Faculty Bibliography

OBJECTIVES/OBJECTIVE:Although hemispheric surgeries are among the most effective procedures for drug-resistant epilepsy (DRE) in the pediatric population, a large variability in outcomes remains. Identifying ideal hemispherectomy candidates is imperative to maximize the potential for seizure freedom. The objective was to develop an online, freely-accesible tool that accurately predicts the probability of seizure freedom for any patient at 1-, 2-, and 5-years post-hemispherectomy to provide clinicians accessible and reliable prognostic information to complement clinical judgement. METHODS:Retrospective data of all pediatric patients with DRE and seizure outcome data from the original Hemispherectomy Outcome Prediction Scale (HOPS) study were included. The primary outcome of interest was time-to-seizure recurrence. A multivariate Cox proportional-hazards regression model was developed to predict the likelihood of post-hemispheric surgery seizure freedom duration based on a combination of variables identified by clinical judgement and inferential statistics as predictive of the primary outcome. The final model from this study was encoded in a publicly accessible online calculator on the (iNEST) website. RESULTS:The selected variables for inclusion in the final model included the 5 original HOPS variables (age at seizure onset, etiologic substrate, seizure semiology, prior non-hemispheric resective surgery, and contralateral FDG-PET hypometabolism) and 3 additional variables (age at surgery, history of infantile spasms, and magnetic resonance (MR) imaging lesion). Predictors of shorter time-to-seizure recurrence included younger age at seizure onset, older age at surgery, prior resective surgery, generalized seizure semiology, FDG-PET hypometabolism contralateral to side of surgery, contralateral MR imaging lesion, non-lesional MR imaging, non-stroke etiologies, and history of infantile spasms. The area under the curve (AUC) of the final model was 73.0%. SIGNIFICANCE/CONCLUSIONS:Online calculators are efficient, cost-free tools that can facilitate physicians in risk-estimation and inform joint decision-making with families, potentially leading to greater satisfaction. Although the HOPS data was previously validated in the first analysis, the authors encourage prospective external validation of this new tool.

BACKGROUND AND OBJECTIVES/OBJECTIVE:Spine surgery has advanced in concert with our deeper understanding of its elements. Narrowly focused bibliometric analyses have been conducted previously, but never on the entire corpus of the field. Using big data and bibliometrics, we appraised the entire corpus of spine surgery publications to study the evolution of the specialty as a scholarly field since 1900. METHODS:We queried Web of Science for all contents from 13 major publications dedicated to spine surgery. We next queried by topic [topic = (spine OR spinal OR vertebrae OR vertebral OR intervertebral OR disc OR disk)]; these results were filtered to include articles published by 49 other publications that were manually determined to contain pertinent articles. Articles, along with their metadata, were exported. Statistical and bibliometric analyses were performed using the Bibliometrix R package and various Python packages. RESULTS:Eighty-five thousand five hundred articles from 62 journals and 134 707 unique authors were identified. The annual growth rate of publications was 2.78%, with a surge after 1980, concurrent with the growth of specialized journals. International coauthorship, absent before 1970, increased exponentially with the formation of influential spine study groups. Reference publication year spectroscopy allowed us to identify 200 articles that comprise the historical roots of modern spine surgery and each of its subdisciplines. We mapped the emergence of new topics and saw a recent lexical evolution toward outcomes- and patient-centric terms. Female and minority coauthorship has increased since 1990, but remains low, and disparities across major publications persist. CONCLUSION/CONCLUSIONS:The field of spine surgery was borne from pioneering individuals who published their findings in a variety of journals. The renaissance of spine surgery has been powered by international collaboration and is increasingly outcomes focused. While spine surgery is gradually becoming more diverse, there is a clear need for further promotion and outreach to under-represented populations.

Diffuse spinal cord gliomas (SCGs) are rare tumors associated with a high morbidity and mortality that affect both pediatric and adult populations. In this retrospective study, we sought to characterize the clinical, pathological, and molecular features of diffuse SCG in 22 patients with histological and molecular analyses. The median age of our cohort was 23.64 years (range 1-82) and the overall median survival was 397 days. K27M mutation was significantly more prevalent in males compared to females. Gross total resection and chemotherapy were associated with improved survival, compared to biopsy and no chemotherapy. While there was no association between tumor grade, K27M status (p = 0.366) or radiation (p = 0.772), and survival, males showed a trend toward shorter survival. K27M mutant tumors showed increased chromosomal instability and a distinct DNA methylation signature.

OBJECTIVE:This study was undertaken to determine whether the vertical parasagittal approach or the lateral peri-insular/peri-Sylvian approach to hemispheric surgery is the superior technique in achieving long-term seizure freedom. METHODS:We conducted a post hoc subgroup analysis of the HOPS (Hemispheric Surgery Outcome Prediction Scale) study, an international, multicenter, retrospective cohort study that identified predictors of seizure freedom through logistic regression modeling. Only patients undergoing vertical parasagittal, lateral peri-insular/peri-Sylvian, or lateral trans-Sylvian hemispherotomy were included in this post hoc analysis. Differences in seizure freedom rates were assessed using a time-to-event method and calculated using the Kaplan-Meier survival method. RESULTS:Data for 672 participants across 23 centers were collected on the specific hemispherotomy approach. Of these, 72 (10.7%) underwent vertical parasagittal hemispherotomy and 600 (89.3%) underwent lateral peri-insular/peri-Sylvian or trans-Sylvian hemispherotomy. Seizure freedom was obtained in 62.4% (95% confidence interval [CI] = 53.5%-70.2%) of the entire cohort at 10-year follow-up. Seizure freedom was 88.8% (95% CI = 78.9%-94.3%) at 1-year follow-up and persisted at 85.5% (95% CI = 74.7%-92.0%) across 5- and 10-year follow-up in the vertical subgroup. In contrast, seizure freedom decreased from 89.2% (95% CI = 86.3%-91.5%) at 1-year to 72.1% (95% CI = 66.9%-76.7%) at 5-year to 57.2% (95% CI = 46.6%-66.4%) at 10-year follow-up for the lateral subgroup. Log-rank test found that vertical hemispherotomy was associated with durable seizure-free progression compared to the lateral approach (p = .01). Patients undergoing the lateral hemispherotomy technique had a shorter time-to-seizure recurrence (hazard ratio = 2.56, 95% CI = 1.08-6.04, p = .03) and increased seizure recurrence odds (odds ratio = 3.67, 95% CI = 1.05-12.86, p = .04) compared to those undergoing the vertical hemispherotomy technique. SIGNIFICANCE/CONCLUSIONS:This pilot study demonstrated more durable seizure freedom of the vertical technique compared to lateral hemispherotomy techniques. Further studies, such as prospective expertise-based observational studies or a randomized clinical trial, are required to determine whether a vertical approach to hemispheric surgery provides superior long-term seizure outcomes.

BACKGROUND:H3K27M-mutant midline lesions were recently reclassified by the World Health Organization (WHO) as "diffuse midline glioma" (DMG) based entirely on their molecular signature. DMG is one of the most common and most lethal pediatric brain tumors; terminal progression is typically caused by local midbrain or brainstem progression, or secondary leptomeningeal dissemination. H3K27M mutations have also been infrequently associated with a histologically and prognostically diverse set of lesions, particularly spinal masses with early leptomeningeal spread. CASE PRESENTATION/METHODS:A 15-year-old girl after 1 week of symptoms was found to have a T2/FLAIR-hyperintense and contrast-enhancing thalamic mass accompanied by leptomeningeal enhancement along the entire neuraxis. Initial infectious workup was negative, and intracranial biopsy was inconclusive. Spinal arachnoid biopsy revealed an H3K27M-mutant lesion with glioneuronal features, classified thereafter as DMG. She received craniospinal irradiation with a boost to the thalamic lesion. Imaging 1-month post-radiation demonstrated significant treatment response with residual enhancement at the conus. CONCLUSIONS:This case report describes the unique presentation of an H3K27M-mutant midline lesion with significant craniospinal leptomeningeal spread on admission and atypical glioneuronal histopathological markers. With such florid leptomeningeal disease, spinal dural biopsy should be considered earlier given its diagnostic yield in classifying the lesion as DMG. Consistent with similar prior reports, this lesion additionally demonstrated synaptophysin positivity-also potentially consistent with a diagnosis of diffuse leptomeningeal glioneuronal tumor (DLGNT). In atypical DMG cases, particularly with leptomeningeal spread, further consideration of clinical and histopathological context is necessary for accurate diagnosis and prognostication.

OBJECTIVE:To develop and validate a model to predict seizure freedom in children undergoing cerebral hemispheric surgery for the treatment of drug-resistant epilepsy. METHODS:We analyzed 1267 hemispheric surgeries performed in pediatric participants across 32 centers and 12 countries to identify predictors of seizure freedom at 3 months after surgery. A multivariate logistic regression model was developed based on 70% of the dataset (training set) and validated on 30% of the dataset (validation set). Missing data were handled using multiple imputation techniques. RESULTS:Overall, 817 of 1237 (66%) hemispheric surgeries led to seizure freedom (median follow-up = 24 months), and 1050 of 1237 (85%) were seizure-free at 12 months after surgery. A simple regression model containing age at seizure onset, presence of generalized seizure semiology, presence of contralateral 18-fluoro-2-deoxyglucose-positron emission tomography hypometabolism, etiologic substrate, and previous nonhemispheric resective surgery is predictive of seizure freedom (area under the curve = .72). A Hemispheric Surgery Outcome Prediction Scale (HOPS) score was devised that can be used to predict seizure freedom. SIGNIFICANCE/CONCLUSIONS:Children most likely to benefit from hemispheric surgery can be selected and counseled through the implementation of a scale derived from a multiple regression model. Importantly, children who are unlikely to experience seizure control can be spared from the complications and deficits associated with this surgery. The HOPS score is likely to help physicians in clinical decision-making.

Epilepsy is a heterogenous group of disorders defined by recurrent seizure activity due to abnormal synchronized activity of neurons. A growing number of epilepsy cases are believed to be caused by genetic factors and copy number variants (CNV) contribute to up to 5% of epilepsy cases. However, CNVs in epilepsy are usually large deletions or duplications involving multiple neurodevelopmental genes. In patients who underwent seizure focus resection for treatment-resistant epilepsy, whole genome DNA methylation profiling identified 3 main clusters of which one showed strong association with receptor tyrosine kinase (RTK) genes. We identified focal copy number gains involving epidermal growth factor receptor (EGFR) and PDGFRA loci. The dysplastic neurons of cases with amplifications showed marked overexpression of EGFR and PDGFRA, while glial and endothelial cells were negative. Targeted sequencing of regulatory regions and DNA methylation analysis revealed that only enhancer regions of EGFR and gene promoter of PDGFRA were amplified, while coding regions did not show copy number abnormalities or somatic mutations. Somatic focal copy number gains of noncoding regulatory represent a previously unrecognized genetic driver in epilepsy and a mechanism of abnormal activation of RTK genes. Upregulated RTKs provide a potential avenue for therapy in seizure disorders.

BACKGROUND:New-onset hydrocephalus following foramen magnum decompression (FMD) for Chiari I malformation (CM-I) is rare; its natural history and pathophysiology are poorly understood. OBJECTIVE:To describe a series of patients who developed hydrocephalus following FMD for CM-I, provide possible explanations of this phenomenon, and outline treatment options. METHODS:Out of patients undergoing FMD for CM-I from 6 different tertiary centers, we evaluated patients presenting with new-onset hydrocephalus following FMD. The retrospectively collected data included demographics, clinical, and radiological findings of the CM-I and hydrocephalus patients. Time from FMD and hydrocephalus onset, treatment, and surgical techniques were assessed. RESULTS:Of 549 patients who underwent FMD for CM-I, 28 (5.1%) subsequently developed hydrocephalus (18 females, 10 males), with a mean age of 11.7 ± 11.9 yr (range 6 mo to 52 yr). Hydrocephalus occurred on average 2.2 ± 2.6 mo after FMD (range 1 wk to 8 mo). Four patients did not have a violation of the arachnoid during the FMD surgery. Main presenting symptoms of hydrocephalus were headaches (17, 41%), vomiting (10, 24.4%), and cerebrospinal fluid (CSF) leak or pseudomeningocele (7, 17%).Overall, 23 patients (82.1%) underwent CSF shunting, 1 patient (3.5%) had an endoscopic third ventriculostomy, 3 patients (10.7%) temporary CSF diversion only, and 1 patient (3.5%) was treated with acetazolamide. CONCLUSION/CONCLUSIONS:Hydrocephalus following FMD for CM-I is uncommon, but important. Based on our series and literature review, its incidence is about 5% to 7% and most likely will require further surgery. Shunting appears to be the favored treatment option.