Neurological Sciences (2022) 43:1311–1326 https://doi.org/10.1007/s10072-021-05317-9 ORIGINAL ARTICLE Diagnosis and treatment of Chiari malformation type 1 in children: the International Consensus Document Luca Massimi 1 & Paola Peretta 2 & Alessandra Erbetta 3 & Alessandra Solari 4 & Mariangela Farinotti 4 & Palma Ciaramitaro 5 & Veronica Saletti 6 & Massimo Caldarelli 1 & Alexandre Casagrande Canheu 7 & Carlo Celada 8 & Luisa Chiapparini 3 & Daniela Chieffo 9 & Giuseppe Cinalli 10 & Federico Di Rocco 11 & Marika Furlanetto 12 & Flavio Giordano 13 & George Jallo 14 & Syril James 15 & Paola Lanteri 16 & Christian Lemarchand 17 & Martina Messing-Jünger 18 & Cecilia Parazzini 19 & Giovanna Paternoster 15 & Gianluca Piatelli 20 & Maria. A. Poca 21 & Prab Prabahkar 22 & Federica Ricci 23 & Andrea Righini 19 & Francesco Sala 24 & Juan Sahuquillo 21 & Marcus Stoodley 25 & Giuseppe Talamonti 26 & Dominic Thompson 27 & Fabio Triulzi 28 & Mino Zucchelli 29 & Laura Valentini 12 & International Experts - Jury of the Chiari & Syringomyelia Consensus Conference, “Milan, November 11–13, 2019” Received: 16 January 2021 / Accepted: 8 May 2021 / Published online: 7 June 2021 # The Author(s) 2021 Abstract Background Chiari malformation type 1 (CM1) is a rare condition where agreed classification and treatment are still missing. The goal of this study is to achieve a consensus on the diagnosis and treatment of CM1 in children. Methods A multidisciplinary panel formulated 57 provisional statements based on a review of the literature. Thirty-four inter- national experts (IE) participated in a Delphi study by independently rating each statement on a 4-point Likert scale (“strongly disagree,” “disagree,” “agree,” “strongly agree”). Statements that were endorsed (“agree” or “strongly agree”) by < 75% of raters were re-formulated, or new statements were added, and another Delphi round followed (up to a maximum of three). Results Thirty-five IE were contacted and 34 agreed to participate. A consensus was reached on 30/57 statements (52.6%) after round 1. Three statements were added, and one removed. After round 2, agreement was reached on 56/59 statements (94.9%). Finally, after round 3, which took place during the 2019 Chiari Consensus Conference (Milan, Italy), agreement was reached on 58/59 statements (98.3%) about four main sections (Definition and Classification, Planning, Surgery, Isolated Syringomyelia). Only one statement did not gain a consensus, which is the “definition of radiological failure 24 month post-surgery.” Conclusions The consensus document consists of 58 statements (24 on diagnosis, 34 on treatment), serving clinicians and researchers following children with CM1. There is a clear need for establishing an international network and registry and to promote collaborative studies to increase the evidence base and optimize the long-term care of this patient population. Keywords Chiari 1 malformation . Syringomyelia . Consensus . Children . Craniovertebral decompression . Management Introduction richer of papers, but in spite of some meta-analyses [1–6] and some international surveys [7–10], it still fails to Chiari malformation type 1 (CM1) has gained a great achieve consensus as far as both methods and results are interest among the scientific community because of the concerned. Moreover, no guidelines have been provided continuously increasing number of diagnoses and several so far, although they are claimed by patients, Patients controversial issues, especially about definition, manage- Associations, and physicians. These problems have to be ment, and outcome assessment. The literature is richer and faced both in affected children and adults. This paper reports and comments on the results of the International Consensus Conference held in Milan in * Luca Massimi November 2019 with regard to the pediatric population. lucamax30@hotmail.com The goal of this meeting was to find a consensus among international experts on the most controversial issues to Extended author information available on the last page of the article clear the way for creating guidelines. 1312 Neurol Sci (2022) 43:1311–1326 Methods Classification and definition The results of the literature review (published in a sepa- This consensus conference arose from the ongoing work of an rate article of the same issue) emphasized the necessity of international task dedicated to the radiological classification a consensus strategy among the CM1 community. The and definition of CM1 and syringomyelia. An initial priority parents of CM1 children, the Parental Associations, and was to ensure that the panelists shared a common language. the clinicians taking part in the diagnostic and treatment The agreement on the classification was as high as 85%, process further confirmed this need. Therefore, a panel of which was considered adequate for the Consensus. The results experts of the Chiari and Syringomyelia Consortium [11] are reported in detail in this issue in the article “Diagnosis and formulated 57 draft statements on the main and controver- Treatment of Chiari Malformation and Syringomyelia in sial topics concerning CM1 and syringomyelia. A group Adults: The International Consensus Document.” of international experts (IE), from within and without In the absence of a better radiological definition, CM1 was Europe, designed by scientific production and by the considered herniation of one or both cerebellar tonsils ≥ 5 mm Patients Associations, and with a cumulative experience below McRae’s line or even 3 to 5 mm but with syringomyelia of more about 8800 children (more than 3500 out of them or peg-like appearance of the tonsils. The transient tonsillar were operated on), were asked to take part in the study as herniation resulting from hydrocephalus or other sources of jury panelists. mass effect is not considered CM1 but acquired tonsillar The statements were distributed in a general addendum ectopia. Therefore, both the acquired tonsillar ectopia and in two separate questionnaires, one concerning pedi- resulting from intracranial hypotension and intracranial hyper- atric patients and the other one adult patients. A Delphi tension should be ruled out with appropriate examinations, process [12] was designed to reach a consensus of at least which are clinical pattern and contrast-enhanced MRI for 75% of agreement. Three Delphi rounds were considered CSF hypotension and clinical pattern, fundoscopy, and ve- adequate as a reasonable effort to reach consensus among nous angio-MRI (or even direct ICP measurement, if needed) the experts. IE received a structured document to be voted for raised ICP. Cough headache, signs and symptoms of on a 4-point Likert-type scale (“strongly disagree,” “dis- brainstem and/or cerebellum and/or spinal cord dysfunction, agree,” “agree,” “strongly agree”). In each round, IE in- otoneurological symptoms, and scoliosis remain the main dicated their level of agreement on the proposed state- findings composing the Chiari syndrome [13]. ments. Statements that did not gain consensus (<75% of Syringomyelia and syringobulbia refer to longitudinally IE voting “agree” or “strongly agree”) were redistributed oriented fluid-filled cavities of any size respectively in the to participants in rounds 2 and 3. spinal cord and brain stem, expanding from the region of its largest diameter in the upper and/or lower direction. However, the definition, diagnosis, and classification of syringomyelia/ syringobulbia still raise many questions as not every fluid- Results and discussion filled cavitation of the spinal cord deserves the diagnosis of syringomyelia and the distinction between syringomyelia and This paper is focused on the results of the pediatric question- central canal dilatation may be difficult [14–16]. Pending a naire and on the part of the general addendum addressing better radiological definition and etiopathogenic classifica- pediatric issues. tion, a classification distinguishing 4 types of syringomyelia Thirty-five international experts (IE) were contacted is still used, type I-a being associated with CM1. and 34 agreed to participate in the Delphi process. The Patients with CM-I and syringobulbia/syringomyelia may IE jury comprised 21 neurosurgeons, five neuro-radiolo- have relevant symptoms because of the brainstem and spinal gists, four pediatric neurologists, one neurologist, one involvement. The most frequent syringobulbia-related symp- psychologist, and two members of Patients Associations. toms, usually in a chronic pattern, are headache, gait and bal- A consensus was reached on 30 statements (52.6%) after ance disorders, limb weakness or dysesthesia, IX and X cra- round 1. Subsequently, three statements were added and nial nerve dysfunction, persistent hiccup, oscillopsia, nystag- one removed. After round 2, agreement was reached on mus, Horner syndrome, and central hypoventilation syndrome 56 statements (94.9%). The final discussion and voting [17]. The typical clinical symptoms of syringomyelia consist took place during the Chiari Consensus Conference held of dysesthesia, sensory disturbances, or pain caused by ma- in Milan, Italy, November 2019, with a 98.3% of final neuvers, such as Valsalva, cough, laughter, or sneezing in the agreement (Fig. 1). Only one statement, regarding the corresponding dermatomes, while motor deficits tend to be a definition of radiological failure after surgery at 24 late symptom. A centrally positioned syrinx typically causes months follow-up, remained under the requested agree- dissociated sensory loss, while a syrinx involving the posterior ment percentage (Fig. 2). horns causes neuropathic pain, often described as a burning Neurol Sci (2022) 43:1311–1326 1313 Fig. 1 Flowchart of the Delphi study STATE OF THE ART: lack of a general agreement and wide discussion on relevant aspects on treatments and medical decisions for CM1 children patients 57 evidence-based statements drafted by the 35 CM1 International Experts (IE) invited: Jun-Jul Multidisciplinary Panel (MP) 2019 First Delphi Round: Sept 2019 34 IE participated 30/57 statements endorsed (52.6%) Revision of statements: Oct 2019 27/57 (47%) statements revised based on IE comments ( 15 re-written, 11 re-worded, 1 deleted), and 3 statements added Second Delphi Round: Oct 2019 33/34 IE participated (97%) 56/59 statements endorsed (94.9%) Third Delphi Round: November 2019 (Chiari Consensus Conference, Milan, Italy) 33/34 IE (two of whom e-voters) 58/59 statements endorsed (98.3%) 58-statement Consensus Document type of constant pain aggravated during resting periods [15, Pediatric neurosurgery (2004, 2018) [9, 10], and by the 18, 19]. Hydromyelia (thin, centrally located dilatation of the Brazilian Society for Pediatric Neurosurgery (2020) [7]. This spinal cord) is usually found to be asymptomatic. policy is reinforced by the rarity of abrupt and severe (post- traumatic) onset in previously asymptomatic patients [20–22]. Section 1—Planning for CM1 in children The presence of syringomyelia is frequently considered the most important criteria for surgery in an asymptomatic patient Table 1 summarizes the results of Part A: Indications to sur- as long as the syrinx is thicker than 5–8 mm or progressively gery This section strongly confirms conservative management enlarging. The cut-off (> 5 mm or > 8 mm) is still debated, and in asymptomatic children without syringomyelia, even in case there is little evidence to correlate syringomyelia size with the of significant tonsillar descent on MRI. Such an attitude al- presence of symptoms. However, the progression of syringo- ready emerged in previous surveys, provided by the Pediatric myelia seems to be more straightforward. The appearance of Section of the American Association of Neurological symptoms remains the main indication of surgery regardless Surgeons (2000) [8], by the International Society for of the size of the syrinx. 1314 Neurol Sci (2022) 43:1311–1326 Fig. 2 Agreement (%) on each statement of the Children Consensus Document in the three Delphi rounds (35 experts) There is also a consensus that Chiari surgery should not be disturbances since there is no evidence yet of correlations offered to children with CM1 and epilepsy as a means of between the two conditions and, in particular, no evidence improving seizure control. The high agreement on this topic that the treatment of CM1 improves the behavior disorder results from both daily clinical practice and literature, based [25–28]. However, in this subset of patients, a careful clinical on the evidence that the association is random [23, 24]. and instrumental assessment is mandatory because the affect- Similarly, there is not an indication to operate on the CM1 ed children may not be able to accurately report CM1 symp- in children with autism or other cognitive/behavioral toms and clinical signs may be hard to detect. On these Neurol Sci (2022) 43:1311–1326 1315 Table 1 Planning for CM1 in children: indications to surgery 1 In asymptomatic children with incidentally discovered, isolated CM1 and no syringomyelia, Agreement: 94.1% surgery is not indicated 2 In asymptomatic children with incidentally discovered CM1 and syringomyelia, surgery is Agreement: 82.4% indicated in cases of syrinx larger than 5–8 mm, and smaller syrinx increasing in size 3 In children with epilepsy and CM1, surgical treatment of CM1 does not improve the seizure disorder Agreement: 94.1% 4 In children with CM1 and cognitive and/or behavioral disorders (such as autism) not able to correctly Agreement: 97.1% report their symptoms because of communication impairment, careful clinical and instrumental assessments are mandatory to detect symptoms and signs of cerebellar tonsils ectopia 5 In children with CM1 and cognitive and/or behavioral disorders (such as autism) and no clear CM1 Agreement: 91.2% symptoms, surgery is not indicated to improve the clinical picture 6 Surgical treatment is not decided on MRI pattern in asymptomatic children with tonsillar ectopia ≥ 20 mm Agreement: 88.2% without syringomyelia grounds, autistic children who are symptomatic for CM1 and The use of neurophysiological examinations (SSEPs, who undergo successful surgery can show an improvement in MEPs, AEPs) is not routine but should be driven by clinical their cognitive and behavioral performances, but this results and/or radiological criteria. These should not be considered from the reduction of pain or other misdiagnosed symptoms. firstline examinations and their role in the diagnosis and eval- Some reports investigating the role of genetic mutations in uation of CM1 is unproven. Additionally, in spite of their isolated cases showed that the association between CM1 and utility in case of brainstem or spinal cord involvement, their autism and/or epilepsy is occasional, except for very rare and role in the intraoperative monitoring at the moment of posi- specific syndromes [29–32]. According to the experience of tioning and during the posterior fossa decompression remains some panelists, the ventral compression of the basilar artery controversial [41, 42]. Polysomnography is indicated to con- (due to dens malposition) may overt seizures or cognitive firm the diagnosis of sleep apneas at any age, in particular in deficits related to raised ICP. infants and small children with significant overcrowding of the posterior fossa. The occurrence of sleep-disordered breath- A synopsis of the results of Part B: Symptoms and follow-up is ing in children with CM1 is well-documented [43–45], and reported in Table 2 This section addresses the problem of the even a certain correlation between radiological and polysom- follow-up in asymptomatic subjects and the management of nographic picture has been found [46]. symptoms in the symptomatic ones. As far as the first group is concerned, there is agreement on the follow-up children with Part C: Associated malformations: the results are summarized an incidental diagnosis of CM-1 until the end of their growth. in Table 3 There was general agreement that, when present, Actually, although CM1 and syringomyelia tend to remain hydrocephalus should be treated in the first instance reserving silent in the majority of asymptomatic children, a clinical foramen magnum decompression for cases where symptoms and/or radiological progression cannot be excluded in a mi- persist in spite of adequately controlled ICP. The treatment of nority of them [33–36]. Although some examples of schedule hydrocephalus is addressed first to restore the CSF pathways and are quite widely accepted (e.g., controls at 1, 3, and 5 years), to relieve from raised ICP (which is often also the main source of the clinical and radiological check-up should be tailored ac- symptoms), thus limiting the risks of complications (cerebellar cording to each patient. If MRI is planned, it should include ptosis, pseudomeningocele) in case of following posterior fossa both the brain and whole spinal cord. decompression [47]. Moreover, it has been demonstrated that In symptomatic children, the role of the pediatric neurolo- many children undergoing the treatment for hydrocephalus by gist seems to be crucial in achieving a correct indication to endoscopic third ventriculostomy show a significant improve- surgery. Firstly, it is important for the differential diagnosis ment of the CM1/syringomyelia and so do not require any spe- between CM1 headache and migraine or headaches resulting cific therapy for CM1 and the associated syrinx [48, 49]. from other conditions. Inadequate and inaccurate assessment Because of their etiopathogenetic role in acquired CM1, of headache will result in a wrong indication for surgery [37, non-syndromic craniosynostoses (mainly oxycephaly but also 38]. Several studies have attempted to address this topic and posterior lambdoid and sagittal synostosis) have been univer- proposed criteria to correctly diagnose the Chiari headache sally assumed to be treated before than CM1, whose manage- (cough headache, Valsalva headache, occipital or ment should be considered only in case of persistent symp- suboccipital, lasting a few minutes) [39, 40]. Moreover, a toms and clear resolution of the synostosis picture. It is worth careful neurological evaluation is mandatory to rule out co- reminding that the rate of symptomatic CM1 subjects with morbidities and to correctly understand complex children undiagnosed craniosynostosis (namely, scaphocephaly) can (such as those with behavior disorders). be surprisingly high (15.5%) [50]. 1316 Neurol Sci (2022) 43:1311–1326 Table 2 Planning for CM1 in children: symptoms and follow- 1 In asymptomatic children with incidentally discovered CM1 and no syringomyelia, Agreement: up neurological follow-up and whole neuraxis MRI should be performed until the end of 91.2% growth, with a schedule based on clinical picture and degree of tonsils herniation. 2 Neuro-pediatric evaluation is mandatory in all children with CM1 and headache Agreement: 94.1% 3 Neuro-pediatric evaluation is mandatory in all children with CM1 and symptoms and/or Agreement: signs of the brainstem, cerebellar, and/or cervical cord dysfunction to identify 91.2% co-pathologies 4 Neuro-pediatric evaluation is mandatory in all children with CM1 and cognitive and/or Agreement: behavioral disorders 91.2% 5 Somatosensory evoked potentials (SEPs) may be used in CM1 children only in Agreement: association with other tools (both clinical and instrumental) 90.9% 6 Auditory evoked potentials (BAEPs) may be used in CM1 children only in association Agreement: with other tools (both clinical and instrumental) 87.9% 7 Motor evoked potentials (MEPs) may be used in CM1 children only in association with Agreement: other tools (both clinical and instrumental) 84.8% 8 Polysomnography is indicated in very young children (< 6 years), in case of suspected Agreement: apneas, and in case of severe cerebellar tonsils descent 88.2% The same considerations apply to syndromic between intracranial volume, venous hypertension, disordered craniosynostoses, where the restoration of a proper cranial vol- CSF circulation, and skull base abnormality. The management ume plays an important role. The association between syndromic of CM1 in this instance needs to be evaluated in the wider con- craniosynostosis and CMI represents a complex interaction text of craniofacial management. This is best dealt with by Table 3 Planning for CM1 in children: associated 1 In symptomatic children with CM1 and hydrocephalus, it is recommended to treat Agreement: malformations hydrocephalus first to relieve raised intracranial pressure and to avoid post-operatory 90.9% complications. CM1 can be treated afterwards if symptoms do not disappear 2 In CM1 children with non-syndromic craniosynostosis (sagittal or lambdoid synostosis, Agreement: oxycephaly), the craniosynostosis is better treated before the CM1 100% 3 In infants with syndromic craniosynostosis and CM1, the surgery should first increase Agreement: the cranial volume, with the proper vault remodeling for each syndrome 90.9% 4 In case of persistent CM1, in children with syndromic craniosynostosis already Agreement: submitted to cranioplasty, the surgical approach depends on the syndrome, cranial 100% volume obtained by previous operations, posterior fossa volume, and CM1 symptoms/associated syringomyelia 5 In CM1 toddlers with polisynostosis and prevalent brachycephaly (and in selected cases Agreement: in the other age classes), a posterior vault osteogenic distraction could be considered 95.2% before performing a posterior fossa decompression 6 Angio-RM or angio-CT is mandatory to rule out anomalous subcutaneous drainage Agreement: before craniovertebral decompression in CM1 children with syndromic 90.9% craniosynostosis 7 CM1 is rarely associated with dysraphisms*and tethered cord syndrome (*tethering of Agreement: the medulla at any level due to split cord malformation, limited dorsal myeloschisis, 100% retained medullary cord, terminal myelocystocele, conus lipomas, thickened, and fatty filum with a low-lying conus (below L3)) 8 In the rare occurrence of CM1 in children with tethered cord syndrome, the de-tethering Agreement: procedure should be performed to prevent neuro-urological deterioration and has no 95.2% influence on CM1. 9 The association of CM1 with “occult tethered spinal cord” (a tethering syndrome with a Agreement: specific urodynamic pattern with a conus normally positioned above L2) has never 81.8% been demonstrated. 10 The intradural section of the filum terminale in CM1 children is recommended just to Agreement: treat tethered cord syndrome and it plays no role in the management of a possible 100% CM1 syndrome. 11 The extradural section of the filum terminale in CM1 children is not recommended Agreement: either to treat tethered cord syndrome or for the management of a possible CM1 100% syndrome. Neurol Sci (2022) 43:1311–1326 1317 specialist craniofacial teams. There is a high rate of clinical and related ones). Accordingly, bony decompression is suggested radiological recurrence in this subset of patients, and in situations in children without syringomyelia (and without severe symp- of clinical/radiological persistence of CM1, a new operation toms), taking into account a possible risk of symptom recur- should be carefully weighted according to the syndrome and rence. On the other hand, duraplasty is preferable when syrin- the results of the previous cranioplasty/craniofacial distraction. gomyelia (and marked symptoms) is present, taking into ac- Should the CM1 picture be clearly predominant, it can be ad- count a certain risk of complications. The agreement on this is dressed directly if the intracranial hydrodynamics have been ad- high but not complete (80%), because some panelists prefer to equately optimized. The posterior osteogenic distraction, pro- perform the most radical treatment as the first step (duraplasty posed by some authors in children with recurrent CM1 [51], with or without tonsil coagulation) to avoid re-operations and should be limited to patients with synostotic brachycephaly. In to favor a quick resolution of the syringomyelia, while others these children, the posterior distraction is likely to cure both the do not accept the surgical risk of duraplasty and acknowledge craniosynostosis and the associated CM1. Should a posterior the low improvement provided by the bony decompression fossa decompression be needed in syndromic children, a careful alone. Several panelists suggested the use of intraoperative preoperative workup based on angio-RM is mandatory to rule ultrasounds to determine the need for dural opening out anomalous venous drainages and for a correct surgical plan- (duraplasty in case of suboptimal CSF flow and tonsils pulsa- ning [52]. tions). The only prospective study available on this topic (82 The association between CM1 and the tethered cord is fre- adolescents, 40 treated by bony decompression and 42 by quently debated in clinical practice and in the literature mainly duraplasty) shows a similar clinical outcome and syrinx im- because of the postulated “occult tethered cord syndrome” [7]. provement between the two techniques, with longer operation We found strong consensus on this topic: (1) the association times and hospital stay and higher risk of complication by between CM1 and the “true” or “manifest” tethered cord is duraplasty [58]. Subsequently, many panelists highlighted universally found to be very rare and occasional [53]; (2) in that the strategy “syringomyelia = duraplasty” should not be those rare instances where a tethered cord syndrome is present assumed as an absolute rule. Therefore, a small or an asymp- in CM1 subjects, a de-tethering procedure is successfully per- tomatic syrinx can be successfully managed by bony decom- formed to cure the syndrome but does not produce effects on pression alone, while a clearly symptomatic or a recurring one the CM1 [54]; (3) the occult tethered cord syndrome remains a could require even a IV ventricle stent according to some controversial and questionable entity [55] and more than 80% authors. of panelists questioned its existence; (4) in case of symptom- A higher agreement (86.4–95.5%) was reached in respect atic tethered cord, an intradural section of the filum terminale of the technical details. For bony decompression alone, the is recommended. The patient and his/her family should be crucial region to be decompressed is that involving the aware that this operation is not addressing the associated bulbo-cevical region, which is represented by the foramen CM1 [56, 57]; (5) the international experts were not aware magnun and the C1 posterior arch that should be opened with of any evidence to support the use of the extradural section resection of the transverse dural band at this level. The occip- of the filum for either tethered cord syndrome or CM1. ital squama should not be opened widely, to avoid the cere- bellar ptosis; furthermore, extensive muscle strip and C2 Section 2—Surgery for CM1 in children laminectomy should be avoided where possible to reduce the risk of craniovertebral instability. Once again, the extent The results of Part A: Surgical techniques are reported in of the bone opening and its landmarks should be tailored to the Table 4 The most appropriate surgical paradigm to treat pedi- characteristics of each patient. In the case of duraplasty, the atric CM1 is one that reflects the etiological heterogeneity of subarachnoid space should not be violated (unless this condition. Once predisposing factors such as hydroceph- arachnoiditis is present) because this maneuver increases the alus have been dealt with, foramen magnum decompression risk of CSF leakage and arachnoid scarring. Similarly, the remains the mainstay of treatment. In the literature, there are a subpial coagulation of the tonsils should be limited to very large number of meta-analyses addressing the relative merits low tonsillar ectopia (below C2) and/or recurrent syringomy- of bone-only decompression of the posterior fossa and decom- elia and/or severe hindbrain dysfunction, since this maneuver pression with duraplasty [1–6]. Most of these articles recently adds some morbidity other than a risk of arachnoid scarring. A appeared (last 5 years) and report on a large number of pa- crucial point in the case of duraplasty is the dural closure, tients, sometimes composing purely pediatric series or, more which should be capacious and watertight at the same time, often, mixed series. Almost invariably, the comparison be- possibly with non-resorbable stitches to ensure a longer en- tween the two techniques shows that the bony decompression durance. In this context, both autologous grafts and allografts alone has a very low rate of complications but a lower success are suggested as a good option rather than artificial grafts. rate; conversely, the duraplasty ensures better results but with Although the latter are burdened by a higher risk of specific a higher rate of complications (namely, the CSF-leakage- complications (foreign body reaction, systemic immune 1318 Neurol Sci (2022) 43:1311–1326 Table 4 Surgery for CM1 in children: techniques 1 In symptomatic CM1 children without syringomyelia, the bony decompression of the Agreement: posterior fossa alone could be performed for the low complication rate, if the family 80.9% accepts the perspective of possible second surgery 2 In CM1 children with syringomyelia, bony decompression + duraplasty is preferable Agreement: 81.8% 3 The extent of the bony decompression of the posterior fossa should be wide on the Agreement: foramen, always including C1 laminectomy, and never extended to C2 for the risk of 86.4% CVJ instability. 4 In CM1 without arachnoiditis, it is indicated to preserve the arachnoid membrane to avoid Agreement: CSF leakage and delayed scarring 86.4% 5 Cerebellar tonsils coagulation/resection is indicated in cases of very low-lying tonsils and Agreement: recurrent or residual syringomyelia 86.4% 6 Autologous and allograft dural patches are preferable to artificial graft; both are suitable, Agreement: according to the surgeon’s preference, while there are experiences suggesting to avoid 81.8% the artificial ones 7 A watertight suture helps preventing CSF leakage, by non-resorbable stitches, together Agreement: with a strict muscle and soft tissue closure. 95.5% response, premature graft dissolution, high costs), their use is operation included worsening/persistence of clinical signs widespread [59–61]. The technique of the closure is more and/or symptoms, judged as the best way to assess the surgical important than the materials used to do it. outcome. Such a conclusion seems to conflict with the indica- tion for surgery in asymptomatic, large syringomyelia (see Part B: Surgical outcomes (Table 5) This section addresses one Section 2, part A, question 2) and encourages (1) to define of the most heterogeneous aspects of the CM1 management, MRI criteria for failure, inclusive of functional studies of CSF which is the definition and the assessment of the surgical spaces, and (2) to collect large multicenter series evaluated by outcome. A standardized method to evaluate the postoperative comparable outcome scales. outcome for CM1 has not been widely embraced [62]. In clinical practice, the time to declare failure and the clinical Part C: Diagnosis and treatment of the main causes of surgical and radiological criteria for failure may vary significantly in failure (Table 5) Apart from the wrong indication to surgery the different centers and, sometimes, among the members of and the occurrence of complications (surgeon-related causes), the same center. Therefore, it is not surprising that this issue some patient-related causes of failure have been reported in was the only point of “disagreement” (agreement < 75%) reg- some series, such as comorbidities, unfavorable or complex istered among the panelists during the whole vote process. In anatomy, tonsils below C2, diameter of the spinal cord, and spite of this, the definition of clinical surgical failure was pediatric age (if compared with adulthood) [1, 63–65]. As far widely accepted (90.9%), being characterized by the persis- as the technique is concerned, the main cause of failure of the tence of symptoms 12 months after surgery. Such a period is bony decompression alone is judged to be the too small bone usually sufficient to observe an improvement even after a opening/bone regrowth, especially at the level of the foramen bony decompression of the posterior fossa. The clinical eval- magnum [66, 67]. In selected cases (where MRI is not clear uation is suggested also as a mandatory step for the early enough), 3D CT scan may be helpful in estimating the extent assessment of outcome (6 and 12 months from the operation) of the decompression and in planning a new operation to en- together with brain and spinal cord MRI. In this phase, cine- large the bone opening. MRI is regarded as helpful but not necessary in all cases. As far as duraplasty is concerned, incomplete expansion Instead, as mentioned, a sufficient agreement was not reached duraplasty, arachnoid scarring, and wound-related complica- about the radiological definition of surgical failure. Actually, tions are the main factors negatively affecting the outcome although the persistence of CM1 and syringomyelia 24 [65, 67]. Postoperative arachnoiditis is regarded as the most months after surgery seems a reasonable criterion, several important cause of clinical and/or radiological recurrence. It panelists refused to separate the radiological from the clinical can be addressed by a revision surgical procedure to perform a assessment. Moreover, a certain disagreement arose in defin- lysis of the adherences and/or to coagulate the tonsils (to gain ing time to failure, with one-half of panelists suggesting to re- space) or, in case of multiple recurrences, to stent the IV ven- operate a child for persistence of unchanged syrinx after 12 tricle to maintain the patency of the obex [68]. The role of the months (the stability of the syrinx was judged as a good out- IV ventricle stenting is still under debate. come by the remaining panelists). As a result, the consensus Majority agreement was achieved regarding comorbidities was reached only when the definition of failure needing re- which increase the risk of failed surgery independently from Table 5 Surgery for CM1 in children: outcomes, failure, re-intervention Surgical outcomes 1 The early surgical outcome is assessed at 6 and 12 months by Agreement: 90.9% clinical evaluation and whole neuraxis MRI; a cine-MRI may be helpful. 2 Surgical failure is clinically defined by the persistence of Chiari Agreement: 90.9% Neurol Sci (2022) 43:1311–1326 symptoms 12 months post-surgery. 3 Surgical failure is radiologically defined by persistence of low tonsils and Agreement: 69.7% unchanged syringomyelia at 24 months post-surgical MRI. Diagnosis and treatment of the main causes of surgical failure 4 Insufficient bone decompression is one of the causes of failure, it is diagnosed Agreement: 82.4% by 3D CT scan and the treatment is widening its extension. 5 Posterior fossa arachnoiditis is one of the causes of failure: its treatment is adhesiolysis Agreement: 87.9% and/or tonsil resection; possible adjunctive procedures may be stenting of the IV ventricle with perimedullary space. 6 Postoperative CSF leakage is a predisposing factor for infections and surgical Agreement: 97.1% failure due to arachnoiditis. 7 An intracranial hypertension (IIH) may be a cause of failure. When intracranial Agreement: 97.1% hypertension is present, angio-MRI for venous study and 3DCT scan should be performed to exclude other causes of raised ICP such as pseudotumor, hydrocephalus, or craniosynostosis. 8 A CVJ instability is one of the causes of failure. To diagnose it, a dynamic CVJ Agreement: 88.2% study is indicated, especially in CM 1.5 patients. Surgical re-intervention 9 In case of symptomatic CSF leakage, a new operation is necessary. Agreement: 91.2% 10 In case of asymptomatic CSF collection, conservative management is Agreement: 91.2% indicated as the first option. 11 In case of unresolved/increasing CSF collection despite conservative treatment, Agreement: 94.1% a diagnostic re-evaluation is necessary to decide on the surgical option. 12 Asymptomatic children without syrinx with persistent tonsil descent should be Agreement: 82.4% followed up for at least 24 months to monitor the appearance of clinical symptoms. 13 Asymptomatic children with persistent syrinx at MRI at 12 months follow-up should be Agreement: 85.3% strictly followed up, and re-operated if scoliosis and/or symptoms occur. 14 Children with persistent symptoms and unchanged MRI (no tonsils ascent and absent flow) Agreement: 85.3% at 6 or 12 months follow-up should be re-operated on. 15 Children with persistent symptoms and syringomyelia at MRI at 6 or 12 months follow-up Agreement: 85.3% should be re-operated on. 16 In case of success of surgery, the long-term postoperative follow-up is performed by a Agreement: 88.2% clinical examination and whole neuraxis MRI for at least 10 years, or until the end of growth, with a timetable depending on clinical and MRI patterns. 1319 1320 Neurol Sci (2022) 43:1311–1326 the used technique. Failure to appreciate and address important management (diuretic therapy, steroids, bandage, wait and see) causative factors for Chiari such as raised intracranial pressure is advised in case of asymptomatic “closed” CSF collections. and craniovertebral instability is a predominant cause of treat- However, should the latter persist for a long time or increase, a ment failure. The most feared complication is CSF leakage new diagnostic work-up and, possibly, a re-operation have to be (which, though very rarely, can occur also after bony decompres- considered. sion alone) that is considered a predisposing factor for As mentioned, the radiologic persistence of tonsils ectopia is arachnoiditis (especially because of the resulting infective or not felt to be a failure. Therefore, if asymptomatic and without aseptic meningitis). Raised ICP, on the other hand, is a possibly syringomyelia, children with persistent radiological CM1 should misdiagnosed cause of failure. If suspected, it should be ruled out only be followed up to rule out the appearance of symptoms. In clinically (fundoscopy, clinical history) and radiologically the panelists’ opinion, the minimum follow-up for recurrence of (angio-MRI in case of presumed pseudotumor cerebri, CT scan symptoms is 2 years after surgery but, more properly, it should be in case of craniosynostosis) to avoid unnecessary re-operations protracted till the end of the patient development. The same on CM1/syringomyelia. Similarly, an underestimated CVJ insta- policy is advised for asymptomatic children with persistent sy- bility is likely to cause persistence of symptoms after surgery. Its ringomyelia (which means persisting at least 1 year after sur- role in the clinical picture should be properly addressed by clin- gery). A new surgical operation is carried out in case of occur- ical assessment and by a dynamic radiological study. rence of symptoms or scoliosis. Scoliosis is actually found to be an active sign of CM1 with/without syringomyelia in several Part D: Surgical re-intervention (Table 5) This part was devoted cases [69, 70]. to the management of the complications/comorbidities presented A significant agreement was reached also about children with in part C and the failed surgery. The first 3 questions addressed persistent symptoms and missed radiological improvement the management of CSF leakage, which was differentiated be- (CM1 and/or syringomyelia persisting 6 or 12 months after sur- tween symptomatic (open CSF leak or painful, closed subcuta- gery): they should be re-operated on. Six months can be pro- neous CSF collection) and asymptomatic (subcutaneous CSF posed as the minimum time to wait before the declaration of collection that does not cause symptoms or esthetic impact). failure (to be shortened if the patient is severely symptomatic), The true CSF leakages and the symptomatic CSF collections while 12 months is the maximum one. deserve an aggressive management, which is a surgical revision Finally, children who underwent a successful surgery are of the duraplasty and the surgical cavity (plus external lumbar advised to be followed up until the end of growth or at least for drainage, if needed). On the other hand, a conservative 10 years, clinically and radiologically (at least one brain and Table 6 Specific conditions related to CVJ malformations: 1 CM 1.5 may be associated with basilar invagination or impressio basilaris. Only cases Agreement: surgical options with related symptoms need to be operated. 95.2% 2 The preferred, etiological, surgical option for symptomatic basilar invagination Agreement: associated with CM1 without atlanto-axial instability, could be anterior 85.7% decompression, when posterior reduction has already failed. 3 The preferred surgical option for basilar invagination with atlanto-axial dislocation is Agreement: posterior fixation. 100% 4 Craniovertebral junction (CVJ) instability is a mobile dislocation between C0, C1, and Agreement: C2 (according to neuro-radiological exams) leading to neuro axial compression, 85.7% neurological deficits, progressive deformity, or structural pain. 5 The standard diagnostic work-up for CVJ instability in CM should include (other than Agreement: MRI) dynamic X-rays + dynamic CT scan with 3D reconstructions. 81% 6 CVJ fixation, with or without posterior decompression, is not indicated in CM1 patients Agreement: without a documented CVJ instability. 90.5% 7 Posterior decompression and CVJ fixation is the preferred surgical option for CM Agreement: patient with CVJ instability and related symptoms. 90.5% 8 In order to identify the best surgical option for CVJ instrumentation in a CM patient it is Agreement: mandatory to identify the following: (A) the vertebral artery course by preoperative 90.5% neuro-radiological studies (Angio-MRI, Angio-CT) and (B) the bone thickness of the occipital crest, the C2 isthmus diameter, the volume of C3 lateral masses. 9 To identify the best surgical option of C1–C2 instrumentation it is mandatory to define Agreement: the following: (A) the vertebral artery course by preoperative imaging (angio-MRI, 85.7% angio-CT) and (B) the C2 isthmus diameter 10 Fixations by C0-C3 or C1-C2 in CM patients with CVJ instability should be decided on Agreement: the basis of local anatomy. 95.2% Neurol Sci (2022) 43:1311–1326 1321 spinal cord MRI), to exclude recurrences. The frequency of Section 3—Isolated/non-CM1 pediatric syringomyelia the follow-up controls should be scheduled through a person- alized plan. Part A: Differential diagnosis (Table 7) As shown, syringomy- elia is frequently associated with CM1 and it is a discriminat- Part E: Surgical options for specific conditions related to CVJ ing factor influencing the indication for surgery and the as- malformations (Table 6) A separate section was dedicated to sessment of outcome [75–77]. Its management is strictly re- the CVJ instability because of its still unclear relationship with lated to the management of CM1. On the other hand, non- CM1 and the still missing general agreement on its manage- CM1 syringomyelia, which is likewise frequent, deserves a ment, which is often different and even independent from separate dissertation because of its varied etiology and man- CM1 [71–73]. Particularly controversial is the use of fixation agement. In this context, the first crucial step to be addressed to manage CM1 patients without CVJ anomalies [74]. is the differential diagnosis. Since this type of syringomyelia A first, large agreement was achieved about the need to is often clinically silent, such a differential diagnosis is obtain- operate on only symptomatic subjects with basilar ed radiologically. A general agreement was expressed on the invagination/impression basilaris-related CM 1.5. This re- need for a whole spinal cord MRI to rule out associated anom- sult is apparently obvious, but in clinical practice, a cer- alies (namely, but not only, spinal dysraphisms). A high tain trend to propose prophylactic surgery emerged (prob- agreement was also reached on the need for contrast medium ably due to the more severe radiological picture). As far administration to rule out associated tumors (or vascular as symptomatic basilar invagination without atlanto-axial malformations). Similarly, MRI with CISS-sequences or, in instability is concerned, the proposed option is to attempt very selected cases, myelo-CT scan can be considered useful a posterior reduction first and, in case of failure, to per- to detect small arachnoid cysts or the signs of arachnoiditis, form an etiologic treatment by anterior decompression although the latter diagnosis may be hard to obtain and the (followed by posterior fusion). The option of the posterior sensitivity of these techniques is not absolute. Finally, the reduction first, as observed by the panelists, allows also to need for dynamic studies in case of suspected CVJ or spine rule out microinstability and to verify if the odontoid is instability was reaffirmed. reducible, thus avoiding anterior decompression, if unnec- essary. On the other hand, subjects with symptomatic bas- Part B: Surgical indications (Table 7) As for CM1, there is no ilar invagination associated with atlanto-axial instability reason to operate on children with asymptomatic, isolated, and require treatment by reduction and posterior fixation, stable syringomyelia (universal agreement), based on the low accepting that, in some instances, an anterior decompres- reported risk of evolution [35, 78–80]. In this instance, it is sion may be indicated for persisting the compression with advised to perform a clinical and radiological follow-up, ac- symptoms. The same option applies to children with CM1 cording to the characteristics of each patient. On the other associated with CVJ instability where, in addition, the hand, in case of appearance of symptoms and/or clear radio- posterior fossa decompression can be added. It was wide- logical progression and/or neurophysiological deterioration, ly agreed that there is no indication for CVJ fixation in surgery is indicated. It is worth noting that, in pediatric cases, CM1 children if CVJ instability or hypermobility is not scoliosis is considered a possible marker of syringomyelia documented. Similarly, there was complete agreement to progression [13]. Of course, to be considered an indication select the treatment (e.g., C0–C3 fixation versus C1–C2 for surgery, the scoliosis progression should be associated fixation) based on the anatomical condition and the insta- with a large syrinx (not with idiopathic hydromyelia, which bility and not on the personal belief of the surgeon. is commonly coupled with scoliosis). On these grounds, some questions were devoted to the definition (question 4) and the diagnostic work-up of CVJ Part C: Surgical technique options (Table 7) This conclusive instability (questions 5, 8, 9). The proposed definition in- part addresses the surgical options according to the differ- cludes also the clinical findings because instability is not ever ent settings possibly associated with non-CM1 syringo- easy to demonstrate radiologically. A good agreement was myelia. The need to perform treatment directed according achieved about the need to perfect the diagnosis of CVJ insta- to etiology is strongly confirmed. As a consequence, sy- bility with dynamic 3D CT scan (thus, not only by dynamic X- ringomyelia associated with spinal dysraphism should be rays) and to carefully investigate the course of the vertebral treated by de-tethering of the spinal cord, while that relat- artery and the volume and morphology of the occipital squa- ed to spinal cord tumors by excision of the tumor. ma and cervical vertebrae prior to surgery. This appears par- Similarly, the challenging syringomyelia resulting from ticularly pertinent in children, where the anatomical condi- post-traumatic or post-surgical arachnoiditis should be tions may vary significantly according to age. For the “sim- treated by lysis of the adherences when symptomatic or ple” diagnosis, on the other hand, dynamic X-rays and MRI progressive. In the case of post-traumatic/post-surgical are enough (so that the load of CT-related X-rays is avoided). arachnoiditis, the surgical results may be disappointing; 1322 Neurol Sci (2022) 43:1311–1326 Agreement: 97.1% Agreement: 88.2% Agreement: 94.1% Agreement: 82.4% Agreement: 81.8% Agreement: 90.9% Agreement: 81.8% Agreement: 100% Agreement: 100% Agreement: 100% Agreement: 100% therefore, lysis should be planned only in case of clearly symptomatic patients. These results sound quite obvious; however, they definitively affirm the important concept that a direct treatment of syringomyelia is not routinely necessary nor advised. Indeed, a direct approach (e.g., shunting) is required only in case of failure of the etio- logic treatment [81]. Conclusions In case of symptomatic/evolutive syringomyelia secondary to arachnoiditis due to previous trauma and/or surgery, adhesiolysis is indicated In case of symptomatic/evolutive syringomyelia after failure of all the previous treatments (de-tethering, tumor removal, or adhesiolysis) The consensus process on the controversial topics in children was fruitful and allowed the authors to get some results that can be used as a base for future studies looking for recommen- dations or guidelines. They can be summarized as follows: In case of increasing or symptomatic syringomyelia (neurological/neurophysiological deterioration) surgery is indicated (1) The old definition of CM1 is still accepted, although the split cord malformation, limited dorsal myeloschisis, retained medullary cord, terminal myelocystocele, conus definition based on level of descent in millimeters alone has little clinical correlation. Attention must be paid not only on the degree of tonsillar descent but also to the Whole neuraxis MRI to diagnose an associated dysraphism (tethering of the medulla at any level due to morphology and volume of the posterior fossa. In case of isolated syringomyelia with progressive scoliosis, surgery for syringomyelia is indicated. Differential diagnosis: In children with non-Chiari syringomyelia, a painstaking diagnostic assessment should include: Transient tonsillar descent resulting from remitting pri- CISS-sequence MRI and/or myelo-CT to diagnose associated arachnoidal cysts or arachnoiditis. mary diseases is not a CM1. Syringomyelia is considered Isolated/non-CM1 syringomyelia in children: differential diagnosis, surgical indications, and techniques Asymptomatic isolated syringomyelia should be followed up, clinically and radiologically In case of associated spinal cord tumor, its removal is indicated to cure the syringomyelia if large and/or progressing and/or symptomatic (thin In case of syringomyelia-associated dysraphism, a de-tethering procedure is indicated hydromyelia is a para-physiological finding); a spino-peritoneal, spino-subarachnoidal, or spino-pleural shunt may be performed (2) No surgical indications are recognized in asymptomatic children with CM1 but without syringomyelia; Dynamic studies to diagnose spinal cord (congenital or acquired) instability (3) To date, no etiological relationship has been found be- lipomas, thickened, and fatty filum with a low-lying conus (below L3)) tween CM1 and epilepsy or autism; (4) Asymptomatic children should remain in contact with their physicians until the end of their growth. If needed, clinical and radiological controls are scheduled accord- ing to the characteristics of each patient; Contrast-enhanced MRI to diagnose spinal cord tumor (5) Symptomatic subjects benefit from a multidisciplinary team to rule out symptoms/signs unrelated to CM1 (e.g., key role of the neurologist in case of migraine- like headache). Some tools (polysomnography, SSEPs, MEPs) are useful in selected, doubtful cases; (6) In CM1 with associated hydrocephalus, hydrocephalus should be treated first to reduce the intracranial pressure, limiting the posterior fossa decompression to the chil- dren with persisting symptoms; (7) CM1 can result from both non-syndromic and syndromic craniosynostoses whose treatment needs to be incorpo- rated into the treatment strategy. Cranial vault surgery Surgical indications—results may address cerebellar ectopia. The posterior fossa de- Surgical options—results compression or the posterior distraction should be limit- ed to selected cases; (8) Tethered cord is rarely and sporadically associated with CM1 and its management is independent of CM1. A manifest and symptomatic tethered cord is treated by Table 7 intradural de-tethering but no effects on CM1 are 10 11 expected; 1 2 3 4 5 6 7 8 9 Neurol Sci (2022) 43:1311–1326 1323 (9) Bony posterior decompression and duraplasty are both Author contribution All authors contributed to the study conception and design. Material preparation, data collection, and analysis were per- acceptable techniques of foramen magnum decompres- formed by Luca Massimi, Paola Peretta, Alessandra Erbetta, Alessandra sion. The first offers a very low rate of complications and Solari, Mariangela Farinotti, Palma Ciaramitaro, Veronica Saletti, and a short hospital stay but shows a higher risk of persisting Laura Valentini. The first draft of the manuscript was written by Luca symptoms: it can be considered in children without se- Massimi and Laura Valentini. All authors commented on previous ver- sions of the manuscript. All authors read and approved the final vere symptoms or large syringomyelia. The second one manuscript. ensures more consistent radiological results but with a higher rate of (CSF-related) complications; Funding Open access funding provided by Università Cattolica del Sacro (10) The bony decompression has to be focused on a proper Cuore within the CRUI-CARE Agreement. opening of the foramen magnum and C1 (no need for large opening of the occipital squama or C2); Availability of data and material Data is available at the reader’s request. (11) The key points of duraplasty are to keep unviolated the arachnoid plane and to perform a proper dural closure Code availability Not applicable. (no need of tonsils coagulation unless this appears nec- essary to effect an effective and capacious decompres- Declarations sion: e.g., tonsils extending below C2); Ethical approval Not applicable. (12) The surgical failure can be defined by the persistence of symptoms 1 year after surgery. The radiological persis- Consent to participate Not applicable. tence of CM1/syringomyelia should be interpreted in clinical context before a decision to re-operate; Consent for publication Not applicable. (13) Too small opening and incorrect indication are the main causes of failure of bony decompression alone. Re- Conflict of interest The authors declare no competing interests. operation with a larger decompression and duraplasty Open Access This article is licensed under a Creative Commons are the respective solutions; Attribution 4.0 International License, which permits use, sharing, adap- (14) Arachnoiditis is an important cause of failure of tation, distribution and reproduction in any medium or format, as long as duraplasty. Proper surgical technique, re-operation you give appropriate credit to the original author(s) and the source, pro- with arachnoid lysis, and, in very selected cases, IV vide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included ventricle stenting are the solutions; in the article's Creative Commons licence, unless indicated otherwise in a (15) Asymptomatic postoperative CSF collection can be credit line to the material. If material is not included in the article's managed conservatively, while they should be treated Creative Commons licence and your intended use is not permitted by promptly, if symptomatic; statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this (16) CVJ instability or craniovertebral deformity (basilar impres- licence, visit http://creativecommons.org/licenses/by/4.0/. sion) must be ruled out in any (CM1) patient presenting with atypical clinical and/or radiological findings. Only symp- tomatic subjects should be treated, using a technique chosen according to the patient’s characteristics. The posterior de- References compression for CM1 can be added in selected cases; (17) Syringomyelia must be always ruled out in CM1 chil- 1. 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Affiliations Luca Massimi 1 & Paola Peretta 2 & Alessandra Erbetta 3 & Alessandra Solari 4 & Mariangela Farinotti 4 & Palma Ciaramitaro 5 & Veronica Saletti 6 & Massimo Caldarelli 1 & Alexandre Casagrande Canheu 7 & Carlo Celada 8 & Luisa Chiapparini 3 & Daniela Chieffo 9 & Giuseppe Cinalli 10 & Federico Di Rocco 11 & Marika Furlanetto 12 & Flavio Giordano 13 & George Jallo 14 & Syril James 15 & Paola Lanteri 16 & Christian Lemarchand 17 & Martina Messing-Jünger 18 & Cecilia Parazzini 19 & Giovanna Paternoster 15 & Gianluca Piatelli 20 & Maria. A. Poca 21 & Prab Prabahkar 22 & Federica Ricci 23 & Andrea Righini 19 & Francesco Sala 24 & Juan Sahuquillo 21 & Marcus Stoodley 25 & Giuseppe Talamonti 26 & Dominic Thompson 27 & Fabio Triulzi 28 & Mino Zucchelli 29 & Laura Valentini 12 & International Experts - Jury of the Chiari & Syringomyelia Consensus Conference, “Milan, November 11–13, 2019” 1 16 Pediatric Neurosurgery, Fondazione Policlinico Universitario A. Department of Diagnostic and Technology, Neurophysiopathology Gemelli IRCCS, Largo A. Gemelli, 8, 00168 Rome, Italy Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, 2 Milan, Italy Pediatric Neurosurgery, AOU Citta’ della Salute e della Scienza di 17 Torino, Torino, Italy Conseil Scientifique APAISER S&C, Treillières, France 3 18 Department of Neuroradiology, Fondazione IRCCS Istituto Pädiatrische Neurochirurgie, Asklepios Kinderklinik, Sankt Neurologico Carlo Besta, Milan, Italy Augustin, Germany 4 Neuroepidemiology Unit – Scientific Directorate, Fondazione 19 Department of Pediatric Radiology and Neuroradiology, Children IRCCS Istituto Neurologico Carlo Besta, Milan, Italy Hospital V. Buzzi, Milan, Italy 5 20 Department of Neuroscience, AOU Citta’ della Salute e della Department of Neurosurgery, Gaslini Children’s Hospital, Scienza di Torino, Torino, Italy Genoa, Italy 6 21 Department of Pediatric Neurology, Fondazione IRCCS Istituto Neurosurgery and Pediatric Neurosurgery, Vall d’Hebron Hospital Neurologico Carlo Besta, Milan, Italy Universitari, Neurotrauma and Neurosurgery Research Unit, and 7 Universitat Autònoma de Barcelona, Barcelona, Spain Pediatric Neurosurgery Division, Universidade Estadual de 22 Londrina, Londrina, Brazil Department of Neurology, Great Ormond Street Hospital for Children, London, UK 8 “Associazione Italiana Siringomielia e Arnold Chiari”, Garino, Italy 23 9 Pediatric Neuropsychiatric Unit, AOU Citta’ della Salute e della Clinical Psychology Unit, Fondazione Policlinico Universitario A Scienza di Torino, Torino, Italy Gemelli IRCCS and UCSC, Rome, Italy 24 10 Section of Neurosurgery, Department of Neurosciences, Pediatric Neurosurgery, Santobono-Pausilipon Children’s Hospital, Biomedicine and Movement Sciences, University Hospital, Naples, Italy Verona, Italy 11 Pediatric Neurosurgery Department, Université de Lyon, INSERM 25 Department of Clinical Medicine, Macquarie University Clinical U1033, Hopital Femme Mère Enfant, Lyon, France Associates, Sidney, Australia 12 Department of Neurosurgery, Fondazione IRCCS Istituto 26 Department of Neurosurgery, ASST Niguarda, Milan, Italy Neurologico Carlo Besta, Milan, Italy 27 13 Department of Neurosurgery, Great Ormond Street Hospital for Department of Neurosurgery, Meyer Pediatric Hospital, Children, London, UK Florence, Italy 28 14 Department of Pathophysiology and Transplantation, Institute for Brain Protection Sciences, Johns Hopkins All Neuroradiology Unit, University of Milan, Fondazione IRCCS Cà Children’s Hospital, St. Petersburg, FL, USA Granda, Ospedale Maggiore Policlinico, Milan, Italy 15 Department of Pediatric Neurosurgery, Necker Enfants Malades 29 Neurochirurgia Pediatrica, IRCCS Istituto delle Scienze Hospital, Paris, France Neurologiche di Bologna, Bologna, Italy