Factors associated with syrinx size in pediatric patients treated for Chiari malformation type I and syringomyelia: a study from the Park-Reeves Syringomyelia Research Consortium

OBJECTIVE

Factors associated with syrinx size in pediatric patients undergoing posterior fossa decompression (PFD) or PFD with duraplasty (PFDD) for Chiari malformation type I (CM-I) with syringomyelia (SM; CM-I+SM) are not well established.

METHODS

Using the Park-Reeves Syringomyelia Research Consortium registry, the authors analyzed variables associated with syrinx radiological outcomes in patients (< 20 years old at the time of surgery) with CM-I+SM undergoing PFD or PFDD. Syrinx resolution was defined as an anteroposterior (AP) diameter of ≤ 2 mm or ≤ 3 mm or a reduction in AP diameter of ≥ 50%. Syrinx regression or progression was defined using 1) change in syrinx AP diameter (≥ 1 mm), or 2) change in syrinx length (craniocaudal, ≥ 1 vertebral level). Syrinx stability was defined as a < 1-mm change in syrinx AP diameter and no change in syrinx length.

RESULTS

The authors identified 380 patients with CM-I+SM who underwent PFD or PFDD. Cox proportional hazards modeling revealed younger age at surgery and PFDD as being independently associated with syrinx resolution, defined as a ≤ 2-mm or ≤ 3-mm AP diameter or ≥ 50% reduction in AP diameter. Radiological syrinx resolution was associated with improvement in headache (p < 0.005) and neck pain (p < 0.011) after PFD or PFDD. Next, PFDD (p = 0.005), scoliosis (p = 0.007), and syrinx location across multiple spinal segments (p = 0.001) were associated with syrinx diameter regression, whereas increased preoperative frontal-occipital horn ratio (FOHR; p = 0.007) and syrinx location spanning multiple spinal segments (p = 0.04) were associated with syrinx length regression. Scoliosis (HR 0.38 [95% CI 0.16-0.91], p = 0.03) and smaller syrinx diameter (5.82 ± 3.38 vs 7.86 ± 3.05 mm; HR 0.60 [95% CI 0.34-1.03], p = 0.002) were associated with syrinx diameter stability, whereas shorter preoperative syrinx length (5.75 ± 4.01 vs 9.65 ± 4.31 levels; HR 0.21 [95% CI 0.12-0.38], p = 0.0001) and smaller pB-C2 distance (6.86 ± 1.27 vs 7.18 ± 1.38 mm; HR 1.44 [95% CI 1.02-2.05], p = 0.04) were associated with syrinx length stability. Finally, younger age at surgery (8.19 ± 5.02 vs 10.29 ± 4.25 years; HR 1.89 [95% CI 1.31-3.04], p = 0.01) was associated with syrinx diameter progression, whereas increased postoperative syrinx diameter (6.73 ± 3.64 vs 3.97 ± 3.07 mm; HR 3.10 [95% CI 1.67-5.76], p = 0.003), was associated with syrinx length progression. PFD versus PFDD was not associated with syrinx progression or reoperation rate.

CONCLUSIONS

These data suggest that PFDD and age are independently associated with radiological syrinx improvement, although forthcoming results from the PFDD versus PFD randomized controlled trial (NCT02669836, clinicaltrials.gov) will best answer this question.

High Prevalence of Gram-Negative Rod and Multi-Organism Surgical Site Infections after Pediatric Complex Tethered Spinal Cord Surgery: Preliminary Report from a Single-Center Study

BACKGROUND

Surgical site infections (SSIs) are one of the most common complications following pediatric complex tethered spinal cord release. This patient population is similar in some ways to the neuromuscular scoliosis population, in which higher-than-expected rates of gram-negative SSIs have been identified.

METHODS

We conducted a single-center retrospective chart review of all patients who underwent complex tethered spinal cord release over a 10-year period between 2007 and 2017.

RESULTS

A total of 69 patients were identified, with 10 documented SSIs (14%). 50% of the SSIs were polymicrobial or included at least 1 gram-negative organism. Among the organisms isolated, 3 were fully or -partially resistant to cefazolin, the most common antibiotic prophylaxis in this population.

CONCLUSION

Among children undergoing complex tethered spinal cord release, gram-negative and polymicrobial infections are a significant cause of SSIs. Although further multicenter data are needed, these findings suggest that standard antibiotic prophylaxis with cefazolin may not be sufficient.

Opioid-Sparing Multimodal Analgesia After Selective Dorsal Rhizotomy

OBJECTIVES

Multimodal analgesia (MMA) may reduce opioid use among children who are hospitalized, and may contribute toward enhanced recovery after selective dorsal rhizotomy (SDR) for patients with spasticity in pediatric cerebral palsy. In this retrospective cohort study, we assess an MMA protocol consisting of scheduled nonsteroidal antiinflammatory drug doses (ketorolac or ibuprofen), alternating with scheduled acetaminophen and diazepam doses, with as-needed opioids. It was hypothesized that protocol use would be associated with reductions in opioid requirements and other clinical improvements.

METHODS

Data were obtained for 52 patients undergoing SDR at an academic tertiary care pediatric hospital (2012-2017, with the protocol implemented in 2014). Using a retrospective cohort design, we compared outcomes between protocol and nonprotocol patients, employing both univariate t test and Wilcoxon rank test comparisons as well as multivariable regression methods. The primary outcome was total as-needed opioid requirements over postoperative days (PODs) 0 to 2, measured in oral morphine milligram equivalents per kilogram. Additional outcomes included antiemetic medication doses, discharge opioid prescriptions, total direct cost, and length of stay.

RESULTS

Twelve patients received the MMA protocol, and 40 patients did not. POD-0 MMA initiation was independently associated with a reduction of 0.14 morphine milligram equivalents per kilogram in mean opioid requirements over PODs 0 to 2 in the multiple regression analysis (95% confidence interval 0.01 to 0.28; P = .04). No statistically significant differences were demonstrated in doses of antiemetic medications, discharge opioid prescriptions, total direct cost, and length of stay.

CONCLUSIONS

This MMA protocol may help reduce opioid use after SDR. Improving protocol implementation in a prospective, multisite study will help elucidate further MMA effects on pain, costs, and recovery.

Increased complications without neurological benefit are associated with prophylactic spinal cord untethering prior to scoliosis surgery in children with myelomeningocele

PURPOSE

Children with myelomeningocele (MMC) are at increased risk of developing neuromuscular scoliosis and spinal cord re-tethering (Childs Nerv Syst 12:748-754, 1996; Neurosurg Focus 16:2, 2004; Neurosurg Focus 29:1, 2010). Some centers perform prophylactic untethering on asymptomatic MMC patients prior to scoliosis surgery because of concern that additional traction on the cord may place the patient at greater risk of neurologic deterioration peri-operatively. However, prophylactic untethering may not be justified if it carries increased surgical risks. The purpose of this study was to determine if prophylactic untethering is necessary in asymptomatic children with MMC undergoing scoliosis surgery.

METHODS

A multidisciplinary, retrospective cohort study from seven children's hospitals was performed including asymptomatic children with MMC < 21 years old, managed with or without prophylactic untethering prior to scoliosis surgery. Patients were divided into three groups for analysis: (1) untethering at the time of scoliosis surgery (concomitant untethering), (2) untethering within 3 months of scoliosis surgery (prior untethering), and (3) no prophylactic untethering. Baseline data, intra-operative reports, and 90-day post-operative outcomes were analyzed to assess for differences in neurologic outcomes, surgical complications, and overall length of stay.

RESULTS

A total of 208 patients were included for analysis (mean age 9.4 years, 52% girls). No patient in any of the groups exhibited worsened motor or sensory function at 90 days post-operatively. However, comparing the prophylactic untethering groups with the group that was not untethered, there was an increased risk of surgical site infection (SSI) (31.3% concomitant, 28.6% prior untethering vs. 12.3% no untethering; p = 0.0104), return to the OR (43.8% concomitant, 23.8% prior untethering vs. 17.4% no untethering; p = 0.0047), need for blood transfusion (51.6% concomitant, 57.1% prior untethering vs. 33.8% no untethering; p = 0.04), and increased mean length of stay (LOS) (13.4 days concomitant, 10.6 days prior untethering vs. 6.8 days no untethering; p < 0.0001). In multivariable logistic regression analysis, prophylactic untethering was independently associated with increased adjusted relative risks of surgical site infection (aRR = 2.65, 95% CI 1.17-5.02), unplanned re-operation (aRR = 2.17, 95% CI 1.02-4.65), and any complication (aRR = 2.25, 95% CI 1.07-4.74).

CONCLUSION

In this study, asymptomatic children with myelomeningocele who underwent scoliosis surgery developed no neurologic injuries regardless of prophylactic untethering. However, those who underwent prophylactic untethering were more likely to experience SSIs, return to the OR, need a blood transfusion, and have increased LOS than children not undergoing untethering. Based on these data, prophylactic untethering in asymptomatic MMC patients prior to scoliosis surgery does not provide any neurological benefit and is associated with increased surgical risks.

Assessment of craniocervical motion in Down syndrome: a pilot study of two measurement techniques

OBJECTIVE

Hypermobility of the craniocervical junction (CCJ) in patients with Down syndrome (DS) is common. Whereas atlantoaxial (C1-2) hypermobility is well characterized, occipitoatlantal (Oc-C1) laxity is recognized but poorly defined. A clear understanding of the risks associated with DS-related hypermobility is lacking. Research efforts to address the topic of axial cervical spine instability in the patient with DS require a reliable and reproducible means of assessing CCJ mobility. The authors conducted a pilot study comparing two methods of quantifying motion of the CCJ on dynamic (flexion/extension) plain radiographs: the delta-condyle-axial interval (ΔCAI) and the delta-basion-axial interval (ΔBAI) methods.

METHODS

Dynamic radiographs from a cohort of 10 patients with DS were evaluated according to prescribed standards. Independent movement of Oc-C1, C1-2, and Oc-C2 was calculated. Interrater and intrarater reliability for CCJ mobility was then calculated for both techniques.

RESULTS

Measurement using the ΔCAI technique had excellent fidelity with intraclass correlation coefficients (ICCs) of 0.77, 0.71, and 0.80 for Oc-C1, C1-2, and Oc-C2, respectively. The ΔBAI technique had lower fidelity, yielding respective ICCs of 0.61, 0.65, and 0.50.

CONCLUSIONS

This pilot study suggests that ΔCAI is a superior measurement technique compared to ΔBAI and may provide reliable assessment of the mobility of the CCJ on dynamic radiographs in the pediatric patient with DS. The use of reliable and reproducible measurement techniques strengthens the validity of research derived from pooled database efforts.

Radiological and clinical predictors of scoliosis in patients with Chiari malformation type I and spinal cord syrinx from the Park-Reeves Syringomyelia Research Consortium

OBJECTIVE

Scoliosis is frequently a presenting sign of Chiari malformation type I (CM-I) with syrinx. The authors' goal was to define scoliosis in this population and describe how radiological characteristics of CM-I and syrinx relate to the presence and severity of scoliosis.

METHODS

A large multicenter retrospective and prospective registry of pediatric patients with CM-I (tonsils ≥ 5 mm below the foramen magnum) and syrinx (≥ 3 mm in axial width) was reviewed for clinical and radiological characteristics of CM-I, syrinx, and scoliosis (coronal curve ≥ 10°).

RESULTS

Based on available imaging of patients with CM-I and syrinx, 260 of 825 patients (31%) had a clear diagnosis of scoliosis based on radiographs or coronal MRI. Forty-nine patients (5.9%) did not have scoliosis, and in 516 (63%) patients, a clear determination of the presence or absence of scoliosis could not be made. Comparison of patients with and those without a definite scoliosis diagnosis indicated that scoliosis was associated with wider syrinxes (8.7 vs 6.3 mm, OR 1.25, p < 0.001), longer syrinxes (10.3 vs 6.2 levels, OR 1.18, p < 0.001), syrinxes with their rostral extent located in the cervical spine (94% vs 80%, OR 3.91, p = 0.001), and holocord syrinxes (50% vs 16%, OR 5.61, p < 0.001). Multivariable regression analysis revealed syrinx length and the presence of holocord syrinx to be independent predictors of scoliosis in this patient cohort. Scoliosis was not associated with sex, age at CM-I diagnosis, tonsil position, pB-C2 distance (measured perpendicular distance from the ventral dura to a line drawn from the basion to the posterior-inferior aspect of C2), clivoaxial angle, or frontal-occipital horn ratio. Average curve magnitude was 29.9°, and 37.7% of patients had a left thoracic curve. Older age at CM-I or syrinx diagnosis (p < 0.0001) was associated with greater curve magnitude whereas there was no association between syrinx dimensions and curve magnitude.

CONCLUSIONS

Syrinx characteristics, but not tonsil position, were related to the presence of scoliosis in patients with CM-I, and there was an independent association of syrinx length and holocord syrinx with scoliosis. Further study is needed to evaluate the nature of the relationship between syrinx and scoliosis in patients with CM-I.

Morphometric changes at the craniocervical junction during childhood

OBJECTIVE

Current understanding of how the pediatric craniocervical junction develops remains incomplete. Measurements of anatomical relationships at the craniocervical junction can influence clinical and surgical decision-making. The purpose of this analysis was to quantitatively define clinically relevant craniocervical junction measurements in a population of children with CT scans that show normal anatomy.

METHODS

A total of 1458 eligible patients were identified from children between 1 and 18 years of age who underwent cervical spine CT scanning at a single institution. Patients were separated by both sex and age in years into 34 groups. Following this, patients within each group were randomly selected for inclusion until a target of 15 patients in each group had been reached. Each patient underwent measurement of the occipital condyle-C1 interval (CCI), pB-C2, atlantodental interval (ADI), basion-dens interval (BDI), basion-opisthion diameter (BOD), basion-axial interval (BAI), dens angulation, and canal diameter at C1. Mean values were calculated in each group. Each measurement was performed by two teams and compared for intraclass correlation coefficient (ICC).

RESULTS

The data showed that CCI, ADI, BDI, and dens angulation decrease in magnitude throughout childhood, while pB-C2, PADI, BAI, and BOD increase throughout childhood, with an ICC of fair to good (range 0.413-0.912). Notably, CCI decreases continuously on coronal CT scans, whereas on parasagittal CT scans, CCI does not decrease until after age 9, when it shows a continuous decline similar to measurements on coronal CT scans.

CONCLUSIONS

These morphometric analyses establish parameters for normal pediatric craniocervical spine growth for each year of life up to 18 years. The data should be considered when evaluating children for potential surgical intervention.

Cerebral Vasospasm after Open Fenestration of an Arachnoid Cyst in a 4-Year-Old Boy: Case Report and Review of the Literature

Cerebral vasospasm is associated with significant morbidity, and most commonly occurs following subarachnoid hemorrhage. Rarely, vasospasm can follow tumor resection and traumatic brain injury. We present the first reported case of a young child who developed diffuse vasospasm following open fenestration of an arachnoid cyst and was promptly treated, with full recovery of neurologic function. Although vasopasm after arachnoid cyst fenestration is rare, it can be included in the differential for a new focal neurologic deficit.

Traumatic Occipitocervical Distraction Injuries in Children: A Systematic Review

BACKGROUND

Occipitocervical distraction injuries (OCDI) in children occur on a wide spectrum of severity, and decisions about treatment suffer from a lack of rigorous guidelines and significant inter-institutional variability. While clear cases of frank atlanto-occipital dislocation (AOD) are treated with surgical stabilization, the approach for less severe cases of OCDI is not standardized. These patients require a careful assessment of both radiographic and clinical criteria, as part of a complex risk-benefit analysis, to establish whether occipitocervical fusion (OCF) is indicated. Here, we performed a systematic review of the literature that describes traumatic OCDI in children < 18 years of age.

SUMMARY

We performed a systematic review, according to PRISMA guidelines, of children < 18 years of age presenting with traumatic etiologies of OCDI. We searched PubMed to identify papers congruent with these criteria. Exclusion criteria included (1) reports on atraumatic causes of OCDI and (2) studies with insufficient clinical and radiographic details on individual patients. We identified 16 reports describing a total of 144 patients treated for pediatric traumatic OCDI. Based on the synthesis of these findings and the collective experience of the authors, we present the demographic, clinical, and radiographic factors that underlie OC instability, which we hope will serve as components of a grading system in the future. We considered various clinical and radiographic findings including: (1) the mechanism of injury, (2) the patient's age, (3) CT/CT angiography of head and neck findings and parameters, (4) MRI findings, and (5) neurological exam, for the purpose of determining the severity of the OCDI and offering treatment guidelines based on the summative risk of underlying OC instability. Key Messages: OCDI is a potentially devastating injury, especially in children. Although missing the diagnosis can have potentially catastrophic consequences, reverting to surgical fixation in less severe cases can subject children to unnecessary operative risk and permanently reduce their range of motion. After reviewing all the available reports of pediatric traumatic OCDI in the neurosurgical literature, we propose an outline of clinical and radiographic factors influencing underlying OC instability that could be incorporated into a grading scale to guide treatment. We hope this study stimulates discussion on the standardization of treatment for pediatric OCDI.

Variation in the management of isolated craniosynostosis: a survey of the Synostosis Research Group

OBJECTIVEThe authors created a collaborative network, the Synostosis Research Group (SynRG), to facilitate multicenter clinical research on craniosynostosis. To identify common and differing practice patterns within the network, they assessed the SynRG surgeons' management preferences for sagittal synostosis. These results will be incorporated into planning cooperative studies.METHODSThe SynRG consists of 12 surgeons at 5 clinical sites. An email survey was distributed to SynRG surgeons in late 2016, and responses were collected through early 2017. Responses were collated and analyzed descriptively.RESULTSAll of the surgeons-7 plastic/craniofacial surgeons and 5 neurosurgeons-completed the survey. They varied in both experience (1-24 years) and sagittal synostosis case volume in the preceding year (5-45 cases). Three sites routinely perform preoperative CT scans. The preferred surgical technique for children younger than 3 months is strip craniectomy (10/12 surgeons), whereas children older than 6 months are all treated with open cranial vault surgery. Pre-incision cefazolin, preoperative complete blood count panels, and an arterial line were used by most surgeons, but tranexamic acid was used routinely at 3 sites and never at the other 2 sites. Among surgeons performing endoscopic strip craniectomy surgery (SCS), most create a 5-cm-wide craniectomy, whereas 2 surgeons create a 2-cm strip. Four surgeons routinely send endoscopic SCS patients to the intensive care unit after surgery. Two of the 5 sites routinely obtain a CT scan within the 1st year after surgery.CONCLUSIONSThe SynRG surgeons vary substantially in the use of imaging, the choice of surgical procedure and technique, and follow-up. A collaborative network will provide the opportunity to study different practice patterns, reduce variation, and contribute multicenter data on the management of children with craniosynostosis.

Development of best practices to minimize wound complications after complex tethered spinal cord surgery: a modified Delphi study

OBJECTIVEComplications after complex tethered spinal cord (cTSC) surgery include infections and cerebrospinal fluid (CSF) leaks. With little empirical evidence to guide management, there is variability in the interventions undertaken to limit complications. Expert-based best practices may improve the care of patients undergoing cTSC surgery. Here, authors conducted a study to identify consensus-driven best practices.METHODSThe Delphi method was employed to identify consensual best practices. A literature review regarding cTSC surgery together with a survey of current practices was distributed to 17 board-certified pediatric neurosurgeons. Thirty statements were then formulated and distributed to the group. Results of the second survey were discussed during an in-person meeting leading to further consensus, which was defined as ≥ 80% agreement on a 4-point Likert scale (strongly agree, agree, disagree, strongly disagree).RESULTSSeventeen consensus-driven best practices were identified, with all participants willing to incorporate them into their practice. There were four preoperative interventions: (1, 2) asymptomatic AND symptomatic patients should be referred to urology preoperatively, (3, 4) routine preoperative urine cultures are not necessary for asymptomatic AND symptomatic patients. There were nine intraoperative interventions: (5) patients should receive perioperative cefazolin or an equivalent alternative in the event of allergy, (6) chlorhexidine-based skin preparation is the preferred regimen, (7) saline irrigation should be used intermittently throughout the case, (8) antibiotic-containing irrigation should be used following dural closure, (9) a nonlocking running suture technique should be used for dural closure, (10) dural graft overlay should be used when unable to obtain primary dural closure, (11) an expansile dural graft should be incorporated in cases of lipomyelomeningocele in which primary dural closure does not permit free flow of CSF, (12) paraxial muscles should be closed as a layer separate from the fascia, (13) routine placement of postoperative drains is not necessary. There were three postoperative interventions: (14) postoperative antibiotics are an option and, if given, should be discontinued within 24 hours; (15) patients should remain flat for at least 24 hours postoperatively; (16) routine use of abdominal binders or other compressive devices postoperatively is not necessary. One intervention was prioritized for additional study: (17) further study of additional gram-negative perioperative coverage is needed.CONCLUSIONSA modified Delphi technique was used to develop consensus-driven best practices for decreasing wound complications after cTSC surgery. Further study is required to determine if implementation of these practices will lead to reduced complications. Discussion through the course of this study resulted in the initiation of a multicenter study of gram-negative surgical site infections in cTSC surgery.

Comparison of Fusion Rates Based on Graft Material Following Occipitocervical and Atlantoaxial Arthrodesis in Adults and Children

BACKGROUND

Fusion rates following rigid internal instrumentation for occipitocervical and atlantoaxial instability approach 100% in many reports. Based on this success and the morbidity that can be associated with obtaining autograft for fusion, surgeons increasingly select alternative graft materials.

OBJECTIVE

To examine fusion failure using various graft materials in a retrospective observational study.

METHODS

Insurance claims databases (Truven Health MarketScan® [Truven Health Analytics, Ann Arbor, Michigan] and IMS Health Lifelink/PHARMetrics [IMS Health, Danbury, Connecticut]) were used to identify patients with CPT codes 22590 and 22595. Patients were divided by age (≥18 yr = adult) and arthrodesis code, establishing 4 populations. Each population was further separated by graft code: group 1 = 20938 (structural autograft); group 2 = 20931 (structural allograft); group 3 = other graft code (nonstructural); group 4 = no graft code. Fusion failure was assigned when ≥1 predetermined codes presented in the record ≥90 d following the last surgical procedure.

RESULTS

Of 522 patients identified, 419 were adult and 103 were pediatric. Fusion failure occurred in 10.9% (57/522) of the population. There was no statistically significant difference in fusion failure based on graft material. Fusion failure occurred in 18.9% of pediatric occipitocervical fusions, but in 9.2% to 11.1% in the other groups.

CONCLUSION

Administrative data regarding patients who underwent instrumented occipitocervical or atlantoaxial arthrodesis do not demonstrate differences in fusion rates based on the graft material selected. When compared to many contemporary primary datasets, fusion failure was more frequent; however, several recent studies have shown higher failure rates than previously reported. This may be influenced by broad patient selection and fusion failure criteria that were selected in order to maximize the generalizability of the findings.

Growth and alignment of the pediatric subaxial cervical spine following rigid instrumentation and fusion: a multicenter study of the Pediatric Craniocervical Society

OBJECTIVE The long-term effects of surgical fusion on the growing subaxial cervical spine are largely unknown. Recent cross-sectional studies have demonstrated that there is continued growth of the cervical spine through the teenage years. The purpose of this multicenter study was to determine the effects of rigid instrumentation and fusion on the growing subaxial cervical spine by investigating vertical growth, cervical alignment, cervical curvature, and adjacent-segment instability over time. METHODS A total of 15 centers participated in this multi-institutional retrospective study. Cases involving children less than 16 years of age who underwent rigid instrumentation and fusion of the subaxial cervical spine (C-2 and T-1 inclusive) with at least 1 year of clinical and radiographic follow-up were investigated. Charts were reviewed for clinical data. Postoperative and most recent radiographs, CT, and MR images were used to measure vertical growth and assess alignment and stability. RESULTS Eighty-one patients were included in the study, with a mean follow-up of 33 months. Ninety-five percent of patients had complete clinical resolution or significant improvement in symptoms. Postoperative cervical kyphosis was seen in only 4 patients (5%), and none developed a swan-neck deformity, unintended adjacent-level fusion, or instability. Of patients with at least 2 years of follow-up, 62% demonstrated growth across the fusion construct. On average, vertical growth was 79% (4-level constructs), 83% (3-level constructs), or 100% (2-level constructs) of expected growth. When comparing the group with continued vertical growth to the one without growth, there were no statistically significant differences in terms of age, sex, underlying etiology, surgical approach, or number of levels fused. CONCLUSIONS Continued vertical growth of the subaxial spine occurs in nearly two-thirds of children after rigid instrumentation and fusion of the subaxial spine. Failure of continued vertical growth is not associated with the patient's age, sex, underlying etiology, number of levels fused, or surgical approach. Further studies are needed to understand this dichotomy and determine the long-term biomechanical effects of surgery on the growing pediatric cervical spine.

Identifying Factors Predictive of Atlantoaxial Fusion Failure in Pediatric Patients: Lessons Learned From a Retrospective Pediatric Craniocervical Society Study

STUDY DESIGN

Multicenter retrospective cohort study with multivariate analysis.

OBJECTIVE

To determine factors predictive of posterior atlantoaxial fusion failure in pediatric patients.

SUMMARY OF BACKGROUND DATA

Fusion rates for pediatric posterior atlantoaxial arthrodesis have been reported to be high in single-center studies; however, factors predictive of surgical non-union have not been identified by a multicenter study.

METHODS

Clinical and surgical details for all patients who underwent posterior atlantoaxial fusion at seven pediatric spine centers from 1995 to 2014 were retrospectively recorded. The primary outcome was surgical failure, defined as either instrumentation failure or fusion failure seen on either plain x-ray or computed tomography scan. Multiple logistic regression analysis was undertaken to identify clinical and technical factors predictive of surgical failure.

RESULTS

One hundred thirty-one patients met the inclusion criteria and were included in the analysis. Successful fusion was seen in 117 (89%) of the patients. Of the 14 (11%) patients with failed fusion, the cause was instrumentation failure in 3 patients (2%) and graft failure in 11 (8%). Multivariate analysis identified Down syndrome as the single factor predictive of fusion failure (odds ratio 14.6, 95% confidence interval [3.7-64.0]).

CONCLUSION

This retrospective analysis of a multicenter cohort demonstrates that although posterior pediatric atlantoaxial fusion success rates are generally high, Down syndrome is a risk factor that significantly predicts the possibility of surgical failure.

LEVEL OF EVIDENCE

3.

Use of Fetal Magnetic Resonance Image Analysis and Machine Learning to Predict the Need for Postnatal Cerebrospinal Fluid Diversion in Fetal Ventriculomegaly

IMPORTANCE

Which children with fetal ventriculomegaly, or enlargement of the cerebral ventricles in utero, will develop hydrocephalus requiring treatment after birth is unclear.

OBJECTIVE

To determine whether extraction of multiple imaging features from fetal magnetic resonance imaging (MRI) and integration using machine learning techniques can predict which patients require postnatal cerebrospinal fluid (CSF) diversion after birth.

DESIGN, SETTING, AND PATIENTS

This retrospective case-control study used an institutional database of 253 patients with fetal ventriculomegaly from January 1, 2008, through December 31, 2014, to generate a predictive model. Data were analyzed from January 1, 2008, through December 31, 2015. All 25 patients who required postnatal CSF diversion were selected and matched by gestational age with 25 patients with fetal ventriculomegaly who did not require CSF diversion (discovery cohort). The model was applied to a sample of 24 consecutive patients with fetal ventriculomegaly who underwent evaluation at a separate institution (replication cohort) from January 1, 1998, through December 31, 2007. Data were analyzed from January 1, 1998, through December 31, 2009.

EXPOSURES

To generate the model, linear measurements, area, volume, and morphologic features were extracted from the fetal MRI, and a machine learning algorithm analyzed multiple features simultaneously to find the combination that was most predictive of the need for postnatal CSF diversion.

MAIN OUTCOMES AND MEASURES

Accuracy, sensitivity, and specificity of the model in correctly classifying patients requiring postnatal CSF diversion.

RESULTS

A total of 74 patients (41 girls [55%] and 33 boys [45%]; mean [SD] gestational age, 27.0 [5.6] months) were included from both cohorts. In the discovery cohort, median time to CSF diversion was 6 days (interquartile range [IQR], 2-51 days), and patients with fetal ventriculomegaly who did not develop symptoms were followed up for a median of 29 months (IQR, 9-46 months). The model correctly classified patients who required CSF diversion with 82% accuracy, 80% sensitivity, and 84% specificity. In the replication cohort, the model achieved 91% accuracy, 75% sensitivity, and 95% specificity.

CONCLUSION AND RELEVANCE

Image analysis and machine learning can be applied to fetal MRI findings to predict the need for postnatal CSF diversion. The model provides prognostic information that may guide clinical management and select candidates for potential fetal surgical intervention.

Temporary occipital fixation in young children with severe cervical-thoracic spinal deformity

OBJECTIVE The long-term effects of instrumentation and fusion of the occipital-cervical-thoracic spine on spinal growth in young children are poorly understood. To mitigate the effects of this surgery on the growing pediatric spine, the authors report a novel technique used in 4 children with severe cervical-thoracic instability. These patients underwent instrumentation from the occiput to the upper thoracic region for stabilization, but without bone graft at the craniovertebral junction (CVJ). Subsequent surgery was then performed to remove the occipital instrumentation, thereby allowing further growth and increased motion across the CVJ. METHODS Three very young children (15, 30, and 30 months old) underwent occipital to thoracic posterior segmental instrumentation due to cervical or upper thoracic dislocation, progressive kyphosis, and myelopathy. The fourth child (10 years old) underwent similar instrumentation for progressive cervical-thoracic scoliosis. Bone graft was placed at and distal to C-2 only. After follow-up CT scans demonstrated posterior arthrodesis without unintended fusion from the occiput to C-2, 3 patients underwent removal of the occipital instrumentation. RESULTS Follow-up cervical spine flexion/extension radiographs demonstrated partial restoration of motion at the CVJ. One patient has not had the occipital instrumentation removed yet, because only 4 months have elapsed since her operation. CONCLUSIONS Temporary fixation to the occiput provides increased biomechanical stability for spinal stabilization in young children, without permanently eliminating motion and growth at the CVJ. This technique can be considered in children who require longer instrumentation constructs for temporary stabilization, but who only need fusion in more limited areas where spinal instability exists.

Molecular Analyses Reveal Inflammatory Mediators in the Solid Component and Cyst Fluid of Human Adamantinomatous Craniopharyngioma

Pediatric adamantinomatous craniopharyngioma (ACP) is a highly solid and cystic tumor, often causing substantial damage to critical neuroendocrine structures such as the hypothalamus, pituitary gland, and optic apparatus. Paracrine signaling mechanisms driving tumor behavior have been hypothesized, with IL-6R overexpression identified as a potential therapeutic target. To identify potential novel therapies, we characterized inflammatory and immunomodulatory factors in ACP cyst fluid and solid tumor components. Cytometric bead analysis revealed a highly pro-inflammatory cytokine pattern in fluid from ACP compared to fluids from another cystic pediatric brain tumor, pilocytic astrocytoma. Cytokines and chemokines with particularly elevated concentrations in ACPs were IL-6, CXCL1 (GRO), CXCL8 (IL-8) and the immunosuppressive cytokine IL-10. These data were concordant with solid tumor compartment transcriptomic data from a larger cohort of ACPs, other pediatric brain tumors and normal brain. The majority of receptors for these cytokines and chemokines were also over-expressed in ACPs. In addition to IL-10, the established immunosuppressive factor IDO-1 was overexpressed by ACPs at the mRNA and protein levels. These data indicate that ACP cyst fluids and solid tumor components are characterized by an inflammatory cytokine and chemokine expression pattern. Further study regarding selective cytokine blockade may inform novel therapeutic interventions.

Analysis and interrater reliability of pB-C2 using MRI and CT: data from the Park-Reeves Syringomyelia Research Consortium on behalf of the Pediatric Craniocervical Society

OBJECTIVE The distance to the ventral dura, perpendicular to the basion to C2 line (pB-C2), is commonly employed as a measure describing the anatomy of the craniovertebral junction. However, both the reliability among observers and the clinical utility of this measurement in the context of Chiari malformation Type I (CM-I) have been incompletely determined. METHODS Data were reviewed from the first 600 patients enrolled in the Park-Reeves Syringomyelia Research Consortium with CM-I and syringomyelia. Thirty-one cases were identified in which both CT and MRI studies were available for review. Three pediatric neurosurgeons independently determined pB-C2 values using common imaging sequences: MRI (T1-weighted and T2-weighted with and without the inclusion of retro-odontoid soft tissue) and CT. Values were compared and intraclass correlations were calculated among imaging modalities and observers. RESULTS Intraclass correlation of pB-C2 demonstrated strong agreement between observers (intraclass correlation coefficient [ICC] range 0.72-0.76). Measurement using T2-weighted MRI with the inclusion of retro-odontoid soft tissue showed no significant difference with measurement using T1-weighted MRI. Measurements using CT or T2-weighted MRI without retro-odontoid soft tissue differed by 1.6 mm (4.69 and 3.09 mm, respectively, p < 0.05) and were significantly shorter than those using the other 2 sequences. Conclusions pB-C2 can be measured reliably by multiple observers in the context of pediatric CM-I with syringomeyelia. Measurement using T2-weighted MRI excluding retro-odontoid soft tissue closely approximates the value obtained using CT, which may allow for the less frequent use of CT in this patient population. Measurement using T2-weighted MRI including retro-odontoid soft tissue or using T1-weighted MRI yields a more complete assessment of the extent of ventral brainstem compression, but its association with clinical outcomes requires further study.

Morphometric analysis of the developing pediatric cervical spine

OBJECTIVE Our understanding of pediatric cervical spine development remains incomplete. The purpose of this analysis was to quantitatively define cervical spine growth in a population of children with normal CT scans. METHODS A total of 1458 children older than 1 year and younger than 18 years of age who had undergone a cervical spine CT scan at the authors' institution were identified. Subjects were separated by sex and age (in years) into 34 groups. Following this assignment, subjects within each group were randomly selected for inclusion until a target of 15 subjects in each group had been measured. Linear measurements were performed on the midsagittal image of the cervical spine. Twenty-three unique measurements were obtained for each subject. RESULTS Data showed that normal vertical growth of the pediatric cervical spine continues up to 18 years of age in boys and 14 years of age in girls. Approximately 75% of the vertical growth occurs throughout the subaxial spine and 25% occurs across the craniovertebral region. The C-2 body is the largest single-segment contributor to vertical growth, but the subaxial vertebral bodies and disc spaces also contribute. Overall vertical growth of the cervical spine throughout childhood is dependent on individual vertebral body growth as well as vertical growth of the disc spaces. The majority of spinal canal diameter growth occurs by 4 years of age. CONCLUSIONS The authors' morphometric analyses establish parameters for normal pediatric cervical spine growth up to 18 years of age. These data should be considered when evaluating children for potential surgical intervention and provide a basis of comparison for studies investigating the effects of cervical spine instrumentation and fusion on subsequent growth.

Chiari malformation Type I surgery in pediatric patients. Part 1: validation of an ICD-9-CM code search algorithm

OBJECTIVE Administrative billing data may facilitate large-scale assessments of treatment outcomes for pediatric Chiari malformation Type I (CM-I). Validated International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) code algorithms for identifying CM-I surgery are critical prerequisites for such studies but are currently only available for adults. The objective of this study was to validate two ICD-9-CM code algorithms using hospital billing data to identify pediatric patients undergoing CM-I decompression surgery. METHODS The authors retrospectively analyzed the validity of two ICD-9-CM code algorithms for identifying pediatric CM-I decompression surgery performed at 3 academic medical centers between 2001 and 2013. Algorithm 1 included any discharge diagnosis code of 348.4 (CM-I), as well as a procedure code of 01.24 (cranial decompression) or 03.09 (spinal decompression or laminectomy). Algorithm 2 restricted this group to the subset of patients with a primary discharge diagnosis of 348.4. The positive predictive value (PPV) and sensitivity of each algorithm were calculated. RESULTS Among 625 first-time admissions identified by Algorithm 1, the overall PPV for CM-I decompression was 92%. Among the 581 admissions identified by Algorithm 2, the PPV was 97%. The PPV for Algorithm 1 was lower in one center (84%) compared with the other centers (93%-94%), whereas the PPV of Algorithm 2 remained high (96%-98%) across all subgroups. The sensitivity of Algorithms 1 (91%) and 2 (89%) was very good and remained so across subgroups (82%-97%). CONCLUSIONS An ICD-9-CM algorithm requiring a primary diagnosis of CM-I has excellent PPV and very good sensitivity for identifying CM-I decompression surgery in pediatric patients. These results establish a basis for utilizing administrative billing data to assess pediatric CM-I treatment outcomes.

Chiari malformation Type I surgery in pediatric patients. Part 2: complications and the influence of comorbid disease in California, Florida, and New York

OBJECTIVE Chiari malformation Type I (CM-I) is a common and often debilitating pediatric neurological disease. However, efforts to guide preoperative counseling and improve outcomes research are impeded by reliance on small, single-center studies. Consequently, the objective of this study was to investigate CM-I surgical outcomes using population-level administrative billing data. METHODS The authors used Healthcare Cost and Utilization Project State Inpatient Databases (SID) to study pediatric patients undergoing surgical decompression for CM-I from 2004 to 2010 in California, Florida, and New York. They assessed the prevalence and influence of preoperative complex chronic conditions (CCC) among included patients. Outcomes included medical and surgical complications within 90 days of treatment. Multivariate logistic regression was used to identify risk factors for surgical complications. RESULTS A total of 936 pediatric CM-I surgeries were identified for the study period. Overall, 29.2% of patients were diagnosed with syringomyelia and 13.7% were diagnosed with scoliosis. Aside from syringomyelia and scoliosis, 30.3% of patients had at least 1 CCC, most commonly neuromuscular (15.2%) or congenital or genetic (8.4%) disease. Medical complications were uncommon, occurring in 2.6% of patients. By comparison, surgical complications were diagnosed in 12.7% of patients and typically included shunt-related complications (4.0%), meningitis (3.7%), and other neurosurgery-specific complications (7.4%). Major complications (e.g., stroke or myocardial infarction) occurred in 1.4% of patients. Among children with CCCs, only comorbid hydrocephalus was associated with a significantly increased risk of surgical complications (OR 4.5, 95% CI 2.5-8.1). CONCLUSIONS Approximately 1 in 8 pediatric CM-I patients experienced a surgical complication, whereas medical complications were rare. Although CCCs were common in pediatric CM-I patients, only hydrocephalus was independently associated with increased risk of surgical events. These results may inform patient counseling and guide future research efforts.

Bilateral occipital endoscopic choroid plexus cauterization for persistent hydrocephalus following frontal endoscopic third ventriculostomy and choroid plexus cauterization--the "bowling ball" technique

Endoscopic third ventriculostomy with choroid plexus cauterization (ETV/CPC) as a primary treatment for hydrocephalus is gaining popularity in North America, particularly among the infant population. Unfortunately, despite considerable experience with ETV/CPC at several centers, treatment failures still exist. Early reports have suggested that greater than 90 % cauterization of the choroid plexus is associated with improved clinical outcomes. However, individual patient anatomy and smaller overall ventricular size can limit the amount of choroid plexus cauterization that is technically possible through a single frontal burr hole. Furthermore, the degree of cauterization achieved by surgeons using this technique is difficult to quantify objectively. In this report, we describe the case of an infant who failed initial ETV/CPC but then had successful resolution of hydrocephalus after additional choroid plexus cauterization performed through bilateral occipital burr holes. The child remains shunt-free over a year after treatment, suggesting that this three-pronged CPC approach (the "bowling ball" technique) may be successful in some young children with persistent hydrocephalus after ETV/CPC from a single frontal burr hole.