Intradural pathology and pathophysiology associated with Chiari I malformation in children and adults with and without syringomyelia

Impact of intradural abnormalities on symptoms and clinical outcomes in Chiari malformation

PURPOSE

This study aims to investigate the impact of intradural abnormalities on symptoms and clinical outcomes in Chiari malformation.

METHODS

A retrospective study was conducted on 189 patients with Chiari malformation who underwent posterior fossa decompression with duraplasty or tonsillectomy. Intradural abnormalities were categorized as arachnoid abnormalities, foramen of Magendie (FoM) obstruction, and tonsillar abnormalities. Clinical outcomes were assessed using the symptoms improvements, Chicago Chiari Outcome Scale (CCOS), complications and re-operation.

RESULTS

A total of 189 patients with Chiari malformation were included in the study. 79.4 % of the patients were female, with a mean age of 45.0 ± 10.7 years (range: 16-62 years). Common intradural abnormalities included arachnoid adhesions (68.3 %), obstruction of the foramen of Magendie (FoM) (50.3 %), and tonsillar hypertrophy (38.6 %). Obstruction of FoM was more frequently observed in patients with Valsalva provoked headaches (53.7 % vs. 12.8 %, p < 0.001), syringomyelia (93.7 % vs. 67.0 %, p < 0.001). CCOS scores (12.5 ± 2.3 vs. 13.3 ± 2.0, p = 0.027) and improved (53.7 % vs. 78.7 %, p = 0.001) were lower in the obstruction group. Tonsillar abnormalities were associated with higher incidence of Valsalva provoked headaches (61.6 % vs. 15.5 %, p < 0.001) and gait instability (43.8 % vs. 6.0 %, p < 0.001).

CONCLUSIONS

Intradural abnormalities, particularly obstruction of FoM and tonsillar abnormalities, are correlated with symptoms and clinical outcomes in Chiari malformation.

Effectiveness of Cerebellar Tonsillectomy Treatment for Revision Chiari Malformation Surgery: A Series of 63 Patients

BACKGROUND

Revision surgery for patients with persistent, recurrent, or progressive syringomyelia following Foramen Magnum Decompression for Chiari malformation with syringomyelia (CM-SM) is not uncommon and presents both strategic and technical challenges.

METHODS

We conducted a retrospective study including all patients who underwent revision Cerebellar Tonsillectomy (CTL) for CM-SM between 2003 and 2023. Additionally, we performed univariate and multivariate analyses to identify possible factors contributing to failed CTL outcomes.

RESULTS

Sixty-three consecutive patients (13 males; average age 45.86 ± 11.18 years) underwent surgical treatment for persistent (n = 29), progressive (n = 21), or recurrent (n = 13) syringomyelia, with an average interval of 65.57 ± 73.33 months (range: 3-480 months) between the two surgeries. Factors significantly associated with the effectiveness of the revision CTL included dural incision and tonsil manipulation during the first surgery, severe intradural adhesions during the revision CTL, and spinal cord atrophy before the revision CTL. Multivariate logistic regression revealed that dural incision (P = 0.031, odds ratio [OR] = 6.779, 95% confidence interval {CI} [1.187∼38.719]), tonsillar manipulation (P = 0.037, OR = 7.432, 95% CI [1.131∼48.835]), and severe intradural adhesions (P = 0.030, OR = 11.465, 95% CI [1.264∼103.967]) constituted risk factors significantly statistical associated with prognosis outcomes. Long-term follow-up (average 18.75 ± 6.86 months, range: 12-72 months) of revision CTL demonstrated clinical stabilization in 55.6% of cases for at least 1.5 years. The complication rate for revision CTL was 14.3% (n = 9).

CONCLUSIONS

Dural incision and tonsillar manipulation during the first surgery, spinal cord atrophy prior to revision CTL, and severe intradural adhesions during revision CTL are significant risk factors associated with poor prognosis in revision surgery for CM-SM.

Anomalies of the Craniocervical Junction (Chiari Malformations)

Arnold Chiari malformations include a combination of posterior fossa, hindbrain, and cervical occipital junction abnormalities, sometimes associated with spinal cord abnormalities such as spina bifida, syringomyelia, and syringobulbia. The most frequent form is Chiari I syndrome but two other variants, progressively more severe, have been described. Chiari malformations are the result of defective development of posterior fossa and can be due to genetic mutations, skeletal malformations, and intrautero factors. Clinical manifestations depend on the compression of the nerve structures within the foramen magnum and the spinal canal and mainly consist in headache or neck pain, gait disturbances, sensory or motor abnormalities, and autonomic signs. However, a high number of cases of Chiari I is asymptomatic and the diagnosis is occasional. Diagnosis is performed through nuclear magnetic resonance imaging of the brain and cervical tract, although other investigations may support the diagnosis. First-line treatment for candidate patients is a surgical procedure that involves decompression of the posterior cranial fossa and the craniocervical junction, as well as correction of associated malformations with techniques that depend on the severity of the case. Anyhow, some symptomatic patients benefit from conservative medical treatment with nonsteroidal anti-inflammatory drugs.

The Role of Phase-Contrast MRI in Diagnosing Cerebrospinal Fluid Flow Abnormalities

Background Cerebrospinal fluid (CSF) dynamics play a crucial role in maintaining the homeostasis of the central nervous system (CNS). Any disruption in CSF flow can lead to various congenital and acquired conditions, impacting neurological function and overall health. This study aims to analyze the significance of phase-contrast MRI in evaluating abnormalities in CSF flow and its diagnostic utility in various CSF-related disorders. Phase contrast MRI has emerged as a valuable tool for evaluating CSF dynamics non-invasively by examining CSF flow characteristics such as pulsatile flow patterns, hyperdynamic or hypodynamic flow, and disruptions in CSF circulation. Alterations in CSF pulsatility and stroke volume can indicate changes in intracranial compliance, vascular resistance, or CSF production and absorption rates. The findings of this study will advance our understanding of CSF physiology and its relevance in neurological pathologies, potentially leading to improved patient outcomes and management approaches. Materials and methods The study involved 36 patients and was conducted as an observational, prospective study over 18 months (October 2020 to March 2022) at the Department of Radiology, Saveetha Medical College and Hospital, Chennai. We utilized a 1.5 T Philips Multiva MRI scanner by Philips Healthcare in Amsterdam, Netherlands. The study included patients with suspected CSF flow abnormalities and abnormal MRI findings (normal pressure hydrocephalus (NPH), age-related brain atrophy, aqueduct stenosis (AS), Chiari malformation type 1, syringomyelia, or arachnoid cyst), alongside control exhibiting normal neurological symptoms and MRI results. Exclusions involved individuals with febrile seizures, neurological diseases, cerebrovascular accidents, anti-convulsive medication use, cardiac arrhythmia, or MRI contraindications. Post-processing involved analyzing stroke volume (SV), peak systolic velocity (PSV), end diastolic velocity (EDV), and mean flux. Statistical analysis was conducted using the Statistical Package for the Social Sciences (IBM SPSS Statistics for Windows, IBM Corp., Version 24.0, Armonk, NY), employing the χ2-test for categorical variables and nonparametric tests like Mann-Whitney U and Kruskal-Wallis H-tests for quantitative variables. A p-value < 0.05 was considered significant. Results The 36 patients, aged 1 to 80 years, were referred by the neurology department and categorized into four subgroups based on clinical history and conventional MRI findings: NPH, AS, age-related brain atrophy, and a normal control group. MRI CSF flowmetry evaluation focused on PSV, PDV, and SV. We found peak diastolic velocity (PDV), PSV, and average blood velocity (ABV) to be significantly higher in NPH compared to the control group (PSV, EDV, and SV: 9.96 +/- 1.73, 4.72 +/- 0.62, and 63 +/- 12.88 for NPH versus 4.8 +/- 0.39, 3.21 +/- 0.55, and 20.72 +/- 5.7 for control, respectively; p = 0.000). Conversely, patients with age-related brain atrophy and AS exhibited lower values (1.6 +/- 0.44, 1.13 +/- 0.09, and 6.33 +/- 2.08 for AS, and 2.07 +/- 0.09, 1.62 +/- 0.33, and 6.8 +/- 2.16 for age-related brain atrophy versus control; p = 0.002). Conclusion MRI CSF flowmetry emerges as a rapid, accurate, and non-invasive diagnostic tool for various neurological disorders associated with abnormal CSF flow. Additionally, this technique may aid in selecting appropriate treatment strategies.

Evaluation and Treatment of Patients with Small Posterior Cranial Fossa and Chiari Malformation, Types 0 and 1

The diagnosis of Chiari I malformation is straightforward in patients with typical signs and symptoms of Chiari I malformation and magnetic resonance imaging (MRI) confirming ≥5 mm of cerebellar tonsillar ectopia, with or without a syrinx. However, in many cases, Chiari I malformation is discovered incidentally on MRI to evaluate global headache, cervical radiculopathy, or other conditions. In those cases, the clinician must consider if cerebellar tonsillar ectopia is related to the presenting symptoms. Surgical decompression of the cerebellar tonsils and foramen magnum in patients with symptomatic Chiari I malformation effectively relieves suboccipital headache, reduces syrinx distension, and arrests syringomyelia progression. Neurosurgeons must avoid operative treatments decompressing incidental tonsillar ectopia, not causing symptoms. Such procedures unnecessarily place patients at risk of operative complications and tissue injuries related to surgical exploration. This chapter reviews the typical signs and symptoms of Chiari I malformation and its variant, Chiari 0 malformation, which has <5 mm of cerebellar tonsillar ectopia and is often associated with syringomyelia. Chiari I and Chiari 0 malformations are associated with incomplete occipital bone development, reduced volume and height of the posterior fossa, tonsillar ectopia, and compression of the neural elements and cerebrospinal fluid (CSF) pathways at the foramen magnum. Linear, angular, cross-sectional area, and volume measurements of the posterior fossa, craniocervical junction, and upper cervical spine identify morphometric abnormalities in Chiari I and Chiari 0 malformation patients. Chiari 0 patients respond like Chiari I patients to foramen magnum decompression and should not be excluded from surgical treatment because their tonsillar ectopia is <5 mm. The authors recommend the adoption of diagnostic criteria for Chiari 0 malformation without syringomyelia. This chapter provides updated information and guidance to the physicians managing Chiari I and Chiari 0 malformation patients and neuroscientists interested in Chiari malformations.

Individualized surgical treatment of Chiari 1 malformation: A single-center experience

OBJECTIVE

To present our experience with an individualized surgical approach to treat Chiari malformation type 1.

METHODS

Based on (1) neurological symptoms, (2) the existence and extent of a syrinx and (3) the degree of the tonsillar descent we performed four types of approaches on a case-by-case basis in 81 patients: (1) foramen magnum decompression (FMD) with dura splitting (FMDds); (2) FMD with duraplasty (FMDdp); (3) FMD with duraplasty and tonsillar manipulation (FMDao); and (4) tonsillar resection/reduction (TR). Patient characteristics, Chiari Severity Index (CSI), fourth ventricular roof angle (FVRA) and Chicago Chiari Outcome Scale (CCOS) were analyzed.

RESULTS

CCOS was between 13 and 16 points in 8/11 (73 %) patients after FMDds, 38/45 (84 %) patients after FMDdp, and 24/24 (100 %, one patient lost to follow-up) patients after TR. We experienced an overall complication rate of 13.6 % (11/81) in this series, whereas seven of these eleven complications (64 %) occurred in the FMDao group and the complication rate increased with the invasiveness of the approach (0 % FMDds; 4 % FMDdp; 12 % TR).

CONCLUSION

Given the clear correlation between the extend of the approach and the complication rate the least invasive approach necessary to achieve clinical improvement should be selected. Due to the high complication rates, FMDao should not be used as a treatment option. The severity of the tonsillar descent, basilar invagination and current CM1 scores could be used to aid in the approach selection.

Cerebellar Tonsillar Descent Mimicking Chiari Malformation

Chiari I malformation has been defined as cerebellar tonsillar descent greater than 5 mm below the foramen magnum. Suboccipital decompression remains the mainstay of treatment for symptomatic patients. Other conditions sometimes have imaging features that mimic Chiari I malformation. These patients are at risk of misdiagnosis and mismanagement, including surgery that may be unnecessary or may even worsen the underlying condition. The aim of this study was to analyse a series of Chiari I malformation mimics and identify differentiating imaging features. The mimics are categorised as post-traumatic cranio-cervical junction arachnoiditis, dural band, spontaneous intracranial hypotension, idiopathic intracranial hypertension, and cysts. Better understanding of these conditions will assist with diagnosis and optimal management, including avoiding unnecessary surgery.

Knowledge mapping of syringomyelia from 2003 to 2022: A bibliometric analysis

BACKGROUND

Syringomyelia is a chronic, progressive disease of the spinal cord. Syringomyelia is an etiologically diverse affliction caused by disturbance of normal cerebrospinal fluid flow dynamics. Lesions are characterized by the formation of tubular cavities in the gray matter of the spinal cord and gliosis; however, the etiology is unknown and treatment methods differ. Many existing studies have focused on the relationship between other diseases and syringomyelia. There is a lack of comprehensive and objective reports on the research status of syringomyelia. Therefore, this study aimed to conduct a bibliometric analysis to quantify studies on Syringomyelia and trending issues in the last 20 years.

METHODS

Articles were acquired from the Web of Science Core Collection database. We used the Library Metrology online analysis platform, BICOMB, gCLUTO, CiteSpace bibliometrics tools for analysis, VOSviewer 1.6.16 (Nees Jan van Eck and Ludo Waltman, 2010), and Microsoft Excel 2019 to perform bibliometric analysis and visualization. Individual impact and collaborative information were quantified by analyzing annual publications, journals, co-cited journals, countries/regions, institutions, authors, and co-cited authors. We then identified the trending research areas of syringomyelia by analyzing the co-occurrence of keywords and co-cited references.

RESULTS

From January 2003 to August 2022, 9,556 authors from 66 countries published a total of 1,902 research articles on syringomyelia in 518 academic journals. Most publications come from the United States, China, the United Kingdom, and Japan, with the United States dominating. Nanjing University and the University of Washington are the most active institutions, Dr. Claire Rusbridge has published the most papers, and Miholat has the most co-citations. The Journal of Neurosurgery has the highest number of co-cited articles, which are mainly in the fields of neurology, surgery, and biology. High-frequency keywords included syringomyelia, Chiari-I malformation, children, surgical treatment, and spinal cord.

CONCLUSIONS

The number of articles on syringomyelia has increased steadily over the past two decades. At present, research on syringomyelia is mainly focused on the age of onset, potential therapeutic interventions, surgical treatment, avoidance of recurrence, and delay of pain. The use of surgical treatment of the disease and the mechanism of further treatment are the current hot research topics. The correlation between trauma and congenital factors, translational application, the effect of surgical treatment, postoperative recurrence, and complications are further hot research areas. These may provide ideas for further research into a radical cure for syringomyelia.

Three-dimensional phase-contrast magnetic resonance imaging for the detention of a small communicating defect in a patient with a spinal extradural arachnoid cyst: illustrative case

BACKGROUND

Spinal extradural arachnoid cysts are thought to be pouches that communicate with the intraspinal subarachnoid space through a dural defect. The treatment for these cysts is resection of the cyst wall followed by obliteration of the communicating defect, which is often elusive.

OBSERVATIONS

The authors report the case of a 22-year-old man with an extradural arachnoid cyst with claudication and progressive motor weakness. Regular magnetic resonance imaging (MRI) and computed tomography did not reveal the location of the defect in the cyst. However, three-dimensional (3D) phase-contrast MRI clearly indicated the location of the defect and the flow of cerebrospinal fluid into the cyst. These findings allowed the authors to perform the least invasive surgery; the patient recovered motor function and could walk more smoothly.

LESSONS

3D phase-contrast MRI can reveal a subtle dural defect in patients with spinal extradural arachnoid cysts.

Chiari Malformation Type 1 and Syringomyelia: Why Do Patients Claim for International Guidelines? Commentary on the 2021 Chiari and Syringomyelia Consensus Document

The diagnosis of Chiari malformation type 1 (CM1) and Syringomyelia (Syr) has become increasingly common during the past few years. Contemporarily, the body of literature on these topics is growing, although randomized controlled studies on significant case series to drive guidelines are missing in the pediatric and adult populations. As a result of the different opinions about surgical indications and techniques raised by CM1-Syr, an increasing number of well-informed but disoriented patients is emerging. To bridge this gap, an International Consensus Conference on CM1-Syr held in Milan in November 2019 aimed to find a consensus among international experts, to suggest some recommendations that, in the near future, could lead to guidelines. Here, we comment on the most relevant recommendations about the definition, diagnosis, surgical management, failures and re-intervention, and outcome. We also focus on some "wrong" indications or techniques that, although widely disapproved by the experts, and negatively experienced by many patients, are still largely in use.

Cerebrospinal Fluid Hydrodynamics in Chiari I Malformation and Syringomyelia: Modeling Pathophysiology

Anatomic MRI, MRI flow studies, and intraoperative ultrasonography demonstrate that the Chiari I malformation obstructs CSF pathways at the foramen magnum and prevents normal CSF movement through the foramen magnum. Impaired CSF displacement across the foramen magnum during the cardiac cycle increases pulsatile hindbrain motion, pressure transmission to the spinal subarachnoid space, and the amplitude of CSF subarachnoid pressure waves driving CSF into the spinal cord. Central canal septations in adults prevent syrinx formation by CSF directly transmitting its pressure wave from the fourth ventricle to the central canal.

Compromised Cranio-Spinal Suspension in Chiari Malformation Type 1: A Potential Role as Secondary Pathophysiology

In Chiari Malformation Type I (CM1), low-lying tonsils obstruct the cisterna magna at the foramen magnum, thereby compromising the essential juncture between the cranial and spinal compartments. The anatomical obstruction of the cisterna magna inhibits bi-directional CSF flow as well as CSF pulse pressure equilibration between the intracranial compartment and the intraspinal compartment in response to instances of increased intracranial pressure. Less understood, however, are the roles of the spinal cord suspension structures at the craniocervical junction which lend viscoelastic support to the spinal cord and tonsils, as well as maintain the anatomical integrity of the cisterna magna and the dura. These include extradural ligaments including the myodural bridges (MDBs), as well as intradural dentate ligaments and the arachnoid framework. We propose that when these elements are disrupted by the cisterna magna obstruction, tonsillar pathology, and altered CSF dynamics, there may arise a secondary pathophysiology of compromised and dysfunctional cranio-spinal suspension in CM1. We present intraoperative images and videos captured during surgical exposure of the craniocervical junction in CM1 to illustrate this proposal.

The leptomeninges as a critical organ for normal CNS development and function: First patient and public involved systematic review of arachnoiditis (chronic meningitis)

BACKGROUND & IMPORTANCE

This patient and public-involved systematic review originally focused on arachnoiditis, a supposedly rare "iatrogenic chronic meningitis" causing permanent neurologic damage and intractable pain. We sought to prove disease existence, causation, symptoms, and inform future directions. After 63 terms for the same pathology were found, the study was renamed Diseases of the Leptomeninges (DLMs). We present results that nullify traditional clinical thinking about DLMs, answer study questions, and create a unified path forward.

METHODS

The prospective PRISMA protocol is published at Arcsology.org. We used four platforms, 10 sources, extraction software, and critical review with ≥2 researchers at each phase. All human sources to 12/6/2020 were eligible for qualitative synthesis utilizing R. Weekly updates since cutoff strengthen conclusions.

RESULTS

Included were 887/14286 sources containing 12721 DLMs patients. Pathology involves the subarachnoid space (SAS) and pia. DLMs occurred in all countries as a contributor to the top 10 causes of disability-adjusted life years lost, with communicable diseases (CDs) predominating. In the USA, the ratio of CDs to iatrogenic causes is 2.4:1, contradicting arachnoiditis literature. Spinal fusion surgery comprised 54.7% of the iatrogenic category, with rhBMP-2 resulting in 2.4x more DLMs than no use (p<0.0001). Spinal injections and neuraxial anesthesia procedures cause 1.1%, and 0.2% permanent DLMs, respectively. Syringomyelia, hydrocephalus, and arachnoid cysts are complications caused by blocked CSF flow. CNS neuron death occurs due to insufficient arterial supply from compromised vasculature and nerves traversing the SAS. Contrast MRI is currently the diagnostic test of choice. Lack of radiologist recognition is problematic.

DISCUSSION & CONCLUSION

DLMs are common. The LM clinically functions as an organ with critical CNS-sustaining roles involving the SAS-pia structure, enclosed cells, lymphatics, and biologic pathways. Cases involve all specialties. Causes are numerous, symptoms predictable, and outcomes dependent on time to treatment and extent of residual SAS damage. An international disease classification and possible treatment trials are proposed.

The Small Posterior Cranial Fossa Syndrome and Chiari Malformation Type 0

Patients showing typical Chiari malformation type 1 (CM1) signs and symptoms frequently undergo cranial and cervical MRI. In some patients, MRI documents >5 mm of cerebellar tonsillar herniation (TH) and the diagnosis of CM1. Patients with 3−5 mm TH have “borderline” CM1. Patients with less than 3 mm of TH and an associated cervical syrinx are diagnosed with Chiari “zero” malformation (CM0). However, patients reporting CM1 symptoms are usually not diagnosed with CM if MRI shows less than 3−5 mm of TH and no syrinx. Recent MRI morphometric analysis of the posterior fossa and upper cervical spine detected anatomical abnormalities in and around the foramen magnum (FM) that explain these patients’ symptoms. The abnormalities include a reduced size of the posterior fossa, FM, and upper cervical spinal canal and extension of the cerebellar tonsils around the medulla rather than inferior to the foramen magnum, as in CM1. These morphometric findings lead some neurologists and neurosurgeons to diagnose CM0 in patients with typical CM1 signs and symptoms, with or without cervical syringes. This article reviews recent findings and controversies about CM0 diagnosis and updates current thinking about the clinical and radiological relationship between CM0, borderline CM1, and CM1.

Neurological deterioration after posterior fossa decompression for adult syringomyelia: Proposal for a summarized treatment algorithm

Background

Patients with syringomyelia who present with new neurological symptoms after posterior fossa decompression (PFD) are not uncommon. However, systematic reports on different pathologies are few in the literature.

Objective

The purpose of this study was to summarize our experience for failed PFD.

Methods

Between January 2015 and December 2019, 85 consecutive failed PFD patients were identified. The neurological courses were summarized with Klekamp J (KJ) or mJOA score system for all patients. Long-term results were summarized with Kaplan-Meier method.

Results

Twenty-eight consecutive patients underwent FMDD (Foramen magnum and foramen of Magendie dredging) (Group I), extradural PFD and manipulation of tonsil was significantly associated with lower failure rates. Twenty patients underwent craniocervical fixation (Group II), nine underwent local spinal segment decompression (Group III), six underwent CSF diversion procedures, and one were treated for persistent pain by radiofrequency. Neuropathic pain was most significantly improved in Group I while swallowing improved in Group II within 1 year after the surgery. In the long term, late postoperative deterioration-free possibility in Group II was better than in Group I. All patients in Group III improved (P = 0.0088). Six cases of CSF diversion procedures were relieved in a short time. Pain in one patient persisted after PFD, and trial of radiofrequency failed.

Conclusion

Not only does the recurrent cerebrospinal fluid flow obstruct the foramen magnum, but also spinal pathologies and craniocervical instabilities may occur. This study provides the largest summarized clinical experience that may assist surgeons with different therapeutic decisions for failed PFD.

Biopsy and histologic findings of the dura mater at the level of the foramen magnum in 121 CKCS with Chiari-like malformation

To describe histopathologic features found in dural biopsies of Cavalier King Charles Spaniels (CKCS) with Chiari-like malformation (CM) and identify any associations between age, duration of clinical signs, syrinx location or syringomyelia (SM, and quality of life (QOL). The medical records of 121 consecutive client owned CKCS with CM and SM, confirmed by whole body magnetic resonance imaging (MRI), that underwent foramen magnum decompression (FMD) with cranioplasty and durectomy with biopsy from 2006 to 2016 were retrospectively reviewed. Dural biopsies were submitted to a board-certified veterinary pathologist for histopathologic interpretation. The chi-square test was used to analyze associations between histologic findings and categorical variables. For continuous measures, the Kruskal–Wallis non-parametric test was used to compare distributions across pathology categories. A result was considered statistically significant at the p < 0.05 level of significance. The mean age, duration of pre-surgical clinical signs, and pre-operative QOL (1–5 scale) were 44.27 months, 44.78 weeks, and 2.72, respectively. Syringomyelia was found in the cervical region only in 39 of 121 (32.23%) of dogs, in the cervical and thoracic region only in 17 of 121 (14.05%) of dogs, and in the cervical, thoracic, and lumbar region combined in 65 of 121 (53.72%) of dogs. Sixty-six of one hundred twenty-one (54.55%) dural biopsy specimens had histopathology changes; fifty-five (45.45%) did not. Forty-three of one hundred twenty-one (35.54%) dural biopsy specimens had osseous metaplasia, 16 of 121 (13.22%) had evidence of fibrosis, 4 of 121 (3.31%) had arachnoid hyperplasia, and 3 of 121 (2.48%) had evidence of mineralization. Most dogs with CM were found to have histopathologic changes in the dura at the time of FMD cranioplasty was performed. These dural changes can be observed in dogs experiencing clinical signs for a time period as short as 4 weeks prior to presentation. The histopathologic changes were not associated with age, breed, duration of clinical signs, the location of syringomyelia or QOL. The influence of histopathologic changes on long-term prognosis in dogs without dural decompression is unknown since all dogs in this study had dural resection.

Chiari malformation type I surgery in children: French multicenter 10-year cohort

OBJECTIVE

Chiari malformation type I (CM-I) is frequent in children and remains a surgical challenge. Several techniques have been described for posterior fossa decompression. No decision algorithm has been validated, and strategies are highly variable between institutions. The goal of this study was to define therapeutic guidelines that take into consideration patient specificities.

METHODS

The authors retrospectively collected data from patients who were < 18 years of age, were diagnosed with CM-I, and were treated surgically between 2008 and 2018 in 8 French pediatric neurosurgical centers. Data on clinical features, morphological parameters, and surgical techniques were collected. Clinical outcomes at 3 and 12 months after surgery were assessed by the Chicago Chiari Outcome Scale. The authors used a hierarchical clustering method to define clusters of patients by considering their anatomical similarities, and then compared outcomes between surgical strategies in each of these clusters.

RESULTS

Data from 255 patients were collected. The mean age at surgery was 9.6 ± 5.0 years, syringomyelia was reported in 60.2% of patients, the dura mater was opened in 65.0% of patients, and 17.3% of patients underwent a redo surgery for additional treatment. The mean Chicago Chiari Outcome Scale score was 14.4 ± 1.5 at 3 months (n = 211) and 14.6 ± 1.9 at 12 months (n = 157). The hierarchical clustering method identified three subgroups with potentially distinct mechanisms underlying tonsillar herniation: bony compression, basilar invagination, and foramen magnum obstruction. Each cluster matched with specific outcomes.

CONCLUSIONS

This French multicenter retrospective cohort study enabled the identification of three subgroups among pediatric patients who underwent surgery for CM-I, each of which was associated with specific outcomes. This morphological classification of patients might help in understanding the underlying mechanisms and providing personalized treatment.

MRI CSF flowmetry in evaluation of different neurological diseases

Background

Phase contrast MR imaging is a rapid and non-invasive technique which is sensitive in diagnosis and follow-up of different neurological diseases that cause CSF flow abnormality. MRI CSF flowmetry will be currently assessed in different neurological diseases that may cause CSF flow abnormalities.

Results

This study includes 39 patients with their ages ranging from 1 to 65 years; they were referred from the neurology department, with nine individuals of matched age and sex as a control group. Based on clinical history and conventional MRI, patients were subdivided into five subgroups; normal pressure hydrocephalus (NPH), hydrocephalus, idiopathic intracranial hypertension (IIH), brain atrophy (BA), and Chiari malformation type I (CM-I). All patients and control were subjected to MRI CSF flowmetry evaluation with stress on peak diastolic velocity (PDV), peak systolic velocity (PSV), stroke volume (SV), and maximum velocity (Vmax). PDV, PSV, and SV were found significantly higher in NPH, CM-I, and hydrocephalus compared to control (4.2, 4.96, and 83.23 for NPH; 3.95, 4.93, and 37.38 for CM-I; and 4.2, 5.6, and 125 in hydrocephalus versus 2.11, 2.73, and 75.33 in control, respectively; P = 0.0004, 0.0008, and 0.0009 for NPH; 0.03, 0.003, and 0.06 for CM-I; and 0.0005, 0.0002, and 0.0003, respectively). On the other hand, patients with BA showed significantly lower values (1.37, 1.66, and 1.53, respectively) compared to control (P = 0.001, 0.001, and 0.004, respectively).

Conclusion

MRI CSF flowmetry provides an easy, accurate, and non-invasive method for diagnosis of different neurological diseases that cause CSF flow abnormality. Moreover, this diagnostic modality could be helpful in selecting the therapeutic option.

Cognitive and Psychological Functioning in Chiari Malformation Type I Before and After Surgical Decompression - A Prospective Cohort Study

BACKGROUND

Chiari Malformation Type I (CM-I) is defined as cerebellar tonsil displacement more than 5 mm below the foramen magnum. This displacement can alter cerebrospinal fluid flow at the cervicomedullary junction resulting in Valsalva-induced headaches and syringomyelia and compress the brainstem resulting in bulbar symptoms. However, little is known about cognitive and psychological changes in CM-I.

OBJECTIVE

To prospectively assess cognitive and psychological performance in CM-I and determine whether changes occur after surgical decompression.

METHODS

Blinded evaluators assessed symptomatic CM-I patients ages ≥18 with a battery of neuropsychological and psychological tests. Testing was conducted preoperatively and 6 to 18 mo postoperatively. Data were converted to Z-scores based on normative data, and t-tests were used to analyze pre-post changes.

RESULTS

A total of 26 patients were included, with 19 completing both pre- and post-op cognitive assessments. All patients had resolution of Valsalva-induced headaches and there was improvement in swallowing dysfunction (P < .0001), ataxia (P = .008), and sleep apnea (P = .021). Baseline performances in visual perception and construction (z = -1.11, P = .001) and visuospatial memory (z = -0.93, P = .002) were below average. Pre-post comparisons showed that CM-I patients had stable cognitive and psychological functioning after surgery, without significant changes from preoperative levels.

CONCLUSION

CM-I patients had below average performance in visuospatial and visuoconstructional abilities preoperatively. Prospective longitudinal data following surgery demonstrated improved neurologic status without any decline in cognition or psychological functioning. Routine pre- and postoperative formal neuropsychological assessment in CM-I patients help quantify cognitive and behavioral changes associated with surgical decompression.

Fourth ventricle roof angle as a measure of fourth ventricle bowing and a radiographic predictor of brainstem dysfunction in Chiari malformation type I

OBJECTIVE

Chiari malformation type I (CM-I) is a congenital and developmental abnormality that results in tonsillar descent 5 mm below the foramen magnum. However, this cutoff value has poor specificity as a predictor of clinical severity. Therefore, the authors sought to identify a novel radiographic marker predictive of clinical severity to assist in the management of patients with CM-I.

METHODS

The authors retrospectively reviewed 102 symptomatic CM-I (sCM-I) patients and compared them to 60 age-matched normal healthy controls and 30 asymptomatic CM-I (aCM-I) patients. The authors used the fourth ventricle roof angle (FVRA) to identify fourth ventricle "bowing," a configuration change suggestive of fourth ventricle outlet obstruction, and compared these results across all three cohorts. A receiver operating characteristic (ROC) curve was used to identify a predictive cutoff for brainstem dysfunction. Binary logistic regression was used to determine whether bowing of the fourth ventricle was more predictive of brainstem dysfunction than tonsillar descent, clival canal angle, or obex position in aCM-I and sCM-I patients.

RESULTS

The FVRA had excellent interrater reliability (intraclass correlation 0.930, 95% CI 0.905-0.949, Spearman r2 = 0.766, p < 0.0001). The FVRA was significantly greater in the sCM-I group than the aCM-I and healthy control groups (59.3° vs 41.8° vs 45.2°, p < 0.0001). No difference was observed between aCM-I patients and healthy controls (p = 0.347). ROC analysis indicated that an FVRA of 65° had a specificity of 93% and a sensitivity of 50%, with a positive predictive value of 76% for brainstem dysfunction. FVRA > 65° was more predictive of brainstem dysfunction (OR 5.058, 95% CI 1.845-13.865, p = 0.002) than tonsillar herniation > 10 mm (OR 2.564, 95% CI 1.050-6.258, p = 0.039), although increasing age was also associated with brainstem dysfunction (OR 1.045, 95% CI 1.011-1.080, p = 0.009). A clival canal angle < 140° (p = 0.793) and obex below the foramen magnum (p = 0.563) had no association with brainstem dysfunction.

CONCLUSIONS

The authors identified a novel radiographic measure, the FVRA, that can be used to assess fourth ventricular bowing in CM-I and is more predictive of brainstem dysfunction than tonsillar herniation. The FVRA is easy to measure, has excellent interrater variability, and can be a reliable universal radiographic measure. The FVRA will be useful in further describing CM-I radiographically and clinically by identifying patients more likely to be symptomatic as a result of brainstem dysfunction.

Extradural decompression versus duraplasty in Chiari malformation type I with syrinx: outcomes on scoliosis from the Park-Reeves Syringomyelia Research Consortium

OBJECTIVE

Scoliosis is common in patients with Chiari malformation type I (CM-I)-associated syringomyelia. While it is known that treatment with posterior fossa decompression (PFD) may reduce the progression of scoliosis, it is unknown if decompression with duraplasty is superior to extradural decompression.

METHODS

A large multicenter retrospective and prospective registry of 1257 pediatric patients with CM-I (tonsils ≥ 5 mm below the foramen magnum) and syrinx (≥ 3 mm in axial width) was reviewed for patients with scoliosis who underwent PFD with or without duraplasty.

RESULTS

In total, 422 patients who underwent PFD had a clinical diagnosis of scoliosis. Of these patients, 346 underwent duraplasty, 51 received extradural decompression alone, and 25 were excluded because no data were available on the type of PFD. The mean clinical follow-up was 2.6 years. Overall, there was no difference in subsequent occurrence of fusion or proportion of patients with curve progression between those with and those without a duraplasty. However, after controlling for age, sex, preoperative curve magnitude, syrinx length, syrinx width, and holocord syrinx, extradural decompression was associated with curve progression > 10°, but not increased occurrence of fusion. Older age at PFD and larger preoperative curve magnitude were independently associated with subsequent occurrence of fusion. Greater syrinx reduction after PFD of either type was associated with decreased occurrence of fusion.

CONCLUSIONS

In patients with CM-I, syrinx, and scoliosis undergoing PFD, there was no difference in subsequent occurrence of surgical correction of scoliosis between those receiving a duraplasty and those with an extradural decompression. However, after controlling for preoperative factors including age, syrinx characteristics, and curve magnitude, patients treated with duraplasty were less likely to have curve progression than patients treated with extradural decompression. Further study is needed to evaluate the role of duraplasty in curve stabilization after PFD.

External validation of current prediction systems of improvement after decompression surgery in Chiari malformation type I patients: can we do better?

OBJECTIVE

The Chiari Severity Index (CSI) and points-based algorithm of Thakar et al. are two prognostic tools that have been developed to predict the likelihood of improvement after suboccipital decompression in adult patients with Chiari malformation type I (CM-I). This study aimed to externally validate and critically evaluate these algorithms in the interest of guiding the development of improved prediction systems.

METHODS

A consecutive cohort of CM-I patients undergoing suboccipital decompression between September 2006 and September 2018 were included. The CSI and Thakar point score were computed for all patients, and associations with improvement were analyzed. The ability of both prediction systems to predict improvement as measured by different Chicago Chiari Outcome Scale (CCOS) cutoffs was assessed using receiver operating curve analysis. Post hoc correlations between the algorithms and different CCOS subcomponents were also assessed.

RESULTS

The surgical cohort was composed of 149 adult CM-I patients, of whom 39 (26%) had a syrinx. Most patients experienced improvement after surgery (80% CCOS ≥ 13; 96% CCOS ≥ 11). The proportion of patients improving decreased with increasing CSI, but the results were not statistically significant (p = 0.246). No statistically significant difference in the mean Thakar point score was identified between improved and nonimproved patients using both CCOS cutoffs (p = 0.246 for a cutoff of 13 and p = 0.480 for a cutoff of 11). The CSI had a poor ability in identifying improved patients at a CCOS cutoff of 13 (area under the curve [AUC] 0.582) and 11 (AUC 0.646). The Thakar point score similarly had poor discrimination at a cutoff of 13 (AUC 0.467) and 11 (AUC 0.646). Neither algorithm had significant correlation with any of the CCOS subcomponents except for CSI and nonpain symptom improvement (coefficient = -0.273, p = 0.001).

CONCLUSIONS

Previously published algorithms failed to provide prediction value with regard to clinically meaningful improvement following suboccipital decompression in adult CM-I patients. Future models and practical scoring systems are still required to improve the decision-making process.

Posterior Fossa Decompression and Duraplasty with and without Arachnoid Preservation for the Treatment of Adult Chiari Malformation Type 1: A Systematic Review and Meta-Analysis

BACKGROUND

The best surgical treatment for adult Chiari malformation type 1 remains widely debated.

OBJECTIVE

This study aimed to assess the efficacy of posterior fossa decompression and duraplasty with arachnoid preservation compared with arachnoid dissection for the treatment of adult Chiari malformation type 1.

METHODS

Two reviewers (M.O.-G. and M.A.) performed a PubMed, MEDLINE, and Embase literature search using the following terms: ("Chiari" OR "Chiari 1") AND ("duraplasty" OR "arachnoid preservation" OR "arachnoid spar∗" OR "posterior fossa surgery" OR "posterior fossa decompression" OR "foramen magnum decompression"). Studies assessing the efficacy of posterior fossa decompression with duraplasty for the treatment of patients aged >18 years with Chiari malformation type 1 were included. Case reports with <10 patients, editorials, and non-English studies were excluded.

RESULTS

Of 195 studies identified, 24 were included for meta-analysis. In the 1006 participants, there was no difference in postoperative clinical or radiologic improvement between the 2 techniques. Patients who underwent posterior fossa decompression with duraplasty and arachnoid dissection had a greater prevalence of total complications (0.20, 95% confidence interval [CI], 0.13-0.29 vs. 0.09, 95% CI, 0.05-0.14; Q = 6.47; P = 0.01) and cerebrospinal fluid-related complications (0.15, 95% CI, 0.10-0.22 vs. 0.05, 95% CI, 0.02-0.12; Q = 4.88; P = 0.03) compared with arachnoid preservation. Furthermore, the prevalence of reoperation in the arachnoid dissection group was 25 times greater than in the arachnoid preservation group (0.08, 95% CI, 0.06-0.10 vs. 0.003, 95% CI, 0.00-0.02; Q = 10.73; P > 0.001).

CONCLUSIONS

Posterior fossa decompression and duraplasty with arachnoid preservation is a beneficial technique to treat Chiari malformation type 1 and reduces the risk of complications, particularly cerebrospinal fluid-related complications and the rate of reoperation.

Association between craniovertebral junction abnormalities and syringomyelia in patients with chiari malformation type-1

Objectives:

To assess the correlation between craniovertebral junction (CVJ) abnormalities and syringomyelia in patients with Chiari malformation type-1 (CM1).

Methods:

This was a retrospective study including patients with CM1. Identification of cases was done by searching a radiology database at a university hospital from 2012 to 2017. Patients were divided into 2 groups based on whether CVJ abnormalities were present (CVJ+) or absent (CVJ-). The patients’ demographic and clinical data were reviewed. All magnetic resonance imaging studies were examined by a certified neuroradiologist.

Results:

Sixty-four consecutive patients with CM1 were included. The mean age was 24±17 years; 59% were females. The CVJ+ group had more female patients (p = 0.012). The most frequent CVJ abnormality was platybasia (71%), followed by short clivus (44%) and cervical kyphosis (33%). The CVJ abnormalities were more in Syringomyelia cases (p = 0.045). However, the results were not significant when hydrocephalus cases were excluded.

Conclusion:

Among CM1 patients, CVJ abnormalities were found more in patients with syringomyelia. Future studies with larger sample size are required to further study the correlation between CVJ abnormalities and both syringomyelia and hydrocephalus in CM1 patients.

A novel classification and its clinical significance in Chiari I malformation with syringomyelia based on high-resolution MRI

BACKGROUND

The existing classification in Chiari I malformation (CM-I) has limited significance for the selection of surgical methods.

OBJECTIVE

The purpose of this study was to investigate the surgery of CM-I with syringomyelia based on the high-resolution MR imaging (HRMRI) findings.

METHODS

Data from 115 patients were collected and retrospectively analyzed. For those with syringomyelia up to the level of C1, HRMRI was performed and according to the communication status between the fourth ventricle and the syringomyelia, patients can be divided into four types, namely Type A: classic communicating; Type B: partial communicating; Type C: non-communicating; Type D: atrophic. All operations were performed with Foramen magnum and Magendie dredging (FMMD), and all intradural factors that may have induced the obstruction of CSF circulation were recorded. The efficiency of operation on syringomyelia was evaluated by mJOA, imaging findings, and complications in the follow-up periods.

RESULTS

The postoperative follow-up period was from 12 to 24 months, with an average of 14.3 months. At 1 year, the mJOA of 115 patients was significantly higher than that before the operations (before surgery 12.1 ± 2.3 vs. after surgery 14. 2 ± 1.4, P < 0.05). In addition, postoperative re-examination showed that the size of the syringomyelia was reduced or completely resolved in patients of Type A, 100% (2/2); Type B, 81% (9/11); Type C, 84% (81/97); and Type D, 20% (1/5).

CONCLUSIONS

According to our new classification based on HRMRI, FMMD is the key to surgical treatment, especially for Type A and Type B patients.

Histological and intraoperative evaluations of the arachnoid in patients with Chiari I malformation

BACKGROUND

Arachnoid dissection for decompression of Chiari I malformation is controversial. Whether arachnoid changes have an impact on the clinical course is not established. This paper documents the histological spectrum of arachnoid changes and evaluates correlations with preoperative, intraoperative, and postoperative data.

METHOD

Arachnoid samples of 162 consecutive foramen magnum decompressions from 2006 to 2016 were studied. Arachnoid thickness and degrees of fibrosis and cellularity were determined with the examiner blinded for clinical data. Based on 145 first time decompressions, a histological classification for arachnoid features was developed.

RESULTS

The arachnoid was thicker in secondary compared with primary decompressions (176.1 ± 158.2 μm vs. 35.9 ± 43.5 μm; p = 0.0026) and in adults compared to children (37.3 ± 45.3 μm vs. 21.8 ± 7.7 μm; p = 0.0007). In primary decompressions, arachnoid thickness, degrees of fibrosis, and cellularity followed a normal distribution with all features shifted significantly to higher grades in secondary decompressions. The histological classification correlated with the preoperative severity of gait ataxia, motor weakness, and sensory deficits, whereas it had no predictive power for postoperative short- or long-term results. By comparison, the intraoperative evaluation of arachnoid changes accounting for relationships between arachnoid and surrounding tissues showed higher correlations with preoperative symptoms and had significant predictive power for postoperative short- and long-term results.

CONCLUSIONS

Histological changes of the arachnoid correlate with preoperative symptoms. Relationships between arachnoid and surrounding tissues show even higher correlations with predictive power for short- and long-term outcomes. These findings suggest a pathophysiological role for the arachnoid in Chiari I malformation.

Coexisting Retrocerebellar Arachnoid Cyst and Chiari Type 1 Malformation: 3 Pediatric Cases of Surgical Management Tailored to the Pathogenic Mechanism and Systematic Review of the Literature

INTRODUCTION

Arachnoid cysts are benign cerebrospinal fluid collection within a duplication of arachnoid membrane and, when found in the retrocerebellar site, they may be associated with tonsils herniation. This rare situation of coexisting retrocerebellar arachnoid cyst (AC) and Chiari malformation type 1 (CM-1) have been previously reported in few cases (10 patients) with syringomyelia and hydrocephalus described to be the most relevant issues. The aim of this paper is to describe 3 pediatric cases of this condition with a systematic review of the literature, underlining the importance of surgical management tailored to the pathogenic mechanism.

METHODS

A restrospective analysis of patients treated for coexisting CM-1 and ACs at the authors' institution has been carried out.

RESULTS

A case of a 10-month-old baby with coexisting AC and CM-1 with tri-ventricular hydrocephalus treated with endoscopic third ventriculostomy, a case of a 1-year-old child with a huge retrocerebellar AC and CM-1 treated with a cysto-peritoneal shunt, and a case of a 15-year-old child with retrocerebellar AC causing symptomatic CM-1 treated with C0-C2 decompression, AC fenestration and duraplasty are described. A long-term follow-up is reported.

CONCLUSIONS

Surgical management of coexisting ACs and CM-1 should not aim at the complete resolution of the cyst or of tonsil herniation, especially when pediatric patients are treated. Rather, the purpose of the neurosurgeon should be to understand the underlying pathogenic mechanism, and then restoring both the cerebrospinal fluid flow in the posterior fossa and the dynamic equilibrium between ventricles, cyst, and subarachnoid space.

The Perplexity Surrounding Chiari Malformations - Are We Any Wiser Now?

Chiari malformations are a diverse group of abnormalities of the brain, craniovertebral junction, and the spine. Chiari 0, I, and 1.5 malformations, likely a spectrum of the same malformation with increasing severity, are due to the inadequacy of the para-axial mesoderm, which leads to insufficient development of occipital somites. Chiari II malformation is possibly due to nonclosure of the caudal end of the neuropore, with similar pathogenesis in the rostral end, which causes a Chiari III malformation. There have been significant developments in the understanding of this complex entity owing to insights into the pathogenesis and advancements in imaging modalities and neurosurgical techniques. This article aims to review the different types and pathophysiology of the Chiari malformations, along with a description of the various associated abnormalities. We also highlight the role of ante- and postnatal imaging, with a focus on the newer techniques in the presurgical evaluation, with a brief mention of the surgical procedures and the associated postsurgical complications.

Intradural Pathology Causing Cerebrospinal Fluid Obstruction in Syringomyelia and Effectiveness of Foramen Magnum and Foramen of Magendie Dredging Treatment

OBJECTIVE

This article discusses the procedure of foramina magnum and Magendie dredging, summarizing the pathologic changes in the intradural region of the craniocervical junction in patients with syringomyelia and the pathophysiologic mechanism of cerebrospinal fluid (CSF) circulation obstruction.

METHODS

Clinical data from 50 adult patients with syringomyelia treated at Xuanwu Hospital from July 2018 to January 2019 were collected and retrospectively analyzed. All operations were performed with foramina magnum and Magendie dredging, and all intradural factors that may have induced the obstruction of CSF circulation were recorded.

RESULTS

Intradural pathology was found in all patients. The pathologic changes that may have caused obstruction of the CSF circulation include tonsil occupying the foramen magnum and overlying foramen of Magendie in 88% (44/50), intertonsillar arachnoid adhesions in 36% (18/50), tonsil to medulla arachnoid adhesions in 18% (9/50), medialized tonsils in 70% (35/50), vermian branch of posterior inferior cerebellar artery in 22% (11/50), arachnoid veil in 16% (8/50), cisterna magna cyst in 4% (2/50), and tonsil to dura mater arachnoid adhesions in 8% (4/50). Mean duration of follow-up was 13.3 months. The long-term effective rate was 96.0%. Postoperative magnetic resonance imaging revealed that the size of the syringomyelia was reduced or completely resolved in 88% of patients. The mean preoperative Japanese Orthopaedic Association score was 12.9 ± 3.1, which improved to 14.7 ± 3.2 (P < 0.05) at last clinical follow-up.

CONCLUSIONS

Intradural pathology that causes CSF circulation obstruction exists in many forms. Relieving the obstruction of the foramen magnum and foramen of Magendie is key to surgical treatment.

Management of Chiari I malformations: a paradigm in evolution

PURPOSE

Despite decades of experience and research, the etiology and management of Chiari I malformations (CM-I) continue to raise more questions than answers. Controversy abounds in every aspect of management, including the indications, timing, and type of surgery, as well as clinical and radiographic outcomes. This review aims to outline past experiences, consolidate current evidence, and recommend directions for the future management of the Chiari I malformation.

METHODS

A review of recent literature on the management of CM-I in pediatric patients is presented, along with our experience in managing 1073 patients who were diagnosed with CM-I over the past two decades (1998-2018) at Children's National Medical Center (CNMC) in Washington DC.

RESULTS

The general trend reveals an increase in the diagnosis of CM-I at younger ages with a significant proportion of these being incidental findings (0.5-3.6%) in asymptomatic patients as well as a rise in the number of patients undergoing Chiari posterior fossa decompression surgery (PFD). The type of surgical intervention varies widely. At our institution, 104 (37%) Chiari surgeries were bone-only PFD with/without outer leaf durectomy, whereas 177 (63%) were PFD with duraplasty. We did not find a significant difference in outcomes between the PFD and PFDD groups (p = 0.59). An analysis of failures revealed a significant difference between patients who underwent tonsillar coagulation versus those whose tonsils were not manipulated (p = 0.02).

CONCLUSION

While the optimal surgical intervention continues to remain elusive, there is a shift away from intradural techniques in favor of a simple, extradural approach (including dural delamination) in pediatric patients due to high rates of clinical and radiographic success, along with a lower complication rate. The efficacy, safety, and necessity of tonsillar manipulation continue to be heavily contested, as evidence increasingly supports the efficacy and safety of less tonsillar manipulation, including our own experience.

Fourth Ventricle Enlargement in Chiari Malformation Type I

OBJECTIVE

How Chiari malformation type I (CM-I) affects posterior fossa brain structures and produces various symptoms remains unclear. The fourth ventricle is surrounded by critical structures required for normal function. The foramen of Magendie can be obstructed in CM-I; therefore, fourth ventricle changes may occur. To test this hypothesis, we assessed fourth ventricle volume in CM-I compared with healthy controls.

METHODS

Using our database from 2007-2016, we studied 72 patients with CM-I and 30 age-matched healthy control subjects. Fourth and lateral ventricle volumes and posterior fossa volumes (PFV) were assessed and correlated with clinical signs and symptoms. Statistical analysis was performed.

RESULTS

Patients with CM-I had larger fourth ventricle volumes compared with control subjects (1.31 vs. 0.95 mL; P = 0.012). There were no differences in lateral ventricle volume or PFV. CM-I fourth ventricle volume was associated with tonsillar descent (P = 0.030). CM-I fourth ventricle volume variance was larger than healthy controls (F_71,29 = 8.33; P < 0.0001). Patients with CM-I with severe signs and symptoms had a significantly larger fourth ventricle than patients with CM-I with mild signs and symptoms (1.565 vs. 1.015 mL; P = 0.0002).

CONCLUSIONS

The fourth ventricle can be enlarged in CM-I independent of lateral ventricle size and is associated with greater tonsillar descent. Most importantly, fourth ventricle enlargement was associated with a worse clinical and radiographic presentation independent of PFV. Fourth ventricle enlargement can affect critical structures and may be a mechanism contributing to symptoms unexplained by tonsil descent. Fourth ventricle enlargement is a useful adjunct in assessing CM-I.

Syringobulbia in Patients with Chiari Malformation Type I: A Systematic Review

This study aimed to summarize the clinical features, diagnosis, and treatment of Chiari malformation type I- (CM-1-) associated syringobulbia. We performed a literature review of CM-1-associated syringobulbia in PubMed, Ovid MEDLINE, and Web of Science databases. Our concerns were the clinical features, radiologic presentations, treatment therapies, and prognoses of CM-1-associated syringobulbia. This review identified 23 articles with 53 cases. Symptoms included headache, neck pain, cranial nerve palsy, limb weakness/dysesthesia, Horner syndrome, ataxia, and respiratory disorders. The most frequently involved area was the medulla. Most of the patients also had syringomyelia. Surgical procedures performed included posterior fossa decompression, foramen magnum decompression, cervical laminectomy, duraplasty, and syringobulbic cavity shunt. Most patients experienced symptom alleviation or resolution postoperatively. A syringobulbic cavity shunt provided good results in refractory cases. Physicians should be aware of the possibility of syringobulbia in CM-1 patients, especially those with symptoms of sudden-onset brain-stem involvement. The diagnosis relies on the disorder's specific symptomatology and magnetic resonance imaging. Our review suggests that the initial therapy should be posterior fossa decomposition with or without duraplasty. In refractory cases, additional syringobulbic cavity shunt is the preferred option.

Cerebellar Tonsillar Cysts Associated with Chiari Malformation in Adults: A Short Series

BACKGROUND

Authors analyzed surgical patients with Chiari malformation (CM) associated with cerebellar tonsillar cyst. This association is quite rarely encountered in the literature.

CASE DESCRIPTION

We retrospectively reviewed 60 surgical adult patients with MRI evaluation who underwent posterior fossa decompression for treatment of CM type I. All surgeries were performed between January 1995 and July 2015. From 60 patients with CM, four cases presented cerebellar tonsillar cysts (male=2). Basilar invagination (BI) (n=4) and syringomyelia (n=1) were associated. There were pyramidal signs (n=4) and low cranial nerves dysfunction (n=1). Radiological evaluation showed T1-hypointense and T2-hyperintense image on the cystic tissue (n=4). The surgical technique was suboccipital craniectomy, C1-C2 laminectomy (if needed), y-shaped durotomy, total resection and coagulation/aspiration of tonsils.

CONCLUSIONS

In the present series, we were able to identify 7% of tonsillar cysts among 60 patients with CM. MRI with Flair and Diffusion sequences should be pre-operatively used for evaluation of tissue characteristics as differential diagnosis of cystic lesion and gliosis. The clinical presentation endorses surgical indication, with a good chance of clinical improvement. This was the first time that the frequency of tonsillar cysts has been evaluated in a series of adult patients.

Autologous cervical fascia duraplasty in 123 children and adults with Chiari malformation type I: surgical technique and complications

OBJECT Techniques for combined extradural and intradural decompression with expansile duraplasty for Chiari malformation type I (CM-I) have been well described, with various allogenic and autologous materials used for duraplasty. However, the approach and surgical technique used for duraplasty in our treatment of CM-I and developed by the senior author in the 1990s has not been described. METHODS A prospective database was initiated in March 2003 to denote the use of cervical fascia for duraplasty and incorporate an ongoing detailed record of complications during the surgical treatment of children and adults with CM-I with and without syringomyelia. A total of 389 surgeries for CM-I were performed on 379 patients from March 2003 to June 2016. A total of 123 posterior procedures were performed on 123 patients in which both a posterior fossa extradural and intradural decompression with duraplasty (extra-intradural) was performed. In this paper the authors describe the surgical technique for harvesting and using cervical fascia for duraplasty in the surgical treatment of CM-I and analyze and discuss complications from a prospective database spanning 2003-2016. RESULTS The authors found that cervical fascia can be harvested in patients of all ages (2-61 years old) without difficulty, and it provides a good substitute for dura in creating an expansile duraplasty in patients with CM-I. Cervical fascia is an elastic-like material with a consistency that allows for a strong watertight closure. Harvesting the cervical fascia graft does not require any further extension of the incision superiorly or inferiorly to obtain the graft. Complications were uncommon in this study of 123 children and adults. The risk of any type of complication (aseptic meningitis, CSF leak, pseudomeningocele, infection, development of hydrocephalus, and need for ventriculoperitoneal shunt) for the 78 patients in the pediatric age group was 0%. The risk of complication in the adult group was 6.7% (1 patient with aseptic meningitis and 2 patients with CSF leak). CONCLUSIONS Autologous cervical fascia is easy to obtain in patients of all ages and provides an effective material for duraplasty in the treatment of CM-I. Complications from the combination of both an extradural and intradural decompression with autologous cervical fascia duraplasty are uncommon.

Definitions and treatments for chiari-1 malformations and its variants: Focused review

Background:

Reviewing the neurosurgical literature demonstrated that spinal neurosurgeons rarely (0.78%) diagnose chiari-1 malformation (CM-1) in adults on magnetic resonance (MR) studies defined by tonsillar descent >5 mm below the foramen magnum (FM). Children, averaging 10 years of age, exhibit CM-1 in 96/100,000 cases. According to the literature, fewer spinal neurosurgeons additionally recognize and treat the low lying cerebellar tonsil (LLCT) syndrome.

Methods:

The normal location of the cerebellar tonsils on cranial/cervical MR averages 2.9 mm ± 3.4 mm above or up to 3 mm below the FM. The neurosurgical literature revealed that most neurosurgeons diagnose and treat CM-1 where the tonsils are >5 mm to an average of 12 mm below the FM. Fewer spinal neurosurgeons additionally diagnose and treat the LLCT syndrome defined by <5 mm of tonsillar descent below the FM.

Results:

According to the neurosurgical literature, many neurosurgeons perform cranial/spinal decompression with/without fusion and/or duraplasty for CM-1. Fewer neurosurgeons perform these procedures for CM-1 and the LLCT syndrome, for which they additionally perform preoperative cervical traction under anesthesia, and the postoperative placement of occipital neurostimulators (ONS) for intractable headaches following chiari-1/LLCT surgery.

Conclusion:

Reviewing the literature revealed that spinal neurosurgeons rarely diagnose CM-1, and treat them with decompressions with/without fusions and/or duraplasty. Fewer spinal neurosurgeons diagnose/treat both the CM-1 and LLCT syndromes, perform preoperative traction under anesthesia, and place ONS for persistent headaches following CM-1 surgery.

Syringobulbia in pediatric patients with Chiari malformation type I

OBJECTIVE Syringobulbia (SB) is a rare entity, with few cases associated with Chiari malformation type I (CM-I) in the pediatric population. The authors reviewed all pediatric cases of CM-I-associated SB managed at their institution in order to better understand the presentation, treatment, and surgical outcomes of this condition. METHODS A prospectively maintained institutional database of craniovertebral junction abnormalities was analyzed to identify all cases of CM-I and SB from the MRI era (i.e., after 1984). The authors recorded presenting symptoms, physical examination findings, radiological findings, surgical treatment strategy, intraoperative findings, and outcomes. SB cases associated with tumors, infections, or type II Chiari malformations were excluded. RESULTS The authors identified 326 pediatric patients with CM-I who were surgically treated. SB was identified in 13 (4%) of these 326 patients. Headache and neck pain were noted in all 13 cases. Cranial nerve abnormalities were common: vagus and glossopharyngeal nerve dysfunction was the most frequent observation. Other cranial nerves affected included the trigeminal, abducens, and hypoglossal nerves. Several patients exhibited multiple cranial nerve palsies at presentation. Central sleep apnea was present in 6 patients. Syringomyelia (SM) was present in all 13 patients. SB involved the medulla in all cases, and extended rostrally into the pons and midbrain in 2 patients; in 1 of these 2 cases the cavity extended further rostrally to the cerebrum (syringocephaly). SB communicated with the fourth ventricle in 7 of the 13 cases. All 13 patients were treated with posterior fossa decompression with intradural exploration to ensure CSF egress out of the fourth ventricle and through the foramen magnum. The foramen of Magendie was found to be occluded by an arachnoid veil in 9 cases. Follow-up evaluation revealed that SB improved before SM. Cranial nerve palsies regressed in 11 of the 13 patients, and SB improved in all 13. CONCLUSIONS The incidence of SB in our surgical series of pediatric patients with CM-I was 4%, and all of these patients had accompanying SM. The SB cavity involved the medulla in all cases and was found to communicate with the fourth ventricle in 54% of cases. Posterior fossa decompression with intradural exploration and duraplasty is an effective treatment for these patients.