Category: skull base surgery

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The suprabulbar approach for jugular fossa schwannomas: case series and technical nuances

J Neurosurg 145:120–131, 2026

This clinical article details a cadaveric and retrospective clinical study of the suprabulbar approach for resection of jugular fossa schwannomas, describing anatomical measurements, stepwise surgical technique, perioperative protocols, and outcomes in 22 patients treated between 1994 and 2024. The authors report a 77% gross-total resection rate, low morbidity, no mortality, and favorable cranial nerve preservation with mean follow-up of 31.4 months.

The paper emphasizes anatomical rationale from bilateral cadaver dissections to define the presigmoid infralabyrinthine window, operative nuances (mastoidectomy, presigmoid dura management, endoscopic assistance), and the approach’s versatility to combine intradural access with neck dissection for large dumbbell tumors while minimizing cranial nerve and venous complications.

Problem Jugular fossa schwannomas are rare lower cranial nerve tumors whose complex anatomy makes surgery difficult and morbidity-prone, especially for swallowing/voice deficits.

Approach The suprabulbar approach uses a presigmoid infralabyrinthine/retrofacial window created via mastoidectomy to access the jugular fossa while preserving the labyrinth and facial nerve, and enabling jugular bulb decompression.

Anatomic basis Cadaveric measurements characterized the surgical corridor (means: sigmoid sinus width 13.5 ± 3.9 mm; jugular bulb width 10.9 ± 1.4 mm; sigmoid-to-retrofacial space 12.8 ± 3 mm; labyrinth-to–jugular bulb dome 10.6 ± 2.6 mm; jugular foramen diameter 8.1 ± 1.2 mm).

Clinical series 22 patients (1994–2024) underwent resection; tumors were predominantly dumbbell-shaped type D (91%), mean max diameter 2.9 ± 1.1 cm, with frequent presenting dysphagia (64%) and hearing loss (41%).

Technique extensions Intradural tumor can be followed via presigmoid dural opening, distal tumor can be removed endoscopically, and caudal extracranial extension can be addressed with single-stage upper neck dissection when needed.

Resection outcomes Gross-total resection was achieved in 77% (17/22); subtotal resection occurred in 5 cases (including one due to intraoperative arrhythmias).

Safety profile No deaths or permanent neurological deficits; transient postoperative cranial nerve deficits occurred in 14% and resolved during follow-up; one perioperative complication was a suspected CSF leak treated with spinal drainage.

Follow-up/recurrence Mean follow-up was 31.4 months; 64% improved in preoperative neurological deficits; confirmed recurrence occurred in 14% (3/22), all successfully reoperated.

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Skull Base Anatomy Presented in 360° Photogrammetry 3-Dimensional Models

Operative Neurosurgery 30:124–136, 2026

This article presents the creation of seven photorealistic 360° photogrammetric 3D models of the central skull base derived from stepwise dissections of a formalin-fixed, vessel-injected cadaveric head. The workflow—dissection stages, smartphone-based image capture, cloud photogrammetry, refinement in Blender, and VR/MR upload—enables immersive visualization of cranial nerves, ICA/vertebral segments, and regional anatomy.

The models offer progressive exocranial-to-endocranial perspectives for education and preoperative planning, highlighting cavernous sinus, infratemporal and pterygopalatine fossae, petrous bone, and foraminal relationships. Limitations include a single-specimen dataset, color variations from fixation, and resolution constraints in deep cavities; nevertheless, the freely accessible VR models complement traditional dissection and anatomical atlases.

360° Photogrammetric 3D Models: Realistic, photogrammetry-based 3D models of the central skull base were created from cadaveric dissections, offering immersive 360° visualization of complex neuroanatomical structures for enhanced spatial understanding.

Stepwise Dissection and Scanning: Seven progressive anatomical models were generated by systematically dissecting and scanning a formalin-fixed, vessel-injected head specimen, documenting both exocranial and endocranial perspectives.

Key Structures Visualized: The models detail the courses of cranial nerves, major vessels (including all internal carotid artery segments), skull base foramina, infratemporal and pterygopalatine fossae, paranasal sinuses, and deep neck spaces.

Technical Workflow: High-resolution images were captured using a smartphone multi-camera system, processed via cloud-based photogrammetry, refined in 3D software, and made accessible through web, VR, and MR platforms.

Educational Value: The interactive models allow customizable, layered exploration of anatomy, overcoming limitations of traditional 2D images and static atlases, and are freely accessible for educational and preoperative planning purposes.

Limitations: The study used a single specimen, which may not represent anatomical variants; image quality in deep/narrow regions could be further improved with advanced imaging and fixation techniques.

Broad Accessibility: Smartphone-based and cloud photogrammetry methods make high-resolution anatomical modeling more accessible and less resource-intensive, facilitating widespread dissemination.

Conclusions: 360° photorealistic 3D models significantly enhance comprehension of skull base anatomy and are a valuable adjunct to traditional teaching, with potential to improve neurosurgical training and patient outcomes.

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Cerebellopontine Angle Meningiomas: A Multi-Institutional Cohort Study

Neurosurgery 97:105–111, 2025

This multi-institutional study of 95 cerebellopontine angle meningioma cases found that gross total resection, especially with internal auditory canal drilling for intracanalicular invasion, improves symptom control and reduces recurrence. Most patients experienced stable or improved hearing, with postoperative complications and recurrence rates detailed.

• Cerebellopontine angle (CPA) meningiomas are challenging due to their proximity to neurovascular structures and present commonly with hearing loss, ataxia, and headaches.

• Gross total resection (GTR) was achieved in 62.1% of 95 patients; smaller tumor size and drilling the internal auditory canal (IAC) for tumors with intracanalicular invasion were associated with higher GTR rates.

• Most patients had stable or improved hearing postoperatively; only a minority experienced worsening.

• Postoperative complications included cranial nerve dysfunction, CSF leak, and hydrocephalus, but there were no perioperative deaths.

• Tumor progression or recurrence occurred in 25.3% of patients, with higher rates in WHO grade 2 tumors; Simpson grade I/II resection and older age reduced recurrence risk.

• Extent of resection (EOR) is not reliably predicted by tumor size alone; other anatomical factors are important.

• Adjuvant radiation was mainly used for higher-grade tumors with subtotal resection, but most progression cases were managed with observation or salvage therapy.

• Surgical resection is effective for symptom control and reducing recurrence, especially with GTR and appropriate IAC management.

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Evaluating the impact of a hand-crafted 3D-Printed head Model and virtual reality in skull base surgery training

Brain and Spine 5 (2025) 104163

A multimodal neurosurgical training course integrating hand-crafted 3D-printed head models, virtual reality, and cadaveric dissections significantly improved trainees’ anatomical understanding and surgical skills in skull base surgery. While offering a cost-effective, accessible alternative to cadaveric training, further refinement in soft tissue realism is needed.

• A hand-crafted 3D-printed head model and virtual reality (VR) were evaluated for skull base surgery training.

• A two-day course with 12 neurosurgical trainees and 11 faculty combined lectures, VR, cadaveric dissections, and hands-on practice with the 3D-printed model.

• The 3D model included four different skull base tumors and realistic neuroanatomy, assembled using patient imaging data and various materials.

• Trainees showed significant improvement in spatial understanding and knowledge of surgical steps after the course.

• Faculty and trainees rated the educational value and anatomical accuracy of the model highly, though soft tissue realism was rated lower.

• VR was found to enhance anatomical comprehension and surgical planning, complementing traditional methods.

• The approach offers a cost-effective, accessible alternative to cadaveric training, but further refinement in soft tissue simulation is needed.

• Study limitations include small sample size, subjective assessments, and lack of long-term outcome data.

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3D‑exoscopic extradural Hakuba‑Dolenc approach with manipulation of pneumatized anterior clinoid process for the prevention of cerebrospinal fluid leakage

Acta Neurochirurgica (2025) 167:165

This study describes a 3D-exoscopic extradural Hakuba-Dolenc approach with a hybrid technique for anterior clinoidectomy in cases with pneumatized anterior clinoid process, aiming to prevent cerebrospinal fluid leakage during skull base surgery. The technique was effective, with no postoperative CSF leakage observed.

• Describes a modified 3D-exoscopic extradural Hakuba-Dolenc approach to anterior clinoidectomy, focusing on preventing cerebrospinal fluid (CSF) leakage, especially in cases with pneumatized anterior clinoid process (ACP).

• The hybrid technique combines drilling and biting for safe removal of the ACP, minimizing mucosal injury and CSF leak risk.

• Preoperative thin-slice bone CT is essential to identify anatomical variations of ACP and avoid complications.

• Careful interdural dissection of the lateral cavernous wall is performed, with hemostasis for venous bleeding.

• Gelfoam is placed in the sphenoid sinus to isolate mucosa and prevent CSF leakage.

• The approach was effective, with no CSF leakage or neurological deficits postoperatively and at 3-month follow-up.

• Key risks include CSF rhinorrhea and potential optic nerve injury; patients should be informed preoperatively.

• Technique is indicated for paraclinoid aneurysm and certain skull base tumors.

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Lateral compartment of the cavernous sinus from the endoscopic endonasal approach: anatomical considerations and surgical relevance to adenoma surgery

• Objective: The study investigates the lateral compartment of the cavernous sinus (CS) and its surgical relevance in adenoma surgery using the endoscopic endonasal approach.

• Methods: Dissection was performed on 22 colored silicone-injected specimens to identify anatomical landmarks and techniques for mobilizing the internal carotid artery (ICA).

• Findings: The lateral compartment is divided into two subcompartments, with the upper housing the lateral parasellar ligament (LPL) and inferolateral trunk (ILT), and the lower containing sympathetic nerve branches.

• LPL and ILT: The LPL was identified in 86% of hemispheres, with varying configurations, and the ILT was found in 93%, primarily originating from the horizontal ICA segment.

• Techniques: Transection of the LPL, ILT, and COM facilitates medial ICA mobilization, enhancing access to the lateral compartment.

• Conclusions: The study underscores the anatomical intricacies of the lateral compartment and the potential benefits of the lateral transcavernous approach.

• Limitations: The study’s findings are based on cadaveric dissections, which may not fully replicate live surgical conditions.

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Characteristics of optic canal invasion in the large midline nontuberculum sellae anterior skull base meningiomas and the surgical outcomes

Acta Neurochirurgica (2025) 167:31

There is a lack of available data regarding the incidence and characteristics of optic canal invasion (OCI) in large midline non-tuberculum sellae anterior skull base meningiomas (NTSAM), specifically those originating predominantly from the olfactory groove and planum sphenoidale. This study aims to describe the incidence and characteristics of OCI as well as clinical and visual outcomes following extensive tumor resection with optic canal exploration in intra-optic canal tumor removal. In addition, the predictive performance of OCI by preoperative magnetic resonance imaging (MRI) is investigated.

Materials and methods From 2016 to 2024, we retrospectively reviewed 24 patients with large midline NTSAM who underwent extensive tumor resection in our institution. The OCI was evaluated and compared between preoperative MRI and intraoperative findings. The OCI was classified as follows. Type 1 represented no invasion, type 2 represented secondary invasion, type 3 represented partial wall invasion (two subtypes), and type 4 represented invasion into the superior-medialinferior walls of the optic canal. Visual functions were assessed before and after surgery.

Results Among 24 patients, a mean tumor size of 57.2 mm (range 39.0–79.0). The OCI was observed intraoperatively in 22 cases (91.7%), with 19 cases exhibiting bilateral OCI. Among the 48 optic canals in the 24 patients, 18 (37.5%) were type 4, 12 (25.0%) were type 3-inferomedial, 9 (18.8%) were type 3-superomedial, and 2 (4.2%) were type 2, where 7 (14.6%) optic canals were without OCI. A significant correlation was observed between intraoperative OCI and the tumors that exhibited involvement of the tuberculum sellae (TS) on MRI (p < 0.001). For patients with visual impairment, the vision in 27 of 38 (71.1%) eye sides showed improvement following the surgery. There was 1 (4.2%) case of tumor recurrence at the mean follow-up time of 27.3 months (range 4–73 months).

Conclusions A high incidence of OCI was observed in the large midline NTSAM. The identification of TS involvement on MRI can serve as a strong predictor of OCI. Therefore, optic canal exploration to remove the optic canal invasion during the surgical removal of these particular tumors should be contemplated to attain radical tumor resection to enhance the possibility of improving visual function and reduce the risk of recurrence.

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Extended Long-Term Outcome After Conservative Decompressive Microsurgery and Routine Adjuvant Fractionated Stereotactic Radiotherapy for Symptomatic Cavernous Sinus Meningiomas

Neurosurgery 95:834–841, 2024

Cavernous sinus meningiomas (CSM) pose one of the most difficult to treat subgroup of skull base meningiomas. The purpose of this study was to evaluate the efficacy of an interdisciplinary treatment approach for symptomatic CSM which incorporated conservative function preserving microsurgery and routine adjuvant fractionated stereotactic radiotherapy (FSRT).

METHODS: A homogenous group of patients with symptomatic primary CSM with extracavernous extension was treated between 2005 and 2012. All patients were available for a minimum follow-up of 5 years. Clinical follow-up included detailed examination of oculomotor deficits, visual status, and endocrinologic function. Radiologic follow-up was conducted by tumor volumetry.

RESULTS: Overall, 23 patients were included in this study (78.3% women; median age 58 years). Diplopia was the most common presenting symptom, followed by headache and visual disturbances. Surgical morbidity was low (3/23; 13%). FSRT was applied after a median of 2 months after surgery. At a median clinical follow-up of 113 months, 70.45% of the presenting symptoms had improved, 25% remained unchanged, and in 2 cases (4.54%), worsening occurred. Overall tumor regression was evident in 19/21 World Health Organization 1 and in 1/2 of World Health Organization 2 CSM, respectively, at a median radiological follow-up of 103 months.

CONCLUSION: Our findings demonstrate the efficacy of an interdisciplinary treatment approach for symptomatic primary CSM with extracavernous extension with decompression of neurovascular elements followed by FSRT. Precise preoperative planning and intraoperative decision making in combination with routine postoperative radiotherapy can achieve excellent tumor control, improve neurologic function, and minimize long-term morbidity.

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Safe resection of a complex type 3 foramen magnum meningioma with dorsal displacement of the neurovascular bundle

Acta Neurochirurgica (2024) 166:376

We describe techniques for safe resection of a Type 3 foramen magnum meningioma with dorsal displacement of the accessory nerve rootlets and vertebral artery which limits ventral access to the tumor.

Method Partial sectioning of the accessory nerve rootlets may help create larger working space. Topical lidocaine placement on the rootlets of the spinal accessory nerve may mitigate trapezius muscle contraction and facilitates further progress throughout tumor resection.

Conclusion Creating safe working corridors between the lower cranial nerves through mobilization or partial sectioning of rootlets in the case of CN XI facilitates tumor resection through a far lateral approach.

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The complete anterior petrosectomy: an expanded extended-middle fossa approach with removal of the infratrigeminal petrous apex and drilling of the lateral clivus

J Neurosurg 141:195–203, 2024

Intradural exposure in the extended middle fossa anterior transpetrosal approach is traditionally limited to the inferior petrosal sinus inferomedially. Expanding bone removal of the petrous apex around the petrous internal carotid artery (ICA), underneath the trigeminal ganglion/mandibular nerve, and into the lateral component of the clivus can significantly expand the limits of this approach beyond the inferior petrosal sinus and allows for exposure of the midline structures, aspects of the contralateral inferior clival region, and, when high riding, the vertebrobasilar junction.

To date, no descriptive techniques for drilling into the lateral clivus in this approach have been published. The authors provide a detailed stepwise description of their complete anterior petrosectomy, in use at their institution, that involves skeletonization of the posteromedial petrous ICA, gentle elevation of the trigeminal ganglion/mandibular nerve, removal of the infratrigeminal petrous apex, and two techniques for drilling into the lateral clivus along the petroclival fissure.

These techniques provide a direct and unobstructed corridor to the midpetroclival region and ventral brainstem with greater maneuverability and enhanced control of the midline structures, which is especially useful for resection of petroclival meningiomas, chondrosarcomas, and giant vascular lesions of the mid- and upper basilar artery and its proximal branches.

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Pterional approach for tuberculum sellae meningiomas

J Neurosurg 140:1576–1583, 2024

Tuberculum sellae meningiomas (TSMs) are typically in the proximity of the optic nerves and the optic chiasm, thus making the primary aim of surgery the enhancement or stabilization of the patients’ visual acuity. The authors therefore undertook a retrospective review of their 17-year experience with the pterional approach to ascertain the resection rate, neurological outcome, and visual outcome.

METHODS Patients who underwent TSM surgery between September 2003 and December 2020 at the authors’ institution were retrospectively evaluated. Patient demographics, tumor characteristics, surgical parameters, postoperative visual outcomes, and complications were analyzed. Gross-total resection (GTR) and subtotal resection (STR) rates were assessed, along with the impact of surgical approach on visual outcomes.

RESULTS A total of 71 patients with a mean age of 56.9 ± 14.3 years were enrolled in the study. The mean tumor volume was 10.2 ± 12.8 cm 3 . Postoperatively, 38.7% of patients experienced visual improvement, 45.2% had stable visual acuity, and 16.1% showed visual deterioration. Ipsilateral or contralateral surgical approaches were performed based on the side of the most affected visual acuity. No significant difference in postoperative visual outcomes was observed between the two approaches. GTR was achieved in 84.0% and STR in 16.0%. Minor complications occurred in 3 patients (4.2%), while major complications were found in 4 patients (5.6%). Seven patients (9.8%) showed recurrent tumor growth after 53 months. Progression-free survival after GTR was 123.9 ± 12.9 months, and it was 59.3 ± 13.2 months after STR.

CONCLUSIONS This study highlighted the finding that TSMs can be successfully resected using a transcranial pterional approach with a low risk of complications and sufficient visual outcomes. Further studies with larger sample sizes are warranted to confirm these findings and optimize surgical strategies for TSM resection.

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Olfactory groove meningiomas: supraorbital keyhole versus orbitofrontal, frontotemporal, or bifrontal approaches

J Neurosurg 140:1568–1575, 2024

Olfactory groove meningiomas (OGMs) often require surgical removal. The introduction of recent keyhole approaches raises the question of whether these tumors may be better treated through a smaller cranial opening. One such approach, the supraorbital keyhole craniotomy, has never been compared with more traditional open transcranial approaches with regard to outcome. In this study, the authors compared clinical, radiographic, and functional quality of life (QOL) outcomes between the keyhole supraorbital approach (SOA) and traditional transcranial approach (TTA) for OGMs. They sought to examine the potential advantages and disadvantages of open/TTA versus keyhole SOA for the resection of OGMs in a relatively case-matched series of patients.

METHODS A retrospective, single-institution review of 57 patients undergoing a keyhole SOA or larger traditional transcranial (frontotemporal, pterional, or bifrontal) craniotomy for newly diagnosed OGMs between 2005 and 2023 was performed. Extent of resection, olfaction, length of stay (LOS), radiographic volumetric assessment of postoperative vasogenic and cytotoxic edema, and QOL (using the Anterior Skull Base Questionnaire) were assessed.

RESULTS Thirty-two SOA and 25 TTA patients were included. The mean EOR was not significantly different by approach (TTA: 99.1% vs SOA: 98.4%, p = 0.91). Olfaction was preserved or improved at similar rates (TTA: 47% vs SOA: 43%, p = 0.99). The mean LOS was significantly shorter for SOA patients (4.1 ± 2.8 days) than for TTA patients (9.4 ± 11.2 days) (p = 0.002). The authors found an association between an increase in postoperative FLAIR cerebral edema and TTA (p = 0.031). QOL as assessed by the ASQB at last follow-up did not differ significantly between groups (p = 0.74).

CONCLUSIONS The keyhole SOA was associated with a statistically significant decrease in LOS and less postoperative edema relative to traditional open approaches.

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Long-term tumor control in Koos grade IV vestibular schwannomas without the need for gross-total resection

J Neurosurg 140:1591–1604, 2024

The modern management of patients with Koos grade IV vestibular schwannomas (VSs) aims at functional preservation and long-term tumor control. Gross-total resection (GTR) leads to optimal tumor control but frequently also results in permanent facial nerve (FN) palsy. Subtotal resection (STR) or near-total resection (NTR) followed by a waitand-scan protocol and second-line radiation therapy (RT) in case of progressive residuals yields excellent tumor control rates with less permanent morbidity.

METHODS The authors present the results of their prospective cohort of Koos grade IV VS patients who underwent less-than-total resection followed by a wait-and-scan protocol between January 2009 and December 2019 and discuss the latest evidence on this controversial subject. The cohort was followed up with annual clinical and volumetric outcome analyses after standardized MRI.

RESULTS Forty-eight patients were included in the analysis. The mean extent of resection was 87% (median 91%, range 45%–100%), best fitting into the definition of STR rather than NTR. In 2 cases, the proximal portion of the FN at the brainstem could not be reliably identified and monitored during the initial operation, and a second-stage resection was necessary. At 4.4 years after surgery, 81% (39/48) of the tumor residuals regressed or were stable in size. The percentage of regressive tumor residuals increased over time. Nineteen percent (9/48) of the tumor residuals displayed volumetric progression within a mean time of 35 months (median 36 months, range 14–72 months), resulting in a Kaplan-Meier estimate for progression-free survival of 79% after 4 years; higher postoperative volume showed a linear correlation with higher volumetric progression (factor 1.96, 95% CI 1.67–2.30; p < 0.001). Thirty-four of the 48 (71%) patients continue to undergo a wait-and-scan protocol. Second-line RT was performed in 14 patients (29%) within a mean time of 25 months (median 23 months, range 5–54 months), 12 (86%) of whom responded with post-RT pseudoprogression, resulting in an overall tumor control rate of 96%. At the 4.4-year follow-up from the initial resection, 92% of the patients had a good facial outcome (House-Brackmann [HB] grade I or II), 6% had a fair facial outcome (HB grade III), and 2% had a poor facial outcome (HB grades IV–VI). So far, there has been no need for salvage surgery after RT.

CONCLUSIONS STR followed by observation and second-line RT in cases of progression leads to good facial outcome and an excellent tumor control rate in the longer term.

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Orbital reconstruction and volume in the correction of proptosis after resection of spheno-orbital meningiomas

J Neurosurg 140:1305–1311, 2024

The objective of this study was to evaluate the effect of reconstruction and orbital volume on the reduction of proptosis in patients undergoing resection for spheno-orbital meningiomas. Additionally, potential predictors of optimal proptosis reduction after surgery were evaluated.

METHODS Patients with spheno-orbital meningiomas who underwent resection at the authors’ institution between 2005 and 2020 were evaluated retrospectively. The exophthalmos index (EI) was measured on pre- and postoperative imaging to quantify proptosis and calculate the primary outcome measure of proptosis reduction. Patients were excluded if they had no preoperative proptosis (i.e., EI < 1.1), prior resection, or insufficient imaging available for analysis. Clinical and surgical characteristics were collected, including sex, extent of resection, WHO grade, and rigid orbital reconstruction, and assessed as predictors of greater proptosis reduction. Additionally, orbital volumes of the affected and contralateral orbits were measured to correlate postoperative orbital volumes with proptosis reduction.

RESULTS Thirty-three patients, with a mean age of 53 years, met inclusion criteria. The majority of the patients were female (23, 69.7%), and most tumors were classified as WHO grade 1 (29, 87.9%). Six patients (18.2%) underwent rigid orbital reconstruction. The mean EI across all patients decreased from 1.36 ± 0.18 to 1.19 ± 0.15 (p < 0.001). Patients who underwent reconstruction had on average a 76.4% greater reduction in the EI (p = 0.036) and a 9.1 times higher odds of achieving a normal EI (< 1.1) compared with those who did not receive reconstruction (OR 9.1, p = 0.025). Additionally, patients without residual hyperostotic bone compressing the orbit had a 2.16 times greater reduction in EI (p = 0.039). A linear relationship between orbital volume ratios (affected/unaffected orbit) and proptosis reduction was observed (p = 0.029, r = 0.529), including at ratios > 1.0. This suggests that greater orbital volumes postoperatively correlated with greater reductions in proptosis.

CONCLUSIONS Three factors were identified that optimize proptosis correction. First, all abnormal bone compressing the orbital contents must be removed completely. Second, rigid orbital reconstruction leads to improved proptosis correction, possibly by preventing frontal lobe and dural reconstruction from descending onto the compressed orbit. Third, aiming for an orbital volume slightly larger than the contralateral normal side leads to improved proptosis correction.

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Preservation of cranial nerve function in large and giant trigeminal schwannoma resection

Acta Neurochirurgica (2024) 166:198

Trigeminal schwannomas (TSs) are intracranial tumors that can cause significant brainstem compression. TS resection can be challenging because of the risk of new neurologic and cranial nerve deficits, especially with large (≥ 3 cm) or giant (≥ 4 cm) TSs. As prior surgical series include TSs of all sizes, we herein present our clinical experience treating large and giant TSs via microsurgical resection.

Methods This was a retrospective, single-surgeon case series of adult patients with large or giant TSs treated with microsurgery in 2012–2023.

Results Seven patients underwent microsurgical resection for TSs (1 large, 6 giant; 4 males; mean age 39 ± 14 years). Tumors were classified as type M (middle fossa in the interdural space; 1 case, 14%), type ME (middle fossa with extracranial extension; 3 cases, 43%), type MP (middle and posterior fossae; 2 cases, 29%), or type MPE (middle/posterior fossae and extracranial space; 1 case, 14%). Six patients were treated with a frontotemporal approach (combined with transmastoid craniotomy in the same sitting in one patient and a delayed transmaxillary approach in another), and one patient was treated using an orbitofrontotemporal approach. Gross total resection was achieved in 5 cases (2 near-total resections). Five patients had preoperative facial numbness, and 6 had immediate postoperative facial numbness, including two with worsened or new symptoms. Two patients (28%) demonstrated new non-trigeminal cranial nerve deficits over mean follow-up of 22 months. Overall, 80% of patients with preoperative facial numbness and 83% with facial numbness at any point experienced improvement or resolution during their postoperative course. All patients with preoperative or new postoperative non-trigeminal tumor-related cranial nerve deficits (4/4) experienced improvement or resolution on follow-up. One patient experienced tumor recurrence that has been managed conservatively.

Conclusions Microsurgical resection of large or giant TSs can be performed with low morbidity and excellent long-term cranial nerve function.

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Novel classification of foramen magnum meningiomas predicted by topographic position relative to neurovascular bundle

Acta Neurochirurgica (2024) 166:199

Proximity to critical neurovascular structures can create significant obstacles during surgical resection of foramen magnum meningiomas (FMMs) to the detriment of treatment outcomes. We propose a new classification that defines the tumor’s relationship to neurovascular structures and assess correlation with postoperative outcomes.

Methods In this retrospective review, 41 consecutive patients underwent primary resection of FMMs through a far lateral approach. Groups defined based on tumor-neurovascular bundle configuration included Type 1, bundle ventral to tumor; Type 2a-c, bundle superior, inferior, or splayed, respectively; Type 3, bundle dorsal; and Type 4, nerves and/or vertebral artery encased by tumor.

Results The 41 patients (range 29–81 years old) had maximal tumor diameter averaging 30.1 mm (range 12.7–56 mm). Preoperatively, 17 (41%) patients had cranial nerve (CN) dysfunction, 12 (29%) had motor weakness and/or myelopathy, and 9 (22%) had sensory deficits. Tumor type was relevant to surgical outcomes: specifically, Type 4 demonstrated lower rates of gross total resection (65%) and worse immediate postoperative CN outcomes. Long-term findings showed Types 2, 3, and 4 demonstrated higher rates of permanent cranial neuropathy. Although patients with Type 4 tumors had overall higher ICU and hospital length of stay, there was no difference in tumor configuration and rates of postoperative complications or 30-day readmission.

Conclusion The four main types of FMMs in this proposed classification reflected a gradual increase in surgical difficulty and worse outcomes. Further studies are warranted in larger cohorts to confirm its reliability in predicting postoperative outcomes and possibly directing management decisions.

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Anterior Petrosectomy With Intertentorial Approach

Operative Neurosurgery 26:301–308, 2024

The extradural anterior petrosal approach (EAPA) can present a challenge because it deals with critical structures in a narrow, confined corridor. It is associated with several potential approach-related risks including temporal lobe and venous injuries. Tentorial peeling has the potential to largely eliminate these risks during the approach and may offer more options for tailoring the dural opening to the anatomic region that one wants to expose.

METHODS: Anatomic dissections of five adult injected non–formalin-fixed cadaveric heads were performed. Anterior petrosectomy with intertentorial approach (APIA) through a tentorial peeling was completed. Step-by-step documentation of the cadaveric dissections and diagrammatic representations are presented along with an illustrative case.

RESULTS: Tentorial peeling separates the tentorium into a temporal tentorial leaf and posterior fossa tentorial leaf, adding a fourth dural layer to the three classic ones described during a standard EAPA. This opens out the intertentorial space and offers more options for tailoring the dural incisions specific to the pathology being treated. This represents a unique possibility to address brainstem or skull base pathology along the mid- and upper clivus with the ability to keep the entire temporal lobe and basal temporal veins covered by the temporal tentorial leaf. The APIA was successfully used for the resection of a large clival chordoma in the illustrative case.

CONCLUSION: APIA is an interesting modification to the classic EAPA to reduce the approach-related morbidity. The risk reduction achieved is by eliminating the exposure of the temporal lobe while maintaining the excellent access to the petroclival region. It also provides several options to tailor the durotomies based on the localization of the lesion.

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Far lateral approach for dumbbell‑shaped C1 schwannomas

Acta Neurochirurgica (2024) 166:78

Dumbbell-shaped C1 schwannomas are rare lesions that involve both intra- and extradural compartments. Because of the intimate relationships these lesions develop with the third and fourth segments of the vertebral artery, surgical removal of these lesions remains a challenge.

Method We describe the key steps of the far lateral approach for dumbbell-shaped C1 schwannomas with a video illustration. The surgical anatomy is described along with the techniques for protecting the vertebral artery.

Conclusion Dumbbell-shaped C1 schwannomas can be safely removed by using the far lateral approach, surgical anatomy expertise, and intraoperative microvascular Doppler.

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Subclassification of Koos grade 4 vestibular schwannoma: insights into tumor morphology for predicting postoperative facial nerve function

J Neurosurg 140:127–137, 2024

OBJECTIVE Koos grade 4 vestibular schwannoma (KG4VS) is a large tumor that causes brainstem displacement and is generally considered a candidate for surgery. Few studies have examined the relationship between morphological differences in KG4VS other than tumor size and postoperative facial nerve function. The authors have developed a landmark-based subclassification of KG4VS that provides insights into the morphology of this tumor and can predict the risk of facial nerve injury during microsurgery. The aims of this study were to morphologically verify the validity of this subclassification and to clarify the relationship of the position of the center of the vestibular schwannoma within the cerebellopontine angle (CPA) cistern on preoperative MR images to postoperative facial nerve function in patients who underwent microsurgical resection of a vestibular schwannoma.

METHODS In this paper, the authors classified KG4VSs into two subtypes according to the position of the center of the KG4VS within the CPA cistern relative to the perpendicular bisector of the porus acusticus internus, which was the landmark for the subclassification. KG4VSs with ventral centers to the landmark were classified as type 4V, and those with dorsal centers as type 4D. The clinical impact of this subclassification on short- and long-term postoperative facial nerve function was analyzed.

RESULTS In this study, the authors retrospectively reviewed patients with vestibular schwannoma who were treated surgically via a retrosigmoid approach between January 2010 and March 2020. Of the 107 patients with KG4VS who met the inclusion criteria, 45 (42.1%) were classified as having type 4V (KG4VSs with centers ventral to the perpendicular bisector of the porous acusticus internus) and 62 (57.9%) as having type 4D (those with centers dorsal to the perpendicular bisector). Ventral extension to the perpendicular bisector of the porus acusticus internus was significantly greater in the type 4V group than in the type 4D group (p < 0.001), although there was no significant difference in the maximal ventrodorsal diameter. The rate of preservation of favorable facial nerve function (House-Brackmann grades I and II) was significantly lower in the type 4V group than in the type 4D group in terms of both short-term (46.7% vs 85.5%, p < 0.001) and long-term (82.9% vs 96.7%, p = 0.001) outcomes. Type 4V had a significantly negative impact on short-term (OR 7.67, 95% CI 2.90–20.3; p < 0.001) and long-term (OR 6.05, 95% CI 1.04–35.0; p = 0.045) facial nerve function after surgery when age, tumor size, and presence of a fundal fluid cap were taken into account.

CONCLUSIONS The authors have delineated two different morphological subtypes of KG4VS. This subclassification could predict short- and long-term facial nerve function after microsurgical resection of KG4VS via the retrosigmoid approach. The risk of postoperative facial palsy when attempting total resection is greater for type 4V than for type 4D. This classification into types 4V and 4D could help to predict the risk of facial nerve injury and generate more individualized surgical strategies for KG4VSs with better facial nerve outcomes.

 

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Microsurgical management of midbrain gliomas: surgical results and long-term outcome in a large, single-surgeon, consecutive series

J Neurosurg 140:104–115, 2024

The authors report on a large, consecutive, single-surgeon series of patients undergoing microsurgical removal of midbrain gliomas. Emphasis is put on surgical indications, technique, and results as well as long-term oncological follow-up.

METHODS A retrospective analysis was performed of prospectively collected data from a consecutive series of patients undergoing microneurosurgery for midbrain gliomas from March 2006 through June 2022 at the authors’ institution. According to the growth pattern and location of the lesion in the midbrain (tegmentum, central mesencephalic structures, and tectum), one of the following approaches was chosen: transsylvian (TS), extreme anterior interhemispheric transcallosal (eAIT), posterior interhemispheric transtentorial subsplenial (PITS), paramedian supracerebellar transtentorial (PST), perimedian supracerebellar (PeS), perimedian contralateral supracerebellar (PeCS), and transuvulotonsillar fissure (TUTF). Clinical and radiological data were gathered according to a standard protocol and reported according to common descriptive statistics. The main outcomes were rate of gross-total resection; extent of resection; occurrence of any complications; variation in Karnofsky Performance Status score at discharge, 3 months, and last follow-up; progression-free survival (PFS); and overall survival (OS).

RESULTS Fifty-four patients (28 of them pediatric) met the inclusion criteria (6 with high-grade and 48 with low-grade gliomas [LGGs]). Twenty-two tumors were in the tegmentum, 7 in the central mesencephalic structures, and 25 in the tectum. In no instance did the glioma originate in the cerebral peduncle. TS was performed in 2 patients, eAIT in 6, PITS in 23, PST in 16, PeS in 4, PeCS in 1, and TUTF in 2 patients. Gross-total resection was achieved in 39 patients (72%). The average extent of resection was 98.0% (median 100%, range 82%–100%). There were no deaths due to surgery. Nine patients experienced transient and 2 patients experienced permanent new neurological deficits. At a mean follow-up of 72 months (median 62, range 3–193 months), 49 of the 54 patients were still alive. All patients with LGGs (48/54) were alive with no decrease in their KPS score, whereas 42 showed improvement compared with their preoperative status.

CONCLUSIONS Microneurosurgical removal of midbrain gliomas is feasible with good surgical results and long-term clinical outcomes, particularly in patients with LGGs. As such, microneurosurgery should be considered as the first therapeutic option. Adequate microsurgical technique and anesthesiological management, along with an accurate preoperative understanding of the tumor’s exact topographic origin and growth pattern, is crucial for a good surgical outcome.

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