesions. The park-bench position with appropriate head flexion and rotation offers a gravity-assisted relaxation of the tentorial and petrosal cerebellar surfaces. The endoscope can be an adjunct to illuminate the blind areas of the surgical corridor for an improved tumor resection without significant cerebellar retraction.