Faculty Bibliography

OBJECTIVES/OBJECTIVE:To assess a decade of experience of treating patients with high hearing risk cerebellopontine angle (CPA) epidermoid lesions and examine factors influencing postoperative outcomes, particularly hearing preservation. STUDY DESIGN/METHODS:Retrospective chart review. SETTING/METHODS:Single tertiary-referral center. PATIENTS/METHODS:Adults with CPA epidermoid lesions who presented with hearing loss or evidence of lesion involving vestibulocochlear nerve. INTERVENTIONS/METHODS:The studied intervention was microsurgical resection. MAIN OUTCOME MEASURES/METHODS:Main outcome measures included extent of resection, hearing preservation rate for patients with postoperative audiograms, and disease progression. RESULTS:Twenty-three adults with an average tumor volume of 15.63 ± 16.2 cm3 were included. Five lesions (22%) involved the full internal auditory canal (IAC), 11 (48%) had partial involvement, and 5 (22%) were IAC sparing. Most patients with IAC involvement (88%) had circumferential invasion of the canal. Patients underwent either a retrosigmoid (18, 79%) or combined retrolabyrinthine transpetrosal approach (5, 22%), and gross total resection was achieved in most cases (13, 57%). Of 12 patients with postoperative audiograms, 10 (83%) had preoperative hearing preserved. There was no statistically significant change in hearing scores with treatment based on preoperative extent of IAC involvement. Ten patients (43%) had residual lesions postoperatively, and 6 exhibited progression. One patient ultimately required reoperation 6 years after initial surgery. CONCLUSIONS:Preoperative hearing was preserved in the majority of the patients who underwent resection of CPA epidermoids via a retrosigmoid or transpetrosal approach. CPA epidermoids often invaded the IAC; however, degree of invasion was not associated with hearing outcomes.

BACKGROUND:Arteriovenous malformations (AVMs) are complex vascular anomalies with a high risk of hemorrhage and neurological deficits, especially when located in eloquent brain regions. The eloquence of an AVM location is a critical factor in the treatment planning, influencing both the risk of complications and long-term functional outcomes. This study aims to compare outcomes between eloquent and non-eloquent AVMs. METHODS:This multicenter, retrospective study utilized data from the Multicenter International Study for Treatment of Brain AVMs (MISTA) consortium. Patients with eloquent and non-eloquent AVMs were compared on baseline characteristics, angiographic outcomes, and functional outcomes using the modified Rankin Scale (mRS). Propensity score weighting (IPTW) was applied to adjust for confounding variables. RESULTS:The study included 1,013 patients, with 498 (49.2%) AVMs located in eloquent regions and 515 (50.8%) in non-eloquent regions. In unadjusted analysis, eloquent AVMs had lower complete obliteration rates (67.6% vs. 79.5%, OR: 0.53, 95% CI: 0.39-0.72, p < 0.001) and higher complication rates (24.5% vs. 19.0%, OR: 1.38, 95% CI: 1.02-1.86, p = 0.03) compared to non-eloquent AVMs. After IPTW adjustment, eloquent AVMs continued to show significantly higher odds of overall complications (OR: 1.68, 95% CI: 1.12-2.52, p = 0.01) and symptomatic complications (OR: 1.77, 95% CI: 1.12-2.80, p = 0.01). Secondary analysis within the eloquent group indicated that embolization was linked to an elevated risk of complications. Surgery and radiosurgery showed comparable functional outcomes at last follow-up and complications rates with higher complete obliteration rates in surgery. CONCLUSION/CONCLUSIONS:AVMs in eloquent brain areas present higher risks of complications and lower obliteration rates, emphasizing the need for cautious, individualized treatment planning. Within the eloquent group, embolization increased the risk of complications, while surgery and radiosurgery showed comparable functional outcomes at last follow-up and complication rates with higher complete obliteration rates in surgery. These findings highlight the importance of location in AVM management and support further research focusing on comparing treatment strategies for AVMs in eloquent brain areas.

BACKGROUND:Brain arteriovenous malformations (AVMs) are abnormal connections between feeding arteries and draining veins, associated with significant risks of haemorrhage, seizures and other neurological deficits. Preoperative embolization is commonly used as an adjunct to microsurgical resection, with the aim of reducing intraoperative complications and improving outcomes. However, the efficacy and safety of this approach remain controversial. METHODS:This study is a subanalysis of the Multicenter International Study for Treatment of Brain AVMs consortium. We retrospectively analysed 486 patients with brain AVMs treated with microsurgical resection between January 2010 and December 2023. Patients were divided into two groups: those who underwent microsurgery alone (n=245) and those who received preoperative embolization, followed by microsurgery (n=241). Propensity score matching was employed, resulting in 288 matched patients (144 in each group). The primary outcomes were rates of complete AVM obliteration and functional outcomes (measured by the modified Rankin Scale (mRS)). Secondary outcomes included complication rates, mortality, hospital length of stay and postsurgical rupture. RESULTS:After matching, the complete obliteration rate was 97% with no significant difference between the microsurgery-only group and the preoperative embolization group (p=0.12). The proportion of patients with an mRS score of 0-2 at the last follow-up was similar in both groups (83% vs 84%; p=0.67). The median hospital stay was significantly longer for the embolisation group (9 days vs 7 days; p=0.017). Complication rates (24% vs 22%; p=0.57) and mortality rates (4.9% vs 2.1%; p=0.20) were comparable between the two groups. No significant differences were observed in postsurgical rupture, recurrence or retreatment rates. CONCLUSIONS:In this large multicentre study, preoperative embolization did not significantly improve AVM obliteration rates, functional outcomes or reduce complications compared with microsurgery alone.

The adoption of large language models (LLMs) in healthcare demands a careful analysis of their potential to spread false medical knowledge. Because LLMs ingest massive volumes of data from the open Internet during training, they are potentially exposed to unverified medical knowledge that may include deliberately planted misinformation. Here, we perform a threat assessment that simulates a data-poisoning attack against The Pile, a popular dataset used for LLM development. We find that replacement of just 0.001% of training tokens with medical misinformation results in harmful models more likely to propagate medical errors. Furthermore, we discover that corrupted models match the performance of their corruption-free counterparts on open-source benchmarks routinely used to evaluate medical LLMs. Using biomedical knowledge graphs to screen medical LLM outputs, we propose a harm mitigation strategy that captures 91.9% of harmful content (F1 = 85.7%). Our algorithm provides a unique method to validate stochastically generated LLM outputs against hard-coded relationships in knowledge graphs. In view of current calls for improved data provenance and transparent LLM development, we hope to raise awareness of emergent risks from LLMs trained indiscriminately on web-scraped data, particularly in healthcare where misinformation can potentially compromise patient safety.

BACKGROUND AND OBJECTIVES/OBJECTIVE:Classical biomedical data science models are trained on a single modality and aimed at one specific task. However, the exponential increase in the size and capabilities of the foundation models inside and outside medicine shows a shift toward task-agnostic models using large-scale, often internet-based, data. Recent research into smaller foundation models trained on specific literature, such as programming textbooks, demonstrated that they can display capabilities similar to or superior to large generalist models, suggesting a potential middle ground between small task-specific and large foundation models. This study attempts to introduce a domain-specific multimodal model, Congress of Neurological Surgeons (CNS)-Contrastive Language-Image Pretraining (CLIP), developed for neurosurgical applications, leveraging data exclusively from Neurosurgery Publications. METHODS:We constructed a multimodal data set of articles from Neurosurgery Publications through PDF data collection and figure-caption extraction using an artificial intelligence pipeline for quality control. Our final data set included 24 021 figure-caption pairs. We then developed a fine-tuning protocol for the OpenAI CLIP model. The model was evaluated on tasks including neurosurgical information retrieval, computed tomography imaging classification, and zero-shot ImageNet classification. RESULTS:CNS-CLIP demonstrated superior performance in neurosurgical information retrieval with a Top-1 accuracy of 24.56%, compared with 8.61% for the baseline. The average area under receiver operating characteristic across 6 neuroradiology tasks achieved by CNS-CLIP was 0.95, slightly superior to OpenAI's Contrastive Language-Image Pretraining at 0.94 and significantly outperforming a vanilla vision transformer at 0.62. In generalist classification, CNS-CLIP reached a Top-1 accuracy of 47.55%, a decrease from the baseline of 52.37%, demonstrating a catastrophic forgetting phenomenon. CONCLUSION/CONCLUSIONS:This study presents a pioneering effort in building a domain-specific multimodal model using data from a medical society publication. The results indicate that domain-specific models, while less globally versatile, can offer advantages in specialized contexts. This emphasizes the importance of using tailored data and domain-focused development in training foundation models in neurosurgery and general medicine.

BACKGROUND AND OBJECTIVES/OBJECTIVE:This study assessed the efficacy and safety of stereotactic radiosurgery (SRS) in comparison with watchful waiting for managing Koos grade II vestibular schwannomas (VS). METHODS:A retrospective, multicentric analysis was conducted, focusing on patients with Koos grade II VS who either received SRS (SRS group) or were observed (observation group). To ensure comparability between groups, propensity score matching was used, including factors such as demographic characteristics, tumor dimensions, and hearing assessments. The primary end points examined were tumor control, maintenance of serviceable hearing, and neurological outcomes. RESULTS:A total of 92 patients were equally matched across both cohorts, with a median follow-up of 37 months for the SRS group and 27.5 months for those observed. The SRS cohort exhibited superior tumor control over observation across 3, 5, and 8 years, achieving a 100% control rate vs 47.9%, 40.1%, and 34.3% for the observation group at these time intervals, respectively ( P < .001). Serviceable hearing preservation rates were comparable between the 2 groups throughout 3, 5, and 7 years (72.9% for SRS vs 65.4% for observation at 3 years; P = .86). Moreover, SRS management correlated with a lower incidence of vestibular symptoms (odds ratio = 0.11, P = .002), with no significant disparity in the deterioration of cranial nerve (CN) V or CN VII functions. Notably, the likelihood of experiencing any CN impairment was significantly diminished in the SRS cohort (odds ratio = 0.47, P = .04). CONCLUSION/CONCLUSIONS:For patients with Koos grade II VS, SRS offers superior tumor control rate and a lower risk of CN dysfunction without sacrificing hearing preservation.

BACKGROUND AND OBJECTIVE/OBJECTIVE:This investigation evaluates the safety and efficacy of stereotactic radiosurgery (SRS) vs observation for Koos grade I vestibular schwannomas (VS). METHODS:In a multicenter study, we retrospectively analyzed data of patients with Koos grade I VS who underwent SRS (SRS group) or were observed (observation group). Propensity score matching was used to equilibrate demographics, tumor size, and audiometric data across groups. The outcome analyzed included tumor control, preservation of serviceable hearing, and neurological function. RESULTS:The study matched 142 patients, providing a median follow-up period of 36 months. SRS significantly enhanced tumor control compared with observation, with a 100% control rate at both 5- and 8-year marks in the SRS group vs 48.6% and 29.5% in the observation group at the same time intervals, respectively ( P < .001). Preservation of serviceable hearing outcomes between groups showed no significant difference at 5 and 8 years, ensuring a comparable quality of auditory function (SRS 70.1% vs observation 53.4% at 5 years; P = .33). Furthermore, SRS was associated with a reduced likelihood of tinnitus (odds ratio [OR] = 0.46, P = .04), vestibular dysfunction (OR = 0.17, P = .002), and overall cranial nerve dysfunction (OR = 0.49, P = .03) at last follow-up. CONCLUSION/CONCLUSIONS:SRS management of patients with Koos grade I VS was associated with superior tumor control and reduced odds for cranial nerve dysfunction, while not compromising hearing preservation compared with observation. These findings support the safety and efficacy of SRS as a primary care approach for this patient population.

BACKGROUND AND OBJECTIVES/OBJECTIVE:Stereotactic radiosurgery (SRS) is effective for patients with medically refractory trigeminal neuralgia with a 75%-90% response rate. Consideration of the integral dose (ID) to the target nerve within the 50% isodose line was reported to help select prescription doses to maximize effectiveness and minimize bothersome numbness. The objective of this study was to externally validate the ID as a predictor of outcomes after SRS. METHODS:We reviewed the outcomes and parameters of 94 consecutive patients of type 1 trigeminal neuralgia who had SRS for the first time where nerve ID was calculated. 70% of the prescription doses were 80 Gy, with 28% at 85 Gy, and 2% at 70 Gy. RESULTS:The median follow-up time was 14.4 months. A total of 85 (90%) patients reported significant pain relief (Barrow Neurological Institute I-III) after initial SRS. The median pain recurrence-free survival was 82 months (95% CI 41.1-NA), and estimates at 1, 3, and 5 years were 80.5%, 65.5%, and 55.9%, respectively. The ID was not significantly associated with initial pain relief, or affect the risk of pain recurrence or sensory dysfunction after SRS using the Cox proportional hazards model. A nerve mean dose ≥65 Gy was associated with a reduced risk of pain recurrence on multivariate analysis (hazard ratio 0.408, P = .039). Twenty (21%) patients experienced sensory dysfunction after SRS with 3 (3%) requiring further medications, which was not correlated with the prescription dose or brainstem maximum dose. CONCLUSION/CONCLUSIONS:The ID did not predict recurrence-free survival or sensory dysfunction. Our observations suggest improved nerve coverage by the most powerful area of the isocenter, for instance, by targeting a narrower segment if feasible, could result in more durable pain relief. Further studies to validate these findings are needed.

BACKGROUND:Arteriovenous malformations (AVMs) are uncommon cerebral lesions that can cause significant neurological complications. Surgical resection is the gold standard for treatment, but endovascular embolization and stereotactic radiosurgery (SRS) are viable alternatives. OBJECTIVE:To compare the outcomes of endovascular embolization versus SRS in the treatment of AVMs with Spetzler-Martin grades I-III. METHODS:This study combined retrospective data from 10 academic institutions in North America and Europe. Patients aged 1 to 90 years who underwent endovascular embolization or SRS for AVMs with Spetzler-Martin grades I-III between January 2010 and December 2023 were included. RESULTS:The study included 244 patients, including 84 who had endovascular embolization and 160 who had SRS. Before propensity score matching (PSM), complete obliteration at the last follow-up was achieved in 74.5% of the SRS group compared with 57.8% of the embolization group (OR=0.47; 95% CI 0.26 to 0.48; P=0.01). After propensity score matching, SRS still achieved significantly higher occlusion rates at last follow-up (78.9% vs 55.3%; OR=0.32; 95% CI 0.12 to 0.90; P=0.03).Hemorrhagic complications were higher in the embolization group than in the SRS group, although this difference did not reach statistical significance after PSM (13.2% vs 2.6%; OR=5.6; 95% CI 0.62 to 50.47; P=0.12). Similarly, re-treatment rate was higher in the embolization group (10.5% vs 5.3%; OR=2.11; 95% CI 0.36 to 12.31; P=0.40) compared with the SRS group. CONCLUSION/CONCLUSIONS:Our findings indicate that SRS has a significantly higher obliteration rate at last follow-up compared with endovascular embolization. Also, SRS has a higher tendency for fewer hemorrhagic complications and lower re-treatment rate. Further prospective studies are needed.

BACKGROUND AND OBJECTIVES/OBJECTIVE:Hydrocephalus after Gamma Knife® stereotactic radiosurgery (SRS) for vestibular schwannomas is a rare but manageable occurrence. Most series report post-SRS communicating hydrocephalus in about 1% of patients, thought to be related to a release of proteinaceous substances into the cerebrospinal fluid. While larger tumor size and older patient age have been associated with post-SRS hydrocephalus, the influence of baseline ventricular anatomy on hydrocephalus risk remains poorly defined. METHODS:A single-institution retrospective cohort study examining patients who developed symptomatic communicating hydrocephalus after undergoing Gamma Knife® SRS for unilateral vestibular schwannomas from 2011 to 2021 was performed. Patients with prior hydrocephalus and cerebrospinal fluid diversion or prior surgical resection were excluded. Baseline tumor volume, third ventricle width, and Evans Index (EI)-maximum width of the frontal horns of the lateral ventricles/maximum internal diameter of the skull-were measured on axial postcontrast T1-weighted magnetic resonance imaging. RESULTS:A total of 378 patients met the inclusion criteria; 14 patients (3.7%) developed symptomatic communicating hydrocephalus and 10 patients (2.6%) underwent shunt placement and 4 patients (1.1%) were observed with milder symptoms. The median age of patients who developed hydrocephalus was 69 years (IQR, 67-72) and for patients younger than age 65 years, the risk was 1%. For tumor volumes <1 cm3, the risk of requiring shunting was 1.2%. The odds of developing symptomatic hydrocephalus were 5.0 and 7.7 times higher in association with a baseline EI > 0.28 (P = .024) and tumor volume >3 cm3 (P = .007), respectively, in multivariate analysis. Fourth ventricle distortion on pre-SRS imaging was significantly associated with hydrocephalus incidence (P < .001). CONCLUSION/CONCLUSIONS:Patients with vestibular schwannoma with higher baseline EI, larger tumor volumes, and fourth ventricle deformation are at increased odds of developing post-SRS hydrocephalus. These patients should be counseled regarding risk of hydrocephalus and carefully monitored after SRS.