Bauman, Megan M. J.

OBJECTIVE Maximal safe resection of intra-axial brain tumors near the motor cortex is aided by intraoperative motor mapping. Here, the authors compared outcomes in patients undergoing either low-frequency bipolar stimulation (LFBS) or high-frequency monopolar stimulation (HFMS) for cortical and/or subcortical motor mapping during brain tumor resection. METHODS A retrospective analysis of patients undergoing an asleep craniotomy with motor mapping or an awake craniotomy with motor and speech mapping with a single surgeon was performed. Three cohorts were compared: 1) asleep LFBS (AsLFBS), 2) awake LFBS (AwLFBS; motor + speech mapping), and 3) asleep HFMS. HFMS mapping was not used for awake craniotomies. RESULTS A total of 284 patients who underwent 300 craniotomies with motor mapping were identified. No significant differences in permanent neurological deficits (p = 0.377) or extent of resection (EOR) of nonenhancing tumors (p = 0.453) were identified between LFBS or HFMS motor mapping cases. Both EOR (92.7% vs 83.5%, p = 0.035) and permanent neurological deficits (7.6% vs 3.3%) occurred more frequently in enhancing tumors with LFBS, although the latter was not statistically significant. HFMS was associated with higher rates of subcortical motor pathway identification (p = 0.001) and fewer total intraoperative seizures (p = 0.003) compared with LFBS. Previous resection (HR 0.46, p = 0.003) and a higher cortical threshold (HR 0.95, p = 0.023) were significantly associated with longer survival, while preoperative aphasia (HR 2.24, p = 0.022), hospital length of stay (HR 1.1, p = 0.005), an insular-based tumor (HR 3.5, p = 0.021), and a histological diagnosis of glioblastoma (HR 2.9, p = 0.001) were negative predictors. Interestingly, overall FLAIR EOR was significantly associated with a marginally decreased overall survival (HR 1.01, p = 0.011). CONCLUSIONS No significant differences in postoperative neurological deficits were found between LFBS and HFMS paradigms. HFMS may identify subcortical motor fibers more reliably while resulting in significantly fewer intraoperative seizures. Although LFBS was associated with greater EOR of contrast-enhancing tumors, it may also be associated with higher rates of postoperative deficits, perhaps reflecting less reliable identification of subcortical motor fibers.

BACKGROUND AND OBJECTIVES: Endoscopic transnasal surgery offers a minimally invasive alternative to transcranial approaches for accessing midline skull base lesions involving the petrous apex and petroclival region. However, lateral access, particularly behind the petrous internal carotid artery (ICA), remains limited. The contralateral transmaxillary (CTM) approach provides a more direct surgical trajectory, more parallel to the petrous ICA. Yet, lateral access through this approach can be restricted by anatomic barriers, including the pterygoid process and lateral buttress of the maxillary sinus. We aimed to evaluate the contralateral transmaxillary-transpterygoid (CTMP) approach, with and without the lateral buttress removal (CTMP-LBR), to determine whether these modifications could enhance surgical access to the petroclival region. METHODS: Ten sides from 5 formalin-fixed, latex-injected cadaveric specimens were dissected to compare CTM, CTMP, and CTMP-LBR approaches. Petrous bone drilling was directed posterolaterally behind the petrous ICA toward the region medial to the cochlea. In addition, 30 sides from computed tomography angiography scans were analyzed to obtain radiographic measurements for each approach. RESULTS: Compared with CTM, both CTMP and CTMP-LBR significantly increased access for retrocarotid petrous bone drilling ( P < .001) and yielded a wider surgical angle relative to midline ( P < .001), in both cadaveric and radiographic analyses. In dissections, 20% of sides required CTM only, 50% benefited from CTMP, and 30% required CTMP-LBR to achieve adequate lateral access. Radiographic analysis revealed that CTMP required a median of 4 mm of pterygoid drilling, whereas CTMP-LBR required 9 mm and enabled a trajectory parallel to the petrous ICA with only 11 mm of soft tissue displacement. Patients with smaller angles between the petrous ICA and the horizontal plane were significantly more likely to benefit from CTMP over CTM ( P = .005). CONCLUSION: Modification of the CTM approach with pterygoid drilling and optional LBR improves retrocarotid access. Preoperative evaluation of the petrous ICA angle may help optimize patient-specific planning in endoscopic petroclival surgery.

OBJECTIVE Communicating hydrocephalus may occur following stereotactic radiosurgery (SRS) for vestibular schwannomas (VSs), yet identifying individual patient risk factors associated with this post-SRS complication remains a challenge. This study examined predictors of nonobstructive ventricular enlargement and symptomatic communicating hydrocephalus following primary SRS treatment for VS via a single-center institutional cohort review and meta-analysis of the literature. METHODS A retrospective single-institution cohort study and systematic literature review and meta-analysis examining post-SRS communicating hydrocephalus in VS was performed. RESULTS The institutional cohort consisted of 634 patients who received primary SRS as treatment for VS. The cohort was 51.6% female, with a median age of 64 (range 18–89) years. Following SRS treatment, 364 patients (57.4%) experienced tumor shrinkage, 218 (34.4%) had no change in the size of their lesion, and 52 (8.2%) experienced tumor growth. Nonobstructive ventricular enlargement was observed in 23 patients (3.6%) following SRS treatment, of whom 9 (39.1%) remained asymptomatic and 14 (60.9%) required placement of a ventriculoperitoneal (VP) shunt, with a median time to shunt placement of 8 months. In the multivariate analysis, patients ≥ 65 years old (p = 0.038), SRS target volume ≥ 5 cm 3 (p < 0.001), maximum SRS dose ≥ 26 Gy (p = 0.015), and tumor growth at the most recent follow-up (p = 0.002) were associated with an increased risk of post-SRS ventricular enlargement. Similarly, patients with older age (p = 0.049), increased SRS target volume (p = 0.002), and tumor growth (p = 0.016) were at an increased risk of symptomatic communicating hydrocephalus requiring VP shunt placement. Twenty-nine studies, including the cohort in this study, met inclusion criteria in the meta-analysis. Of the pooled 7825 patients, the overall incidence of hydrocephalus following SRS was 5%, and a subanalysis of 7081 patients demonstrated the incidence of symptomatic hydrocephalus requiring a VP shunt to be 4%. In this subanalysis, the overall shunting rate in patients who experienced post-SRS ventriculomegaly was 92%. Among individual studies in the literature, increased tumor size was most commonly found to be a statistically significant risk factor for post-SRS hydrocephalus. CONCLUSIONS Approximately 5% of patients may experience nonobstructive ventricular enlargement following primary SRS treatment for VS. However, not all patients may be symptomatic and require shunting. Patients who are older (≥ 65 years), those with larger tumor volumes, and those with post-SRS tumor growth may be at increased risk of communicating hydrocephalus and may benefit from closer clinical monitoring.

Glioblastoma (GBM), the most common primary malignant brain tumor in adults, has a median survival of 14–15 months despite aggressive treatment. Monitoring relies on MRI, but differentiating tumor progression from pseudo-progression or radiation necrosis remains difficult. Plasma extracellular vesicles (EVs) are emerging as promising non-invasive biomarkers due to their molecular cargos and accessibility. This review evaluates studies that specifically isolated plasma EVs for molecular profiling in GBM diagnosis and monitoring. Biomarkers (miRNA, RNA, DNA, proteins), EV characterization methods, and advancements in enriching tumor-derived EV subpopulations and assessing their diagnostic and prognostic potential are highlighted. Plasma EVs carry diverse cargos, including miRNAs (e.g., miR-21, miR-15b-3p), mRNAs (e.g., EGFRvIII), circRNAs, and proteins (e.g., CD44, GFAP). Composite molecular signatures have achieved sensitivities of 87–100% and specificities of 73–100% for GBM diagnosis. Tumor-derived EVs, enriched using techniques like SEC-CD44 immunoprecipitation, microfluidic platforms, or 5-ALA-induced PpIX fluorescence, enhance biomarker detection. Non-tumor-derived EVs may also reflect GBM’s systemic effects. Challenges include EV heterogeneity, non-EV contamination, and variable biomarker expression across studies. Plasma-EV-based liquid biopsies offer significant potential for GBM monitoring, with advanced enrichment methods improving tumor-specific biomarker detection. Standardizing isolation protocols and validating biomarkers in larger cohorts are critical for clinical translation.

OBJECTIVE Cervical dystonia (or spasmodic torticollis) is a neurological condition that results in abnormal movements and head posture, for which initial surgical intervention typically involves selective denervation of the sternocleidomastoid (SCM) and paraspinal muscles. However, muscle reactivation of the distal SCM stump can result in recurrent symptoms. In this study, the authors present their preliminary experience with distal SCM stump resection following selective denervation, with the aim of evaluating the effectiveness of the procedure and identifying patients who may benefit from this technique. METHODS This is a retrospective single-center cohort study of patients who underwent SCM stump resection as revision surgery for cervical dystonia. RESULTS A total of 18 patients (10 males [56%]) were included with a median (range) age of 54 (40–70) years. All patients received selective denervation of the SCM at the authors’ institution prior to SCM stump resection at a median (range) time of 12 (3–198) months between surgical procedures. At preoperative baseline, 13 patients (72%) possessed a rotational torticollis component to their head deviation, 12 (67%) possessed a laterocollis component, and 2 (11%) possessed a retrocollis component. At the most recent follow-up (median [range] 16 [4–119] months), 6 patients had complete resolution of their cervical dystonia (33%), while 10 had residual deviation (56%) and 2 had recurrent deviation (11%). However, compared to their post–selective denervation head position, 12 patients experienced improvement in their head position (67%), 4 patients had no change in their head position (22%), and 2 had worsening of their cervical dystonia (11%) following SCM stump resection. Importantly, 12 patients experienced improvement in their pain following SCM stump resection (67%). Patients who had a history of other movement/spasmodic disorders were more likely to have improvement in head position and improvement in pain after SCM stump resection, though neither of these results achieved statistical significance (p = 0.054). Additionally, patients who experienced full resolution of their cervical dystonia had shorter time between initial selective denervation surgery and SCM stump resection, though this result also did not achieve statistical significance (p = 0.068). CONCLUSIONS Distal SCM stump resection following selective denervation is a simple, safe, and effective option for many patients in treating refractory cervical dystonia. Patients with more severe preoperative presentations may experience greater benefit from SCM stump resection, though additional investigations are needed.

BACKGROUND Glossopharyngeal neuralgia (GPN) is a rare disorder characterized by severe, episodic pain along the sensory distribution of cranial nerve (CN) IX. Bilateral GPN presents unique challenges for consideration of microsurgical treatment due to potential risks of postoperative dysphagia and cardiac arrhythmias associated with resection of bilateral CN IX/X. Here, the authors describe successful staged bilateral microsurgical rhizotomy of CN IX and upper CN X rootlets to treat bilateral GPN. OBSERVATIONS A 54-year-old female presented with right GPN and underwent a right retrosigmoid craniotomy with rhizotomy, resulting in complete resolution of pain. During the following year, the patient developed left GPN and was considered for the same surgical intervention. However, prior to pursuing surgical intervention, evaluation of her swallowing function was conducted to stratify her risk of pharyngeal sensory denervation or dysphagia, and to confirm her suitability for left-sided rhizotomy. Given the patient’s normal oropharyngeal swallowing function on videofluoroscopic swallow study, she underwent left retrosigmoid craniotomy with rhizotomy. At the 3-month follow-up, the patient described complete resolution of pain and normal swallowing function. LESSONS With the use of comprehensive patient evaluation between surgical stages, staged bilateral microsurgical rhizotomy is a feasible and safe treatment option for carefully selected patients with bilateral GPN. https://thejns.org/doi/10.3171/CASE25359

BACKGROUND AND OBJECTIVE: In skull base surgery, endoscopic endonasal approaches require precise evaluation of the area of exposure and the maneuverability provided by each approach. Current neuroanatomical methodologies for quantifying these parameters primarily rely on computed tomography (CT) scans and neuronavigation systems, which entail significant financial investment. The aim of this study was to develop and validate an innovative, cost-effective methodology using an endoscopic photogrammetric model to measure the exposure area and maneuverability in endoscopic endonasal approaches, offering an accessible alternative to existing techniques. METHODS: Six cadaveric specimens were used to validate the accuracy of endoscopic photogrammetric measurements by comparing them with direct measurements. Subsequently, the exposure area, angle of attack, and surgical freedom were analyzed for 3 endoscopic approaches to the parasellar region: contralateral transmaxillary, single-nostril, and double-nostril approaches. RESULTS: Photogrammetric measurements demonstrated a high level of concordance with direct cadaveric measurements, with a mean difference of 0.02 mm as shown in the Bland-Altman plot. In addition, measurements obtained in comparative analysis describing the exposure area and maneuverability of 3 endoscopic approaches were congruent with those reported in existing literature derived using CT scans and neuronavigation systems. CONCLUSION: To our knowledge, this study is the first to validate endoscopic photogrammetric models as a measurement tool in neuroanatomy. Performing direct measurements on 3D models might eliminate the necessity of expensive CT and neuronavigation systems for volumetric quantification. Our cost-effective methodology allows for the widespread democratization of anatomical quantification within skull base neuroanatomy.

Abstract Professor Albert J. Rhoton Jr., MD, is renowned for his groundbreaking dissections, marking a monumental achievement in the field of neuroanatomy. Alongside his anatomical contributions, he also passed on his knowledge and skills to numerous fellows, leaving behind a profound legacy. Despite the widespread recognition of his influence, little quantitative work has been done to characterize the scholarly impact of his alumni. Data were collected on Rhoton fellows, including fellowship years, country of origin, current institutions, and titles, practice settings, and leadership roles. Scholarly productivity was evaluated by assessing publication counts, including publications before and after the fellowship, and publications focused on surgical anatomy. Additionally, H-indices and citation counts were recorded. Other variables analyzed included ownership of a surgical anatomy laboratory, and participation in organizing hands-on courses. We analyzed 118 alumni from diverse countries. There was a significant increase in publication output following the fellowship, with publications rising from an average of 7 to 76 (p < 0.001). Fellows from high-income countries had higher research productivity than those from middle-income countries, with greater average H-index (p = 0.003), publication count (p = 0.01), and citation score (p = 0.003). Overall, 65% of fellows pursued academic practice, with 18% owning a laboratory and 30% involved in hands-on courses. Dr. Rhoton's mentorship has shaped a generation of neurosurgeons who continue his legacy. His fellows have established careers worldwide, leading in academia, professional organizations, and surgical training. Their global impact underscores the lasting value of structured mentorship in neurosurgery.

OBJECTIVE Calcium phosphate cement (CPC) use has been previously described as a strategy to reduce the rates of pseudomeningocele and CSF leakage following skull base surgery. The authors aimed to present their institutional experience with CPC in retrosigmoid craniotomy and perform a systematic review of the literature to determine the effectiveness of CPC in reducing postoperative complications, including pseudomeningocele and craniotomy-site CSF leakage. METHODS A retrospective single-institution cohort study of patients who underwent retrosigmoid craniotomy with and without CPC cranioplasty from January 2017 to April 2024 was performed. A systematic literature review and meta-analysis of CPC use in retrosigmoid craniotomy was also performed. RESULTS Of 336 patients who underwent retrosigmoid craniotomy, 193 (57%) were female and the median age at surgery was 55 years (range 18–81 years). The median follow-up duration was 23 months (range 3–80 months). CPC was used to seal the edge of the craniotomy in 66 patients (20%). Among all patients, 50 (15%) experienced a postoperative complication, and 28 (8%) were wound-specific complications. Patients in the non-CPC group experienced significantly more postoperative wound-specific complications than those in the CPC group (10% vs 0%, p = 0.002). Specifically, pseudomeningocele occurred in 0 patients (0%) in the CPC group compared with 24 patients (9%) in the non-CPC group (p = 0.006), which progressed to CSF leaks at the craniotomy site in 6 patients (p = 0.60). Additionally, no patients (0%) in the CPC group experienced wound infection, dehiscence, or breakdown compared with 10 patients (4%) in the non-CPC group (p = 0.22). Five patients (8%) in the CPC group reported prolonged mild incisional pain at the craniotomy site, and there were no instances of major complications related to the CPC. In the meta-analysis, 10 studies met the inclusion criteria, yielding a total of 2166 patients (including the current study), 1101 of whom received CPC. In the pooled analysis, CPC was significantly associated with lower risk of CSF leakage at the craniotomy site (OR 0.23, 95% CI 0.13–0.42; p < 0.01) and lower risk of infection (OR 0.17, 95% CI 0.08–0.38; p < 0.01). CONCLUSIONS CPC use in retrosigmoid craniotomies could be a safe and effective strategy to reduce the incidence of pseudomeningocele and craniotomy-site CSF leakage, leading to lower rates of wound-related complications and infection.