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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 international 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., (© 2021. The Author(s).)

Purpose: The association between Chiari type I malformation (CIM) and hydrocephalus raises a great interest because of the still unclear pathogenesis and the management implications. The goal of this paper is to review the theories on the cause-effect mechanisms of such a relationship and to analyze the results of the management of this condition., Methods: A review of the literature has been performed, focusing on the articles specifically addressing the problem of CIM and hydrocephalus and on the series reporting about its treatment. Also, the personal authors' experience is briefly discussed., Results: As far as the pathogenesis is concerned, it seems clear that raised intracranial pressure due to hydrocephalus can cause a transient and reversible tonsillar caudal ectopia ("pressure from above" hypothesis), which is something different from CIM. A "complex" hypothesis, on the other hand, can explain the occurrence of hydrocephalus and CIM because of the venous engorgement resulting from the hypoplasia of the posterior cranial fossa (PCF) and the occlusion of the jugular foramina, leading to cerebellar edema (CIM) and CSF hypo-resorption (hydrocephalus). Nevertheless, such a mechanism can be advocated only in a minority of cases (syndromic craniosynostosis). In non-syndromic CIM subjects, the presence of hydrocephalus could be explained by an occlusion of the basal CSF pathways, which would occur completely in a minority of cases (only 7-10% of CIM patients show hydrocephalus) while it would be partial in the remaining cases (no hydrocephalus). This hypothesis still needs to be demonstrated. As far as the management is concerned, the strategy to treat the hydrocephalus first is commonly accepted. Because of the "obstructive" origin of CIM-related hydrocephalus, the use of endoscopic third ventriculostomy (ETV) is straightforward. Actually, the analysis of the literature, concerning 63 cases reported so far, reveals very high success rates of ETV in treating hydrocephalus (90.5%), CIM (78.5%), and syringomyelia symptoms (76%) as well as in giving a radiological improvement of both CIM (74%) and syringomyelia (89%). The failures of ETV were not attributable to CIM or syringomyelia. Only 11% of cases required PCF decompression after ETV., Conclusions: The association between CIM and hydrocephalus probably results from different, multifactorial, and not yet completely understood mechanisms, which place the affected patients in a peculiar subgroup among those constituting the heterogeneous CIM population. ETV is confirmed as the best first approach for this subset of patients.

Chiari I malformation (CI) continues to raise great interest among physicians due to the larger and larger number of newly diagnosed cases. The clinical and radiological picture and the management options of such a chronic disease are well acknowledged as well as those of the associated syringomyelia. Little is known, on the other hand, about abrupt clinical onset following decompensation of CI/syringomyelia complex. This review on the sudden onset of these two conditions shows that this is a very rare phenomenon; only 41 cases are being reported in the last three decades. In all these cases, acute onset was referable to CI/syringomyelia and the clinical course quickly precipitated. Motor deficits (36.5 %), respiratory failure (29 %), cranial nerve palsy (17 %), and cardiac arrest (14.5 %) were the most common findings, thus confirming that abrupt onset may have severe and life-threatening consequences. Indeed, sudden or early mortality accounted for 19.5 % of cases. In spite of that, most of the surviving subjects had an excellent outcome following either surgical or medical/rehabilitation treatment. Physiopathology of abrupt onset is attributed to the acute compression of the brainstem/upper cervical spinal cord by ectopic tonsils and syringobulbia/syringomyelia, frequently precipitated by a minor injury, followed by impairment of medullary baroreceptors and midbrain reticular substance (cardiac arrest, syncope), medullary chemoreceptors and phrenic nerve nuclei (respiratory failure), lower cranial nerve nuclei (cardiac arrest, cranial nerve palsy), and pyramidal tracts (motor deficits). About 87 % of patients of this review were asymptomatic prior to their acute onset. The problem of the management of asymptomatic subjects is still open.

Introduction: The diagnosis of Chiari I malformation relies mainly on the anatomical demonstration of the abnormal position of the cerebellar tonsils below the foramen magnum, and of the associated bony anomalies of the posterior cranial fossa and craniocervical junction, as well as of the eventually-associated spinal cord cavitations. Consequently, the neuroradiological work-up plays a fundamental role in the definition of the malformation and in the follow-up of operated patients., Review: The authors review the pertinent literature on the neuroradiology of the Chiari I malformation, with special regard to MRI, with the aim of providing the reader with an updated instrument for its diagnosis.

Background: Lumbosacral lipomas (LLs) may remain asymptomatic or lead to progressive neurological deterioration. However, sudden neurological deterioration is a rare and severe event. Herein, we report rare occurrences of sudden clinical deterioration in two previously asymptomatic children harbouring intradural LLs without dermal sinus tracts or signs of occult dysraphism. A review of the pertinent literature is also included.Case Presentation: One child exhibited acute deterioration because of an epidural abscess associated with a filar lipoma without a sinus tract (probably caused by haematogenous spreading from a respiratory tract multiple infection), and the other child exhibited acute deterioration because of a very large, holocord syringomyelia-like cyst associated with a small conus lipoma. Both patients were 4 years old. In case #2, a previously undetected, severe tethered cord (conus at the S3-S4 level) was also present. A complete recovery was attained after an urgent surgical operation in both cases (in addition to targeted antibiotic therapy in case #1). All cases of deterioration in the literature were caused by abscess formation in dermal sinus tracts.Conclusions: Prophylactic surgery may be indicated even in asymptomatic children that have tethered cord and surgically favourable LLs (small dorsal and filar LLs), especially if the conditions are associated with progressive syringomyelia. Similarly, intradural dermal sinus tracts should be regarded as surgery-indicated, even if the conus is in its normal position and the patient is asymptomatic because there is a consistent risk of severe, infection-related complications. Finally, asymptomatic patients with filar LLs and a normally located conus can be candidates for surgery or an accurate clinical and radiological follow-up. [ABSTRACT FROM AUTHOR]