Category: skull base surgery

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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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Does tumoral cavernous carotid stenosis predict an increased risk of future stroke in skull base meningiomas?

J Neurosurg 139:1613–1618, 2023

Skull base meningiomas (SBMs) involving the cavernous sinus encase the internal carotid artery (ICA) and may lead to stenosis of the vessel. Although ischemic stroke has been reported in the literature, there are to the authors’ knowledge no reported studies quantifying the risk of stroke in these patients. The authors aimed to determine the frequency of arterial stenosis in patients with SBMs that encase the cavernous ICA and to estimate the risk of ischemic stroke in these patients.

METHODS Records of all patients with SBM encasing the ICA whose cases were managed by the skull base multidisciplinary team at Salford Royal Hospital between 2011 and 2017 were reviewed using a two-stage approach: 1) clinical and radiological strokes were identified from electronic patient records, and 2) cases were reviewed to examine the correlation between ICA stenosis associated with SBM encasement and anatomically related stroke. Strokes that were caused by another pathology or did not occur in the perfusion territory were excluded.

RESULTS In the review of patient records the authors identified 118 patients with SBMs encasing the ICA. Of these, 62 SBMs caused stenosis. The median age at diagnosis was 70 (IQR 24) years, and 70% of the patients were female. The median follow-up was 97 (IQR 101) months. A total of 13 strokes were identified in these patients; however, only 1 case of stroke was associated with SBM encasement, which occurred in the perfusion territory of a patient without stenosis. Risk of acute stroke during the follow-up period for the entire cohort was 0.85%.

CONCLUSIONS Acute stroke in patients with ICA encasement by SBMs is rare despite the propensity of these tumors to stenose the ICA. Patients with ICA stenosis secondary to their SBM did not have a higher incidence of stroke than those with ICA encasement without stenosis. The results of this study demonstrate that prophylactic intervention to prevent stroke is not necessary in ICA stenosis secondary to SBM.

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International Tuberculum Sellae Meningioma Study: Preoperative Grading Scale to Predict Outcomes and Propensity-Matched Outcomes by Endonasal Versus Transcranial Approach

Neurosurgery 93:1271–1284, 2023

Tuberculum sellae meningiomas are resected via an expanded endonasal (EEA) or transcranial approach (TCA). Which approach provides superior outcomes is debated. The Magill–McDermott (M-M) grading scale evaluating tumor size, optic canal invasion, and arterial involvement remains to be validated for outcome prediction. The objective of this study was to validate the M-M scale for predicting visual outcome, extent of resection (EOR), and recurrence, and to use propensity matching by M-M scale to determine whether visual outcome, EOR, or recurrence differ between EEA and TCA.

METHODS: Forty-site retrospective study of 947 patients undergoing tuberculum sellae meningiomas resection. Standard statistical methods and propensity matching were used.

RESULTS: The M-M scale predicted visual worsening (odds ratio [OR]/point: 1.22, 95% CI: 1.02-1.46, P = .0271) and gross total resection (GTR) (OR/point: 0.71, 95% CI: 0.62-0.81, P < .0001), but not recurrence (P = .4695). The scale was simplified and validated in an independent cohort for predicting visual worsening (OR/point: 2.34, 95% CI: 1.33-4.14, P = .0032) and GTR (OR/point: 0.73, 95% CI: 0.57-0.93, P = .0127), but not recurrence (P = .2572). In propensity-matched samples, there was no difference in visual worsening (P = .8757) or recurrence (P = .5678) between TCA and EEA, but GTR was more likely with TCA (OR: 1.49, 95% CI: 1.02-2.18, P = .0409). Matched patients with preoperative visual deficits who had an EEA were more likely to have visual improvement than those undergoing TCA (72.9% vs 58.4%, P = .0010) with equal rates of visual worsening (EEA 8.0% vs TCA 8.6%, P = .8018).

CONCLUSION: The refined M-M scale predicts visual worsening and EOR preoperatively. Preoperative visual deficits are more likely to improve after EEA; however, individual tumor features must be considered during nuanced approach selection by experienced neurosurgeons.

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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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Endoscopic far‑lateral supracerebellar infratentorial approach for resection of dumbbell‑shaped trigeminal schwannoma

Acta Neurochirurgica (2023) 165:2913–2921

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

Objective We describe the technique of the purely endoscopic far-lateral supracerebellar infratentorial approach (EFLSCITA) for removing dumbbell-shaped TSs and further discuss the feasibility of this approach and our experience. Methods EFL-SCITA was performed for resection of 5 TSs between January 2020 and March 2023. The entire procedure was performed endoscopically with the goal of total tumor resection. During the operation, the tumor was exposed in close proximity and multiple angles under the endoscope, and the peri-tumor nerves were carefully identified and protected, especially the normal trigeminal fiber bundles around the tumor.

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

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

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Extradural disconnection of the cavernous sinus with preservation of the internal carotid artery: indication and technique

Acta Neurochirurgica (2023) 165:2951–2956

Extradural disconnection of the cavernous sinus (CS) with preservation of the internal carotid artery (ICA) is indicated for aggressive and recurrent tumors, in patients presenting loss of oculomotor function and non-functional circle of Willis.

Method Extradural resection of the anterior clinoid process disconnects the CS anteriorly. The ICA is dissected in the foramen lacerum via extradural subtemporal approach. The intracavernous tumor is split and removed following the ICA. Bleeding control of the inferior and superior petrosal and intercavernous sinuses completes posterior CS disconnection.

Conclusion This technique can be proposed for recurrent CS tumors and need of ICA preservation.

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A proposed classification system for presigmoid approaches: a scoping review

J Neurosurg 139:965–971, 2023

The “presigmoid corridor” covers a spectrum of approaches using the petrous temporal bone either as a target in treating intracanalicular lesions or as a route to access the internal auditory canal (IAC), jugular foramen, or brainstem. Complex presigmoid approaches have been continuously developed and refined over the years, leading to great heterogeneity in their definitions and descriptions. Owing to the common use of the presigmoid corridor in lateral skull base surgery, a simple anatomy-based and self-explanatory classification is needed to delineate the operative perspective of the different variants of the presigmoid route. Herein, the authors conducted a scoping review of the literature with the aim of proposing a classification system for presigmoid approaches.

METHODS The PubMed, EMBASE, Scopus, and Web of Science databases were searched from inception to December 9, 2022, following the PRISMA Extension for Scoping Reviews guidelines to include clinical studies reporting the use of “stand-alone” presigmoid approaches. Findings were summarized based on the anatomical corridor, trajectory, and target lesions to classify the different variants of the presigmoid approach.

RESULTS Ninety-nine clinical studies were included for analysis, and the most common target lesions were vestibular schwannomas (60/99, 60.6%) and petroclival meningiomas (12/99, 12.1%). All approaches had a common entry pathway (i.e., mastoidectomy) but were differentiated into two main categories based on their relationship to the labyrinth: translabyrinthine or anterior corridor (80/99, 80.8%) and retrolabyrinthine or posterior corridor (20/99, 20.2%). The anterior corridor comprised 5 variations based on the extent of bone resection: 1) partial translabyrinthine (5/99, 5.1%), 2) transcrusal (2/99, 2.0%), 3) translabyrinthine proper (61/99, 61.6%), 4) transotic (5/99, 5.1%), and 5) transcochlear (17/99, 17.2%). The posterior corridor consisted of 4 variations based on the target area and trajectory in relation to the IAC: 6) retrolabyrinthine inframeatal (6/99, 6.1%), 7) retrolabyrinthine transmeatal (19/99, 19.2%), 8) retrolabyrinthine suprameatal (1/99, 1.0%), and 9) retrolabyrinthine trans-Trautman’s triangle (2/99, 2.0%).

CONCLUSIONS Presigmoid approaches are becoming increasingly complex with the expansion of minimally invasive techniques. Descriptions of these approaches using the existing nomenclature can be imprecise or confusing. Therefore, the authors propose a comprehensive classification based on the operative anatomy that unequivocally describes presigmoid approaches simply, precisely, and efficiently.

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Simplified anterior transpetrosal approach without superior petrosal sinus and tentorial incision for lesions centered in Meckel’s cave

Acta Neurochirurgica (2023) 165:1833–1839

The anterior transpetrosal approach (ATPA) is an effective method to reach lesions in the petroclival region. This approach involves many steps, including superior petrosal sinus (SPS) ligation and tentorial cutting. It is sometimes unnecessary to perform all procedures in the ATPA for certain lesions, especially those centered in the Meckel’s cave. Here, we present a simplified anterior transpetrosal approach (SATPA) without superior petrosal sinus and tentorial incision for lesions centered in the Meckel’s cave as a modified ATPA.

Methods This study included 13 patients treated with SATPA. The initial steps of SATPA are similar to ATPA, excluding a middle cranial fossa dural incision, SPS dissection, or tentorial incision. Histological examination was performed to understand the membrane structure of the trigeminal nerve, which runs through the Meckel’s cave.

Results Pathology revealed trigeminal schwannoma (n=11), extraventricular central neurocytoma (n=1), and a metastatic tumor (n=1). The average tumor size was 2.4 cm. The total removal rate was 76.9% (10/13). Permanent complications included trigeminal neuropathy in four cases and cerebrospinal fluid leakage in one case. Histological examination revealed the trigeminal nerve traverses the subarachnoid space from the posterior fossa subdural space to the Meckel’s cave and is covered with the epineurium in the inner reticular layer.

Conclusions We used SATPA for lesions located in the Meckel’s cave identified using histological examination. This approach may be considered for small- to medium-sized lesions centered in the Meckel space.

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