Category: Surgical technique

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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: Surgical Outcomes and Management Trends

Neurosurgery 93:1259–1270, 2023

Tuberculum sellae meningiomas (TSMs) can be resected through transcranial (TCA) or expanded endonasal approach (EEA). The objective of this study was to report TSM management trends and outcomes in a large multicenter cohort.

METHODS: This is a 40-site retrospective study using standard statistical methods.

RESULTS: In 947 cases, TCA was used 66.4% and EEA 33.6%. The median maximum diameter was 2.5 cm for TCA and 2.1 cm for EEA (P < .0001). The median follow-up was 26 months. Gross total resection (GTR) was achieved in 70.2% and did not differ between EEA and TCA (P = .5395). Vision was the same or better in 87.5%. Vision improved in 73.0% of EEA patients with preoperative visual deficits compared with 57.1% of TCA patients (P < .0001). On multivariate analysis, a TCA (odds ratio [OR] 1.78, P = .0258) was associated with vision worsening, while GTR was protective (OR 0.37, P < .0001). GTR decreased with increased diameter (OR: 0.80 per cm, P = .0036) and preoperative visual deficits (OR 0.56, P = .0075). Mortality was 0.5%. Complications occurred in 23.9%. New unilateral or bilateral blindness occurred in 3.3% and 0.4%, respectively. The cerebrospinal fluid leak rate was 17.3% for EEA and 2.2% for TCA (OR 9.1, P < .0001). The recurrence rate was 10.9% (n= 103). Longer follow-up (OR 1.01 per month, P < .0001), World Health Organization II/III (OR 2.20, P = .0262), and GTR (OR: 0.33, P < .0001) were associated with recurrence. The recurrence rate after GTR was lower after EEA compared with TCA (OR 0.33, P = .0027).

CONCLUSION: EEA for appropriately selected TSM may lead to better visual outcomes and decreased recurrence rates after GTR, but cerebrospinal fluid leak rates are high, and longer follow-up is needed. Tumors were smaller in the EEA group, and follow-up was shorter, reflecting selection, and observation bias. Nevertheless, EEA may be superior to TCA for appropriately selected TSM.

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Scalp Incisions With Stairstep Pericranial Edges to Minimize Sequalae from Poor Wound Healing in Supratentorial Brain Tumor Surgery

Neurosurgery Practice 4:, 2023

Wound healing problems are especially prevalent in craniotomies for intra-axial brain tumors as patients often require radiation, chemotherapy, and chronic steroids. Although newer techniques such as minimally invasive approaches and routine vancomycin powder use have helped overall complication rates, poor skin healing remains a frustratingly persistent cause of morbidity. Therefore, here we describe the novel technique of elevating and closing a stairstep pericranial edge offset from the skin incision to protect hardware and support wound healing, and we report early outcomes using this technique.

METHODS: Ninety-one consecutive patients underwent supratentorial, intra-axial brain tumor surgery with a single surgeon at a single institution using this technique. Patient demographics, pathology, adjuvant interventions, and other independent risk factors were analyzed.

RESULTS: No wound-related complications requiring readmission, intravenous antibiotics, or reoperation were encountered at a median 3-month follow-up. There were also no surgical site infections, dehiscences, or cerebrospinal fluid leaks. Fifty-one patients (57.3%) had postoperative radiotherapy, 85 patients (93.4%) had perioperative steroids, and 56 patients (61.5%) had postoperative chemotherapy. Six patients (6.5%) were placed on a short course of oral antibiotics perioperatively due to concerns with initial scalp healing (ie, excessive scabbing at follow-up), none of whom progressed to infection or required further intervention. These are the cases where this technique is felt to have been most helpful by potentially preventing worse sequelae. One patient developed a shunt infection during this interval that required removal unrelated to the craniotomy site.

CONCLUSION: Here we outline in detail the principles, design, and execution of incisions and closures with stairstep pericranial edges in supratentorial brain surgery. This technique was designed in consultation with plastic surgeons to provide an intact, vascularized layer of pericranium beneath the healing skin and over the bone graft/hardware to optimize wound healing conditions and prevent morbid sequelae in inevitable cases of poor initial healing. Early results are promising.

KEY WORDS: Cerebrospinal fluid leak, Craniotomy, Resection, Surgical site infection, Surgical technique, Woundhealing

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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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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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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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Combined subtarsal contralateral transmaxillary retroeustachian and endoscopic endonasal approaches to the infrapetrous region

J Neurosurg 139:992–1001, 2023

The eustachian tube (ET) limits endoscopic endonasal access to the infrapetrous region. Transecting or mobilizing the ET may result in morbidities. This study presents a novel approach in which a subtarsal contralateral transmaxillary (ST-CTM) corridor is coupled with the standard endonasal approach to facilitate access behind the intact ET.

METHODS Eight cadaveric head specimens were dissected. Endoscopic endonasal approaches (EEAs) (i.e., transpterygoid and inferior transclival) were performed on one side, followed by ST-CTM and sublabial contralateral transmaxillary (SL-CTM) approaches on the opposite side, along with different ET mobilization techniques on the original side. Seven comparative groups were generated. The length of the cranial nerves, areas of exposure, and volume of surgical freedom (VSF) in the infrapetrous regions were measured and compared.

RESULTS Without ET mobilization, the combined ST-CTM/EEA approach provided greater exposure than EEA alone (mean ± SD 288.9 ± 40.66 mm 2 vs 91.7 ± 49.9 mm 2 ; p = 0.001). The VSFs at the ventral jugular foramen (JF), entrance to the petrous internal carotid artery (ICA), and lateral to the parapharyngeal ICA were also greater in ST-CTM/EEA than in EEA alone (p = 0.002, p = 0.002, and p < 0.001, respectively). EEA alone, however, provided greater VSF at the hypoglossal canal (HGC) than did ST-CTM/EEA (p = 0.01). The SL-CTM approach did not increase the EEA exposure (p = 0.48). The ST-CTM/EEA approach provided greater exposure than EEA with extended inferolateral (EIL) or anterolateral (AL) ET mobilization (p = 0.001 and p = 0.02, respectively). The ST-CTM/EEA also increased the VSF lateral to the parapharyngeal ICA in comparison with EEA/EIL ET mobilization (p < 0.001) but not with EEA/AL ET mobilization (p = 0.36). Finally, the VSFs at the HGC and JF were greater in EEA/AL ET mobilization than in ST-CTM/EEA without ET mobilization (p = 0.002 and p = 0.004, respectively).

CONCLUSIONS Combining the EEA with the more laterally and superiorly originating ST-CTM approach allows greater exposure of the infrapetrous and ventral JF regions while obviating the need for mobilizing the ET. The surgical freedom afforded by the combined approaches is greater than that obtained by EEA alone.

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Endoscopic odontoidectomy for brainstem compression in association with posterior fossa decompression and occipitocervical fusion

J Neurosurg 139:1152–1159, 2023

Endonasal endoscopic odontoidectomy (EEO) is an alternative to transoral surgery for symptomatic ventral compression of the anterior cervicomedullary junction (CMJ), allowing for earlier extubation and feeding. Because the procedure destabilizes the C1–2 ligamentous complex, posterior cervical fusion is often performed concomitantly. The authors’ institutional experience was reviewed to describe the indications, outcomes, and complications in a large series of EEO surgical procedures in which EEO was combined with posterior decompression and fusion.

METHODS A consecutive, prospective series of patients who underwent EEO between 2011 and 2021 was studied. Demographic and outcome metrics, radiographic parameters, extent of ventral compression, extent of dens removal, and increase in CSF space ventral to the brainstem were measured on the preoperative and postoperative scans (first and most recent scans).

RESULTS Forty-two patients (26.2% pediatric) underwent EEO: 78.6% had basilar invagination, and 76.2% had Chiari type I malformation. The mean ± SD age was 33.6 ± 3.0 years, with a mean follow-up of 32.3 ± 4.0 months. The majority of patients (95.2%) underwent posterior decompression and fusion immediately before EEO. Two patients underwent prior fusion. There were 7 intraoperative CSF leaks but no postoperative CSF leaks. The inferior limit of decompression fell between the nasoaxial and rhinopalatine lines. The mean ± SD vertical height of dens resection was 11.98 ± 0.45 mm, equivalent to a mean ± SD resection of 74.18% ± 2.56%. The mean increase in ventral CSF space immediately postoperatively was 1.68 ± 0.17 mm (p < 0.0001), which increased to 2.75 ± 0.23 mm (p < 0.0001) at the most recent follow-up (p < 0.0001). The median (range) length of stay was 5 (2–33) days. The median time to extubation was 0 (0–3) days. The median time to oral feeding (defined as, at minimum, toleration of a clear liquid diet) was 1 (0–3) day. Symptoms improved in 97.6% of patients. Complications were rare and mostly associated with the cervical fusion portion of the combined surgical procedures.

CONCLUSIONS EEO is safe and effective for achieving anterior CMJ decompression and is often accompanied by posterior cervical stabilization. Ventral decompression improves over time. EEO should be considered for patients with appropriate indications.

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Endoscopic odontoidectomy for brainstem compression in association with posterior fossa decompression and occipitocervical fusion

J Neurosurg 139:1152–1159, 2023

Endonasal endoscopic odontoidectomy (EEO) is an alternative to transoral surgery for symptomatic ventral compression of the anterior cervicomedullary junction (CMJ), allowing for earlier extubation and feeding. Because the procedure destabilizes the C1–2 ligamentous complex, posterior cervical fusion is often performed concomitantly. The authors’ institutional experience was reviewed to describe the indications, outcomes, and complications in a large series of EEO surgical procedures in which EEO was combined with posterior decompression and fusion.

METHODS A consecutive, prospective series of patients who underwent EEO between 2011 and 2021 was studied. Demographic and outcome metrics, radiographic parameters, extent of ventral compression, extent of dens removal, and increase in CSF space ventral to the brainstem were measured on the preoperative and postoperative scans (first and most recent scans).

RESULTS Forty-two patients (26.2% pediatric) underwent EEO: 78.6% had basilar invagination, and 76.2% had Chiari type I malformation. The mean ± SD age was 33.6 ± 3.0 years, with a mean follow-up of 32.3 ± 4.0 months. The majority of patients (95.2%) underwent posterior decompression and fusion immediately before EEO. Two patients underwent prior fusion. There were 7 intraoperative CSF leaks but no postoperative CSF leaks. The inferior limit of decompression fell between the nasoaxial and rhinopalatine lines. The mean ± SD vertical height of dens resection was 11.98 ± 0.45 mm, equivalent to a mean ± SD resection of 74.18% ± 2.56%. The mean increase in ventral CSF space immediately postoperatively was 1.68 ± 0.17 mm (p < 0.0001), which increased to 2.75 ± 0.23 mm (p < 0.0001) at the most recent follow-up (p < 0.0001). The median (range) length of stay was 5 (2–33) days. The median time to extubation was 0 (0–3) days. The median time to oral feeding (defined as, at minimum, toleration of a clear liquid diet) was 1 (0–3) day. Symptoms improved in 97.6% of patients. Complications were rare and mostly associated with the cervical fusion portion of the combined surgical procedures.

CONCLUSIONS EEO is safe and effective for achieving anterior CMJ decompression and is often accompanied by posterior cervical stabilization. Ventral decompression improves over time. EEO should be considered for patients with appropriate indications.

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Syringopleural shunt for refractory syringomyelia

Acta Neurochirurgica (2023) 165:3039–3043

Surgical treatment of syringomyelia isdirected at the reconstruction of the subarachnoid space and restoration normal cerebrospinal fluid flow. Direct intervention on the syrinx is a rescue procedure and should be offered to patients with refractory syringomyelia.

Methods We provide an overview on indications and technique of syringopleural shunt (SPS). The procedure involves the connection of syrinx with the pleural space using a lumboperitoneal shunt. The occurrence of a negative pressure inside the pleural compartment offers an appropriate gradient for drainage from the syrinx.

Conclusions The SPS allows for a safe and effective treatment of persistent syringomyelia when management of the underlying cause does not yield substantial improvement.

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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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One-Insertion Stereotactic Brain Biopsy Using In Vivo Optical Guidance

Operative Neurosurgery 25:176–182, 2023

Stereotactic neurosurgical brain biopsies are afflicted with risks of inconclusive results and hemorrhage. Such complications can necessitate repeated trajectories and prolong surgical time.

OBJECTIVE: To develop and introduce a 1-insertion stereotactic biopsy kit with direct intraoperative optical feedback and to evaluate its applicability in 3 clinical cases.

METHODS: An in-house forward-looking probe with optical fibers was designed to fit the outer cannula of a side-cutting biopsy kit. A small aperture was made at the tip of the outer cannula and the edges aligned with the optical probe inside. Stereotactic biopsies were performed using the Leksell Stereotactic System. Optical signals were measured in millimeter steps along the preplanned trajectory during the insertion. At the region with the highest 5-aminolevulinic acid (5-ALA)induced fluorescence, the probe was replaced by the inner cannula, and tissue samples were taken. The waiting time for pathology diagnosis was noted.

RESULTS: Measurements took 5 to 10 minutes, and the surgeon received direct visual feedback of intraoperative 5-ALA fluorescence, microcirculation, and tissue gray-whiteness. The 5-ALA fluorescence corroborated with the pathological findings which had waiting times of 45, 50, and 75 minutes. Because only 1 trajectory was required and the patient could be prepared for the end of surgery immediately after sampling, this shortened the total surgical time. CONCLUSION: A 1-insertion stereotactic biopsy procedure with real-time optical guidance has been presented and successfully evaluated in 3 clinical cases. The method can be modified for frameless navigation and thus has great potential to improve safety and diagnostic yield for both frameless and frame-based neurosurgical biopsy procedures.

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Minimally Invasive Dorsal Approach for the Treatment of Giant Presacral Schwannomas

Operative Neurosurgery 25:E66–E70, 2023

The treatment of giant presacral schwannomas is currently a grand challenge for neurosurgeons. Although these tumors are benign and do not infiltrate the surrounding tissues, it is difficult to choose the best surgical approach because they are surrounded by the pelvic organs and great vessels. There is no universally accepted approach to the surgical treatment because giant presacral schwannomas are rare in the population. The anterior approach through laparotomy is more often recommended in the literature. A dorsal approach that involves laminotomy and stabilization is also described in the literature. However, these approaches are rather traumatic for the patient and have both intraoperative and postoperative risks.

OBJECTIVE: To report a minimally invasive dorsal approach for the treatment of giant presacral schwannomas.

METHODS: We present a fundamentally new approach to the treatment of these tumors using a minimally invasive dorsal approach, based on the specific anatomy and growth of giant presacral schwannomas. This approach is using the potential of modern neurosurgery.

RESULTS: We describe 2 cases of successful total tumor resection using this novel surgical approach. No complications have been registered after the surgery.

CONCLUSION: A minimally invasive dorsal approach for the treatment of giant presacral schwannomas is sufficient for complete tumor removal, minimizes intraoperative and postoperative risks, is associated with good cosmetic effect, and can be successfully applied in surgical practice.

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Dynamic Lateral Semisitting Position for Supracerebellar Approaches

Operative Neurosurgery 25:103–111, 2023

It has always been a matter of debate which position is ideal for the supracerebellar approach. The risk of venous air embolism (VAE) is the major deterrent for surgeons and anesthesiologists, despite the fact that sitting and semisitting positions are commonly used in these operations.

OBJECTIVE: To demonstrate a reduction on the risk of VAE and tension pneumocephalus throughout the operation period while taking advantages of the semisitting position.

METHODS: In this study, 11 patients with various diagnoses were operated in our department using the supracerebellar approach in the dynamic lateral semisitting position. We used end-tidal carbon dioxide and arterial blood pressure monitoring to detect venous air embolism.

RESULTS: None of the patients had clinically significant VAE in this study. No tension pneumocephalus or major complications were observed. All the patients were extubated safely after surgery.

CONCLUSION: The ideal position, with which to apply the supracerebellar approach, is still a challenge. In our study, we presented an alternative position that has advantages of the sitting and semisitting positions with a lower risk of venous air embolism.

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The transfrontal isthmus approach for insular glioma surgery

J Neurosurg 139:20–28, 2023

The classic transopercular or transsylvian approach to insular gliomas removes the tumor laterally through the insular cortex. This study describes a new anteroposterior approach through the frontal isthmus for insular glioma surgery.

METHODS The authors detailed the surgical techniques for resection of insular gliomas through the transfrontal isthmus approach. Fifty-nine insular gliomas with at least Berger-Sanai zone I involvement were removed with the new approach, and extent of resection and postoperative neurological outcomes were assessed.

RESULTS Fifty-nine patients were enrolled in the study, including 35 men and 24 women, with a mean (range) age 44.3 (19–75) years. According to the Berger-Sanai classification system, the most common tumor was a giant glioma (67.8%), followed by involvement of zones I and IV (18.6%). Twenty-two cases were Yaşargil type 3A/B, and 37 cases were Yaşargil type 5A/B. The average angle between the lateral plane of the putamen and sagittal line was 33.53°, and the average width of the isthmus near the anterior insular point was 33.33 mm. The average angle between the lateral plane of the putamen and the sagittal line was positively correlated with the width of the isthmus near the anterior insular point (r = 0.935, p < 0.0001). The median (interquartile range [IQR]) preoperative tumor volume was 67.82 (57.64–92.19) cm 3 . Of 39 low-grade gliomas, 26 (66.67%) were totally resected; of 20 high-grade gliomas, 19 (95%) were totally resected. The median (IQR) extent of resection of the whole group was 100% (73.7%–100%). Intraoperative diffusion-weighted imaging showed no cases of middle cerebral artery– or lenticulostriate artery–related stroke. Extent of insular tumor resection was positively correlated with the angle of the lateral plane of the putamen and sagittal line (r = −0.329, p = 0.011) and the width of the isthmus near the anterior insular point (r = −0.267, p = 0.041). At 3 months postoperatively, muscle strength grade exceeded 4 in all cases, and all patients exhibited essentially normal speech. The median (IQR) Karnofsky performance score at 3 months after surgery was 90 (80–90).

CONCLUSIONS The transfrontal isthmus approach changes the working angle from lateral-medial to anterior-posterior, allowing for maximal safe removal of insular gliomas.

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The value of intraoperative indocyanine green angiography in microvascular decompression for hemifacial spasm to avoid brainstem ischemia

Acta Neurochirurgica (2023) 165:747–755

Despite being rarely reported, ischemic insults resulting from compromising small brainstem perforators following microvascular decompression (MVD) remain a potential devastating complication. To avoid this complication, we have been using indocyanine green (ICG) angiography intraoperatively to check the flow within the small brainstem perforators. We aim to evaluate the safety and usefulness of ICG videoangiography in MVD.

Methods We extracted retrospective data of patients who received ICG videoangiography from our prospectively maintained database for microvascular decompression. We noted relevant data including demographics, offending vessels, operative technique, outcome, and complications.

Results Out of the 438 patients, 15 patients with a mean age (SD) of 53 ± 10.5 years underwent intraoperative ICG angiography. Male:female was 1:1.14. The mean disease duration prior to surgery was 7.7 ± 5.3 years. The mean follow-up (SD) was 50.7 ± 42.0 months. In 14 patients, the offending vessel was an artery, and in one patient, a vein. Intraoperative readjustment of the Teflon pledget or sling was required in 20% (3/15) of the cases. No patient had any sort of brainstem ischemia. Eighty percent of the patients (12/15) experienced complete resolution of the spasms. 86.7% (13/15) of the patients reported a satisfactory outcome with marked improvement of the spasms. Three patients experienced slight hearing affection after surgery, which improved in two patients later. There was no facial or lower cranial nerve affection.

Conclusion Intraoperative ICG is a safe tool for evaluating the flow within the brain stem perforators and avoiding brainstem ischemia in MVD for hemifacial spasm.

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A system of anatomical triangles defining dissection routes to brainstem cavernous malformations

J Neurosurg 138:768–784, 2023

Anatomical triangles defined by intersecting neurovascular structures delineate surgical routes to pathological targets and guide neurosurgeons during dissection steps. Collections or systems of anatomical triangles have been integrated into skull base surgery to help surgeons navigate complex regions such as the cavernous sinus. The authors present a system of triangles specifically intended for resection of brainstem cavernous malformations (BSCMs). This system of triangles is complementary to the authors’ BSCM taxonomy that defines dissection routes to these lesions.

METHODS The anatomical triangle through which a BSCM was resected microsurgically was determined for the patients treated during a 23-year period who had both brain MRI and intraoperative photographs or videos available for review.

RESULTS Of 183 patients who met the inclusion criteria, 50 had midbrain lesions (27%), 102 had pontine lesions (56%), and 31 had medullary lesions (17%). The craniotomies used to resect these BSCMs included the extended retrosigmoid (66 [36.1%]), midline suboccipital (46 [25.1%]), far lateral (30 [16.4%]), pterional/orbitozygomatic (17 [9.3%]), torcular (8 [4.4%]), and lateral suboccipital (8 [4.4%]) approaches. The anatomical triangles through which the BSCMs were most frequently resected were the interlobular (37 [20.2%]), vallecular (32 [17.5%]), vagoaccessory (30 [16.4%]), supracerebellar-infratrochlear (16 [8.7%]), subtonsillar (14 [7.7%]), oculomotor-tentorial (11 [6.0%]), infragalenic (8 [4.4%]), and supracerebellar-supratrochlear (8 [4.4%]) triangles. New but infrequently used triangles included the vertebrobasilar junctional (1 [0.5%]), supratrigeminal (3 [1.6%]), and infratrigeminal (5 [2.7%]) triangles. Overall, 15 BSCM subtypes were exposed through 6 craniotomies, and the approach was redirected to the BSCM by one of the 14 triangles paired with the BSCM subtype.

CONCLUSIONS A system of BSCM triangles, including 9 newly defined triangles, was introduced to guide dissection to these lesions. The use of an anatomical triangle better defines the pathway taken through the craniotomy to the lesion and refines the conceptualization of surgical approaches. The triangle concept and the BSCM triangle system increase the precision of dissection through subarachnoid corridors, enhance microsurgical execution, and potentially improve patient outcomes.

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