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Neuroendoscopic transventricular transchoroidal approach for access to the posterior zone of the third ventricle or pineal region

Neurosurgical Review (2023) 46:323

The endoscopic transventricular transchoroidal approach facilitates entry into the posterior part of the third ventricle, allowing a visualization field from the foramen of Monro to the pineal region through this anatomical corridor. Combined surgery to treat the target lesion and possible endoscopic third ventriculostomy (ETV) can be performed through a single burr hole.

A detailed description of this surgical technique is given, and a series of cases from our center is presented. This retrospective study included patients with lesions in the pineal region or posterior zone of the third ventricle who underwent surgery between 2004 and 2022 in our center for tumor biopsy or endoscopic cyst fenestration. In nine cases, the transchoroidal approach was performed. Demographic and clinical variables were collected: sex, age at diagnosis, clinical presentation, characteristics of the lesion, pathological diagnosis, characteristics of the procedure, complications, subsequent treatments, evolution, follow-up time, and degree of success of the endoscopic procedure. The mean and range of the quantitative variables and frequency of the qualitative variables were analyzed, together with the statistical significance (p < 0.05). Surgical planning was carried out by performing a preoperative MRI, calculating the ideal entry point and trajectory for each case. The preoperative planning of the surgical technique is described in detail.

Of our sample, 55.6% were women, with a mean age of 35 years (7–78). The most common clinical presentation was intracranial hypertension (55.6%), with or without a focus. Eight patients presented hydrocephalus at diagnosis. The most frequent procedure was endoscopic biopsy with ETV (66.7%). The pathological diagnosis varied widely. Procedure-related complications included one case of self-limited bleeding of the choroidal fissure at its opening and one intraventricular hemorrhage due to tumor bleeding in the postoperative period. Non-procedure-related complications comprised two ETV failures and one case of systemic infection, while late complications included one case of disease progression and one case of radionecrosis. Four patients died, one due to poor neurological evolution after post-surgical tumor bleeding and three due to causes unrelated to the procedure. The rest of the patients had a favorable evolution and were asymptomatic or stable.

The transchoroidal approach through a single burr hole is a feasible and safe option for access to the posterior part of the third ventricle. Proper planning of each case is necessary to avoid complications.

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A Novel Method for Angioscopic Imaging and Visualizing the Skull Base Using Complementary Metal Oxide Semiconductor Cameras

Neurosurgery 93:1432–1436, 2023

Complementary metal oxide semiconductor (CMOS) electrode arrays are a novel technology for miniaturized endoscopes; however, its use for neurointervention is yet to be investigated. In this proof-of-concept study, we aimed to demonstrate the feasibility of CMOS endoscopes in a canine model by providing direct visualization of the endothelial surface, deploying stents and coils, and accessing the spinal subdural space and skull base.

METHODS: Using 3 canine models, standard guide catheters were introduced into the internal carotid and vertebral arteries through the transfemoral route using fluoroscopy. A 1.2-mm CMOS camera was delivered through the guide catheter to inspect the endothelium. Next, the camera was introduced alongside standard neuroendovascular devices including coils and stents to provide direct visualization of their deployment within the endothelium during fluoroscopy. One canine was used for skull base and extravascular visualization. A lumbar laminectomy was performed, and the camera was navigated within the spinal subdural space until the posterior circulation intracranial vasculature was visualized.

RESULTS: We successfully visualized the endothelial surface and performed several endovascular procedures such as deployment of coils and stents under direct endovascular, angioscopic vision. We also demonstrated a proof of concept for accessing the skull base and posterior cerebral vasculature using CMOS cameras through the spinal subdural space.

CONCLUSION: This proof-of-concept study demonstrates the feasibility of CMOS camera technology to directly visualize endothelium, perform common neuroendovascular procedures, and access the base of the skull in a canine model.

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Endoscopic Endonasal Transpterygoid Approach

Operative Neurosurgery 25:E272, 2023

INDICATIONS: CORRIDOR AND LIMITS OF EXPOSURE: The endoscopic endonasal transpterygoid approach (EETPA) provides direct access to the petrous apex, lateral clivus, inferior cavernous sinus compartment, jugular foramen, and infratemporal fossa. In the coronal plane, it provides exposure far beyond a traditional sphenoidotomy.

ANATOMIC ESSENTIALS: NEED FOR PREOPERATIVE PLANNING AND ASSESSMENT: The pterygoid process of the sphenoid bone forms the junction between the body and greater sphenoid wing before bifurcating because it descends into medial and lateral plates. The key to this exposure lies in the region’s bony foramina: the palatovaginal canal, vidian canal, and foramen rotundum.

ESSENTIALS STEPS OF THE PROCEDURE: After performing a maxillary antrostomy, stepwise exposure of these foramina leads to the pterygopalatine fossa. The sphenopalatine artery is cauterized as it becomes the posterior septal artery at the sphenopalatine foramen, and the maxillary sinus’ posterior wall is opened to expose the pterygopalatine fossa. After mobilizing and retracting the contents of the pterygopalatine fossa, the pterygoid process is removed, improving access in the coronal plane.

PITFALLS/AVOIDANCE OF COMPLICATIONS: Vidian neurectomy causes decreased or absent lacrimation. Injury to the maxillary nerve or its branches results in facial, palatal, or odontogenic anesthesia or neuralgia. In addition, the EEPTA precludes the ability to raise an ipsilateral nasal septal flap, making it crucial to plan reconstruction preoperatively.

VARIANTS AND INDICATIONS FOR THEIR USE: There are 5 variants of the EEPTA: extended pterygopalatine fossa, lateral recess of the sphenoid sinus, petrous apex, infratemporal fossa and petrous carotid artery, and middle and posterior skull base. The patient consented to the procedure.

 

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Comparative Analysis of Surgical Working Corridors for Meckel Cave Trigeminal Schwannomas: A Quantitative Anatomic Study

Operative Neurosurgery 25:E251–E266, 2023

Volumetric analysis of the working corridors of the interdural approach to the Meckel cave may lead to a selection of routes which are anatomically more advantageous for trigeminal schwannoma resection. The herein-reported anatomic study quantitively compares the infratrochlear (IT) transcavernous, anteromedial (AM), and anterolateral (AL) corridors, highlighting their feasibility, indications, advantages, and limitations.

METHODS: Anatomic boundaries and depth of Meckel cave, porus trigeminus, IT transcavernous, AM, and AL corridors were identified in 20 formalin-fixed latex-injected cadaveric heads and were subsequently measured. The corridor areas and volumes were derived accordingly. Each opening angle was also calculated. Angles and volumes were compared using analysis of variance. Statistical significance was set at a P-value <.05.

RESULTS: The IT transcavernous corridor volume was greater than that of the AM and AL. The opening angle of the AM middle fossa triangle was wider than the other 2.

CONCLUSION: The IT corridor can be advantageous for Meckel cave schwannomas invading the cavernous sinus and those with a notable extension into the posterior fossa because the transcavernous approach maximizes the working space into the retrosellar area. The AM middle fossa corridor is strategic in schwannomas confined to the Meckel cave with a minor extension into the posterior fossa. It raises the chance of total resection with a single approach involving the porus trigeminus opening.

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The “candy wrapper” of the pituitary gland: a road map to the parasellar ligaments and the medial wall of the cavernous sinus

Acta Neurochirurgica (2023) 165:3431–3444

The anatomy of the medial wall of the cavernous sinus (MWCS) and parasellar ligaments (PLs) has acquired increasing importance in endoscopic endonasal (EE) surgery of the cavernous sinus (CS), including resection of the MWCS in functioning pituitary adenomas (FPAs). Although anatomical studies have been published, it represents a debated topic due to their complex morphology. The aim is to offer a description of the PLs that originate from the MWCS and reach the lateral wall of the cavernous sinus (LWCS), proposing the “candy wrapper” model. The relationships between the neurovascular structures and histomorphological aspects were investigated.

Methods Forty-two CSs from twenty-one human heads were studied. Eleven specimens were used for EE dissection; five underwent a microscopic dissection. Five specimens were used for histomorphological analysis.

Results Two groups of PLs with a fan-shaped appearance were encountered. The anterior group included the periosteal ligament (55% sides) and the carotico-clinoid complex (100% sides), formed by the anterior horizontal and the carotico-clinoid ligaments. The posterior group was formed by the posterior horizontal (78% sides), and the inferior hypophyseal ligament (34% sides). The periosteal ligament originated inferiorly from the MWCS, reaching the periosteal dura. The anterior horizontal ligament was divided in a superior and inferior branch. The superior one continued as the carotid-oculomotor membrane, and the inferior branch reached the CN VI. The carotico-clinoid ligament between the middle and anterior clinoid was ossified in 3 sides. The posterior horizontal ligament was related to the posterior genu and ended at the LWCS. The inferior hypophyseal ligament followed the homonym artery. The ligaments related to the ICA form part of the adventitia. Conclusion The “candy wrapper” model adds further details to the previous descriptions of the PLs. Understanding this complex anatomy is essential for safe CS surgery, including MWCS resection for FPAs.

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Dorsal column mapping in resection of intramedullary spinal cord tumors: a prospective comparison of two methods and neurological follow‑up

Acta Neurochirurgica (2023) 165:3493–3504

In surgery for intramedullary spinal cord tumors (imSCT), distortion of the anatomy challenges the visual identification of dorsal columns (DC) for midline myelotomy. Dorsal column mapping (DCM) and spinal cord stimulation (SCS) can identify DC neurophysiologically. We compare application and feasibility of both methods.

Methods Patients with surgically treated imSCT were prospectively included between 04/2017 and 06/2019. The anatomical midline (AM) was marked. SSEPs at the DC after stimulation of tibial/median nerve with an 8-channel DCM electrode and cortical SSEP phase reversal at C3/C4 after SCS using a bipolar concentric probe were recorded. Procedural and technical aspects were compared. Standardized neurological examinations were performed preoperatively, 1 week postoperatively and after more than 12 months.

Results The DCM electrode detected the midline in 9/13 patients with handling limitations in the remaining patients. SCS was applicable in all patients with determination of the midline in 9/13. If both recordings could be acquired (6/13), concordance was 100%. If baseline SSEPs were poor, both methods were limited. SCS was less time-consuming (p = 0.001), cheaper, and easier to handle. In 92% of cases, the AM and neurophysiologic midlines were concordant. After myelotomy, 3 patients experienced > 50% reduction in amplitude of SSEPs. Despite early postoperative worsening of DC function, longterm follow-up showed significant recovery and improvement in quality of life.

Conclusion DCM and SCS may help confirm and correct the AM for myelotomy in imSCT, leading to a favorable longterm neurological outcome in this cohort. SCS evolved to be superior concerning applicability, cost-effectiveness, and time expenditure.

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The influence of tumor topography on the surgical outcome of craniopharyngiomas

J Neurosurg 139:1247–1257, 2023

Various topographical classifications for craniopharyngioma have been proposed based on their relationship with optic chiasm and the third ventricular floor. There is a paucity of literature evaluating the surgical outcome based on tumor topography. This study aims to compare the surgical outcomes of retrochiasmatic craniopharyngiomas (RCPs) and nonretrochiasmatic craniopharyngiomas (non-RCPs).

METHODS This retrospective study includes newly diagnosed patients with craniopharyngioma who underwent surgery between January 2000 and December 2015. Clinical features, the extent of resection (EOR), surgical outcomes, tumor recurrence, and progression-free survival (PFS) of craniopharyngiomas were compared with respect to their relationship to the optic chiasm and third ventricular floor.

RESULTS The authors identified RCPs in 104 and non-RCPs in 33 patients. RCPs were significantly larger and more associated with hydrocephalus than were non-RCPs (p < 0.001) at the time of diagnosis. Puget grade 2 hypothalamic involvement was more frequent with RCPs. EOR and PFS following either subtotal resection (p = 0.07) or gross-total resection (p = 0.7) were comparable between RCPs and non-RCPs. There was no significant difference in the postoperative visual outcome. Resection of RCPs resulted in higher postoperative hypopituitarism (64% vs 42%, p = 0.01) and hypothalamic dysfunction (18% vs 3%, p = 0.02). Location of the tumor, either retrochiasmatic (HR 0.5; 95% CI 0.14–2.2; p = 0.4) or nonretrochiasmatic (HR 1.3; 95% CI 0.3–5.5; p = 0.6), did not show association with recurrence. RCPs with extraand intraventricular components (type 3b) had a higher incidence of postoperative hypothalamic morbidities (p = 0.01) and tumor recurrence (36% vs 19%; p = 0.05) during follow-up than the extraventricular (type 3a) RCP. Between prechiasmatic and infrachiasmatic/intrasellar craniopharyngiomas, EOR (p = 0.7), postoperative diabetes insipidus (p = 0.4), endocrinological outcome (p = 0.7), and recurrence (p = 0.1) were comparable. The patients with complex multicompartmental tumors had a lower rate of gross-total resection (25%, p = 0.02) and a higher incidence of tumor recurrence (75%, p = 0.004) than the rest.

CONCLUSIONS The tumor topography can influence the postoperative outcome. RCPs can be associated with a higher incidence of hypopituitarism and hypothalamic morbidities postoperatively. The influence of topography on EOR and tumor recurrence is controversial. However, this study did not find a significant difference in EOR and tumor recurrence between RCPs and non-RCPs. PFS and overall mortality are also comparable.

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Neuronavigated foraminoplasty, shunt removal, and endoscopic third ventriculostomy in a 54‑year‑old patient with third shunt malfunction episode

Acta Neurochirurgica (2023) 165:3289–3296

The application of endoscopic third ventriculostomy (ETV) for the treatment of obstructive hydrocephalus in shunt malfunction represents a paradigm shift, as it allows hydrocephalus to be transformed from a chronic condition treated with an artificial device to a curable disease.

Methods We present a 54-year-old male with a diagnosis of idiopathic Sylvian aqueduct stenosis treated with shunt. The patient presented to our institution with symptoms of shunt malfunction and an increase in ventricular size on imaging, which was his third episode throughout his life. Through a right precoronal approach, with prior informed consent from the patient, we performed foraminoplasty, endoscopic third ventriculostomy, and finally removal of the shunt system.

Conclusion ETV shows promise as a viable treatment option for shunt malfunction in noncommunicating obstructive hydrocephalic patients. Its potential to avoid VPS-related complications, preserve physiological CSF circulation, and provide an alternative drainage pathway warrants further investigation.

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Use of differential stimulation of the nucleus accumbens and anterior limb of the internal capsule to improve outcomes of obsessive-compulsive disorder

J Neurosurg 139:1376–1385, 2023

Personalized stimulation is key to optimizing the outcomes of deep brain stimulation (DBS) for refractory obsessive-compulsive disorder (OCD). However, the contacts in a single conventional electrode cannot be programmed independently, which may affect the therapeutic efficacy of DBS for OCD. Therefore, a novel designed electrode and implantable pulse generator (IPG) that could achieve differential stimulation parameters for different contacts was implanted into the nucleus accumbens (NAc) and anterior limb of the internal capsule (ALIC) of a cohort of patients with OCD.

METHODS Thirteen consecutive patients underwent bilateral DBS of the NAc-ALIC between January 2016 and May 2021. Differential stimulation of the NAc-ALIC was applied at initial activation. Primary effectiveness was assessed on the basis of change in scores on the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) from baseline to 6-month follow-up. Full-response was defined as a 35% decrease in Y-BOCS score. Secondary effectiveness measures were the Hamilton Anxiety Rating Scale (HAMA) and Hamilton Depression Rating Scale (HAMD). The local field potential of bilateral NAcALIC was recorded in 4 patients who were reimplanted with a sensing IPG after battery depletion of the previous IPG.

RESULTS The Y-BOCS, HAMA, and HAMD scores decreased remarkably during the first 6 months of DBS. Ten of 13 patients were categorized as responders (76.9%). Differential stimulation of the NAc-ALIC was favorable to optimization of the stimulation parameters by increasing the parameter configurations. Power spectral density analysis revealed pronounced delta-alpha frequency activity in the NAc-ALIC. Phase-amplitude coupling of the NAc-ALIC showed that strong coupling is present between the phase of delta-theta and broadband gamma amplitude.

CONCLUSIONS These preliminary findings indicate that differential stimulation of the NAc-ALIC can improve the efficacy of DBS for OCD.

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Reducing morbidity associated with subdural drain placement after burr‑hole drainage of unilateral chronic subdural hematomas

Acta Neurochirurgica (2023) 165:3207–3215

Placement of a subdural drain after burr-hole drainage of chronic subdural hematoma (cSDH) significantly reduces risk of its recurrence and lowers mortality at 6 months. Nonetheless, measures to reduce morbidity related to drain placement are rarely addressed in the literature. Toward reducing drain-related morbidity, we compare outcomes achieved by conventional insertion and our proposed modification.

Methods In this retrospective series from two institutions, 362 patients underwent burr-hole drainage of unilateral cSDH with subsequent subdural drain insertion by conventional technique or modified Nelaton catheter (NC) technique. Primary endpoints were iatrogenic brain contusion or new neurological deficit. Secondary endpoints were drain misplacement, indication for computed tomography (CT) scan, re-operation for hematoma recurrence, and favorable Glasgow Outcome Scale (GOS) score (≥ 4) at final follow-up.

Results The 362 patients (63.8% male) in our final analysis included drains inserted in 56 patients by NC and 306 patients by conventional technique. Brain contusions or new neurological deficits occurred significantly less often in the NC (1.8%) than conventional group (10.5%) (P = .041). Compared with the conventional group, the NC group had no drain misplacement (3.6% versus 0%; P = .23) and significantly fewer non-routine CT imaging related to symptoms (36.5% versus 5.4%; P < .001). Re-operation rates and favorable GOS scores were comparable between groups.

Conclusion We propose the NC technique as an easy-to-use measure for accurate drain positioning within the subdural space that may yield meaningful benefits for patients undergoing treatment for cSDH and vulnerable to complication risks.

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Predictors of extent of resection and recurrence following endoscopic endonasal resection of craniopharyngioma

J Neurosurg 139:1235–1246, 2023

Craniopharyngioma is a benign but surgically challenging brain tumor. Controversies exist regarding its ideal treatment strategy, goals of surgery, efficacy of radiation, and the long-term outcomes of these decisions. The authors of this study performed a detailed analysis of factors predictive of the extent of resection and recurrence in large series of craniopharyngiomas removed via an endoscopic endonasal approach (EEA) with long-term follow-up.

METHODS From a prospective database of all EEAs done at Weill Cornell Medical College by the senior author from 2004 to 2022, a consecutive series of histologically proven craniopharyngiomas were identified. Gross-total resection (GTR) was generally the goal of surgery. Radiation was often given if GTR had not been achieved. The stalk was preserved if not infiltrated with tumor but was sacrificed to achieve GTR. Intentional subtotal resection (STR) was performed in select cases to avoid hypothalamic injury.

RESULTS Among the 111 identified cases were 88 adults and 23 children. Newly diagnosed cases comprised 58.6% of the series. GTR was attempted in 77.5% of the patients and among those cases was achieved in 89.5% of treatmentnaive tumors and 72.4% of recurrent tumors. An inability to achieve GTR was predicted by prior surgical treatment (OR 0.13, 95% CI 0.03–0.6, p = 0.009), tumor diameter ≥ 3.5 cm (OR 0.11, 95% CI 0.02–0.53, p = 0.006), and encasement of the optic nerve or a major artery (OR 0.11, 95% CI 0.01–0.8, p = 0.03). GTR with stalk preservation maintained some anterior pituitary function in 64.5% of cases and prevented diabetes insipidus in 25.8%. After a median follow-up of 51 months (IQR 17–80 months), the recurrence rate after GTR was 12.5% compared with 38.5% after non-GTR. The median recurrence-free survival was 5.5 years after STR, 8.3 years after near-total resection (≥ 98%), and not reached after GTR (p = 0.004, log-rank test). GTR was the strongest predictor of recurrence-free survival (OR 0.09, 95% CI 0.02–0.42, p = 0.002), whereas radiation did not show a statistically significant impact (OR 1.17, 95% CI 0.45–3.08). In GTR cases, the recurrence rate was higher if the stalk had been preserved (22.6%) as opposed to a sacrificed stalk (4.9%; OR 5.69, 95% CI 1.09–29.67).

CONCLUSIONS The study data show that GTR should be the goal of surgery in craniopharyngiomas if it can be achieved safely. Although stalk preservation can maintain some endocrine function, the risk of recurrence is higher in such cases. Radiation may not be as effective as previously reported.

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The sub‑occipital transtentorial approach for pineal region tumors

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Acta Neurochirurgica (2023) 165:3461–3465

Two major approaches exist for the surgical removal of pineal region tumors: the supracebellar infratentorial and the sub-occipital transtentorial.

Methods We present the Lyon’s technique of the sub-occipital transtentorial approach for pineal region tumors and our tricks to avoid complications. The principle is to expose the pineal region under the occipital lobe and not through the interhemispheric fissure.

Conclusions The sub-occipital transtentorial approach is a direct, extra cerebral, safe, and effective way to access tumors of the pineal region.

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Validation of Efficacy and Safety of TachoSil ® Tissue Sealant for Vessel Transposition in Microvascular Decompression

Operative Neurosurgery 25:417–425, 2023

Use of TachoSil ® as the transposition material of microvascular decompression (MVD) for hemifacial spasm (HFS) and trigeminal neuralgia (TN) is easy and safe to perform, but the efficacy and safety of this technique are unknown. This study attempted to validate the efficacy and safety of TachoSil ® as a transposition material of MVD.

METHODS: A retrospective study of the surgical results and complications of 63 patients (35 HFS and 28 TN) treated by the TachoSil ® technique between January 2011 and December 2021 was conducted. The efficacy of the treatment was evaluated by Kaplan–Meier survival analysis. Magnetic resonance imaging follow-up study was performed to detect any adverse events including a mass formation.

RESULTS: The rate of complete disappearance of HFS was 91.4% at 1 year and estimated to be 85.7% after a 10-year followup. The rate of no pain without medication for TN was 85.4% at 1 year and estimated to be 69.0% after a 9-year follow-up. These surgical results are comparable with those previously reported. Flaking of TachoSil ® releasing the offending artery was only recognized in one case (1.6%). Therefore, TachoSil ® can be considered as an effective transposition material for MVD. TachoSil ® did not increase the rate of acute and subacute adverse events such as inflammation and delayed facial palsy. Magnetic resonance imaging follow-up identified no abnormalities including mass that suggested granuloma formation.

CONCLUSION: The efficacy of the TachoSil ® technique for HFS and TN and the reliability of TachoSil ® as an adhesive material in MVD were verified. No adverse events associated with TachoSil ® use in MVD were found. We conclude that the TachoSil ® technique has relatively long efficacy and safety for MVD.

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Vestibular Schwannoma Stereotactic Radiosurgery in Octogenarians

Neurosurgery 93:1099–1105, 2023

The management of octogenarians with vestibular schwannomas (VS) has received little attention. However, with the increase in octogenarian population, more effort is needed to clarify the value of stereotactic radiosurgery (SRS) in this population. The aim of this study was to evaluate the safety and efficacy of SRS in this patient age group.

METHODS: A retrospective study of 62 patients aged 80 years or older who underwent single-session SRS for symptomatic VS during a 35-year interval was performed. The median patient age was 82 years, and 61.3% were male. SRS was performed as planned adjuvant management or for delayed progression after prior partial resection in 5 patients.

RESULTS: SRS resulted in a 5-year tumor control rate of 95.6% with a 4.8% risk of adverse radiation effects (ARE). Tumor control was unrelated to patient age, tumor volume, Koos grade, sex, SRS margin dose, or prior surgical management. Four patients underwent additional management including 1 patient with symptomatic progression requiring surgical resection, 2 patients with symptomatic hydrocephalus requiring cerebrospinal fluid diversion, and 1 patient whose tumor-related cyst required delayed cyst aspiration. Three patients developed ARE, including 1 patient with permanent facial weakness (House-Brackmann grade II), 1 who developed trigeminal neuropathy, and 1 who had worsening gait disorder. Six patients had serviceable hearing preservation before SRS, and 2 maintained serviceable hearing preservation after 4 years. A total of 44 (71%) patients died at an interval ranging from 6 to 244 months after SRS.

CONCLUSION: SRS resulted in tumor and symptom control in most octogenarian patients with VS.

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Positioning of epidural electrode for motor cortex stimulation in general anesthesia based on intraoperative electrophysiological monitoring to treat refractory trigeminal neuropathic pain

Acta Neurochirurgica (2023) 165:3403–3407

Motor cortex stimulation (MCS) represents a treatment option for refractory trigeminal neuralgia (TGN). Usually, patients need to be awake during surgery to confirm a correct position of the epidural electrode above the motor cortex, reducing patient’s comfort.

Method Epidural cortical mapping (ECM) and motor evoked potentials (MEPs) were intraoperatively performed for correct localization of motor cortex under general anesthesia that provided comparable results to test stimulation after letting the patient to be awake during the operation.

Conclusion Intraoperative ECM and MEPs facilitate a confirmation of correct MCS-electrode position above the motor cortex allowing the MCS-procedure to be performed under general anesthesia.

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Application of the Robotic-Assisted Digital Exoscope for Resection of Posterior Fossa Tumors in Adults: A Series of 45 Cases

Operative Neurosurgery 25:397–407, 2023

Complete safe resection is the goal when pursuing surgical treatment for posterior fossa (PF) tumors. Efforts have led to the development of the exoscope that delineates tumors from non-neoplastic brain. This investigation aims to assess patient outcomes where PF tumor resection is performed with the exoscope by a retromastoid or suboccipital approach.

METHODS: A retrospective analysis was conducted for patients with PF tumors who underwent exoscope resection from 2017 to 2022. Patient demographics, clinical, operative, and outcome findings were collected. Extent of resection studies were also performed. Associations between perioperative data, discharge disposition, progression-free survival (PFS), and overall survival (OS) were evaluated.

RESULTS: A total of 45 patients (22 male patients) with a median age of 57 years were assessed. Eighteen (40%) and 27 patients (60%) were diagnosed with malignant and benign tumors, respectively. Tumor neurovascular involvement was found in 28 patients (62%). Twenty-four (53%) and 20 (44%) tumors formed in the cerebellum and cerebellopontine angle cistern, respectively. One tumor (2%) was found in the cervicomedullary junction. The mean extent of resection was 96.7% for benign and malignant tumors. The PFS and OS rate at 6 months (PFS6, OS6) was 89.7% and 95.5%, respectively. Neurological complications included sensory loss and motor deficit, with 11 patients reporting no postoperative symptoms. Of the neurological complications, 14 were temporary and 9 were permanent.

CONCLUSION: The exoscope is an effective intraoperative visualization tool for delineating PF tumors. In our series, we achieved low postoperative tumor volumes and a high gross total resection rate.

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Micro‑Doppler for venous sinus localization in approaches to the cerebello‑pontine angle

Acta Neurochirurgica (2023) 165:3467–3472

Main anatomical landmarks of retrosigmoid craniotomy are transverse sinus (TS), sigmoid sinus (SS), and the confluence of both. Anatomical references and guidance based on preoperative imaging studies are less reliable in the posterior fossa than in the supratentorial region. Simple intraoperative real-time guidance methods are in demand to increase safety.

Methods This manuscript describes the localization of TS, SS, and TS-SS junction by audio blood flow detection with a micro-Doppler system.

Conclusion This is an additional technique to increase safety during craniotomy and dura opening, widening the surgical corridor to secure margins without carrying risks nor increase surgical time.

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The pathophysiology of trigeminal neuralgia: a molecular review

J Neurosurg 139:1471–1479, 2023

The goal of this study was to provide a comprehensive overview of the current understanding of molecular and genetic mechanisms underlying the pathophysiology of trigeminal neuralgia (TN).

METHODS The authors searched PubMed systematically for primary research literature investigating specific molecular mechanisms from samples derived from patients with TN. The genes/molecules of interest from the selected literature were then cross-referenced with corresponding studies in animal models of TN.

RESULTS From approximately 345 articles, a total of 12 articles were selected and included in the review, focusing on ionotropic channel expressivity and mutations, reactive oxygen species expressivity, inflammatory marker expressivity, and microRNA expressivity. Of the 12 included articles, only 4 had studies completed in other animal models regarding the corresponding TN mechanism found in humans.

CONCLUSIONS The current literature does not suggest a conclusive disease mechanism for TN in humans. In addition to neurovascular conflict/compression of the trigeminal nerve, recent studies have indicated that TN may be linked to inflammatory and reactive oxygen species signaling as well. Recent genetic studies in patients with TN have yet to be investigated further in animal models.

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Ventriculosinus shunt: a pilot study to investigate new technology to treat hydrocephalus and mimic physiological principles of cerebrospinal fluid drainage

J Neurosurg 139:1412–1419, 2023

Devices draining CSF to the intracranial venous sinus for the treatment of hydrocephalus have been tested in the past, and while clinically effective, have not shown efficacy in the long term. The majority of these devices become obstructed within 3 months due to endothelial overgrowth. In this study, the authors investigated a newly developed ventriculosinus (VS) shunt outlet device with the objective of showing it would remain patent for at least 6 months.

METHODS Twelve patients in need of shunting for hydrocephalus underwent an operation using the investigational device and were followed for 6 months to record patency of the shunt.

RESULTS In 10 patients, the shunt was patent at 6 months, with the outlet device remaining unobstructed. In the remaining 2 patients, one died just before reaching the 6-month endpoint, and in the other the outlet was misplaced during surgery and therefore ceased to function after 3 months. No occlusion of the internal jugular vein or thrombus formation was noted in any of the 12 cases.

CONCLUSIONS These findings indicate that the outlet device can remain patent and has the capability to mimic physiological drainage by diverting CSF to the intracranial sinus. Additional confirmation of its potential as part of a new VS shunt system and ultimately as a viable alternative for ventriculoperitoneal and ventriculoatrial shunting to reduce complication rates requires further clinical trials.

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Preoperative Microsoft HoloLens 2 planning‑assisted surgical clipping of a fetal posterior cerebral artery aneurysm

Acta Neurochirurgica (2023) 165:3371–3374

The treatment of intracranial aneurysms has predominantly shifted towards endovascular strategies, but complex cases still necessitate microsurgery. Preoperative stimulation can be beneficial for inexperienced young neurosurgeons in preparing for safe microsurgery.

Method A 72-year-old female with a left irregular fetal posterior cerebral artery (PCA) aneurysm underwent clipping repair. Microsoft HoloLens 2, utilizing mixed reality technology, was employed for preoperative stimulation and anatomical study. During the operation, we successfully identified the planned relationship between the aneurysm and the fetal PCA. The patient was cured without any complications.

Conclusion We hope that this report will highlight the significance of Microsoft HoloLens 2 in microsurgical planning and education.

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