Interpeduncular angle: A new parameter for assessing intracranial hypotension in fetuses with spinal dysraphism.

OBJECTIVE: To investigate the role of the interpeduncular angle (IPA) as a new indicator of intracranial hypotension in fetuses with open spinal dysraphism (SD). METHODS: Two groups of fetuses undergoing magnetic resonance imaging (MRI) examination were identified. The study group included fetuses with open SD (n = 21), while the control group included fetuses with a normal brain and spine (n = 43). Two observers retrospectively evaluated axial T2-weighted images of the brain and the IPA was identified and measured. Other features of the Chiari II malformation were also evaluated in the study group and correlated with the IPA. RESULTS: The average value (±SD) of the IPA for the study and control groups was 9.8° ± 18.5° and 60.2° ± 5.9°, respectively. The intergroup analysis of the IPA measurements revealed a statistically significant difference between the groups (p < 0.005). Brainstem slumping or cerebellar tonsillar descent, collapse of the fourth ventricle, and ventriculomegaly also had a significant correlation with a lower IPA (p = 0.001). CONCLUSION: Measuring the IPA may be a useful technique for assessing the degree of intracranial hypotension in fetuses with open SD. This technique can also detect less severe cases of prenatal intracranial hypotension, even before cerebellar tonsillar descent. The lower IPA in fetuses with open SD further supports the theory that cerebrospinal fluid leakage, and not traction, is the underlying cause of Chiari II malformation.

Tonsillar herniation spectrum: more than just Chiari I. Update and controversies on classification and management.

Cerebellar tonsil herniation comprises a spectrum of disorders sharing a common neuroimaging finding consisting of downward displacement of the cerebellar tonsils through the foramen magnum and into the upper cervical spinal canal. This not uncommon condition may result from a large host of congenital or acquired causes, and confusion regarding its classification and pathogenesis still exists. Terminology also remains heterogeneous, including inconsistencies in the usage of the "Chiari 1" monicker. In this paper, the hypothesized mechanisms of development of tonsillar herniation are reviewed and strategies of management are discussed, with particular attention to surgical options adapted to the underlying etiology. A focus will be placed on acquired causes of tonsillar herniation.

Chiari I-a 'not so' congenital malformation?

The term Chiari I malformation (CIM) is imbedded in the paediatric neurosurgical lexicon; however, the diagnostic criteria for this entity are imprecise, its pathophysiology variable, and the treatment options diverse. Until recently, CIM has been considered to be a discrete congenital malformation requiring a uniform approach to treatment. Increasingly, it is recognised that this is an oversimplification and that a more critical, etiologically based approach to the evaluation of children with this diagnosis is essential, not only to select those children who might be suitable for surgical treatment (and, of course those who might be better served by conservative management) but also to determine the most appropriate surgical strategy. Whilst good outcomes can be anticipated in the majority of children with CIM following foramen magnum decompression, treatment failures and complication rates are not insignificant. Arguably, poor or suboptimal outcomes following treatment for CIM reflect, not only a failure of surgical technique, but incorrect patient selection and failure to acknowledge the diverse pathophysiology underlying the phenomenon of CIM. The investigation of the child with 'hindbrain herniation' should be aimed at better understanding the mechanisms underlying the herniation so that these may be addressed by an appropriate choice of treatment.

Defining, diagnosing, clarifying, and classifying the Chiari I malformations.

PURPOSE: Chiari malformations (CM) have been traditionally classified into four categories: I, II, III, and IV. In light of more recent understandings, variations of the CM have required a modification of this classification. METHODS: This article discusses the presentation, diagnostics, and treatment of the newer forms of hindbrain herniation associated with the CM type I. RESULTS: The CM 1 is a spectrum that includes some patients who do not fall into the exact category of this entity. CONCLUSIONS: While CM have been categorically recognized as discrete and individual conditions, newer classifications such as CM 0 and CM 1.5 exhibit some degree of continuity with CM 1; however, they require distinct and separate classification as symptoms and treatments can vary among these clinical subtypes.

The newer classifications of the chiari malformations with clarifications: An anatomical review.

In 1891, Hans Chiari described a group of congenital hindbrain anomalies, which were eventually named after him. He classified these malformations into three types (Chiari malformations I, II, and III), and four years later added the Chiari IV malformation. However, numerous reports across the literature do not seem to fit Chiari's original descriptions of these malformations, so researchers have been encouraged to propose new classifications to encompass these variants (e.g., Chiari 0, Chiari1.5, and Chiari 3.5 malformations). Moreover, there is a continued misunderstanding and misuse of the term "Chiari IV malformation." Therefore, the current review intended to describe anatomical, pathophysiological, and clinical aspects of the newer classifications with clarifications of the Chiari malformations. We reviewed available literature about Chiari malformations and their variants using "PubMed" and "Google Scholar." We also looked into the term Chiari IV, clarifying its original description and citing examples where the term has been used erroneously. References in the reviewed articles were searched manually. Variants of the originally described Chiari malformations are termed Chiari 0, Chiari 1.5, and Chiari 3.5. Each has distinct anatomical characteristics and some of these are extremely rare and incompatible with life (e.g. Chiari 3.5). Chiari IV malformation has been further clarified. Some physicians might be unfamiliar with the newer classifications of Chiari malformations because these conditions are rare or even unique. Furthermore, care is needed in using the term "Chiari IV malformation", which must be consistent with Chiari's original description, i.e. an occipital encephalocele containing supratentorial contents. Clin. Anat. 31:314-322, 2018. © 2018 Wiley Periodicals, Inc.

Magnetic resonance imaging features of complex Chiari malformation variant of Chiari 1 malformation.

BACKGROUND: Complex Chiari malformation is a subgroup of Chiari 1 malformation with distinct imaging features. Children with complex Chiari malformation are reported to have a more severe clinical phenotype and sometimes require more extensive surgical treatment than those with uncomplicated Chiari 1 malformation. OBJECTIVE: We describe reported MR imaging features of complex Chiari malformation and evaluate the utility of craniometric parameters and qualitative anatomical observations for distinguishing complex Chiari malformation from uncomplicated Chiari 1 malformation. MATERIALS AND METHODS: We conducted a retrospective search of the institutional imaging database using the keywords "Chiari" and "Chiari 1" to identify children imaged during the 2006-2011 time period. Children with Chiari 2 malformation were excluded after imaging review. We used the first available diagnostic brain or cervical spine MR study for data measurement. Standard measurements and observations were made of obex level (mm), cerebellar tonsillar descent (mm), perpendicular distance to basion-C2 line (pB-C2, mm), craniocervical angle (degrees), clivus length, and presence or absence of syringohydromyelia, basilar invagination and congenital craniovertebral junction osseous anomalies. After imaging review, we accessed the institutional health care clinical database to determine whether each subject clinically met criteria for Chiari 1 malformation or complex Chiari malformation. RESULTS: Obex level and craniocervical angle measurements showed statistically significant differences between the populations with complex Chiari malformation and uncomplicated Chiari 1 malformation. Cerebellar tonsillar descent and perpendicular distance to basion-C2 line measurements trended toward but did not meet statistical significance. Odontoid retroflexion, craniovertebral junction osseous anomalies, and syringohydromyelia were all observed proportionally more often in children with complex Chiari malformation than in those with Chiari 1 malformation. CONCLUSION: Characteristic imaging features of complex Chiari malformation, especially obex level, permit its distinction from the more common uncomplicated Chiari 1 malformation.

Essential features of Chiari II malformation in MR imaging: an interobserver reliability study--part 1.

PURPOSE: Brain MR imaging is essential in the assessment of Chiari II malformation in clinical and research settings concerning spina bifida. However, the interpretation of morphological features of the malformation on MR images may not always be straightforward. In an attempt to select those features that unambiguously characterize the Chiari II malformation, we investigated the interobserver reliability of all its well-known MR features. METHODS: Brain MR images of 79 children [26 presumed to have Chiari II malformation, 36 presumed to have no cerebral abnormalities, and 17 children in whom some Chiari II malformation features might be present; mean age 10.6 (SD 3.2; range, 6-16) years] were blindly and independently reviewed by three observers. They rated 33 morphological features of the Chiari II malformation as present, absent, or indefinable in three planes (sagittal, axial, and coronal). The interobserver reliability was assessed using κ statistics. RESULTS: Twenty-three of the features studied turned out to be unreliable, whereas the interobserver agreement was almost perfect (κ value > 0.8) for nine features (eight in the sagittal plane and one in the axial plane, but none in the coronal plane). CONCLUSIONS: This study presents essential features of the Chiari II malformation on MR images by ruling out the unreliable features. Using these features may improve the assessment of Chiari II malformation in clinical and research settings.

Neuroradiological diagnosis of Chiari malformations.

Chiari malformations 1, 2, 3 represent different degrees of herniation of posterior fossa content into the cervical canal (Chiari 1 and 2), or through an upper-cervical meningocele (Chiari 3), whereas Chiari 4 anomaly consists of hypoplasia of the cerebellum. Chiari 1 malformation (CM1) is the commonest anomaly; it is probably related to a mesodermal defect that create a congenitally small posterior fossa, subsequent overcrowding of its contents and herniation through the foramen magnum. The diagnosis of CM1 is based on the demonstration of the downward displacement and particular shape of the cerebellar tonsils into the upper cervical spinal canal associated with obliteration of the subarachnoid spaces at the level of the foramen magnum. MRI has a fundamental role in the correct identification of the anatomical aspects of this malformation and associated anomalies and represents the imaging modality of choice.

Fetal MRI features related to the Chiari malformations.

Fetal magnetic resonance (MR) imaging may add to ultrasonography some valuable information in the assessment of Chiari malformations during their developmental stage. In Chiari type I, MR imaging role seems mainly related to research on pathophysiology issues rather than to real clinical applications. Some Chiari type II features may be better characterized in utero by MR imaging: such as the degree of downward displacement of cerebellum, possible abnormal signal changes within brain parenchyma and the type of meningocele (covered or uncovered).

Classification of symptomatic Chiari I malformation to guide surgical strategy.

BACKGROUND: Treatment options for Chiari I malformations include posterior fossa decompression (PFD) with additional techniques including laminectomy, intradural exploration, and duraplasty. Neuroimaging findings of cisterna magna volume, syringomyelia, and intraoperative ultrasonography may tailor surgical intervention. METHODS: We developed an algorithm classifying symptomatic Chiari I patients into three groups to define minimum operation. Without syringomyelia, the presence of cisterna magna defined Group A and the absence defined Group B. Patients with syrinx formed Group C. Mild structural pathology (Group A) or adequate space following PFD (Group B, normal intraoperative ultrasound (IOUS)) should be treated by PFD alone. Conversely, presence of syringomyelia (Group C) or inadequate space following PFD (Group B, abnormal IOUS) should additionally have duraplasty. We applied this algorithm to patients treated at a single institution over 16 years. RESULTS: Twenty-four symptomatic Chiari I malformation patients were divided into three groups that did not differ by age, gender, or extent of tonsillar ectopia. All patients treated by this algorithm experienced clinical and radiographic improvement. This included eight Group B patients who underwent PFD only (n=6) or additional duraplasty (n=2) decided by IOUS. CONCLUSION: Treatment of symptomatic Chiari I malformation may have inadequate outcome with conservative strategy or complications with aggressive strategy. This algorithm utilizes preoperative neuroimaging and intraoperative ultrasound to tailor intervention, with excellent clinical outcome and radiographic syrinx resolution on application to 24 patients. Further validation requires prospective multicenter evaluation with larger patient population.

Congenital Chiari malformations.

Chiari malformation is the commonest anomaly of the craniovertebral junction involving both the skeletal as well as the neural structures. This entity has rapidly evolved over the past decade with newer visualization techniques, thus posing new challenges to diagnosis and management. This review includes the developmental theories, the latest nomenclature and existing treatment modalities of this interesting anomaly. Five theories tried to explain the malformation of the hindbrain and the neuraxis but no single theory completes the development of embryonic defects. Several atypical presentations have been reported with either incidental/asymptomatic features resulting in further classifications. The new magnetic resonance imaging flow techniques attempt to substantiate the clinical presentations and correlate with the abnormality which can be subtle in correlation. Surgical correction to improve the cranial volume, decrease the hydrocephalus and improve flow across the foramen magnum is the mainstay but needs to be tailored to a given type of malformation. Further clinical and imageological studies, especially longitudinal natural history, might improve our understanding of the atypical/asymptomatic presentations and the management that is currently available.

Syringomyelia and Chiari Syndrome Registry: advances in epidemiology, clinical phenotypes and natural history based on a North Western Italy cohort.

BACKGROUND: Syringomyelia and Chiari Syndrome are classified as rare diseases, but current known occurrence in Europe is missing. The increased ability to diagnose these pathologies by magnetic resonance imaging and its widespread availability has led to an increase of reported cases, often asymptomatic, with the need to standardize definitions, diagnostic criteria and treatments. AIMS: We present shared Interregional Recommendations developed with the primary aim to estimate Syringomyelia and Chiari Syndrome prevalence and incidence in North Western Italy, with special reference to symptomatic forms. METHODS: An agreement for the standardization of definitions, classifications, diagnostic criteria and surgical Recommendations was reached by the multidisciplinary Interregional Piemonte and Valle d'Aosta Chiari-Syringomyelia Consortium (Delphi method); next, in 2011 a census for Syringomyelia and Chiari Malformation was performed through the Interregional Piemonte and Valle d'Aosta Rare Disease Registry, integrated by a dedicated form in order to estimate prevalence and incidence. RESULTS: 436 patients, 292 females, met shared interregional diagnostic criteria. Syringomyelia prevalence was estimated in 4.84:100 000; Chiari Malformation prevalence was 7.74:100 000; incidence was 0.82:100 000 and 3.08:100 000 respectively. Demographics, neuroradiological parameters and aetiology were reported (in symptomatic and asymptomatic forms). Finally, symptoms and signs, familiar and natural history were analyzed. CONCLUSIONS: First Italian epidemiological data (prevalence, incidence) on Chiari and syringomyelia was collected, according to shared diagnostic Recommendations. Future perspectives include the adoption of these Recommendations at national level to standardize the access to diagnosis and care process and promote multicenter clinical trials.

Malformations of the craniocervical junction (Chiari type I and syringomyelia: classification, diagnosis and treatment).

Chiari disease (or malformation) is in general a congenital condition characterized by an anatomic defect of the base of the skull, in which the cerebellum and brain stem herniate through the foramen magnum into the cervical spinal canal. The onset of Chiari syndrome symptoms usually occurs in the second or third decade (age 25 to 45 years). Symptoms may vary between periods of exacerbation and remission. The diagnosis of Chiari type I malformation in patients with or without symptoms is established with neuroimaging techniques. The most effective therapy for patients with Chiari type I malformation/syringomyelia is surgical decompression of the foramen magnum, however there are non-surgical therapy to relieve neuropathic pain: either pharmacological and non-pharmacological. Pharmacological therapy use drugs that act on different components of pain. Non-pharmacological therapies are primarily based on spinal or peripheral electrical stimulation. It is important to determine the needs of the patients in terms of health-care, social, educational, occupational, and relationship issues, in addition to those derived from information aspects, particularly at onset of symptoms. Currently, there is no consensus among the specialists regarding the etiology of the disease or how to approach, monitor, follow-up, and treat the condition. It is necessary that the physicians involved in the care of people with this condition comprehensively approach the management and follow-up of the patients, and that they organize interdisciplinary teams including all the professionals that can help to increase the quality of life of patients.

Machine learning applied to neuroimaging for diagnosis of adult classic Chiari malformation: role of the basion as a key morphometric indicator.

OBJECTIVE The current diagnostic criterion for Chiari malformation Type I (CM-I), based on tonsillar herniation (TH), includes a diversity of patients with amygdalar descent that may be caused by a variety of factors. In contrast, patients presenting with an overcrowded posterior cranial fossa, a key characteristic of the disease, may remain misdiagnosed if they have little or no TH. The objective of the present study was to use machine-learning classification methods to identify morphometric measures that help discern patients with classic CM-I to improve diagnosis and treatment and provide insight into the etiology of the disease. METHODS Fifteen morphometric measurements of the posterior cranial fossa were performed on midsagittal T1-weighted MR images obtained in 195 adult patients diagnosed with CM. Seven different machine-learning classification methods were applied to images from 117 patients with classic CM-I and 50 controls matched by age and sex to identify the best classifiers discriminating the 2 cohorts with the minimum number of parameters. These classifiers were then tested using independent CM cohorts representing different entities of the disease. RESULTS Machine learning identified combinations of 2 and 3 morphometric measurements that were able to discern not only classic CM-I (with more than 5 mm TH) but also other entities such as classic CM-I with moderate TH and CM Type 1.5 (CM-1.5), with high accuracy (> 87%) and independent of the TH criterion. In contrast, lower accuracy was obtained in patients with CM Type 0. The distances from the lower aspect of the corpus callosum, pons, and fastigium to the foramen magnum and the basal and Wackenheim angles were identified as the most relevant morphometric traits to differentiate these patients. The stronger significance (p < 0.01) of the correlations with the clivus length, compared with the supraoccipital length, suggests that these 5 relevant traits would be affected more by the relative position of the basion than the opisthion. CONCLUSIONS Tonsillar herniation as a unique criterion is insufficient for radiographic diagnosis of CM-I, which can be improved by considering the basion position. The position of the basion was altered in different entities of CM, including classic CM-I, classic CM-I with moderate TH, and CM-1.5. The authors propose a predictive model based on 3 parameters, all related to the basion location, to discern classic CM-I with 90% accuracy and suggest considering the anterior alterations in the evaluation of surgical procedures and outcomes.

Sleep-Related Breathing Disorders in Chiari Malformation Type 1: A Prospective Study of 90 Patients.

Study objective: The aim of the present study is to describe the prevalence of sleep disorders in a large group of patients with Chiari malformation type 1 (CM-1) and determine the presence of risk factors associated with these abnormalities. Methods: Prospective study with consecutive patient selection. We included 90 adult patients with CM-1, defined by the presence of a cerebellar tonsillar descent (TD) ≥3 mm. Clinical, neuroradiological studies, and nocturnal polysomnography (PSG) was carried out. In addition, patients were also subclassified into 2 CM subtypes: CM-1, with the obex above the foramen magnum (FM) and CM-1.5, in which along with a TD ≥3 mm, the obex was located below the FM. Results: We observed a high prevalence (50%) of sleep-related breathing disorders (SRBDs) with predominant hypopnea. Only six patients showed a central apnea index of ≥5. Hypoventilation was observed in only three patients. SRBD severity was associated with male sex, older age, excess weight, and the presence of hydrocephalus. No differences in clinical or PSG parameters were found when comparing CM subtypes (CM-1 and CM-1.5). Sleep architecture study showed decreased sleep efficiency with an increase in arousal and waking after sleep onset. The presence of SRBDs was found to be associated with poorer sleep architecture parameters. Conclusions: This study confirms a high prevalence of SRBDs in patients with CM-1 and CM-1.5, with a predominant obstructive component. Nocturnal PSG recordings should be systematically conducted in these patients, especially those who are male, older, or overweight or those who present hydrocephalus.

Chiari type I malformation in four unrelated patients affected with Fabry disease.

Fabry disease (FD) is an X-linked inborn error of metabolism resulting from the deficient activity of alpha-galactosidase A which leads to the widespread deposition of glycosphingolipids in lysosomes, and to ischemic complications involving kidneys, heart and brain. Among neurological symptoms, strokes and transient ischemic attacks (TIA) have been reported. A 30-year-old male patient, with FD, was referred to us for evaluation of a sudden episode of dizziness, with disequilibrium, and diplopia, in agreement with the diagnosis of a TIA. Head magnetic resonance imaging (MRI) showed no cerebrovascular involvement but revealed the presence of Chiari type I malformation (CMI). We subsequently performed head MRI in a cohort of 44 consecutive hemizygous male patients and seven heterozygous females affected with FD, and identified three additional cases (two males and one female) of CMI. Whether the association is coincidental or not will need further studies but our data suggest that CMI should be ruled out in all Fabry patients.