The safety and utility of the semi-sitting position for clipping of posterior circulation aneurysms.

BACKGROUND: The semi-sitting position offers advantages for surgeries in the posterior cranial fossa. However, data on its safety and effectiveness for clipping aneurysms in the posterior cerebral circulation are limited. This retrospective cohort study evaluates the safety and effectiveness of using the semi-sitting position for these surgeries. METHODS: We conducted a retrospective study of 17 patients with posterior cerebral circulation aneurysms who underwent surgical clipping in the semi-sitting position in the Department of Neurosurgery at Hannover Medical School over a 10-year period. RESULTS: The mean age at surgery was 62 years (range, 31 to 75). Fourteen patients were admitted with subarachnoid hemorrhage and 3 patients had incidental aneurysmas. Fifteen patients had PICA aneurysms, and two had aneurysms of the vertebral artery and the superior cerebellar artery, respectively. The median diameter of the aneurysms was 5 mm (range 3-17 mm). Intraoperative venous air embolism (VAE) occurred in 4 patients, without affecting the surgical or clinical course. VAE was associated with a mild decrease of EtCO2 levels in 3 patients and in 2 patients a decrease of blood pressure occurred which was managed effectively. Surgical procedures proceeded as planned in all instances. There were no complications secondary to VAE. Two patients died secondary to respiratory problems (not related to VAE), and one patient was lost to follow-up. Eleven of fourteen patients were partially or completely independent (Barthel index between 60 and 100) at a median follow-up duration of 13.5 months (range, 3-103 months). CONCLUSION: The semi-sitting position is a safe and effective technique for the surgical clipping of aneurysms in the posterior cerebral circulation. The incidence of VAE is comparable to that seen in tumor surgery. However, it is crucial for the surgical and anesthesiological team to be familiar with potential complications and to react immediately in case of an occurrence of VAE.

Resection of posterior fossa tumors in the semi-sitting position in children younger than 4 years of age.

PURPOSE: The semi-sitting position for resection of posterior fossa tumors is a matter of ongoing debate. Here we report about our experience with this approach in children younger than 4 years of age. METHODS: We retrospectively analyzed data of children younger than 4 years of age operated on in our institution in the semi-sitting position over a 15-year period. Patients were intraoperatively monitored for venous air embolism (VAE) by transthoracic Doppler (TTD) or transesophageal echocardiography (TEE). The severity of VAE was classified according to the Tübingen grading scale. Intraoperative incidents of VAE were recorded and the patients' course was followed postoperatively with a special focus on possible complications. RESULTS: Twenty-four children (18 boys, 6 girls) were operated on in the semi-sitting position (26 operations). Mean age was 2.2 years (± 1.0), range between 0.4 and 3.9 years. External ventricular drains were inserted in 18 children with hydrocephalus preoperatively. VAE was detected in 6 instances during surgery (6/26 (23.1%)). In 3 patients with grade 1 VAE, no additional treatment was necessary. In one patient with grade 2 VAE, intracardiac air suction via the central venous catheter was performed, and in two patients with grade 4 VAE, additional cathecholamine-infusion was administered. No major intraoperative complications occurred. Postoperative CT images showed pneumocephalus in all children. In two children, small asymptomatic impression skull fractures at the site of the Mayfield pin occurred. Revision surgery was necessary in one child with a suboccipital CSF fistula. CONCLUSION: The semi-sitting position for resection of tumors in the posterior fossa in children younger than 4 years of age can be safely performed in experienced centers taking special caution to detect and treat potential complications in an interdisciplinary setting.

The semi-sitting position in patients with indwelling CSF shunts: perioperative management and avoidance of complications.

OBJECTIVE: Posterior fossa or midline tumors are often associated with hydrocephalus and primary tumor removal with or without perioperative placement of an external ventricular drain (EVD) is commonly accepted as first-line treatment. Shunting prior to posterior fossa surgery (PFS) is mostly reserved for symptomatic cases or special circumstances. There are limited data regarding the anticipated risk for symptomatic pneumocephalus and the perioperative management using the semi-sitting position (SSP) in such a scenario. Here, we therefore assessed the safety of performing PFS in a consecutive series of patients over a period of 15 years to allow the elaboration of recommendations for perioperative management. METHODS: According to specific inclusion and exclusion criteria a total of 13 patients who underwent 17 operations was identified. Supratentorial pneumocephalus was evaluated with semiautomatic-volumetric segmentation. The volume of pneumocephalus was evaluated according to age and ventricular size. RESULTS: Ten of the 13 patients had a programmable valve (preoperative valve setting range 6-14 cmH20; mean 7.5 cmH20) while 3 patients had non programmable valves. A variable amount of supratentorial air collection was evident in all patients postoperatively (range 3.2-331 ml; mean 122.32 ml). Positive predictors for the volume of postoperative pneumocephalus were higher age and a preoperative Evans ratio > 0.3. In our series, we encountered no cases of tension pneumocephalus necessitating an air replacement procedure as well as no obstruction, disconnection, infection or hardware malfunction of the shunt system. CONCLUSIONS: Our findings indicate that a CSF shunt in situ is not a contraindication for performing PFS in the semi-sitting position and it does not increase the pre-existing risk for postoperative tension pneumocephalus. In cases of primary shunting for hydrocephalus associated with posterior fossa tumors a programmable valve set at a medium opening pressure with a gravitational device is a valid option when PFS in the semi-sitting position is opted. In patients with an indwelling shunt diversion system special caution is indicated in order to prevent and detect overdrainage especially in not adjustable valves or shunts without antisiphon devices.

Technical note: pre-positioning lower limb SSEP during semi-sitting positioning in posterior fossa surgery- does it matter?

Intra-operative monitoring has been a crucial tool in modern neurosurgery as it allows to optimize surgical outcome whilst reducing neurological deficits. Somatosensory evoked potentials are routinely monitored in most spinal and brain surgeries due to providing invaluable information regarding the functional integrity of sensory pathways. The use of this neurophysiological technique is particular useful when positioning patients in semi-sitting position during posterior fossa surgery. However, there is general agreement within the intra-operative neuromonitoring community that either upper or lower limb SSEPs monitoring typically suffice. Nonetheless, we report a case study of a patient in whom lower limb SSEPs were independently affected from upper limb SSEPs during positioning. In this respect, we suggest that both upper and lower limb SSEPs monitoring should be considered during semi-sitting positioning in patients undergoing posterior fossa surgery.

How I do it: paramedian supracerebellar transtentorial approach for a temporomesial glioma.

BACKGROUND: Classical approaches to the temporomesial region (TMR) include transtemporal, transylvian, or subtemporal. The supracerebellar infratentorial, initially developed to access dorsolateral cavernomas, has of late shown its versatility to access areas around the central core. The TMR is one such area that can be accessed through this approach with the addition of a tentorial incision. METHOD: The paramedian supracerebellar transtentorial approach (PSCTA) is described along with its advantages and limits compared to other approaches to treat TMR gliomas. CONCLUSION: The PSCTA offers a basal panoramic view of the TMR without the need of retraction, cortical incision, and white matter transgression.

Microvascular Decompression for Glossopharyngeal Neuralgia in the Semi-Sitting Position: A Report of Two Cases.

The semi-sitting position is well known to neurosurgeons. However, there are few reports of microvascular decompression surgery for glossopharyngeal neuralgia performed using the semi-sitting position. The semi-sitting position is not widely adopted in Japan, but it is considered to be a very useful neurosurgical position. Microvascular decompression surgery for glossopharyngeal neuralgia is a relatively rare procedure, and the semi-sitting position is very effective, considering the possibility of intraoperative cardiac arrest and postoperative complications of lower cranial nerve palsy. This report describes two cases of glossopharyngeal neuralgia operated in the semi-sitting position. Microvascular decompression was performed on both patients, and postoperative pain controls were good and no complications were observed. We show that the use of the semi-sitting position to perform microvascular decompression for glossopharyngeal neuralgia provides an excellent surgical view of the brainstem.

Occurrence and management of postoperative pneumocephalus using the semi-sitting position in vestibular schwannoma surgery.

BACKGROUND: The semi-sitting position in neurosurgical procedures is still under debate due to possible complications such as venous air embolism (VAE) or postoperative pneumocephalus (PP). Studies reporting a high frequency of the latter raise the question about the clinical relevance (i.e., the incidence of tension pneumocephalus) and the efficacy of a treatment by an air replacement procedure. METHODS: This retrospective study enrolled 540 patients harboring vestibular schwannomas who underwent posterior fossa surgery in a supine (n = 111) or semi-sitting (n = 429) position. The extent of the PP was evaluated by voxel-based volumetry (VBV) and related to clinical predictive factors (i.e., age, gender, position, duration of surgery, and tumor size). RESULTS: PP with a mean volume of 32 ± 33 ml (range: 0-179.1 ml) was detected in 517/540 (96%) patients. The semi-sitting position was associated with a significantly higher PP volume than the supine position (40.3 ± 33.0 ml [0-179.1] and 0.8 ± 1.4 [0-10.2], p < 0.001). Tension pneumocephalus was observed in only 14/429 (3.3%) of the semi-sitting cases, while no tension pneumocephalus occurred in the supine position. Positive predictors for PP were higher age, male gender, and longer surgery duration, while large (T4) tumor size was established as a negative predictor. Air exchange via a twist-drill was only necessary in 14 cases with an intracranial air volume > 60 ml. Air replacement procedures did not add any complications or prolong the ICU stay. CONCLUSION: Although pneumocephalus is frequently observed following posterior fossa surgery in semi-sitting position, relevant clinical symptoms (i.e., a tension pneumocephalus) occur in only very few cases. These cases are well-treated by an air evacuation procedure. This study indicates that the risk of postoperative pneumocephalus is not a contraindication for semi-sitting positioning.

Venous air embolism in the sitting position in cranial neurosurgery: incidence and severity according to the used monitoring.

BACKGROUND: There is an ongoing debate about the sitting position (SP) in neurosurgical patients. The SP provides a number of advantages as well as severe complications such as commonly concerning venous air embolism (VAE). The best monitoring system for the detection of VAE is still controversial. METHODS: In this retrospective analysis we compared 208 patients. Transesophageal echocardiography (TEE) or transthoracic Doppler (TTD) were used as monitoring devices to detect VAE; 101 cases were monitored with TEE and 107 with TTD. RESULTS: The overall incidence of VAE was 23% (TTD: 10%; TEE: 37%), but the incidence of clinically relevant VAE (drop in end-tidal carbon dioxide above 3 mmHg) was higher in the TTD group (9 out of 17 VAE, 53%) compared to the TEE group (19 out of 62 VAE, 31%). None of the patients with recorded VAE had clinically significant sequelae. CONCLUSIONS: In this small sample we found more VAE events in the TEE group, but the incidence of clinically relevant VAE was rare and comparable to other data. There is no consensus in the definition of clinically relevant VAE.

After the Knife: A Detailed Roadmap for Vestibular Schwannoma Resection in the Semi-Sitting Position - How I do it.

BACKGROUND: Vestibular schwannoma surgery remains a neurosurgical challenge, with known risks, dependent on a number of factors, from patient selection to surgical experience of the team. The semi-sitting position has gained popularity as an alternative to the traditional supine position for vestibular schwannoma resection due to potential advantages such as improved surgical exposure due to clearer surgical field and anatomical orientation. However, there is a lack of standardized protocols for performing the procedure in the semi-sitting position, leading to variations in surgical techniques and outcomes. METHODS: In this study, we aimed to establish a standardized approach for vestibular schwannoma resection using the semi-sitting position. Initiating after final position for semi-sitting, the authors have divided the surgical steps into five major parts for improved understanding and replication. Surgical techniques were analyzed through one hundred steps to identify commonalities, determining the optimal procedural steps for the semi-sitting position using surgical video for visual conceptualization. RESULTS: The analysis described one hundred steps for vestibular schwannoma resection in the semi-sitting position, with visual demonstration of the various parts of the procedure through surgical videos. Specific recommendations for each step were outlined, including appropriate approach, monitoring strategies, and tumor and posterior fossa structures manipulation. Five major parts of the procedure were identified, leading to a reproducible standardization of the surgical procedure of vestibular schwannoma resection in the semi-sitting position. CONCLUSIONS: This study provides a comprehensive standardized protocol for the semi-sitting procedure in vestibular schwannoma resection. By establishing a consistent approach, surgeons can minimize variations in surgical techniques and improve patient outcomes. The identified steps and recommendations can serve as a valuable resource for surgical teams involved in vestibular schwannoma resection and facilitate the dissemination and reproducibility of best practices.

Before the Knife: A Detailed Step-by-Step Description of an Optimized Semi-Sitting Position in Posterior Fossa Surgery.

BACKGROUND: In an ample armamentarium in neurosurgery, the semi-sitting position has produced debate regarding its benefits and risks. Although the position is apparently intuitive, many have abandoned its use since its initial inception, because of reported complexity and potential complications, leading to impracticality. However, through standardization, it has been shown not only to be safe but to carry with it many advantages, including less risk of secondary neurovascular injuries and better visualization of the surgical field. As with any surgical technical nuance, the semi-sitting position has advantages and disadvantages that must be weighed before the decision is made to adopt it or not, not only in a case-by-case scenario but also from a departmental standpoint. As we attempt to show, the advantages from a standardized approach for the semi-sitting position in experienced institutions may be more than sufficient to significantly outweigh the disadvantages, making it the preferable option for most, although not all, posterior fossa surgical interventions. METHODS: In the present study, we aim to elaborate a straightforward narrative of the steps before incision, in an attempt to simplify the complexity of the position, alleviating its disadvantages and exponentially concentrating on its benefits. In nearly 100 steps, we carefully describe the points that culminate with the skin incision, initiating the intraoperative part of the procedure. Each step, therefore, is detailed in full, not in an effort to create a strict manual of the semi-sitting position but rather to facilitate understanding and put the technique into effect in a real-life scenario, thus simplifying what some depict as complex and time consuming. CONCLUSIONS: Although several of the steps described are also relevant and integral parts of other surgical positioning, we intend to create a protocol, in a stepwise fashion, to allow facilitated following, to be easily implemented in departments with different levels of experience. The steps comprise nursing care through to electrophysiologic and anesthesiologic approaches, along with neurosurgical cooperation, making it a team approach, not only to avoid position-related complications but also to optimize preoperative standardization, constructing a safe, efficient, and patient-centered scenario, to set the best possible stage for the next step: the intraoperative part of the intervention.

Chiari Malformation Type 1 and Semi-Sitting Position-A Suitable Alternative for Patients with High BMI.

OBJECTIVE: Chiari I malformation results from a mismatch between the posterior fossa bones and neural components. Management usually relies on surgical treatment. Despite being the most common assumed positioning, the prone position can be challenging in high body mass index (BMI) patients (>40 kg/m2). METHODS: Between February 2020 and September 2021, 4 consecutive patients with class III obesity underwent posterior fossa decompression. The authors describe nuances of the positioning and perioperative details. RESULTS: No perioperative complications were reported. These patients are at a lower risk of bleeding and increased intracranial pressure as a consequence of low intra-abdominal pressure and venous return. In this context, the semi-sitting position, with the aid of accurate monitoring for venous air embolism, seems to be an advantageous surgical position in this group of patients. CONCLUSIONS: We present our results and technical nuances on positioning high BMI patients for posterior fossa decompression using a semi-sitting position.

Air-embolism in the semi-sitting position for craniotomy: A narrative review with emphasis on a single centers experience.

Albeit the semi-sitting position in neurosurgery has been in use for several decades, its application remains controversial in the neurosurgical and neuro-anaesthesia communities. The imminent and most feared risk of the sitting position is air entry into the vascular system due to the negative intravascular pressure leading to potentially life-threatening air embolism with its consequences. Recent advents in neurosurgical (improvement of the operating microscope, employment of intra-operative neurophysiological monitoring) and neuro-anaesthesia care (new anaesthetics, advanced monitoring modalities) have significantly impacted the approach to these surgeries. Vigilant intra-operative observation by an experienced team and peri-operative patient management guided by institutional protocols improves the safety profile of these surgeries. This review outlines the workflow and protocols used in our institution for all cases of semi-sitting position for skull base neurosurgery.

Easy-to-use preload stress echocardiography by using combined dynamic postural stress can identify high-risk patients with heart failure with reduced ejection fraction.

AIMS: Haemodynamic assessment during stress testing is not commonly performed in patients with heart failure with reduced ejection fraction (HFrEF) because of its invasiveness, lower feasibility, and safety concerns. This study aimed to assess the haemodynamic characteristics of patients with HFrEF in response to non-invasive preload stress during dynamic postural alterations achieved by combining both semi-sitting position and passive leg-lifting and to evaluate whether combined postural stress could be used for risk stratification in these patients. METHODS AND RESULTS: For this study, 101 patients with HFrEF and 35 age-matched and sex-matched healthy controls were prospectively recruited. After all standard echocardiographic measurements were obtained in the left decubitus position, all subjects underwent postural stress testing, which consisted of changing from semi-sitting position to passive leg-lifting. During a median follow-up period of 12.2 months, 21 (21%) patients developed adverse cardiovascular events. In patients without adverse cardiovascular events, the stroke volume index (SVi) significantly changed from 28 ± 8 to 35 ± 10 mL/m2 (P < 0.001) during combined postural stress. By contrast, ΔSVi during combined dynamic postural stress was significantly smaller in patients with cardiovascular events than in those without events (ΔSVi 3.4 ± 4.0 vs. 6.4 ± 3.8 mL/m2 , P = 0.002), which indicated severely diseased heart operated on a relatively flat portion of the Frank-Starling curve. In a multivariate Cox proportional hazard analysis, ΔSVi (hazard ratio 0.81, P = 0.02) was an independent predictor of future adverse cardiovascular events. CONCLUSIONS: The combined assessment of dynamic postural stress is a non-invasive, simple, quick, and easy-to-use clinical tool for assessing preload reserve and risk stratification in HFrEF patients.

Estimation of the head elevation angle that causes clinically important venous air embolism in a semi-sitting position for neurosurgery: a retrospective observational study.

INTRODUCTION: The benefits of a sitting position for neurosurgery involving the posterior fossa remain controversial. The main concern is the risk of venous air embolism (VAE). A recent study showed that the rate of VAE was higher when the head was elevated to 45° than when it was elevated to 30°. However, the degree of head elevation that causes clinically important VAE is unclear. The purpose of this study was to estimate the head elevation angle at which the probability of VAE is 50% by using EtCO2 monitoring to detect of VAE. METHODS: The anesthesia records of 23 patients who underwent neurosurgery in a sitting position were reviewed retrospectively. Intraoperative ventilation was set to maintain EtCO2 at approximately 38-42 mmHg. The head elevation angle in each case was determined from a photograph taken by the anesthesiologist or brain surgeon. Nineteen of the 23 cases had photographs available that contained a horizontal reference in the background. Seven cases were treated as VAE during the operation. Six of these cases met the criteria for VAE in this study. Data analysis was performed on a total of 18 patients. The angle between the line connecting the hip joint and the shoulder joint and the horizontal reference was obtained by ImageJ software. Logistic regression was performed using the Python programming language to determine the head elevation angle at which the probability of air embolism was 50%. RESULTS: The decision boundary in the logistic regression was 35.7°. This head elevation angle was the boundary where the probability of VAE was 50%. CONCLUSION: The angle of head elevation that caused clinically important VAE was estimated to be 35.7°.

Monitoring of intracranial venous sinus pressure and prevention for venous air embolism during operation with semi-sitting position.

BACKGROUND: Venous air embolism (VAE) during craniotomy operation with semi-sitting position is closely related to intracranial venous pressure. The objective of current study was to explore the relationship between intracranial venous pressure and VAE during operation with semi-sitting position. METHODS: Between April 2018 and January 2019, 25 patients with vestibular schwannoma and 1 patient with posterior fossa meningioma received operation under semi-sitting position. Catheterization at jugular bulb was conducted by puncture of jugular vein with central venous catheter under guidance of ultrasound. The central venous catheter was then connected to a pressure sensor to continuously monitor the jugular bulb pressure (JBP). Both JBP and VAE were continuously monitored during operation to explore the relationship between JBP and intraoperative VAE under semi-sitting position. RESULTS: Under supine position, JBP significantly increased when the head was rotated 45° to the right compared with that recorded at neutral head position. Among all 26 patients, VAE occurred in 4 (15.4%) cases during operation including 2 minor VAE and 2 moderate VAE. Among 3 patients with negative JBP relative to atmosphere pressure, 2 occurred VAE during operation; while only 2 patients occurred VAE among other 23 cases whose JBP was positive relative to atmosphere pressure (P = 0.009). CONCLUSION: The pressure of intracranial sinus could be continuously monitored by catheterization at jugular bulb. JBP monitoring could be used for prediction of intraoperative VAE. The rate of intraoperative VAE was significantly increased when JBP was negative relative to atmosphere pressure.

Paramedian Supracerebellar Approach in Semi-Sitting Position for Endoscopic Resection of Pineal Cyst: 2-Dimensional Operative Video.

In this video, we present the case of a 41-yr-old female with new onset of recurrent syncopal episodes. She underwent extensive evaluations and diagnostic work-up by cardiology and neurology, excluding any other cause than a large pineal cyst that was found on magnetic resonance imaging. Surgical indications for pineal cyst resection are very limited as most pineal cyst can be treated conservatively. Recurrent drop-attacks (without loss of consciousness) or syncopal episodes (with brief loss of consciousness) have been associated with pineal cysts secondary to a possible ball valve effect with shift of position causing sudden obstruction of the ventricular system followed by rapid rising of intracranial pressure. Several approaches, different positions, and alternative surgical techniques (microscopic vs endoscopic) have been proposed for resection of pineal region lesions. The semi-sitting position provides excellent exposure of the pineal region secondary to gravity-based retraction of the cerebellum, and carries minimal risk of air venous embolism when head elevation is reduced to 30° and lower extremities are elevated. The paramedian supracerebellar approach is less invasive and faster than midline supracerebellar approach, because it requires exposure of just 1 transverse sinus (nondominant for centered lesions) and avoids exposure of the torcula. The endoscopic technique greatly improves the ergonomics of the approach when compared to the microscope based technique, and provides excellent visualization of all the neurovascular structures in the pineal region. Surgical resection was successfully performed with no complications and complete cyst resection. Patient was discharged on postoperative day 1 and remains free of syncopal episodes. The patient signed informed consent including the use of photographic and video material for educational or academic purposes.

Vestibular Schwannoma Resection in a Consecutive Series of 502 Cases via the Retrosigmoid Approach: Technical Aspects, Complications, and Functional Outcome.

OBJECTIVE: Outcome in vestibular schwannoma (VS) surgery has improved enormously over the last decades. Surgical positioning remains a matter of discussion. A standardized protocol for diagnostics and management has been applied and evaluated for complications and functional outcome. METHODS: We examined 502 VS tumors in 483 patients (227 men and 256 women) between 2005 and 2016. According to our patient selection and treatment algorithm, 488 operations (97%) were performed in the semi-sitting position, and 14 (3%) were in the supine position. Auditory and facial functions were analyzed before and after surgery as were perioperative complications. RESULTS: There were 182 patients (36%) with small tumors (Hannover classification T1-T3A) and 320 (64%) large tumors (T3B or T4). Of the patients, 14% were neurofibromatosis type 2 cases. Complete tumor resection was achieved in 96.4%. Hearing preservation occurred in 44% of patients with small tumors and 23% of those with large tumors (Hannover classification), and correlated significantly with tumor size (P < 0.001). Facial palsy (House Brackmann grades II-VI) was present in 63 patients before and in 185 patients after surgery. Useful facial function (House Brackmann grades I-III) early after surgery was maintained in 86% of patients with small tumors and in 77% of patients with large tumors. Intraoperative complications included air embolism in 45 cases (9%), sinus injury in 3 cases, cerebrospinal fluid leakage in 46 cases (9%), and local hemorrhage in 19 cases (4%). Surgical revision was indicated in 31 cases (6%). CONCLUSIONS: In a standardized setting, the semi-sitting position allowed a safe approach. This setting offers the advantage of bimanual tumor nerve handling by the surgeon and an optimal visualization of important functional structures.

Retrosigmoid Transmeatal Endoscope-Assisted Approach in Semi-Sitting Position for Resection of Vestibular Schwannoma: 2-D operative Video.

We present a case of a mid-sized vestibular schwannoma (T3b according to the Hannover classification) that was resected through a retrosigmoid transmeatal approach in semi-sitting position under endoscopic assistance. The patient is a 52-year-old male with acute loss of functional hearing on the right side. Audiometry confirmed a loss of up to 60 dB and lost speech discrimination, there were no associated symptoms such as tinnitus or vertigo. This 2D video demonstrates positioning, OR set-up, anatomical and surgical nuances of the skull base approach and the operative technique for microdissection of the tumor from the critical neurovascular structures, especially the facial and cochlear nerves. A gross total resection was achieved and the patient discharged home after four days with unaltered function of the facial nerve (HB I). At one year follow up there was no indication of residual or recurrence. In summary, the retrosigmoid transmeatal approach is an important and powerful tool in the armamentarium for the microsurgical management of all kinds of vestibular schwannomas. Provided the necessary anesthesiological precautions and intraoperative procedures the semi-sitting position is safe and effective. If needed, the approach can be complemented by the use of an endoscope for visualization of the distal internal auditory canal. The link to the video can be found at: https://youtu.be/pPKT4_5nIn0 .

A Systematic Review of the Semi-Sitting Position in Neurosurgical Patients with Patent Foramen Ovale: How Frequent Is Paradoxical Embolism?

BACKGROUND: The semi-sitting position is preferred in some surgeries of the posterior fossa and the cervical spine. At the same time, it is associated with a risk of air embolism. In the presence of a patent foramen ovale (PFO) with an intracardial right-to-left shunt, an air embolism can result in a paradoxical embolism to the heart or brain. It is unclear whether the risk-benefit ratio favors the semi-sitting position in this scenario. METHODS: We conducted a systematic review of the relevant studies published after 2007 by searching the PubMed, Science Direct, and Cochrane Database of Systematic Reviews databases. Studies in which the presence of PFO was stated and the occurrence of paradoxical embolism was evaluated in patients who underwent neurosurgical procedures in the semi-sitting position were included in our analysis. RESULTS: We identified 4 observational studies with a total of 977 patients who underwent surgery of the posterior fossa or cervical spine in the semi-sitting position; among these, 82 had a PFO. Air embolism occurred in 33 of these 82 patients (40.2%). No paradoxical embolisms were detected. CONCLUSIONS: In experienced medical centers, neurosurgery in the semi-sitting position is feasible with acceptable risk even in patients with PFO. If the PFO is large, or if a permanent right-to-left shunt is present in a patient with a history of paradoxical embolism, it may be reasonable to repair the PFO before surgery if the semi-sitting position is strongly preferred. The risk analysis must be done on a case-by-case basis.

Vestibular schwannoma between 1 and 3 cm: importance of the tumor size in surgical and functional outcome.

OBJECTIVE: The aim of the study was to compare the surgical and functional outcomes of the microsurgical osteoplastic retro-sigmoid approach in a semi-sitting position in two groups of patients with vestibular schwannomas (VSs) ranging from 1 to 3 cm in size. METHOD: A 5-year retrospective evaluation was made of these two groups of patients with VS: Patients with VS sizes 1-<2 cm in maximal intra/extrameatal diameter (n=292) were assigned to group "A" and a matched group of patients with VS between 2 and 3 cm in size (n=154) were assigned to group "B". RESULTS: Significant differences in postoperative outcomes (p<0.05) were found for facial nerve function of House-Brackmann grade I (94% group A vs. 78% group B) and preservation of preoperative hearing (51% group B vs. 34% group A). Patients with tumors sizes ranging between 1 and <2 cm exhibited total tumor removal with significantly higher facial nerve preservation and hearing function preservation rates compared with patients with tumors 2-3 cm in size. CONCLUSION: Even a small increase in tumor size correlated with a significant reduction in good hearing and facial preservation postoperatively, which implies that tumor removal should be performed at the earliest stage possible. Furthermore, these results contradict recommending the wait-and-see approach for intra/extrameatal tumors.