The role of reoperation in pediatric cerebellar pilocytic astrocytoma.

OBJECTIVE: Cerebellar pilocytic astrocytomas (cPAs) in childhood have long been recognized to have a good prognosis after total resection, but the outcome after incomplete resective surgery remains largely unpredictable, with the incidence of radiological progressive disease ranging from 18% to 100%. It has been traditionally thought that gross-total resection was required for long-term survival, and small residuals were classically resected in a subsequent operation. METHODS: The authors analyzed their pediatric low-grade glioma (PLGG) database for cases treated between 1985 and 2020 and filtered for intracranial PAs, to determine what clinical or radiological factors precipitated revisional resective surgery in their single quaternary care center cohort. RESULTS: Using the pediatric low-grade glioma database, 283 patients were identified to have a histopathological diagnosis of intracranial PA between 1985 and 2020, of which 200 lesions were within the cerebellum (70.7%). The majority of patients with cPA were between 1 and 10 years of age (n = 145, 72.5%) without gender predominance (M/F = 99:101), usually presenting with 1 lesion (n = 197, 98.5%). Gross-total resection was achieved in 74.5% (n = 149) of initial surgeries for cPA. In patients with subtotal resection, the mean largest diameter of the postoperative residual tumor was 1.06 cm (range 0-2.95 cm). Seven patients with subtotal resection did not require a second resective intervention. In 31 patients the neuro-oncology multidisciplinary team recommended a second resection at a mean time interval of 22.9 months (range 0.13-81.6 months) from the initial surgery. Proportionally, the children who underwent multiple resections were also more likely to receive adjuvant chemo/radiotherapy. Functionally, the children in the multiple operation cohort experienced more complications of therapy including ongoing endocrinopathy, treatment-associated hearing deficit, and neurocognitive deficits. CONCLUSIONS: Residual disease in cPA should be maintained under clinicocoradiological surveillance postoperatively with adoption of a more conservative approach when residual disease is not significantly changing over time.

Early Intervention and Use of Autologous Grafts in Growing Skull Fractures Results in Better Outcomes: Experience From a Tertiary Pediatric Neurosurgery Center.

BACKGROUND AND OBJECTIVES: Growing skull fracture (GSF) is a rare complication of pediatric head trauma. Definitive treatment is surgical repair. We have attempted to assess whether use of autologous grafts for duraplasty and cranioplasty leads to better outcomes. We have also attempted to understand how timing of surgery might affect the degree of underlying damage to cortical tissue. METHODS: This is a single-center retrospective observational study based on review from the Great Ormond Street Hospital Neurosurgery prospective surgical database. All patients undergoing surgery for GSF repair between 1991 and 2015 were included. Surgical techniques included split calvarial grafts in 4 patients, whereas rest had full-thickness bone grafting. In all cases with full-thickness graft, the donor site was covered with morselized bone chips mixed with fibrin glue (Salami technique). RESULTS: Twenty-eight patients were identified (16 males, 12 females). The average age at the time of injury was 13 months. The mean duration of onset of symptoms from the time of injury was 4.4 months. The time interval from symptom onset to surgical repair was 5.92 months. Seven patients had Type I GSF (leptomeningeal cyst with minimal brain parenchyma), 13 had type II (hernia containing gliotic brain), and 8 had type III (porencephalic cyst extending through the skull defect into subgaleal space). Patients with delayed presentation had severe brain injury (Type III) and had more long-term complications (refractory epilepsy requiring temporo-occipito-parietal disconnection and development of hydrocephalus requiring ventriculoperitoneal shunt insertion). CONCLUSION: Autologous pericranium for duraplasty and split-thickness bone graft or the Salami technique are recommended for cranioplasty. Synthetic materials should be used if the index operation fails or there are complications. Patients with high-risk findings should be identified at the time of initial presentation and followed up in clinic early to prevent onset of neurological deficit. Early repair is associated with better neurological outcomes.

Case Report: Two cases of multiples and atypical dermal sinus tracts.

Dermal sinus tracts (DSTs) are congenital lesions that connect the cutaneous ectoderm with the underlying neuroectodermal tissues. They are typically midline, solitary lesions. Multiple, and atypically located DSTs have been only rarely described. We present two cases of multiple and laterally located DSTs. The first presented with bacterial meningitis and two tracts in the right buttock, one of which entered the spinal canal through the S3 neural foramen. The second child had three midline lumbar DSTs, one subcutaneous dermoid cyst and one intradural epidermoid cyst. Complete surgical excision was achieved in both cases with good late follow up. Multiple or atypically located DSTs appear to carry the same risks of infection as the more common, midline, single tracts. Complete surgical excision is recommended to avoid the risks of neurological deterioration, in particular due to infection. Incomplete disjunction is the proposed developmental anomaly for DSTs, however the location of the cases presented here requires an alternative explanation.

International Consensus Statement on the Radiological Evaluation of Dysraphic Malformations of the Spine and Spinal Cord.

Dysraphic malformations of the spine and spinal cord (DMSSC) represent a spectrum of common congenital anomalies typically (though not exclusively) affecting the lower spinal segments. These may be responsible for varying degrees of neurologic, orthopedic, and urologic morbidity. With advances in neuroimaging, it is now possible to better diagnose and evaluate these disorders both prenatally and postnatally. Neuroimaging, performed at the right time and with technique optimization, is integral in guiding clinical management. However, the terminology used to describe these lesions has become increasingly confusing, and there is a lack of consensus regarding the essential radiologic features and their clinical weighting. This variability in radiologic practice risks unstructured decision making and increases the likelihood of suboptimal, less informed clinical management. In this manuscript, the first of a series of consensus statements, we outline a standardized international consensus statement for the radiologic evaluation of children with suspected DMSSC derived from a critical review of the literature, and the collective clinical experience of a multinational group of experts. We provide recommendations for plain radiography, sonography, CT, and MR imaging in the evaluation of DMSSC with an emphasis on technique of imaging and imaging protocols.

Intracardiac migration of distal catheter-a rare complication of VP shunt insertion: case report and literature review.

Intracardiac migration is a rare complication of ventriculoperitoneal shunt insertion. Only 15 cases have been reported, 7 of which were paediatric cases, treated with techniques including interventional radiography, open thoracotomies and direct extraction through the initial shunt incision. The authors report the youngest case of intracardiac shunt migration complicated by significant coiling and knotting within the cardiac chambers and pulmonary vasculature. Migration likely began when the SVC was pierced during initial shunt placement and progressed due to negative intrathoracic pressure. Extrusion was achieved combining thoracoscopic endoscopy, interventional fluoroscopy screening and a posterolateral neck incision with uncoiling of the shunt via a Seldinger guide wire. This offered a minimally invasive solution with rapid post-operative recovery.

Transcallosal approach and post-operative subdural collections: 12-year paediatric neurosurgery tertiary centre experience.

INTRODUCTION: Following transcallosal surgery for tumour resection, the formation of convexity or interhemispheric subdural cerebrospinal fluid collections may lead to clinical deterioration and may influence decision-making with regards to additional interventions. The aim of this study was to determine the incidence, risk factors, and management of subdural collections following the transcallosal approach in a paediatric cohort. METHODS: A retrospective case note and radiological review of all children who underwent transcallosal surgery for intraventricular and thalamic tumours was carried out covering a 12-year period (2012-2023) in a single-centre tertiary paediatric neurosurgery unit. Parameters including demographics and clinical information including lesion location, pathology, extent of resection, need for and type of shunt required, as well as depth, laterality, and location of the collection were analysed prior to shunting, and at approximately 3 weeks, 3 months, and latest follow-up available post-operatively in order to further elucidate the natural history of these subdural collections and their clinical significance. RESULTS: Sixty-four cases satisfied the inclusion criteria of transcallosal surgery for tumour resection; 13 did not have adequate post-operative imaging and were excluded. Of the remaining 51 cases, there were 32 children (63%) with post-operative CSF subdural collections, of which 59% were ipsilateral, with the remainder showing bilateral distribution. The overall shunt insertion rate was 25.5% (12 ventriculoperitoneal and 1 subdural-peritoneal shunt) at 3 months, with a mean time to shunting of 19 days post-operatively. Children who developed post-operative subdural collections had a higher rate of shunting, at 37.5%, compared to 5.2% in those who did not. Pre- and post-operative hydrocephalus and subtotal resection were identified as risk factors for development of subdural collections post-operatively. Subdural collections showed a natural course of reduction and regression over follow-up, with the exception of 3 children where they persisted or increased over time; although none of these required shunting. Those children who underwent shunt insertion showed greater regression in the size of the subdural collection over time compared to the non-shunted group. CONCLUSION: In this paediatric cohort, 25.5 % of children required insertion of a shunt by 3 months following transcallosal surgery. Pre- and post-operative hydrocephalus and subtotal tumour resection were risk factors for development of subdural collections post-operatively.

Limited exposure to preserve stability and achieve complete excision of limited dorsal myeloschisis - the "Skip-Hop Laminectomy" technique: a technical note.

OBJECTIVE: The fibroneural stalk of an LDM has variable thickness, complexity, and length, which can span 5 to 6 vertebral segments from its skin attachment to its "merge point" with the dorsal spinal cord. Therefore, complete resection may require extensive multi-level laminotomies. In this technical note, a modification of the procedure is presented that avoids long segment laminectomies while ensuring complete excision of long LDM stalks. RESULTS: An illustrative case of resection of LDM is presented using skip laminectomies. The technique ensures complete removal of the stalk, thus reducing the risk of future intradural dermoid development, while at the same time minimizes the risk for delayed kyphotic deformity. CONCLUSIONS: A technique of "skip-hop" proximal and distal short segment laminectomies in cases of LDM optimizes the objectives of complete stalk resection with preservation of spinal integrity.

Os odontoideum and craniovertebral junction instability secondary to dystonia: case series and review of the literature.

INTRODUCTION: Os odontoideum refers to a rounded ossicle detached from a hypoplastic odontoid process at the body of the axis. The aetiology has been debated and believed to be either congenital or acquired (resulting from trauma). Os odontoideum results in incompetence of the transverse ligament and thus predisposes to atlantoaxial instability and spinal cord injury. METHODS/RESULTS: Three cases of children with severe dystonic cerebral palsy presenting with myelopathic deterioration secondary to atlantoaxial instability due to os odontoideum are presented. This observation supports the hypothesis of os odontoideum being an acquired phenomenon, secondary to chronic excessive movement with damage to the developing odontoid process. CONCLUSION: In children with cerebral palsy and dystonia, pre-existing motor deficits may conceal an evolving myelopathy and result in delayed diagnosis of clinically significant atlantoaxial subluxation.

Lumbosacral lipoma in childhood, how strong is the evidence base? A systematic review.

OBJECTIVE: Conus region lumbosacral lipomas (LSLs) are highly heterogeneous in their morphology, clinical presentation, and outcome, with an incompletely understood natural history and often treacherous surgical anatomy. This systematic review aims to critically evaluate and assess the strength of the current LSL evidence base to guide management strategies. METHODS: According to a systematic review following PRISMA guidelines, a search was conducted using the key term "lumbosacral lipoma" across MEDLINE (OVID), Embase, Cochrane Library, and PubMed databases from January 1951 to April 2021. All studies containing ten or more paediatric conus lipomas were included. Data heterogeneity and bias were assessed. RESULTS: A total of 13 studies were included, containing 913 LSLs (predominantly transitional type-58.5%). Two-thirds (67.5%) of all patients (treated and non-treated) remained clinically stable and 17.6% deteriorated. Neuropathic bladder was present in 8.6% at final follow-up. Of patients managed surgically, near-total resection vs. subtotal resection deterioration-free survival rates were 77.2-98.4% and 10-67% respectively. 4.5% (0.0-27.3%) required re-do untethering surgery. Outcomes varied according to lipoma type. Most publications contained heterogeneous populations and used variable terminology. There was a lack of consistency in reported outcomes. CONCLUSION: Amongst published series, there is wide variability in patient factors such as lipoma type, patient age, and methods of (particularly urological) assessment. Currently, there is insufficient evidence base upon which to make clear recommendations for the management of children with LSL. There is an imperative for neurosurgeons, neuroradiologists, and urologists to collaborate to better standardise the terminology, assessment tools, and surgical interventions for this challenging group of conditions.

Incomplete spinal cord injury following minor trauma in two siblings with spondylocostal dysostis type 6.

Biallelic pathogenic variants of the RIPPLY2 gene have been recognized to cause a subtype of autosomal recessive spondylocostal dysostosis (SCDO6), characterized by predominant cervical spine malformation with minor or absent involvement of the ribs. To date, RIPPLY2 associated SCDO6 has been described in ten patients in five studies with accompanying clinical symptoms varying from transient and recurrent torticollis to flaccid quadriplegia. Here, we describe two additional patients in one family in which the c.A238T:p.Arg80* RIPPLY2 mutation in the homozygous state, was associated with severe malformation of the posterior elements of the cervical vertebral column. In both cases neurological symptoms occurred early in life due to spinal cord compromise. These two cases, in keeping with previous reports, highlight the early and progressive natural history of cervical deformity in this rare skeletal dysplasia and the need for close neurological and radiological surveillance. Surgical decision-making needs to carefully balance the need for early intervention to protect spinal cord function on one hand, with the problem of bone malformation and skeletal immaturity on the other.

Surgical Techniques of, and Outcomes after, Distal Muscle Stabilization in Transfemoral Amputation: A Systematic Review and Narrative Synthesis.

BACKGROUND: Distal muscle stabilization, such as myodesis (suturing muscles to bone) or myoplasty (suturing agonistic-antagonistic muscles together), can aid residual limb stabilization, provide a good soft-tissue covering, and increase rehabilitation potential. However, surgical practice varies due to scant clinical data. The aim of this review is to summarize and evaluate the literature regarding techniques and associated outcomes of distal muscle stabilization in transfemoral amputation (TFA). METHODS: A systematic review and narrative synthesis was performed following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Resources, including observational studies, nonobservational scientific papers, conference proceedings, and textbooks, detailing techniques of TFA distal muscle stabilization were identified from standard medical repositories and library search. A supplementary search of YouTube and Google was undertaken to identify additional resources. Quality assessment was undertaken using Risk Of Bias In Nonrandomized Studies-of Interventions; Authority, Accuracy, Coverage, Objectivity, Date, Significance; and modified-Discern tools. RESULTS: Forty seven resources were identified, including 17 journal articles, 17 textbooks, 5 educational websites/eBooks, 5 videos, 2 online presentations, and 1 webpage. Thirty seven described myodesis, 11 described myoplasty, and 6 described closure without distal muscle stabilization. Eight observational studies presented outcome data for 302 TFAs. No studies comparing closure with or without distal muscle stabilization were identified. All papers describing myodesis secured the adductors to the femur, and most also secured the quadriceps and/or hamstrings to this complex. Number of femoral drill holes varied from 1 to 6. Early wound complications occurred in 17% of amputations, whereas myodesis failure occurred in 9.5%. Prosthetic fitting rates were 73% and, where reported, 100% of patients maintained neutral femoral alignment. CONCLUSIONS: Distal muscle stabilization, particularly myodesis, is a commonly described technique for TFA, although operative techniques are heterogenous. There is a paucity of outcome data, and no studies comparing it to closures without distal muscle stabilization. However, these low-quality data suggest wound healing rates are equivalent to TFA without distal muscle stabilization while demonstrating improvement to patients' rehabilitation potential.

Recommendations for neuroradiological examinations in children living with achondroplasia: a European Society of Pediatric Radiology and European Society of Neuroradiology opinion paper.

Children living with achondroplasia are at an increased risk of developing neurological complications, which may be associated with acute and life-altering events. To remediate this risk, the timely acquisition of effective neuroimaging that can help to guide clinical management is essential. We propose imaging protocols and follow-up strategies for evaluating the neuroanatomy of these children and to effectively identify potential neurological complications, including compression at the cervicomedullary junction secondary to foramen magnum stenosis, spinal deformity and spinal canal stenosis. When compiling these recommendations, emphasis has been placed on reducing scan times and avoiding unnecessary radiation exposure. Standardized imaging protocols are important to ensure that clinically useful neuroimaging is performed in children living with achondroplasia and to ensure reproducibility in future clinical trials. The members of the European Society of Pediatric Radiology (ESPR) Neuroradiology Taskforce and European Society of Neuroradiology pediatric subcommittee, together with clinicians and surgeons with specific expertise in achondroplasia, wrote this opinion paper. The research committee of the ESPR also endorsed the final draft. The rationale for these recommendations is based on currently available literature, supplemented by best practice opinion from radiologists and clinicians with subject-specific expertise.

Fetal Surgery for Myelomeningocele: Neurosurgical Perspectives.

More than 30 years have elapsed since it was recognised that folic acid supplementation could substantially reduce the risk of open neural tube defects (ONTDs). During that time, many countries have adopted policies of food fortification with demonstrable reduction in the incidence of both cranial and spinal ONTDs. Improved prenatal detection and termination has also resulted in a reduction in the number of affected live births. Nonetheless, in the USA about 1500 children, and in the UK around 500 children are born each year with myelomeningocele (MMC) and so the management of MMC and its complications continues to constitute a significant clinical workload for many paediatric neurosurgical units around the world.Until recently, the options available following antenatal diagnosis of MMC were termination of pregnancy or postnatal repair. As a result of the MOMS trial, prenatal repair has become an additional option in selected cases (Adzick et al., N Engl J Med 364(11):993-1004, 2011). Fetal surgery for myelomeningocele is now offered in more than 30 centres worldwide. The aim of this chapter is to review the experimental basis of prenatal repair of MMC, to critically evaluate the neurosurgical implications of this intervention and to describe the technique of 'open' repair, comparing this with emerging minimally invasive alternatives.

The Current Status of the Surgical Management of Complex Spinal Cord Lipomas: Still Navigating the Labyrinth?

This review summarises the classification, anatomy and embryogenesis of complex spinal cord lipomas and describes in some detail the technique of total lipoma resection and radical reconstruction of the affected neural placode. Its specific mission is to tackle two main issues surrounding the management of complex dysraphic lipomas: whether total resection confers better long-term benefits than partial resection and whether total resection does better than conservative treatment, i.e. no surgery, for asymptomatic lipomas. Accordingly, the 24-year progression-free survival data of the senior author and colleagues' series of over 300 cases of total resection are compared with historical data from multiple series (including our own) of partial resection, and total resection data specifically for asymptomatic lesions are compared with the two known series of non-surgical treatment of equivalent patients. These comparisons so far amply support the author's recommendation of total resection for most complex lipomas, with or without symptoms. The notable exception is the asymptomatic chaotic lipoma, whose peculiar anatomical relationship with the neural tissue defies even our aggressive surgical approach, and consequently projects worse results (admittedly of small number of cases) than for the other two lipoma subtypes of dorsal and transitional lesions. Prophylactic resection of asymptomatic chaotic lipomas is therefore not currently endorsed. We have also recently found that some dorsal lipomas with clear outline of the conus on preoperative imaging had a significantly better long-term prognosis of preserving neurourological functions without surgery. Whether this subset of lipomas should be managed conservatively until symptoms arise is now an open question awaiting a longer follow-up of a larger cohort of such patients.

Intracranial invasive group A streptococcus: a neurosurgical emergency in children.

OBJECTIVE: Invasive group A streptococcus (iGAS) infections are associated with a high rate of morbidity and mortality. CNS involvement is rare, with iGAS accounting for only 0.2%-1% of all childhood bacterial meningitis. In 2022, a significant increase in scarlet fever and iGAS was reported globally with a displacement of serotype, causing a predominance of the emm1.0 subtype. Here, the authors report on iGAS-related suppurative intracranial complications requiring neurosurgical intervention and prolonged antibiotic therapy. METHODS: The authors performed a retrospective chart review of consecutive cases of confirmed GAS in pediatric neurosurgical patients. RESULTS: Five children with a median age of 9 years were treated for intracranial complications of GAS infection over a 2-month period between November 2022 and December 2022. All patients had preceding illnesses, including chicken pox and upper respiratory tract infections. Infections included subdural empyema with associated encephalitis (n = 2), extradural empyema (n = 1), intracranial abscess (n = 1), and diffuse global meningoencephalitis (n = 1). Streptococcus pyogenes was cultured from 4 children, and 2 were of the emm1.0 subtype. Antimicrobial therapy in all patients included a third-generation cephalosporin but varied in adjunctive therapy, often including a toxin synthesis inhibitor antibiotic such as clindamycin. Neurological outcomes varied; 3 patients returned to near neurological baseline, 1 had significant residual neurological deficits, and 1 patient died. CONCLUSIONS: Despite the worldwide increased incidence, intracranial complications remain rarely reported resulting in a lack of awareness of iGAS-related intracranial disease. Awareness of intracranial complications of iGAS and prompt referral to a pediatric neurology/neurosurgical center is crucial to optimize neurological outcomes.

Comparison of endoscopic sinus sampling versus intracranial sampling for microbiological diagnosis of intracranial infection in children: a case series and literature review.

INTRODUCTION: Intracranial infection is often associated with contiguous sinus infection, with Streptococcus intermedius being the most common pathogen. Microbiological assessment is possible via sinus or intracranial sampling. While a sinus approach is minimally invasive, it is not clear whether this yields definitive microbiological diagnosis leading to optimized antimicrobial therapy and avoidance of intracranial surgery. METHODS: A retrospective review of a prospectively collected electronic departmental database identified patients between 2019 and 2022. Further demographic and microbiological information was obtained from electronic patient records and laboratory management systems. RESULTS: Thirty-one patients were identified with intracranial subdural and/or epidural empyema and concurrent sinus involvement during the 3-year study period. The median age of onset was 10 years with a slight male predominance (55%). All patients had intracranial sampling with 15 patients undergoing sinus sampling in addition. Only 1 patient (7%) demonstrated identical organism(s) grown from both samples. Streptococcus intermedius was the most common pathogen in intracranial samples. Thirteen patients (42%) had mixed organisms from their intracranial cultures and 57% of samples undergoing bacterial PCR identified additional organisms, predominantly anaerobes. Sinus samples had a significant addition of nasal flora and Staphylococcus aureus which was rarely grown from intracranial samples. Of concern, 7/14 (50%) of sinus samples did not identify the main intracranial pathogen diagnosed on intracranial culture and additional PCR. Literature review identified 21 studies where sinus drainage was used to treat intracranial empyemas, with only 6 authors reporting concurrent microbiology results. This confirmed our cohort to be the largest comparative study in the current literature. No center has observed a greater than 50% concordance in microbiological diagnoses. CONCLUSION: Endoscopic sinus surgery may have therapeutic benefit, but it is not an appropriate approach for microbiological diagnosis in pediatric subdural empyemas. High rates of contaminating nasal flora can lead to misdiagnosis and inappropriate treatment. Routine addition of 16S rRNA PCR to intracranial samples is recommended.

Unravelling the pathogenesis of foramen magnum stenosis in patients with severe achondroplasia: a CT-based comparison with age-matched controls and FGFR3 craniosynostosis syndromes.

OBJECTIVE: Foramen magnum(FM) stenosis can be responsible for acute and chronic damage to the cervicomedullary junction in children with achondroplasia. The bony anatomy and patterns of suture fusion of the FM in this context are incompletely understood, yet becoming increasingly important in the light of novel medical therapies for achondroplasia. The objective of this study was to describe and quantify bony anatomy and fusion patterns of FM stenosis in patients with achondroplasia using CT scans, comparing them to age-matched controls and other FGFR3 craniosynostosis patients. METHODS: Patients with achondroplasia and severe FM stenosis, classified as achondroplasia foramen magnum score(AFMS) grades 3 and 4, were identified from a departmental operative database. All had pre-operative CT scans of the craniocervical junction. Measurements obtained comprised sagittal diameter (SD), transverse diameter (TD), foramen magnum area, and opisthion thickness. Anterior and posterior interoccipital synchondroses (AIOS and PIOS) were graded by the extent of fusion. These measurements were then compared with CT scans from 3 age-matched groups: the normal control group, children with Muenke syndrome, and children with Crouzon syndrome with acanthosis nigricans (CSAN). RESULTS: CT scans were reviewed in 23 cases of patients with achondroplasia, 23 normal controls, 20 Muenke, and 15 CSAN. Children with achondroplasia had significantly smaller sagittal diameter (mean 16.2 ± 2.4 mm) compared to other groups (control 31.7 ± 2.4 mm, p < 0.0001; Muenke 31.7 ± 3.5 mm, p < 0.0001; and CSAN 23.1 ± 3.4 mm, p < 0.0001) and transverse diameters (mean 14.3 ± 1.8 mm) compared with other groups (control 26.5 ± 3.2 mm, p < 0.0001; Muenke 24.1 ± 2.6 mm, p < 0.0001; CSAN 19.1 ± 2.6 mm, p < 0.0001). This translated into a surface area which was 3.4 times smaller in the achondroplasia group compared with the control group. The median grade of the AIOS fusion achondroplasia group was 3.0 (IQR 3.0-5.0), which was significantly higher compared with the control group (1.0, IQR 1.0-1.0, p < 0.0001), Muenke group (1.0, IQR 1.0-1.0, p < 0.0001), and CSAN (2.0, IQR 1.0-2.0, p < 0.0002). Median PIOS fusion grade was also highest in the achondroplasia group (5.0, IQR 4.0-5.0) compared with control (1.0, IQR 1.0-1.0, p < 0.0001), Muenke (2.5, IQR 1.3-3.0, p < 0.0001), and CSAN (4.0, IQR 4.0-4.0, p = 0.2). Distinct bony opisthion spurs projecting into the foramen magnum were seen in achondroplasia patients but not others, resulting in characteristic crescent and cloverleaf shapes. CONCLUSION: Patients with AFMS stages 3 and 4 have significantly reduced FM diameters, with surface area 3.4 times smaller than age-matched controls. This is associated with premature fusion of the AIOS and PIOS in comparison with controls and other FGFR3-related conditions. The presence of thickened opisthion bony spurs contributes to stenosis in achondroplasia. Understanding and quantifying bony changes at the FM of patients with achondroplasia will be important in the future quantitative evaluation of emerging medical therapies.

Endoscopic third ventriculostomy for the management of children with cerebrospinal fluid disorders, ventriculomegaly, and associated Chiari I malformation.

OBJECTIVES: Our objective was to review the outcomes of children with CIM and associated cerebrospinal fluid (CSF) disorders and ventriculomegaly undergoing endoscopic third ventriculostomy (ETV) as a primary intervention. MATERIALS AND METHODS: A retrospective, single-center, observational cohort study was conducted of consecutive children with CIM with associated CSF disorders and ventriculomegaly treated first by ETV between January 2014 and December 2020. RESULTS: Raised intracranial pressure symptoms were the most frequent in ten patients, followed by posterior fossa and syrinx symptoms in three cases. One patient had a later stoma closure and required a shunt insertion. The success rate of the ETV in the cohort was 92% (11/12). There was no surgical mortality in our series. No other complications were reported. The median herniation of the tonsils was not statistically different in the pre vs. post-operative MRI (1.14 vs. 0.94, p=0.1). However, the median Evan's index (0.4 vs. 0.36, p<0.01) and the median diameter of the third ventricle (1.35 vs. 0.76, p<0.01) were statistically different between the two measurements. The preoperative length of the syrinx did not change significantly compared with the postoperative (5 vs. 1; p=0.052); nevertheless, the median transverse diameter of the syrinx did improve significantly after the surgery (0.75 vs. 0.32, p=0.03). CONCLUSIONS: Our study supports ETV's safety and effectiveness for managing children with CSF disorders, ventriculomegaly, and associated CIM.

A topographical analysis of encephalocele locations: generation of a standardised atlas and cluster analysis.

OBJECTIVE: Encephaloceles are considered to result from defects in the developing skull through which meninges, and potentially brain tissue, herniate. The pathological mechanism underlying this process is incompletely understood. We aimed to describe the location of encephaloceles through the generation of a group atlas to determine whether they occur at random sites or clusters within distinct anatomical regions. METHODS: Patients diagnosed with cranial encephaloceles or meningoceles were identified from a prospectively maintained database between 1984 and 2021. Images were transformed to atlas space using non-linear registration. The bone defect, encephalocele and herniated brain contents were manually segmented allowing for a 3-dimensional heat map of encephalocele locations to be generated. The centroids of the bone defects were clustered utilising a K-mean clustering machine learning algorithm in which the elbow method was used to identify the optimal number of clusters. RESULTS: Of the 124 patients identified, 55 had volumetric imaging in the form of MRI (48/55) or CT (7/55) that could be used for atlas generation. Median encephalocele volume was 14,704 (IQR 3655-86,746) mm3 and the median surface area of the skull defect was 679 (IQR 374-765) mm2. Brain herniation into the encephalocele was found in 45% (25/55) with a median volume of 7433 (IQR 3123-14,237) mm3. Application of the elbow method revealed 3 discrete clusters: (1) anterior skull base (22%; 12/55), (2) parieto-occipital junction (45%; 25/55) and (3) peri-torcular (33%; 18/55). Cluster analysis revealed no correlation between the location of the encephalocele with gender (χ2 (2, n = 91) = 3.86, p = 0.15). Compared to expected population frequencies, encephaloceles were relatively more common in Black, Asian and Other compared to White ethnicities. A falcine sinus was identified in 51% (28/55) of cases. Falcine sinuses were more common (χ2 (2, n = 55) = 6.09, p = 0.05) whilst brain herniation was less common (χ2 (2, n = 55) = .16.24, p < 0.0003) in the parieto-occipital location. CONCLUSION: This analysis revealed three predominant clusters for the location of encephaloceles, with the parieto-occipital junction being the most common. The stereotypic location of encephaloceles into anatomically distinct clusters and the coexistence of distinct venous malformations at certain sites suggests that their location is not random and raises the possibility of distinct pathogenic mechanisms unique to each of these regions.