Augmented reality–assisted microsurgical resection of brain arteriovenous malformations: illustrative case

Background: Arteriovenous malformations (AVMs) of the brain are vessel conglomerates of feeding arteries and draining veins that carry a risk of spontaneous and intraoperative rupture. Augmented reality (AR)-assisted neuronavigation permits continuous, real-time, updated visualization of navigation information through a heads-up display, thereby potentially improving the safety of surgical resection of AVMs. Observations: The authors report a case of a 37-year-old female presenting with a 2-year history of recurrent falls due to intermittent right-sided weakness and increasing clumsiness in the right upper extremity. Magnetic resonance imaging, magnetic resonance angiography, and cerebral angiography of the brain revealed a left parietal Spetzler-Martin grade III AVM. After endovascular embolization of the AVM, microsurgical resection using an AR-assisted neuronavigation system was performed. Postoperative angiography confirmed complete obliteration of arteriovenous shunting. The postsurgical course was unremarkable, and the patient remains in excellent health. Lessons: Our case describes the operative setup and intraoperative employment of AR-assisted neuronavigation for AVM resection. Application of this technology may improve workflow and enhance patient safety

Magnetic Resonance-Guided Laser Interstitial Thermal Therapy for Management of Low-Grade Gliomas and Radiation Necrosis: A Single-Institution Case Series

Background: Laser interstitial thermal therapy (LITT) has emerged as a minimally invasive treatment modality for ablation of low-grade glioma (LGG) and radiation necrosis (RN). Objective: To evaluate the efficacy, safety, and survival outcomes of patients with radiographically presumed recurrent or newly diagnosed LGG and RN treated with LITT. Methods: The neuro-oncological database of a quaternary center was reviewed for all patients who underwent LITT for management of LGG between 1 January 2013 and 31 December 2020. Clinical data including demographics, lesion characteristics, and clinical and radiographic outcomes were collected. Kaplan-Meier analyses comprised overall survival (OS) and progression-free survival (PFS). Results: Nine patients (7 men, 2 women; mean [SD] age 50 [16] years) were included. Patients underwent LITT at a mean (SD) of 11.6 (8.5) years after diagnosis. Two (22%) patients had new lesions on radiographic imaging without prior treatment. In the other 7 patients, all (78%) had surgical resection, 6 (67%) had intensity-modulated radiation therapy and chemotherapy, respectively, and 4 (44%) had stereotactic radiosurgery. Two (22%) patients had lesions that were wild-type IDH1 status. Volumetric assessment of preoperative T1-weighted contrast-enhancing and T2-weighted fluid-attenuated inversion recovery (FLAIR) sequences yielded mean (SD) lesion volumes of 4.1 (6.5) cm(3) and 26.7 (27.9) cm(3), respectively. Three (33%) patients had evidence of radiographic progression after LITT. The pooled median (IQR) PFS for the cohort was 52 (56) months, median (IQR) OS after diagnosis was 183 (72) months, and median (IQR) OS after LITT was 52 (60) months. At the time of the study, 2 (22%) patients were deceased. Conclusions: LITT is a safe and effective treatment option for management of LGG and RN, however, there may be increased risk of permanent complications with treatment of deep-seated subcortical lesions

CCR2 of Tumor Microenvironmental Cells Is a Relevant Modulator of Glioma Biology.

Glioblastoma multiforme (GBM) shows a high influx of tumor-associated macrophages (TAMs). The CCR2/CCL2 pathway is considered a relevant signal for the recruitment of TAMs and has been suggested as a therapeutic target in malignant gliomas. We found that TAMs of human GBM specimens and of a syngeneic glioma model express CCR2 to varying extents. Using a Ccr2-deficient strain for glioma inoculation revealed a 30% reduction of TAMs intratumorally. This diminished immune cell infiltration occurred with augmented tumor volumes likely based on increased cell proliferation. Remaining TAMs in Ccr2-/- mice showed comparable surface marker expression patterns in comparison to wildtype mice, but expression levels of inflammatory transcription factors (Stat3, Irf7, Cox2) and cytokines (Ifnβ, Il1β, Il12α) were considerably affected. Furthermore, we demonstrated an impact on blood vessel integrity, while vascularization of tumors appeared similar between mouse strains. The higher stability and attenuated leakiness of the tumor vasculature imply improved sustenance of glioma tissue in Ccr2-/- mice. Additionally, despite TAMs residing in the perivascular niche in Ccr2-/- mice, their pro-angiogenic activity was reduced by the downregulation of Vegf. In conclusion, lacking CCR2 solely on tumor microenvironmental cells leads to enhanced tumor progression, whereby high numbers of TAMs infiltrate gliomas independently of the CCR2/CCL2 signal

Magnetic Resonance-Guided Laser Interstitial Thermal Therapy for Management of Low-Grade Gliomas and Radiation Necrosis: A Single-Institution Case Series

Background: Laser interstitial thermal therapy (LITT) has emerged as a minimally invasive treatment modality for ablation of low-grade glioma (LGG) and radiation necrosis (RN). Objective: To evaluate the efficacy, safety, and survival outcomes of patients with radiographically presumed recurrent or newly diagnosed LGG and RN treated with LITT. Methods: The neuro-oncological database of a quaternary center was reviewed for all patients who underwent LITT for management of LGG between 1 January 2013 and 31 December 2020. Clinical data including demographics, lesion characteristics, and clinical and radiographic outcomes were collected. Kaplan–Meier analyses comprised overall survival (OS) and progression-free survival (PFS). Results: Nine patients (7 men, 2 women; mean [SD] age 50 [16] years) were included. Patients underwent LITT at a mean (SD) of 11.6 (8.5) years after diagnosis. Two (22%) patients had new lesions on radiographic imaging without prior treatment. In the other 7 patients, all (78%) had surgical resection, 6 (67%) had intensity-modulated radiation therapy and chemotherapy, respectively, and 4 (44%) had stereotactic radiosurgery. Two (22%) patients had lesions that were wild-type IDH1 status. Volumetric assessment of preoperative T1-weighted contrast-enhancing and T2-weighted fluid-attenuated inversion recovery (FLAIR) sequences yielded mean (SD) lesion volumes of 4.1 (6.5) cm3 and 26.7 (27.9) cm3, respectively. Three (33%) patients had evidence of radiographic progression after LITT. The pooled median (IQR) PFS for the cohort was 52 (56) months, median (IQR) OS after diagnosis was 183 (72) months, and median (IQR) OS after LITT was 52 (60) months. At the time of the study, 2 (22%) patients were deceased. Conclusions: LITT is a safe and effective treatment option for management of LGG and RN, however, there may be increased risk of permanent complications with treatment of deep-seated subcortical lesions

Resection of Quadrigeminal Midbrain Cavernous Malformation Using the Supracollicular Safe Entry Zone

Brainstem cavernous malformations (BSCMs) are rare and challenging neurosurgical lesions that demand a sophisticated and nuanced strategy for resection. A key element of surgical planning for BSCM resection is brainstem safe entry zones, a set of neuroanatomically defined locations where a pial resection can be executed with minimal risk to the adjacent central nervous system tracts and nuclei. Quadrigeminal BSCMs are particularly unusual and can be accessed via the supra-, inter-, or infracollicular safe entry zones. We report a unique demonstration of the supracollicular safe entry zone for the resection of a symptomatic hemorrhagic quadrigeminal plate BSCM. A man in his early 60s presented with transient hearing loss and visual dysfunction. A right quadrigeminal midbrain cavernous malformation was identified on magnetic resonance imaging. Surgical resection was performed with the patient in the sitting position. A bipedicular suboccipital flap, torcular craniotomy, and midline supracerebellar infratentorial approach were used. The lesion itself was accessed via the supracollicular safe entry zone, where pial hemosiderin staining was also encountered, using a linear transverse incision just above the right superior colliculus. Gross total resection was achieved, and the patient recovered from surgery with no new neurologic deficits (Video 1)

Thrombotic, dolichoectatic, distal PCA aneurysm treated with excision and P2-P2 reanastomosis

Posterior cerebral artery (PCA) aneurysms are rare and often optimally treated with clip reconstruction. Complex cases may require aneurysm excision with in situ reanatomosis. A woman in her early 40s presented with 2 weeks of severe headache and received a diagnosis of a thrombotic, dolichoectatic, distal right P2 aneurysm. Clip reconstruction was recommended. After providing consent, the patient underwent a right subtemporal approach. The P2 aneurysm was encountered in the ambient cistern. The aneurysm and its inflow and outflow arteries were isolated, and bleeding was controlled with temporary clips. Primary clip reconstruction was aborted due to a neck configuration that precluded preservation of the outflow vessels during primary clip reconstruction. The decision was made to excise the aneurysm and perform a P2-P2 end-to-end reanastomosis. After completion of the initial bypass, indocyanine green (ICG) videoangiography indicated bypass thrombosis, which was thought to be attributable to poor tissue quality from inadequate vessel trimming at the anastomosis site. We elected to excise the bypass, trim both P2 ends back to healthy tissue, and perform a repeat end-to-end P2-P2 reanastomosis, which ultimately resulted in successful revascularization with ICG confirmation. Postoperative angiography confirmed complete obliteration of the aneurysm with stable graft patency, and the patient remained intact at her neurologic baseline through last follow-up at 6 weeks after discharge from the hospital. This video demonstrates microsurgical nuances for deep end-to-end reanastomosis as well as intraoperative troubleshooting in the setting of a complex ruptured posterior circulation aneurysm. Used with permission from Barrow Neurological Institute, Phoenix, Arizona

Sphenoparietal Sinus Transposition: Operative Technique for Optimizing Pretemporal Posterior Circulation Access While Preserving the Sylvian Venous Complex

BACKGROUND: Transsylvian approaches are a cornerstone of complex cranial operations, with wide applicability across cerebrovascular, skull base, and neuro-oncology operations. Deep lesions, especially those involving the basilar apex, midbrain, or interpeduncular fossa, require wide exposures that may be inhibited by the presence of a large complex of superficial sylvian veins (SSV) draining into the sphenoparietal sinus. This report describes technical and clinical aspects of the sphenoparietal sinus transposition (SPST) technique. METHODS: Technical case report of the SPST technique, including a step-by-step neuroanatomic description, overview of common indications, clinical pearls and pitfalls, and illustrative case examples. RESULTS: Once the benefits of proceeding with SPST have been established, the maneuver is initiated with 2 stepwise dural incisions: an incision from lateral to medial along the lateral margin of the lesser sphenoid wing, followed by an orthogonal cut across the temporal pole down the middle fossa floor. The pretemporal dura is peeled off the lateral wall of the cavernous sinus, allowing mobilization of the SSV complex and temporal pole posteriorly without disrupting or straining the connection point at the sphenoparietal sinus. Illustrative case examples include a clip reconstruction of a basilar apex aneurysm for which earlier endovascular treatment had failed and microsurgical resection of a peduncular cavernous malformation. CONCLUSIONS: SPST is a simple but versatile technique with important applications in complex cranial surgery. By mobilizing the SSV complex together with its dural attachment, the transsylvian corridor can be markedly widened, allowing access to the basilar apex region and ventral midbrain

Genetics and Emerging Therapies for Brain Arteriovenous Malformations

Brain arteriovenous malformations (AVMs) are characterized by a high-pressure, low-resistance vascular nidus created by direct shunting of blood from feeding arteries into arterialized veins, bypassing intervening capillaries. AVMs pose a risk of spontaneous rupture because the vessel walls are continuously exposed to increased shear stress and abnormal flow phenomena, which lead to vessel wall inflammation and distinct morphologic changes. The annual rupture rate is estimated at 2%, and once an AVM ruptures, the risk of rerupture increases 5-fold. The ability of AVMs to grow, regress, recur, and undergo remodeling shows their dynamic nature. Identifying the underlying cellular and molecular pathways of AVMs not only helps us understand their natural physiology but also allows us to directly block vital pathways, thus preventing AVM development and progression. Management of AVMs is challenging and often necessitates a multidisciplinary approach, including neurosurgical, endovascular, and radiosurgical expertise. Because many of these procedures are invasive, carry a risk of inciting hemorrhage, or are controversial, the demand for pharmacologic treatment options is increasing. In this review, we introduce novel findings of cellular and molecular AVM physiology and highlight key signaling mediators that are potential targets for AVM treatment. Furthermore, we give an overview of syndromes associated with hereditary and nonhereditary AVM formation and discuss causative genetic alterations