Chiari Type 1 Malformation-induced Intracranial Hypertension with Diffuse Brain Edema Treated with Foramen Magnum Decompression: A Case Report

Multiparametric prenatal imaging characterization of fetal brain edema in Chiari II malformation might help to select candidates for fetal surgery

OBJECTIVE

To identify brain edema in fetuses with Chiari II malformation using a multiparametric approach including structural T2-weighted, diffusion tensor imaging (DTI) metrics, and MRI-based radiomics.

METHODS

A single-center retrospective review of MRI scans obtained in fetuses with Chiari II was performed. Brain edema cases were radiologically identified using the following MR criteria: brain parenchymal T2 prolongation, blurring of lamination, and effacement of external CSF spaces. Fractional anisotropy (FA) values were calculated from regions of interest (ROI), including hemispheric parenchyma, internal capsule, and corticospinal tract, and compared group-wise. After 1:1 age matching and manual single-slice 2D segmentation of the fetal brain parenchyma using ITK-Snap, radiomics features were extracted using pyradiomics. Areas under the curve (AUCs) of the features regarding discriminating subgroups were calculated.

RESULTS

Ninety-one fetuses with Chiari II underwent a total of 101 MRI scans at a median gestational age of 24.4 weeks and were included. Fifty scans were visually classified as Chiari II with brain edema group and showed significantly reduced external CSF spaces compared to the nonedema group (9.8 vs. 18.3 mm, p < 0.001). FA values of all used ROIs were elevated in the edema group (p < 0.001 for all ROIs). The 10 most important radiomics features showed an AUC of 0.81 (95%CI: 0.71, 0.91) for discriminating between Chiari II fetuses with and without edema.

CONCLUSIONS

Brain edema in fetuses with Chiari II is common and radiologically detectable on T2-weighted fetal MRI sequences, and DTI-based FA values and radiomics features provide further evidence of microstructure differences between subgroups with and without edema.

CLINICAL RELEVANCE STATEMENT

A more severe phenotype of fetuses with Chiari II malformation is characterized by prenatal brain edema and more postnatal clinical morbidity and disability. Fetal brain edema is a promising prenatal MR imaging biomarker candidate for optimizing the risk-benefit evaluation of selection for fetal surgery.

KEY POINTS

Brain edema of fetuses prenatally diagnosed with Chiari II malformation is a common, so far unknown, association. DTI metrics and radiomics confirm microstructural differences between the brains of Chiari II fetuses with and without edema. Fetal brain edema may explain worse motor outcomes in this Chiari II subgroup, who may substantially benefit from fetal surgery.

Revisiting the Pathophysiology of Intracranial Hemorrhage in Fetuses with Chiari II Malformation: Novel Imaging Biomarkers of Disease Severity?

BACKGROUND AND PURPOSE

Intracranial hemorrhage (ICH) has emerged as a notable concern in Chiari II malformation (CM II), yet its origins and clinical implications remain elusive. This study aims to validate the in utero prevalence of ICH in CM II and investigate contributing factors, and visualize the findings in a network format.

MATERIALS AND METHODS

A single-center retrospective review of fetal MRI scans obtained in fetuses with CM II (presenting January 2007 to December 2022) was performed for ICH utilizing EPI-T2* blood-sensitive sequence. Fetuses with aqueduct stenosis (AS) were included as a control group. The incidence of ICH and corresponding gestational ages were compared between CM II and AS cases, and morphometric measurements (inner/outer CSF spaces, posterior fossa, venous structure) were compared among the 4 1:1 age-matched groups: CM II+ICH, CM II-ICH, AS+ICH, and AS-ICH. Additionally, a co-occurrence network was constructed to visualize associations between phenotypic features in ICH cases.

RESULTS

A total of 101 fetuses with CM II and 90 controls with AS at a median gestational age of 24.4 weeks and 22.8 weeks (P = .138) were included. Prevalence of ICH in fetuses with CM II was higher compared with the AS cases (28.7% versus 18.9%, P = .023), accompanied by congested veins (deep vein congestion mainly in young fetuses, and cortical veins may also be affected in older fetuses). ICH was notably correlated with specific anatomic features, essentially characterized by reduced outer CSF spaces and clivus-supraocciput angle. The co-occurrence network analysis reveals complex connections including bony defects, small posterior fossa dimensions, vermis ectopia, reduced CSF spaces, as well as venous congestion and venous sinus stenosis as pivotal components within the network.

CONCLUSIONS

The high prevalence of ICH-detected by fetal MRI-among fetuses with CM emphasizes the pathophysiologic importance of venous congestion, ICH, and vasogenic edema. As indicators of disease severity, these features may serve as helpful additional imaging biomarkers for the identification of potential candidates for fetal surgery.

Surgical Management of Chiari Malformation Type I and Instability of the Craniocervical Junction Based on Its Pathogenesis and Classification

We investigated the mechanism underlying Chiari malformation type I (CM-I) and classified it according to the morphometric analyses of posterior cranial fossa (PCF) and craniocervical junction (CCJ). Three independent subtypes of CM-I were confirmed (CM-I types A, B, and C) for 484 cases and 150 normal volunteers by multiple analyses. CM-I type A had normal volume of PCF (VPCF) and occipital bone size. Type B had normal VPCF and small volume of the area surrounding the foramen magnum (VAFM) and occipital bone size. Type C had small VPCF, VAFM, and occipital bone size. Morphometric analyses during craniocervical traction test demonstrated instability of CCJ. Foramen magnum decompression (FMD) was performed in 302 cases. Expansive suboccipital cranioplasty (ESCP) was performed in 102 cases. Craniocervical posterolateral fixation (CCF) was performed for CCJ instability in 70 cases. Both ESCP and FMD showed a high improvement rate of neurological symptoms and signs (84.4%) and a high recovery rate of the Japanese Orthopaedic Association (JOA) score (58.5%). CCF also showed a high recovery rate of the JOA score (69.7%), with successful joint stabilization (84.3%). CM-I type A was associated with other mechanisms that caused ptosis of the brainstem and cerebellum (CCJ instability and traction and pressure dissociation between the intracranial cavity and spinal canal cavity), whereas CM-I types B and C demonstrated underdevelopment of the occipital bone. For CM-I types B and C, PCF decompression should be performed, whereas for small VPCF, ESCP should be performed. CCF for CCJ instability (including CM-I type A) was safe and effective.

Regional Brain Tissue Displacement and Strain is Elevated in Subjects with Chiari Malformation Type I Compared to Healthy Controls: A Study Using DENSE MRI

While the degree of cerebellar tonsillar descent is considered the primary radiologic marker of Chiari malformation type I (CMI), biomechanical forces acting on the brain tissue in CMI subjects are less studied and poorly understood. In this study, regional brain tissue displacement and principal strains in 43 CMI subjects and 25 controls were quantified using a magnetic resonance imaging (MRI) methodology known as displacement encoding with stimulated echoes (DENSE). Measurements from MRI were obtained for seven different brain regions-the brainstem, cerebellum, cingulate gyrus, corpus callosum, frontal lobe, occipital lobe, and parietal lobe. Mean displacements in the cerebellum and brainstem were found to be 106 and 64% higher, respectively, for CMI subjects than controls (p < .001). Mean compression and extension strains in the cerebellum were 52 and 50% higher, respectively, in CMI subjects (p < .001). Brainstem mean extension strain was 41% higher in CMI subjects (p < .001), but no significant difference in compression strain was observed. The other brain structures revealed no significant differences between CMI and controls. These findings demonstrate that brain tissue displacement and strain in the cerebellum and brainstem might represent two new biomarkers to distinguish between CMI subjects and controls.

The relationship between spontaneous cerebrospinal fluid leak and idiopathic intracranial hypertension

Surgical treatment of spontaneous cerebrospinal fluid (CSF) leak is now performed by ENT surgeons, endonasal endoscopy being preferred to craniotomy as less invasive. However, it is often the symptom of underlying idiopathic intracranial hypertension, which lies outside the traditional sphere of ENT competence. Surgery is a necessary step, but should not obscure the need to treat the underlying pathology. This treatment is complex, and requires multidisciplinary team-work between otorhinolaryngologist, ophthalmologist, neurologist, neurosurgeon, radiologist, dietician, endocrinologist and psychotherapist. The present update details this multidisciplinary management to which the ENT surgeons must be attentive before and after spontaneous CSF leak repair.

Outcomes and resource utilization in surgery for Chiari I malformation in a national network of children's hospitals

INTRODUCTION

Chiari malformation type 1 (CM-1) is a common congenital or acquired malformation of the posterior fossa. We aimed to characterize preoperative risk factors, perioperative complications, and postoperative outcomes related to CM-1 surgery in pediatric populations across a nationwide network of pediatric hospitals in the United States (US).

METHODS

The Children's Hospital Association's Pediatric Health Information System (PHIS) database was used to examine patients < 21 years old in the US-based nationwide database who underwent inpatient surgery for CM-1 from 2007 to 2015. Data analyzed included patient characteristics, preoperative comorbidities, perioperative outcomes, short-term postoperative surgical and medical complications, and healthcare resource utilization.

RESULTS

Among the 5976 patients identified, those age 0-4 years had higher medical and surgical complication rates compared to older patients. Those with pre-existing comorbidity of hydrocephalus had higher odds of 30- and 90-day medical and surgical complications. Those with any complications at 90 days had an increased length of stay and higher healthcare costs compared to those without complications. 6.88% of complications were surgical and 1.67% medical. Patients with medical complications had the longer mean stay and associated costs compared to those with surgical complications (13 vs. 6.9 at 95% CI, and $71,300-94,500 vs. $110,400-195,000 at 95% CI).

CONCLUSIONS

Use of a US-based national children's hospital database presents outcomes and resource utilization from a multi-institutional, real-world experience in pediatric hospitals. There was a higher risk of perioperative complications in younger patients and those with pre-existing comorbidities, namely hydrocephalus. Understanding preoperative risk factors, perioperative complications, and postoperative outcomes, as well as healthcare utilization and costs, can help target areas for improvement and guide preoperative counseling and risk stratification.