Microsurgical Resection of Brainstem Cavernous Malformations in Older Adults: A Multicenter, 30-Year Experience.

BACKGROUND AND OBJECTIVES: Microsurgical resection is the only curative intervention for symptomatic brainstem cavernous malformations (BSCMs), but the management of these lesions in older adults (≥65 years) is not well described. This study sought to address this gap by examining the safety and efficacy of BSCM resection in a cohort of older adults. METHODS: Records of patients who underwent BSCM resection over a 30-year period were reviewed retrospectively. Baseline characteristics and outcomes were compared between older (≥65 years) and younger (<65 years) patients. RESULTS: Of 550 patients with BSCM who met inclusion criteria, 41 (7.5%) were older than 65 years. Midbrain (43.9% vs 26.1%) and medullary lesions (19.5% vs 13.6%) were more common in the older cohort than in the younger cohort ( P = .01). Components of the Lawton BSCM grading system (ie, lesion size, crossing axial midpoint, developmental venous anomaly, and timing of hemorrhage) were not significantly different between cohorts ( P ≥ .11). Mean (SD) Elixhauser comorbidity score was significantly higher in older patients (1.86 [1.06]) than in younger patients (0.66 [0.95]; P < .001). Older patients were significantly more likely than younger patients to have poor outcomes at final follow-up (28.9% vs 13.8%, P = .01; mean follow-up duration, 28.7 [39.1] months). However, regarding relative neurological outcome (preoperative modified Rankin Scale to final modified Rankin Scale), rate of worsening was not significantly different between older and younger patients (23.7% vs 14.9%, P = .15). CONCLUSION: BSCMs can be safely resected in older patients, and when each patient's unique health status and life expectancy are taken into account, these patients can have outcomes similar to younger patients.

Eloquent noneloquence: redefinition of cortical eloquence based on outcomes of superficial cerebral cavernous malformation resection.

OBJECTIVE: Cerebral cavernous malformations (CMs) are pathological lesions that cause discrete cortical disruption with hemorrhage, and their transcortical resections can cause additional iatrogenic disruption. The analysis of microsurgically treated CMs might identify areas of "eloquent noneloquence," or cortex that is associated with unexpected deficits when injured or transgressed. METHODS: Patients from a consecutive microsurgical series of superficial cerebral CMs who presented to the authors' center over a 13-year period were retrospectively analyzed. Neurological outcomes were measured using the modified Rankin Scale (mRS), and new, permanent neurological or cognitive symptoms not detected by changes in mRS scores were measured as additional functional decline. Patients with multiple lesions and surgical encounters for different lesions within the study interval were represented within the cohort as multiple patient entries. Virtual object models for CMs and approach trajectories to subcortical lesions were merged into a template brain model for subtyping and Quicktome connectomic analyses. Parcellation outputs from the models were analyzed for regional cerebral clustering. RESULTS: Overall, 362 CMs were resected in 346 patients, and convexity subtypes were the most common (132/362, 36.5%). Relative to the preoperative mRS score, 327 of 362 cases (90.3%) were in patients who improved or remained stable, 35 (9.7%) were in patients whose conditions worsened, and 47 (13.0%) were in patients who had additional functional decline. Machine learning analyses of lesion objects and trajectory cylinder mapping identified 7 hotspots of novel eloquence: supplementary motor area (bilateral), anterior cingulate cortex (bilateral), posterior cingulate cortex (bilateral), anterior insula (left), frontal pole (right), mesial temporal lobe (left), and occipital cortex (right). CONCLUSIONS: Transgyral and transsulcal resections that circumvent areas of traditional eloquence and navigate areas of presumed noneloquence may nonetheless result in unfavorable outcomes, demonstrating that brain long considered by neurosurgeons to be noneloquent may be eloquent. Eloquent hotspots within multiple large-scale networks redefine the neurosurgical concept of eloquence and call for more refined dissection techniques that maximize transsulcal dissection, intracapsular resection, and tissue preservation. Human connectomics, awareness of brain networks, and prioritization of cognitive outcomes require that we update our concept of cortical eloquence and incorporate this information into our surgical strategies.

Early Treatment of Ruptured Cerebral Arteriovenous Malformations: Analysis of Neurological Outcomes and Health Care Costs.

BACKGROUND: The timing of surgical resection is controversial when managing ruptured arteriovenous malformations (AVMs) and varies considerably among centers. OBJECTIVE: To retrospectively analyze clinical outcomes and hospital costs associated with delayed treatment in a ruptured cerebral AVM patient cohort. METHODS: Patients undergoing surgical treatment for a ruptured cerebral AVM (January 1, 2015-December 31, 2020) were retrospectively analyzed. Patients who underwent emergent treatment of a ruptured AVM because of acute herniation were excluded, as were those treated >180 days after rupture. Patients were stratified by the timing of surgical intervention relative to AVM rupture into early (postbleed days 1-20) and delayed (postbleed days 21-180) treatment cohorts. RESULTS: Eighty-seven patients were identified. The early treatment cohort comprised 75 (86%) patients. The mean (SD) length of time between AVM rupture and surgical resection was 5 (5) days in the early cohort and 73 (60) days in the delayed cohort ( P < .001). The cohorts did not differ with respect to patient demographics, AVM size, Spetzler-Martin grade, frequency of preoperative embolization, or severity of clinical presentation ( P ≥ .15). Follow-up neurological status was equivalent between the cohorts ( P = .65). The associated mean health care costs were higher in the delayed treatment cohort ($241 597 [$99 363]) than in the early treatment cohort ($133 989 [$110 947]) ( P = .02). After adjustment for length of stay, each day of delayed treatment increased cost by a mean of $2465 (95% CI = $967-$3964, P = .002). CONCLUSION: Early treatment of ruptured AVMs was associated with significantly lower health care costs than delayed treatment, but surgical and neurological outcomes were equivalent.

A taxonomy for deep cerebral cavernous malformations: subtypes of basal ganglia lesions.

OBJECTIVE: Anatomical taxonomy is a practical tool that has successfully guided clinical decision-making for patients with brain arteriovenous malformations and brainstem cavernous malformations (CMs). Deep CMs are similarly complex lesions that are difficult to access and highly variable in size, shape, and position. The authors propose a novel taxonomy for deep CMs in the basal ganglia based on clinical presentation (syndromes) and anatomical location. METHODS: The taxonomy system was developed and applied to an extensive 2-surgeon experience over 19 years (2001-2019). Lesions involving the basal ganglia were identified and subtyped on the basis of the predominant superficial presentation identified on preoperative MRI. Three subtypes of basal ganglia CMs were defined: caudate (31, 57%), putaminal (16, 30%), and pallidal (7, 13%). Neurological outcomes were assessed using the modified Rankin Scale (mRS). Postoperative mRS scores ≤ 2 were defined as a favorable outcome, and scores > 2 were defined as a poor outcome. Clinical and surgical characteristics and neurological outcomes were compared among subtypes. RESULTS: Fifty-four basal ganglia lesions were identified in 54 patients. Each basal ganglia CM subtype was associated with a recognizable constellation of neurological symptoms. The most common symptoms at presentation were severe or worsening headaches (25, 43%), mild hemiparesis (13, 24%), seizures (7, 13%), and dysmetria or ataxia (6, 11%). Patients with caudate CMs were the most likely to present with headaches and constitutional symptoms. Patients with putaminal CMs were the most likely to present with hemibody sensory deficits and dysmetria or ataxia. Patients with pallidal CMs were the most likely to present with mild hemiparesis and visual field deficits. A single surgical approach was preferred (> 80% of cases) for each basal ganglia subtype: caudate (contralateral transcallosal-transventricular, 28/31, 90%), putaminal (transsylvian-anterior transinsular, 13/16, 81%), and pallidal (transsylvian supracarotid-infrafrontal, 7/7, 100%). Most patients with follow-up had stable or improved mRS scores postoperatively (94%, 44/47); mRS scores of > 2 at final follow-up did not differ among the 3 basal ganglia subtypes. CONCLUSIONS: The study confirms the authors' hypothesis that this taxonomy for basal ganglia CMs meaningfully guides the selection of surgical approach and resection strategy. Furthermore, the proposed taxonomy can increase the diagnostic acumen at the patient bedside, help identify optimal surgical approaches, enhance the consistency of clinical communications and publications, and improve patient outcomes.

Expanding the reach of the trans-middle cerebellar peduncle approach: pontine cavernous malformations, tissue transgression beyond the safe entry zone, and the invisible triangle.

OBJECTIVE: In the authors' microsurgical experience, the trans-middle cerebellar peduncle (MCP) approach to the lateral and central pons has been the most common approach to brainstem cavernous malformations (BSCMs). This approach through a well-tolerated safe entry zone (SEZ) allows a wide vertical or posterior trajectory, reaching pontine lesions extending into the midbrain, medulla, and pontine tegmentum. Better understanding of the relationships among lesion location, surgical trajectory, and long-term clinical outcomes could determine areas of safe passage. METHODS: A single-surgeon cohort study of all primary trans-MCP BSCM resections was conducted from July 1, 2017, to June 30, 2021. Preoperative and postoperative MR images were independently reviewed by 3 investigators blinded to the intervention, using a standardized rubric to define BSCM regions of interest (ROIs) involved with a lesion or microsurgical tract. Statistical testing, including the chi-square test with the Bonferroni correction, logistic regression, and structural equation modeling, was performed to analyze relationships between ROIs and clinical outcomes. RESULTS: Thirty-one patients underwent primary trans-MCP BSCM resection during the study period. The median age was 50 years (IQR 24-49 years); 19 (61%) patients were female, and 12 (39%) were male. Seven (23%) patients had familial cavernous malformation syndromes. The median follow-up was 9 months (range 6-37 months). At the last follow-up, composite neurological outcomes were favorable: 22 (71%) patients had 0 (n = 12, 39%) or 1 (n = 10, 32%) major persistent deficit, 5 patients (16%) had 2 deficits, 2 (7%) had 3 deficits, and 1 patient each (3%) had 4 or 6 deficits. Unfavorable composite outcomes were significantly associated with lesions (OR 7.14, p = 0.04) or surgical tracts (OR 12.18, p < 0.001) extending from the superior cerebellar peduncle (SCP) into the contralateral medial midbrain. The ipsilateral dorsal pons was the most frequently implicated ROI involving a surgical tract and the development of new postoperative deficits. This region involved the rhomboid pontine territory and transgression of the pontine tegmentum (OR 7.53, p < 0.001). Structural equation modeling supported medial midbrain and pontine tegmentum transgression as the primary drivers of morbidity. CONCLUSIONS: Trans-MCP resection is a safe and effective treatment for BSCMs, including lesions with marked superior or inferior ipsilateral extension. Two trajectories are associated with increased neurological risk: first, a superomedial trajectory to lesions extending into the midbrain that transgresses the SCP, its decussation, or both; and second, a posteromedial trajectory to lesions extending into the pontine tegmentum. The corticospinal tract, SCP, and pontine tegmentum form an invisible triangle within the pontine white matter tolerant of transgression. When the surgeon works within this triangle, most deep pontine BSCMs, including large lesions, those with contralateral or posterior extension, and others extending into the midbrain and medulla, can be resected safely with the trans-MCP approach.

Radiation-Induced Cerebral Cavernous Malformations: A Single-Center Experience and Systematic Literature Review.

OBJECTIVE: Radiation was first demonstrated to be associated with cavernomagenesis in 1992. Since then, a growing body of literature has shown the unique course and presentation of radiation-induced cavernous malformations (RICMs). This study summarizes the literature on RICMs and presents a single-center experience. METHODS: A prospectively maintained single institution vascular malformation database was searched for all cases of intracranial cavernous malformation (January 1, 1997-December 31, 2021). For patients with a diagnosis of RICM, information on demographic characteristics, surgical treatments, radiation, and surgical outcomes was obtained and analyzed. A comprehensive literature search was conducted using PubMed, Embase, Cochrane, and Web of Science databases for all reported cases of RICM. RESULTS: A retrospective review of 1662 patients treated at a single institution yielded 10 patients with prior radiation treatment in the neck or head region and a subsequent diagnosis of intracranial RICM. The median (interquartile range) latency between radiation and presentation was 144 (108-192) months. Nine of 10 patients underwent surgery; symptoms improved for 5 patients, worsened for 3, and were stable for 1. The systematic literature review yielded 64 publications describing 248 patients with RICMs. Of the 248 literature review cases, 71 (28.6%) involved surgical resection. Of 39 patients with reported surgical outcomes, 32 (82%) experienced improvement. CONCLUSIONS: RICMs have a unique course and epidemiology. RICMs should be considered when patients with a history of radiation present with neurologic impairment. When RICMs are identified, symptomatic patients can be treated effectively with surgical excision and close follow-up.

Radiation-induced cavernous malformations in the spine: patient series.

BACKGROUND: Radiation-induced spinal cord cavernous malformations (RISCCMs) are a rare subset of central nervous system lesions and are more clinically aggressive than congenital cavernous malformations (CMs). The authors assessed the characteristics and outcomes of patients with RISCCM at a single institution and systematically reviewed the pertinent literature using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. OBSERVATIONS: Among the 146 spinal CMs at the authors' institution, 3 RISCCMs were found. Symptom duration ranged from 0.1 to 8.5 months (mean [standard deviation], 3.2 [4.6] months), and latency ranged from 16 to 29 years (22.4 [9.6] years). All 3 RISCCMs were surgically treated with complete resection; 2 patients had stable outcomes, and 1 improved postoperatively. A review of 1240 articles revealed 20 patients with RISCCMs. Six of these patients were treated with resection, 13 were treated conservatively, and in 1 case, the treatment type was not stated. Five of the 6 patients treated surgically reported improvement postoperatively or at follow-up; 1 was stable, and none reported worsened outcomes. LESSONS: RISCCMs are rare sequelae following radiation that inadvertently affect the spinal cord. Altogether, the frequency of stable and improved outcomes on follow-up suggests that resection could prevent further patient decline caused by symptoms of RISCCM. Therefore, surgical management should be considered primary therapy in patients presenting with RISCCMs.

A taxonomy for deep cerebral cavernous malformations: subtypes of thalamic lesions.

OBJECTIVE: Anatomical taxonomy is a practical tool to successfully guide clinical decision-making for patients with brain arteriovenous malformations and brainstem cavernous malformations (CMs). Deep cerebral CMs are complex, difficult to access, and highly variable in size, shape, and position. The authors propose a novel taxonomic system for deep CMs in the thalamus based on clinical presentation (syndromes) and anatomical location (identified on MRI). METHODS: The taxonomic system was developed and applied to an extensive 2-surgeon experience from 2001 through 2019. Deep CMs involving the thalamus were identified. These CMs were subtyped on the basis of the predominant surface presentation identified on preoperative MRI. Six subtypes among 75 thalamic CMs were defined: anterior (7/75, 9%), medial (22/75, 29%), lateral (10/75, 13%), choroidal (9/75, 12%), pulvinar (19/75, 25%), and geniculate (8/75, 11%). Neurological outcomes were assessed using modified Rankin Scale (mRS) scores. A postoperative score ≤ 2 was defined as a favorable outcome and > 2 as a poor outcome. Clinical and surgical characteristics and neurological outcomes were compared among subtypes. RESULTS: Seventy-five patients underwent resection of thalamic CMs and had clinical and radiological data available. Their mean age was 40.9 (SD 15.2) years. Each thalamic CM subtype was associated with a recognizable constellation of neurological symptoms. The common symptoms were severe or worsening headaches (30/75, 40%), hemiparesis (27/75, 36%), hemianesthesia (21/75, 28%), blurred vision (14/75, 19%), and hydrocephalus (9/75, 12%). The thalamic CM subtype determined the selection of surgical approach. A single approach was associated with each subtype for most patients. The main exception to this paradigm was that in the surgeons' early experience, pulvinar CMs were resected through a superior parietal lobule-transatrial approach (4/19, 21%), which later evolved to the paramedian supracerebellar-infratentorial approach (12/19, 63%). Relative outcomes implied by mRS scores were unchanged or improved in most patients (61/66, 92%) postoperatively. CONCLUSIONS: This study confirms the authors' hypothesis that this taxonomy for thalamic CMs can meaningfully guide the selection of surgical approach and resection strategy. The proposed taxonomy can increase diagnostic acumen at the patient bedside, help identify optimal surgical approaches, enhance the clarity of clinical communications and publications, and improve patient outcomes.

Experience and Balance: Long-Term Trends in Preferred Skull Base Approach for a Case Series of Cavernous Malformation Resections.

BACKGROUND: Skull base approaches are a foundation of modern cerebrovascular surgery; however, their application over time has varied. OBJECTIVE: To assess trends in skull base approach selection for cavernous malformation (CM) resection. METHODS: This is a retrospective case series of all first-time CM resections by a single surgeon from 1997 to 2021. Cases were classified by craniotomy and approach. Four sets of common comparator skull base approaches were identified by coauthor consensus: pterional and orbitozygomatic; retrosigmoid, extended retrosigmoid (xRS), and far-lateral; suboccipital and torcular; and trans-cerebellar peduncle (MCP) and transcerebellopontine angle. Counts were binned by 5-year or 10-year clusters for descriptive statistical assessment of temporal trends. RESULTS: In total, 372 primary CM resections met the study criteria and were included. Orbitozygomatic approach use increased during the second 5-year period, after which the pterional approach rapidly became and remained the preferred approach. During the first two 5-year periods, the far-lateral approach was preferred to the retrosigmoid and xRS approaches, but the xRS approach grew in popularity and accounted for >50% of operations in this comparator group. Trans-MCP use compared with the transcerebellopontine angle approach closely mirrored the change in xRS use. The midline suboccipital approach accounted for a larger proportion (range, 62%-88%) of cases than the torcular approach (range, 12%-38%) across all periods. CONCLUSION: The xRS and trans-MCP approaches have been increasingly used over time, while the orbitozygomatic and far-lateral approaches have become less common. These trends seem to reflect versatility, efficiency, and safety of these techniques.

Safety of brainstem safe entry zones: comparison of microsurgical outcomes associated with superficial, exophytic, and deep brainstem cavernous malformations.

OBJECTIVE: Safe entry zones (SEZs) enable safe tissue transgression to lesions beneath the brainstem surface. However, evidence for the safety of SEZs is scarce and is based on anatomical studies, case reports, and small series. METHODS: A cohort of 154 patients who underwent microsurgical brainstem cavernous malformation (BSCM) treatment during a 23-year period and who had preoperative MR images and intraoperative photographs or videos was retrospectively examined. This study assessed the safety of SEZs for access to deep BSCMs, preoperative MRI to predict BSCM surface proximity, and the relationships between BSCM subtype, surgical approach, and SEZs. Lesions were characterized as exophytic, superficial, or deep on the basis of preoperative MRI and intraoperative inspection. Outcomes were scored as good (modified Rankin Scale [mRS] score ≤ 2) or poor (mRS score > 2) and relative outcomes as stable/improved or worse relative to baseline (± 1 point). RESULTS: Resections included 34 (22%) in the midbrain, 102 (66%) in the pons, and 18 (12%) in the medulla. Of those, 23 (15%) were exophytic, 57 (37%) were superficial, and 74 (48%) were deep. Established SEZs were used for 97% (n = 72) of deep lesions; the preferred SEZ associated with its subtype was used for 91% (n = 67). MR images accurately depicted exophytic BSCMs that did not require SEZ approaches (sensitivity, 96%) but overestimated the proximity of lesions superficial to brainstem surfaces (specificity, 67%), resulting in unanticipated SEZ use. Final neurological outcomes were good in 80% of patients with follow-up data (119/149), and relative outcomes were stable/improved in 93% (139/149). Outcomes for patients with brainstem transgression through an SEZ did not differ from outcomes for patients with superficial or exophytic lesions that did not require SEZ use (final mRS score ≤ 2 in 72% of all patients with deep lesions vs 82% of all patients with superficial or exophytic lesions [p = 0.10]). Among patients with follow-up, the rates of permanent new cranial nerve deficits in patients with deep BSCMs and superficial or exophytic BSCMs were 21% and 20%, respectively (p = 0.81), with no significant change in overall cranial nerve deficit (0 and -1, p = 0.65). CONCLUSIONS: Neurological outcomes for patients with deep BSCMs were equivalent to those for superficial or exophytic BSCMs, validating the safety of SEZs for deep BSCMs. Preoperative T1-weighted MR images overestimated the lesion's surface proximity, necessitating detailed knowledge of SEZs and readiness to use them in cases of radiological-microsurgical discordance. Most patients achieved favorable outcomes despite the transgression of eloquent brainstem tissue in and around SEZs.

Assessing the volume-outcome relationship of carotid artery stenting in nationwide administrative data: a challenge of patient population bias.

BACKGROUND: Studies have shown an association between surgical treatment volume and improved quality metrics. This study evaluated nationwide results in carotid artery stenting (CAS) procedural readmission rates, costs, and length of stay based on hospital treatment volume. METHODS: We used the Nationwide Readmissions Database for carotid stenosis from 2010 to 2015. Patients receiving CAS were matched based on demographics, illness severity, and relevant comorbidities. Patients were matched 1:1 between low- and high-volume centers using a non-parametric preprocessing matching program to adjust for parametric causal inferences. Nearest-neighbor propensity score matching was performed using logit distance. RESULTS: Low- and high-volume centers admitted a mean (SD) of 4.68 (3.79) and 25.10 (16.86) patients undergoing CAS per hospital, respectively. Comorbidities were significantly different and initially could not be adequately matched. Because of significant differences in baseline patient population characteristics after attempted matching between low- and high-volume centers, we used propensity adjustment with multivariate analysis. Using this alternative approach, no significant differences were observed between low- and high-volume centers for the presence of any complication, postoperative stroke, postoperative myocardial infarction, and readmission at 30 days. CONCLUSION: In 1:1 nearest-neighbor matching with a high number of patients, our analysis did not result in well-matched cohorts for the effect of case volume on outcomes. Comparing analytical techniques for various outcomes highlights that outcome disparities may not be related to quality differences based on hospital size, but rather variability in patient populations between low- and high-volume institutions.

A system of anatomical triangles defining dissection routes to brainstem cavernous malformations: definitions and application to a cohort of 183 patients.

OBJECTIVE: 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.

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.

Cavernous Malformations and Artificial Intelligence: Machine Learning Applications.

Significant progress has been made in the use of artificial intelligence (AI) in clinical medicine over the past decade, but the clinical development of AI faces challenges. Although the spectrum of AI applications is growing within clinical medicine, including in subspecialty neurosurgery, applications focused on cerebral cavernous malformations (CCMs) are relatively scarce. The recently introduced brainstem cavernous malformation (BSCM) grading scale, approach triangles, and safe entry zone systems provide a discrete framework to explore future machine learning (ML) applications of AI systems. Given the immense scalability of these models, significant resources will likely be allocated to pursuing these future efforts.

Analyzing international medical graduate research productivity for application to US neurosurgery residency and beyond: A survey of applicants, program directors, and institutional experience.

Background: The authors investigated perceived discrepancies between the neurosurgical research productivity of international medical graduates (IMGs) and US medical graduates (USMGs) through the perspective of program directors (PDs) and successfully matched IMGs. Methods: Responses to 2 separate surveys on neurosurgical applicant research productivity in 115 neurosurgical programs and their PDs were analyzed. Neurosurgical research participation was analyzed using an IMG survey of residents who matched into neurosurgical residency within the previous 8 years. Productivity of IMGs conducting dedicated research at the study institution was also analyzed. Results: Thirty-two of 115 (28%) PDs responded to the first research productivity survey and 43 (37%) to the second IMG research survey. PDs expected neurosurgery residency applicants to spend a median of 12-24 months on research (Q1-Q3: 0-12 to 12-24; minimum time: 0-24; maximum time: 0-48) and publish a median of 5 articles (Q1-Q3: 2-5 to 5-10; minimum number: 0-10; maximum number: 4-20). Among 43 PDs, 34 (79%) ranked "research institution or associated personnel" as the most important factor when evaluating IMGs' research. Forty-two of 79 (53%) IMGs responding to the IMG-directed survey reported a median of 30 months (Q1-Q3: 18-48; range: 4-72) of neurosurgical research and 12 published articles (Q1-Q3: 6-24; range: 1-80) before beginning neurosurgical residency. Twenty-two PDs (69%) believed IMGs complete more research than USMGs before residency. Of 20 IMGs conducting dedicated neuroscience/neurosurgery research at the study institution, 16 of 18 who applied matched or entered a US neurosurgical training program; 2 applied and entered a US neurosurgical clinical fellowship. Conclusion: The research work of IMGs compared to USMGs who apply to neurosurgery residency exceeds PDs' expectations regarding scientific output and research time. Many PDs perceive IMG research productivity before residency application as superior to USMGs. Although IMGs comprise a small percentage of trainees, they are responsible for a significant amount of US-published neurosurgical literature. Preresidency IMG research periods may be improved with dedicated mentoring and advising beginning before the research period, during the period, and within a neurosurgery research department, providing a formal structure such as a research fellowship or graduate program for IMGs aspiring to train in the US.

Neurosurgery Subspecialty Practice During a Pandemic: A Multicenter Analysis of Operative Practice in 7 U.S. Neurosurgery Departments During Coronavirus Disease 2019.

OBJECTIVE: Changes to neurosurgical practices during the coronavirus disease 2019 (COVID-19) pandemic have not been thoroughly analyzed. We report the effects of operative restrictions imposed under variable local COVID-19 infection rates and health care policies using a retrospective multicenter cohort study and highlight shifts in operative volumes and subspecialty practice. METHODS: Seven academic neurosurgery departments' neurosurgical case logs were collected; procedures in April 2020 (COVID-19 surge) and April 2019 (historical control) were analyzed overall and by 6 subspecialties. Patient acuity, surgical scheduling policies, and local surge levels were assessed. RESULTS: Operative volume during the COVID-19 surge decreased 58.5% from the previous year (602 vs. 1449, P = 0.001). COVID-19 infection rates within departments' counties correlated with decreased operative volume (r = 0.695, P = 0.04) and increased patient categorical acuity (P = 0.001). Spine procedure volume decreased by 63.9% (220 vs. 609, P = 0.002), for a significantly smaller proportion of overall practice during the COVID-19 surge (36.5%) versus the control period (42.0%) (P = 0.02). Vascular volume decreased by 39.5% (72 vs. 119, P = 0.01) but increased as a percentage of caseload (8.2% in 2019 vs. 12.0% in 2020, P = 0.04). Neuro-oncology procedure volume decreased by 45.5% (174 vs. 318, P = 0.04) but maintained a consistent proportion of all neurosurgeries (28.9% in 2020 vs. 21.9% in 2019, P = 0.09). Functional neurosurgery volume, which declined by 81.4% (41 vs. 220, P = 0.008), represented only 6.8% of cases during the pandemic versus 15.2% in 2019 (P = 0.02). CONCLUSIONS: Operative restrictions during the COVID-19 surge led to distinct shifts in neurosurgical practice, and local infective burden played a significant role in operative volume and patient acuity.

Giant cerebral cavernous malformations: redefinition based on surgical outcomes and systematic review of the literature.

OBJECTIVE: Giant cerebral cavernous malformations (GCCMs) are rare vascular malformations. Unlike for tumors and aneurysms, there is no clear definition of a "giant" cavernous malformation (CM). As a result of variable definitions, working descriptions and outcome data of patients with GCCM are unclear. A new definition of GCCM related to surgical outcomes is needed. METHODS: An institutional database was searched for all patients who underwent resection of CMs > 1 cm in diameter. Patient information, surgical technique, and clinical and radiographic outcomes were assessed. A systematic review was performed to augment an earlier published review. RESULTS: In the authors' institutional cohort of 183 patients with a large CM, 179 with preoperative and postoperative modified Rankin Scale (mRS) scores were analyzed. A maximum CM diameter of ≥ 3 cm was associated with greater risk of severe postoperative decline (≥ 2-point increase in mRS score). After adjustment for age and deep versus superficial location, size ≥ 3 cm was strongly predictive of severe postoperative decline (OR 4.5, 95% CI 1.2-16.9). A model with CM size and deep versus superficial location was developed to predict severe postoperative decline (area under the receiver operating characteristic curve 0.79). Thirteen more patients with GCCMs have been reported in the literature since the most recent systematic review, including some patients who were treated earlier and not discussed in the previous review. CONCLUSIONS: The authors propose that cerebral CMs with a diameter ≥ 3 cm be defined as GCCMs on the basis of the inflection point for functional and neurological outcomes. This definition is in line with the definitions for other giant lesions. It is less exclusive than earlier definitions but captures the rarity of these lesions (approximately 1% incidence) and variation in outcomes. GCCMs remain operable with potentially favorable outcomes. The term "giant" is not meant to deter or contraindicate surgery.

Mini-Open Lateral Approach for Corpectomy in the Thoracolumbar Spine.

The thoracolumbar spine poses unique challenges when considering surgical treatment options. In the era of modern medicine, nonoperative treatments have become more available for pathology of the thoracolumbar spine, including infectious, oncologic, traumatic, and degenerative etiologies. However, surgery is often warranted in the presence of deformity or with spinal cord compression resulting in neurologic deficits. Traditionally, posterior or anterior approaches were used for surgical treatment in the thoracolumbar spine. The mini-open lateral approach for corpectomy in the thoracolumbar spine is relatively new but not yet widely utilized, is less invasive, and is a less morbid surgical option for treating what has historically been a challenging surgical location. A thorough understanding of the anatomy associated with this approach is essential to perform safe and successful surgery with this technique. This review outlines the preoperative and anatomical considerations, surgical technique, contraindications, potential complications, and clinical outcomes associated with performing corpectomies in the thoracolumbar spine via the mini-open lateral approach. This is a safe, successful, and appealing surgical option for appropriately selected patients with diseases of the thoracolumbar region.

Anatomical Triangles for Use in Skull Base Surgery: A Comprehensive Review.

Procedures performed along the skull base require technical prowess and a thorough knowledge of cranial anatomy to navigate the operative field. Anatomical triangles created by unique anatomical structures serve as landmarks to guide the surgeon during meticulous skull base procedures. The corridors rapidly orient the surgeon to the operative field and permit greater confidence regarding skull base position during dissection. A literature review was performed with use of the PubMed database and reference list searches from full-text reviewed articles, which resulted in the identification of 31 distinct anatomical triangles of the skull base. The 31 anatomical triangles are categorized into a corresponding cranial fossa or the extracranial subsection. The triangles described in the manuscript include junctional, interoptic, precommunicating, opticocarotid, supracarotid, parasellar, clinoidal, oculomotor, carotid-oculomotor, supratrochlear, infratrochlear, anteromedial, quadrangular, anterolateral, posteromedial, posterolateral, lateral, superior petrosal, oculomotor-tentorial, inferomedial, inferolateral, glossopharyngo-cochlear, vagoaccessory, suprahypoglossal, hypoglossal-hypoglossal, infrahypoglossal, parapetrosal, suprameatal, retromeatal, suboccipital, and the inferior suboccipital. The goal of this review is to create a comprehensive resource for existing skull base triangles that includes borders, contents, surgical applications, and illustrations to enhance awareness and inform microsurgical dissection.