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Background Context: Intraoperative neurophysiological monitoring (IONM) is used to reduce the risk of spinal cord injury during pediatric spinal deformity surgery. Significant reduction and/or loss of IONM signals without immediate recovery may lead the surgeon to acutely abort the case. The timing of when monitorable signals return remains largely unknown., Purpose: The goal of this study was to investigate the correlation between IONM signal loss, clinical examination, and subsequent normalization of IONM signals after aborted pediatric spinal deformity surgery to help determine when it is safe to return to the operating room., Study Design/setting: This is a multicenter, multidisciplinary, retrospective study of pediatric patients (<18 years old) undergoing spinal deformity surgery whose surgery was aborted due to a significant reduction or loss of IONM potentials., Patient Sample: Sixty-six patients less than 18 years old who underwent spinal deformity surgery that was aborted due to IONM signal loss were enrolled into the study., Outcome Measures: IONM data, operative reports, and clinical examinations were investigated to determine the relationship between IONM loss, clinical examination, recovery of IONM signals, and clinical outcome., Methods: Information regarding patient demographics, deformity type, clinical history, neurologic and ambulation status, operative details, IONM information (eg, quality of loss [SSEPs, MEPs], laterality, any recovery of signals, etc.), intraoperative wake-up test, postoperative neurologic exam, postoperative imaging, and time to return to the operating were all collected. All factors were analyzed and compared with univariate and multivariate analysis using appropriate statistical analysis., Results: Sixty-six patients were enrolled with a median age of 13 years [IQR 11-14], and the most common sex was female (42/66, 63.6%). Most patients had idiopathic scoliosis (33/66, 50%). The most common causes of IONM loss were screw placement (27/66, 40.9%) followed by rod correction (19/66, 28.8%). All patients had either complete bilateral (39/66, 59.0%), partial bilateral (10/66, 15.2%) or unilateral (17/66, 25.8%) MEP loss leading to termination of the case. Overall, when patients were returned to the operating room 2 weeks postoperatively, nearly 75% (40/55) had monitorable IONM signals. Univariate analysis demonstrated that bilateral SSEP loss (p=.019), bilateral SSEP and MEP loss (p=.022) and delayed clinical neurologic recovery (p=.008) were significantly associated with having unmonitorable IONM signals at repeat surgery. Multivariate regression analysis demonstrated that delayed clinical neurologic recovery (> 72 hours) was significantly associated with unmonitorable IONM signals when returned to the operating room (p=.006). All patients ultimately made a full neurologic recovery., Conclusions: In children whose spinal deformity surgery was aborted due to intraoperative IONM loss, there was a strong correlation between combined intraoperative SSEP/MEP loss, the magnitude of IONM loss, the timing of clinical recovery, and the time of electrophysiological IONM recovery. The highest likelihood of having a prolonged postoperative neurological deficit and undetectable IONM signals upon return to the OR occurs with bilateral complete loss of SSEPs and MEPs., Competing Interests: Declaration of competing interest One or more of the authors declare financial or professional relationships on ICMJE-TSJ disclosure forms., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Lumbar interbody fusion (LIF) is a well-established approach in treating spinal deformity and degenerative conditions of the spine. Since its inception in the 20th century, LIF has continued to evolve, allowing for minimally invasive approaches, high fusion rates, and improving disability scores with favorable complication rates. The anterior to the psoas (ATP) approach utilizes a retroperitoneal pathway medial to the psoas muscle to access the L1-S1intervertebral disc spaces. In contrast to the transpsoas arppoach, its primary advantage is avoiding transgressing the psoas muscle and the contained lumbar plexus, which potentially decreases the risk of injury to the lumbar plexus. Avoiding transgression of the psoas may minimize the risk of transient or permanent neurological deficits secondary to lumbar plexus injury. Indications for ATP approaches may expand as it is shown to be a safe and effective method of achieving spinal arthrodesis., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Objective: The focus of this modified Delphi study was to investigate and build consensus regarding the medical management of children with moderate and severe acute spinal cord injury (SCI) during their initial inpatient hospitalization. This impetus for the study was based on the AANS/CNS guidelines for pediatric SCI published in 2013, which indicated that there was no consensus provided in the literature describing the medical management of pediatric patients with SCIs., Methods: An international, multidisciplinary group of 19 physicians, including pediatric neurosurgeons, orthopedic surgeons, and intensivists, were asked to participate. The authors chose to include both complete and incomplete injuries with traumatic as well as iatrogenic etiologies (e.g., spinal deformity surgery, spinal traction, intradural spinal surgery, etc.) due to the overall low incidence of pediatric SCI, potentially similar pathophysiology, and scarce literature exploring whether different etiologies of SCI should be managed differently. An initial survey of current practices was administered, and based on the responses, a follow-up survey of potential consensus statements was distributed. Consensus was defined as ≥ 80% of participants reaching agreement on a 4-point Likert scale (strongly agree, agree, disagree, strongly disagree). A final meeting was held virtually to generate final consensus statements., Results: Following the final Delphi round, 35 statements reached consensus after modification and consolidation of previous statements. Statements were categorized into the following eight sections: inpatient care unit, spinal immobilization, pharmacological management, cardiopulmonary management, venous thromboembolism prophylaxis, genitourinary management, gastrointestinal/nutritional management, and pressure ulcer prophylaxis. All participants stated that they would be willing or somewhat willing to change their practices based on consensus guidelines., Conclusions: General management strategies were similar for both iatrogenic (e.g., spinal deformity, traction, etc.) and traumatic SCIs. Steroids were recommended only for injury after intradural surgery, not after acute traumatic or iatrogenic extradural surgery. Consensus was reached that mean arterial pressure ranges are preferred for blood pressure targets following SCI, with goals between 80 and 90 mm Hg for children at least 6 years of age. Further multicenter study of steroid use following acute neuromonitoring changes was recommended.

Background: Graduate surgical education is highly variable across regions and institutions regarding case volume and degree of trainee participation in each case. Dedicated educational curriculum using cadaveric tissue has been shown to enhance graduate surgical training, however with associated financial and utility burden to the institution., Objective: To investigate the utility of educational and cost applications of a novel method of combining mixed organic hydrogel polymers and 3-dimensional printed anatomic structures to create a complete "start-to-finish" simulation for resident education in spinal anatomy, instrumentation, and surgical techniques., Methods: This qualitative pilot study investigated 14 international participants on achievement of objective and personal learning goals in a standardized curriculum using biomimetic simulation compared with cadaveric tissue. A questionnaire was developed to examine trainee evaluation of individual anatomic components of the biomimetic simulators compared with previous experience with cadaveric tissue., Results: A total of 210 responses were acquired from 14 participants. Six participants originated from US residency education programs and 8 from transcontinental residency programs. Survey results for the simulation session revealed high user satisfaction. Score averages for each portion of the simulation session indicated learner validation of anatomic features for the simulation compared with previous cadaveric experience. Cost analysis resulted in an estimated savings of $10 833.00 for this single simulation session compared with previous cadaveric tissue sessions., Conclusion: The results of this study indicate a strong potential of establishing biomimetic simulation as a cost-effective and high-quality alternative to cadaveric tissue for the instruction of fundamental spine surgical techniques., (Copyright © Congress of Neurological Surgeons 2022. All rights reserved.)

Phrenic nerve injury can occur anywhere along its course and clinically results in diaphragm paralysis. Although most patients with Parsonage-Turner syndrome and phrenic nerve dysfunction improve without treatment, some patients do not recover spontaneously. In these cases, an initial autoimmune response produces scarring along the affected nerve(s). This scar, known as an hourglass constriction, causes focal compression of the nerve at the site of the scar, which prevents the nerve from spontaneously recovering. Thus, the authors present a unique case of phrenic nerve injury secondary to Parsonage-Turner syndrome that improved with internal neurolysis. The video can be found here: https://stream.cadmore.media/r10.3171/2022.10.FOCVID22105., Competing Interests: Disclosures Dr. Visco: personal fees from AMSSM, outside the submitted work; and board member of the Association of Academic Physiatry.Dr. Visco: personal fees from AMSSM, outside the submitted work; and board member of the Association of Academic Physiatry., (© 2023, The Authors.)

Purpose: To validate the Scoliosis Research Society-22r (SRS-22r) question 11 (Q11) response as a measure to assess and quantify opioid consumption., Methods: A post hoc analysis of a prospective study regarding opioid use during ASD surgery was performed. Data were collected at enrollment and 2-year follow-up including the SRS-22r and a standardized data collection form (CRF) for self-reported opioid consumption. Responses to Q11 of the SS-22r were compared with responses to the opioid consumption CRF (as measured by morphine equivalent dose (MED)). Inter-rater agreement was calculated. Sensitivity and specificity for the Q11 (+) responses were calculated using MED reports as the "true" value., Results: Cohen's kappa indicated almost perfect agreement between the MED CRF and Q11 (k = 0.878, p < 0.001). Mean daily MED consumption for patients reporting "Daily Narcotic" use was 62.0 (Median: 38.7, SD 87.5) mg; for patients reporting "Narcotics weekly or less", mean daily MED consumption was 21.6 (15.0, 29.0) mg. The positive Q11 responses were 96% sensitive and 92% specific for opioid users., Conclusion: SRS-22r Q11 exhibits almost perfect agreement with an independent questionnaire designed to assess opioid consumption in this cohort. "Daily narcotic" users report nearly three times the mean daily MED of "Weekly or less" users (62.0 ± 87.5 mg vs 21.6 ± 29 mg, p = 0.037). Q11 exhibited excellent sensitivity and specificity for determining opioid users and non-users. Given the need for opioid research in ASD, Q11 may be useful to use existing registries and observational cohorts to design more definitive studies regarding opioid consumption., Level of Evidence: III., (© 2022. The Author(s), under exclusive licence to Scoliosis Research Society.)

Objective: The goal of this study was to assess the social determinants that influence access and outcomes for pediatric neurosurgical care for patients with Chiari malformation type I (CM-I) and syringomyelia (SM)., Methods: The authors used retro- and prospective components of the Park-Reeves Syringomyelia Research Consortium database to identify pediatric patients with CM-I and SM who received surgical treatment and had at least 1 year of follow-up data. Race, ethnicity, and insurance status were used as comparators for preoperative, treatment, and postoperative characteristics and outcomes., Results: A total of 637 patients met inclusion criteria, and race or ethnicity data were available for 603 (94.7%) patients. A total of 463 (76.8%) were non-Hispanic White (NHW) and 140 (23.2%) were non-White. The non-White patients were older at diagnosis (p = 0.002) and were more likely to have an individualized education plan (p < 0.01). More non-White than NHW patients presented with cerebellar and cranial nerve deficits (i.e., gait ataxia [p = 0.028], nystagmus [p = 0.002], dysconjugate gaze [p = 0.03], hearing loss [p = 0.003], gait instability [p = 0.003], tremor [p = 0.021], or dysmetria [p < 0.001]). Non-White patients had higher rates of skull malformation (p = 0.004), platybasia (p = 0.002), and basilar invagination (p = 0.036). Non-White patients were more likely to be treated at low-volume centers than at high-volume centers (38.7% vs 15.2%; p < 0.01). Non-White patients were older at the time of surgery (p = 0.001) and had longer operative times (p < 0.001), higher estimated blood loss (p < 0.001), and a longer hospital stay (p = 0.04). There were no major group differences in terms of treatments performed or complications. The majority of subjects used private insurance (440, 71.5%), whereas 175 (28.5%) were using Medicaid or self-pay. Private insurance was used in 42.2% of non-White patients compared to 79.8% of NHW patients (p < 0.01). There were no major differences in presentation, treatment, or outcome between insurance groups. In multivariate modeling, non-White patients were more likely to present at an older age after controlling for sex and insurance status (p < 0.01). Non-White and male patients had a longer duration of symptoms before reaching diagnosis (p = 0.033 and 0.004, respectively)., Conclusions: Socioeconomic and demographic factors appear to influence the presentation and management of patients with CM-I and SM. Race is associated with age and timing of diagnosis as well as operating room time, estimated blood loss, and length of hospital stay. This exploration of socioeconomic and demographic barriers to care will be useful in understanding how to improve access to pediatric neurosurgical care for patients with CM-I and SM.

Pediatric glioblastoma multiforme (GBM) involving the spine is an aggressive tumor with a poor quality of life for patients. Despite this, there is only a limited number of reports describing the outcomes of pediatric spinal GBMs, both as primary spinal GBMs and metastases from an intracranial tumor. Here, we performed an individual patient meta-analysis to characterize factors affecting prognosis of pediatric spinal GBM. MEDLINE, Embase, and the Cochrane databases were searched for published studies on GBMs involving the spine in pediatric patients (age ≤ 21 years old). Factors associated with the survival were assessed with multi-factor ANOVAs, Cox hazard regression, and Kaplan-Meier analyses. We extracted data on 61 patients with spinal GBM from 40 studies that met inclusion criteria. Median survival was significantly longer in the primary spinal GBM compared that those with metastatic GBM (11 vs 3 months, p < 0.001). However, median survival of metastatic GBM patients was 10 months following diagnosis of their primary brain tumor, which was not different from that of primary spinal GBM patients (p = 0.457). Among primary spinal GBM patients, chemotherapy (hazard ratio (HR) = 0.255 [0.106-0.615], p = 0.013) and extent of resection (HR = 0.582 [0.374-0.905], p = 0.016) conferred a significant survival benefit. Younger age (less than 14 years) was associated with longer survival in patients treated with chemotherapy than those who did not undergo chemotherapy (β = - 1.12, 95% CI [- 2.20, - 0.03], p < 0.05). In conclusion, survival after presentation of metastases from intracranial GBM is poor in the pediatric population. In patients with metastatic GBM, chemotherapy may have provided the most benefit in young patients, and its efficacy might have an association with extent of surgical resection.

Background: Occipital-cervical fusion (OCF) and ventral decompression (VD) may be used in the treatment of pediatric Chiari-1 malformation (CM-1) with syringomyelia (SM) as adjuncts to posterior fossa decompression (PFD) for complex craniovertebral junction pathology., Objective: To examine factors influencing the use of OCF and OCF/VD in a multicenter cohort of pediatric CM-1 and SM subjects treated with PFD., Methods: The Park-Reeves Syringomyelia Research Consortium registry was used to examine 637 subjects with cerebellar tonsillar ectopia ≥ 5 mm, syrinx diameter ≥ 3 mm, and at least 1 yr of follow-up after their index PFD. Comparisons were made between subjects who received PFD alone and those with PFD + OCF or PFD + OCF/VD., Results: All 637 patients underwent PFD, 505 (79.2%) with and 132 (20.8%) without duraplasty. A total of 12 subjects went on to have OCF at some point in their management (PFD + OCF), whereas 4 had OCF and VD (PFD + OCF/VD). Of those with complete data, a history of platybasia (3/10, P = .011), Klippel-Feil (2/10, P = .015), and basilar invagination (3/12, P < .001) were increased within the OCF group, whereas only basilar invagination (1/4, P < .001) was increased in the OCF/VD group. Clivo-axial angle (CXA) was significantly lower for both OCF (128.8 ± 15.3°, P = .008) and OCF/VD (115.0 ± 11.6°, P = .025) groups when compared to PFD-only group (145.3 ± 12.7°). pB-C2 did not differ among groups., Conclusion: Although PFD alone is adequate for treating the vast majority of CM-1/SM patients, OCF or OCF/VD may be occasionally utilized. Cranial base and spine pathologies and CXA may provide insight into the need for OCF and/or OCF/VD., (Copyright © 2020 by the Congress of Neurological Surgeons.)

Objective: The subventricular zone (SVZ), housed in the lateral walls of the lateral ventricles, is the largest neurogenic niche in the brain. In adults, high-grade gliomas in contact or involved with the SVZ are associated with decreased survival. Whether this association holds true in the pediatric population remains unexplored. To address this gap in knowledge, the authors conducted this retrospective study in a pediatric population with high-grade gliomas treated at three comprehensive centers in the United States., Methods: The authors retrospectively identified 63 patients, age ≤ 21 years, with supratentorial WHO grade III-IV gliomas treated at three academic centers. Basic demographic and clinical data regarding presenting signs and symptoms and common treatment variables were obtained. Preoperative MRI studies were evaluated to assess SVZ contact by tumor and to quantify tumor volume., Results: Sixty-three patients, including 34 males (54%), had a median age of 12.3 years (IQR 6.50-16.2) and a median tumor volume of 39.4 ml (IQR 19.4-65.8). Tumors contacting the SVZ (SVZ+) were noted in 34 patients (54%) and overall were larger than those not in contact with the SVZ (SVZ-; 51.1 vs 27.3, p = 0.002). The SVZ+ tumors were also associated with decreased survival. However, age, tumor volume, tumor grade, and treatment with chemotherapy and/or radiation were not associated with survival in the 63 patients. In the univariable analysis, near-total resection, gross-total resection, and seizure presentation were associated with increased survival (HR = 0.23, 95% CI 0.06-0.88, p = 0.03; HR = 0.26, 95% CI 0.09-0.74, p = 0.01; and HR = 0.46, 95% CI 0.22-0.97, p = 0.04, respectively). In a multivariable stepwise Cox regression analysis, only SVZ+ tumors remained significantly associated with decreased survival (HR = 1.94, 95% CI 1.03-3.64, p = 0.04)., Conclusions: High-grade glioma contact with the SVZ neural stem cell niche was associated with a significant decrease in survival in the pediatric population, as it is in the adult population. This result suggests that tumor contact with the SVZ is a general negative prognosticator in high-grade glioma independent of age group and invites biological investigations to understand the SVZ's role in glioma pathobiology.

Background: Multiple studies have reported higher rates of glioma in areas with higher socioeconomic status (SES) but to the authors' knowledge have not stratified by other factors, including race/ethnicity or urban versus rural location., Methods: The authors identified the average annual age-adjusted incidence rates and calculated hazard ratios for death for gliomas of various subtypes, stratified by a county-level index for SES, race/ethnicity, US region, and rural versus urban status., Results: Rates of glioma were highest in counties with higher SES (rate ratio, 1.18; 95% CI, 1.15-1.22 comparing the highest with the lowest quintiles [P < .001]). Stratified by race/ethnicity, higher rates in high SES counties persisted for white non-Hispanic individuals. Stratified by rural versus urban status, differences in incidence by SES were more pronounced among urban counties. Survival was higher for residents of high SES counties after adjustment for age and extent of surgical resection (hazard ratio, 0.82; 95% CI, 0.76-0.87 comparing the highest with the lowest quintile of SES [P < .001]). Survival was higher among white Hispanic, black, and Asian/Pacific Islander individuals compared with white non-Hispanic individuals, after adjustment for age, SES, and extent of surgical resection, and when restricted to those individuals with glioblastoma who received radiation and chemotherapy., Conclusions: The incidence of glioma was higher in US counties of high compared with low SES. These differences were most pronounced among white non-Hispanic individuals and white Hispanic individuals residing in urban areas. Better survival was observed in high SES counties, even when adjusting for extent of surgical resection, and when restricted to those who received radiation and chemotherapy for glioblastoma. Differences in incidence and survival were associated with SES and race, rather than rural versus urban status., (© 2019 American Cancer Society.)

Background: Pediatric epilepsy affects 0.5-1% of children, with 10-30% of these children refractory to medical anticonvulsant therapy and potentially requiring surgical intervention. Analysis of resting state functional MRI (rsMRI) signal temporal differences (latency) has been proposed to study the pathological cognitive processes., Purpose/hypothesis: To quantitatively and qualitatively analyze the correlation of rsMRI signal latency to pediatric refractory extratemporal epilepsy seizure foci lateralization., Study Type: Retrospective review., Population: With Institutional Review Board approval, rsMRI and anatomical MRI scans were obtained from 38 registered pediatric epilepsy surgery patients from Washington University and 259 healthy control patients from the ADHD-200 dataset., Field Strength/sequence: 3 T echo planar imaging (EPI) blood oxygenation level-dependent (BOLD) sequence., Assessment: The images were transformed to pediatric atlases in Talairach space. Preoperative voxelwise latency maps were generated with parabolic interpolation of the rsMRI signal lateness or earliness when compared with the global mean signal (GMS) using cross-covariance analysis., Statistical Tests: Latency z-score maps were created for each epilepsy patient by voxelwise calculation using healthy control mean and standard deviation maps. Voxelwise hypothesis testing was performed via multiple comparisons corrected (false discovery and familywise error rate) and uncorrected methods to determine significantly late and early voxels. Significantly late and/or early voxels were counted for the right and left hemisphere separately. The hemisphere with the greater proportion of significantly late and/or early voxels was hypothesized to contain the seizure focus. Preoperative rsMRI latency analysis hypotheses were compared with postoperative seizure foci lateralization determined by resection images., Results: Preoperative rsMRI latency analysis correctly identified seizure foci lateralization of 64-85% of postoperative epilepsy resections with the proposed methods. RsMRI latency lateralization analysis was 77-100% sensitive and 58-79% specific. In some patients, qualitative analysis yielded preoperative rsMRI latency patterns specific to procedure performed., Data Conclusion: Preoperative rsMRI signal latency of pediatric epilepsy patients was correlated with seizure foci lateralization. J. Magn. Reson. Imaging 2019;49:1347-1355., (© 2018 International Society for Magnetic Resonance in Medicine.)

Aneurysmal subarachnoid hemorrhage (SAH) is rare in neonates. The authors present a unique report of a neonate with SAH from anterior inferior cerebellar artery (AICA) aneurysm rupture that was successfully treated with Onyx embolization. This case report demonstrates the utility of Onyx embolization for posterior circulation aneurysms in neonates and the successful management of SAH in this population.

Purpose: The goal of this longitudinal, population-level study was to examine factors affecting mortality in preterm infants with intraventricular hemorrhage (IVH)., Methods: The study examined patients who were born at 36 weeks estimated gestational age (EGA) or less with a diagnosis of IVH between the years 2005 and 2014 using data from the New York and Nebraska State Inpatient Databases. Potential predictors for mortality were investigated with multivariable survival analysis., Results: The cohort included 7437 preterm infants with IVH. All-cause inpatient mortality occurred in 746 (10.0%). The majority of deaths were in infants born at less than 25 weeks EGA (378 or 50.7%) and with birthweight less than 750 g (459 or 61.5%). Mortality was highest for children with grade IV IVH (306/848 or 36.1%), followed by grades III (203/955 or 21.3%), II (103/1328 or 7.8%), and I (134/4306 or 3.1%). Hydrocephalus was diagnosed within 6 months in 627 (8.4%) patients, with cerebrospinal fluid shunts required in 237 (3.2%). Shunts were eventually revised in 122 (51.5% of shunts), and 43 (18.1%) had infections. Multivariable Cox survival analyses found male sex (HR 1.3 [95% CI 1.1-1.5]), Asian race (HR 1.5 [1.1-2.2]), lower EGA (HR 9.9 [6.3-15.5] for < 25 weeks), higher IVH grade (HR 6.1 [4.9-7.6] for grade IV), gastrostomy (HR 4.0 [2.0-7.7]), tracheostomy (HR 3.5 [1.7-7.1]), and shunt infection (HR 3.2 [1.0-9.9]) to be independently associated with increased mortality risk., Conclusions: This database is the first of its kind assembled for population-based investigations of long-term neurosurgical outcomes in preterm infants with IVH.

Background: Neuroinflammation has been implicated in the pathophysiology of post-hemorrhagic hydrocephalus (PHH) of prematurity, but no comprehensive analysis of signaling molecules has been performed using human cerebrospinal fluid (CSF)., Methods: Lumbar CSF levels of key cytokines (IL-1α, IL-1β, IL-4, IL-6, IL-8, IL-10, IL-12, TNF-α, TGF-β1, IFN-γ) and chemokines (XCL-1, CCL-2, CCL-3, CCL-19, CXCL-10, CXCL-11, CXCL-12) were measured using conventional and multiplexed Enzyme-linked Immunosorbent Assays and compared between preterm infants with PHH and those with no known neurological injury. The relationships between individual biomarker levels and specific CSF cell counts were examined., Results: Total protein (TP) CSF levels were elevated in the PHH subjects compared to controls. CSF levels of IL-1α, IL-4, IL-6, IL-12, TNF-α, CCL-3, CCL-19, and CXCL-10 were significantly increased in PHH whereas XCL-1 was significantly decreased in PHH. When normalizing by TP, IL-1α, IL-1β, IL-10, IL-12, CCL-3, and CCL-19 levels were significantly elevated compared to controls, while XCL-1 levels remained significantly decreased. Among those with significantly different levels in both absolute and normalized levels, only absolute CCL-19 levels showed a significant correlation with CSF nucleated cells, neutrophils, and lymphocytes. IL-1β and CXCL-10 also were correlated with total cell count, nucleated cells, red blood cells, and neutrophils., Conclusions: Neuroinflammation is likely to be an important process in the pathophysiology of PHH. To our knowledge, this is the first study to investigate CSF levels of chemokines in PHH as well as the only one to show XCL-1 selectively decreased in a diseased state. Additionally, CCL-19 was the only analyte studied that showed significant differences between groups and had significant correlation with cell count analysis. The selectivity of CCL-19 and XCL-1 should be further investigated. Future studies will further delineate the role of these cytokines and chemokines in PHH.