Rare functional genetic variants in COL7A1, COL6A5, COL1A2 and COL5A2 frequently occur in Chiari Malformation Type 1

Human genetics and molecular genomics of Chiari malformation type 1

Chiari malformation type 1 (CM1) is the most common structural brain disorder involving the craniocervical junction, characterized by caudal displacement of the cerebellar tonsils below the foramen magnum into the spinal canal. Despite the heterogeneity of CM1, its poorly understood patho-etiology has led to a 'one-size-fits-all' surgical approach, with predictably high rates of morbidity and treatment failure. In this review we present multiplex CM1 families, associated Mendelian syndromes, and candidate genes from recent whole exome sequencing (WES) and other genetic studies that suggest a significant genetic contribution from inherited and de novo germline variants impacting transcription regulation, craniovertebral osteogenesis, and embryonic developmental signaling. We suggest that more extensive WES may identify clinically relevant, genetically defined CM1 subtypes distinguished by unique neuroradiographic and neurophysiological endophenotypes.

A Novel Craniocervical Junction Compression Severity Index-Based Grading System for Multidirectional Quantification of the Biomechanics at Foramen Magnum of Chiari Malformation Type I

Objective  This study aimed to establish a novel grading system, based on the craniovertebral junction compression severity index (CVJCSI) for multidirectional quantification at the foramen magnum plane for Chiari malformation type I (CMI). Methods  The CVJCSI grading system was established to stratify patients based on the ventral (modified clivoaxial angle < 138°), dorsal (tonsil herniation), and central (brainstem herniation) CVJ (craniovertebral junction) compression, the CVJCSI grading system was established to stratify patients. The optimal surgical method for each grade was recommended by intragroup comparisons regarding the efficacy of the three operations. Finally, according to the CVJCSI grading system, a prospective validation trial was performed and surgically treated for internal validation. Results  Based on the retrospective study ( n  = 310), the CVJCSI included six grades: I: syrinx alone without compression; II: dorsal compression; III: dorsal and central compression; IV: ventral compression; V: dorsal and ventral compression; and VI: ventral, dorsal, and central compression. Among all available variables, only the CVJCSI and surgical methods significantly affected the CCOS. The CCOS scores, overall and for each CVJCSI grade, increased in the prospective cohort ( n  = 42) compared with that in the retrospective analysis. Conclusions  The CVJCSI can be used to stratify CMI patients. The higher the CVJCSI grade, the more severe the CVJ compression and the worse posterior fossa deformity. Meanwhile, the CVJCSI was negatively correlated with the CCOS. The lower the CVJCSI grade, the better the response to surgery, and the less-invasive surgical procedures were warranted. Finally, the prospective cohort study validated the proposed CVJCSI-based surgical protocols.

Decoding Chiari Malformation and Syringomyelia: From Epidemiology and Genetics to Advanced Diagnosis and Management Strategies

Chiari Malformation and Syringomyelia are neurosurgical entities that have been the subject of extensive research and clinical interest. Globally prevalent, these disorders vary demographically and have witnessed evolving temporal trends. Chiari Malformation impacts the normal cerebrospinal fluid flow, consequently affecting overall health. Key observations from canine studies offer pivotal insights into the pathogenesis of Syringomyelia and its extrapolation to human manifestations. Genetics plays a pivotal role; contemporary knowledge identifies specific genes, illuminating avenues for future exploration. Clinically, these disorders present distinct phenotypes. Diagnostically, while traditional methods have stood the test of time, innovative neurophysiological techniques are revolutionizing early detection and management. Neuroradiology, a cornerstone in diagnosis, follows defined criteria. Advanced imaging techniques are amplifying diagnostic precision. In therapeutic realms, surgery remains primary. For Chiari 1 Malformation, surgical outcomes vary based on the presence of Syringomyelia. Isolated Syringomyelia demands a unique surgical approach, the effectiveness of which is continually being optimized. Post-operative long-term prognosis and quality of life measures are crucial in assessing intervention success. In conclusion, this review amalgamates existing knowledge, paving the way for future research and enhanced clinical strategies in the management of Chiari Malformation and Syringomyelia.

Chiari Syndrome: Advances in Epidemiology and Pathogenesis: A Systematic Review

Arnold Chiari syndrome is a rare congenital disease of unknown prevalence and whose origin is still under study. It is encompassed within the posterior cranial malformations, showing a wide spectrum of symptomatology that can range from severe headache, dizziness, and paresthesia to complete asymptomatology. It is for this reason that early diagnosis of the disease is difficult, and it is usually diagnosed in adolescence. Treatment is based on remodeling and decompression of the malformed posterior cranial fossa, although the risk of residual symptoms after surgery is high. The aim of this review is to update all the existing information on this pathology by means of an exhaustive analysis covering all the scientific literature produced in the last 5 years. In addition, it has been carried out following the PRISMA model and registered in PROSPERO with code CRD42023394490. One of the main conclusions based on the results obtained in this review is that the origin of the syndrome could have a genetic basis and that the treatment of choice is the decompression of the posterior cerebral fossa.

Chiari I malformation: management evolution and technical innovation

BACKGROUND AND DEFINITION

In recent years thanks to the growing use of radiological assessment, Chiari I malformation became one of the major diseases for a neurosurgeon to deal with. CIM can be classified according to the extent of cerebellar tonsil tip into the foramen magnum being a protrusion over five mm considered pathological. Such a disease is a heterogeneous condition with a multifactorial pathogenetic mechanism that can subdivided into a primary and secondary form. Regardless of the form, it seems that CIM is the result of an imbalance between the volume of the braincase and its content. Acquired CIMs are secondary to conditions causing intracranial hypertension or hypotension while the pathogenesis of primary forms is still controversial.

PATHOGENESIS AND TREATMENT

There are several theories in the literature but the most accepted one implies an overcrowding due to a small posterior cranial fossa. While asymptomatic CIM do not need treatment, symptomatic ones prompt for surgical management. Several techniques are proposed being the dilemma centered in the need for dural opening procedures and bony decompression ones.

CONCLUSION

Alongside the paper, the authors will address the novelty presented in the literature on management, diagnosis and pathogenesis in order to offer a better understanding of such a heterogeneous pathology.

A Critical Update of the Classification of Chiari and Chiari-like Malformations

Chiari malformations are a group of craniovertebral junction anomalies characterized by the herniation of cerebellar tonsils below the foramen magnum, often accompanied by brainstem descent. The existing classification systems for Chiari malformations have expanded from the original four categories to nine, leading to debates about the need for a more descriptive and etiopathogenic terminology. This review aims to examine the various classification approaches employed and proposes a simplified scheme to differentiate between different types of tonsillar herniations. Furthermore, it explores the most appropriate terminology for acquired herniation of cerebellar tonsils and other secondary Chiari-like malformations. Recent advances in magnetic resonance imaging (MRI) have revealed a higher prevalence and incidence of Chiari malformation Type 1 (CM1) and identified similar cerebellar herniations in individuals unrelated to the classic phenotypes described by Chiari. As we reassess the existing classifications, it becomes crucial to establish a terminology that accurately reflects the diverse presentations and underlying causes of these conditions. This paper contributes to the ongoing discussion by offering insights into the evolving understanding of Chiari malformations and proposing a simplified classification and terminology system to enhance diagnosis and management.

Amyotrophic Lateral Sclerosis Mimic Syndrome in a 24-Year-Old Man with Chiari 1 Malformation and Syringomyelia: A Clinical Case

Chiari 1 Malformation (CM1) is classically defined as a caudal displacement of the cerebellar tonsils through the foramen magnum into the spinal cord. Modern imaging techniques and experimental studies disclose a different etiology for the development of CM1, but the main etiology factor is a structural defect in the skull as a deformity or partial reduction, which push down the lower part of the brain and cause the cerebellum to compress into the spinal canal. CM1 is classified as a rare disease. CM1 can present with a wide variety of symptoms, also non-specific, with consequent controversies on diagnosis and surgical decision-making, particularly in asymptomatic or minimally symptomatic. Other disorders, such as syringomyelia (Syr), hydrocephalus, and craniocervical instability can be associated at the time of the diagnosis or appear secondarily. Therefore, CM1-related Syr is defined as a single or multiple fluid-filled cavities within the spinal cord and/or the bulb. A rare CM1-related disorder is syndrome of lateral amyotrophic sclerosis (ALS mimic syndrome). We present a unique clinical case of ALS mimic syndrome in a young man with CM1 and a huge singular syringomyelic cyst with a length from segment C2 to Th12. At the same time, the clinical picture showed upper hypotonic-atrophic paraparesis in the absence of motor disorders in the lower extremities. Interestingly, this patient did not have a disorder of superficial and deep types of sensitivity. This made it difficult to diagnose CM1. For a long time, the patient's symptoms were regarded as a manifestation of ALS, as an independent neurological disease, and not as a related disorder of CM1. Surgical treatment for CM1 was not effective, but it allowed to stabilize the course of CM1-related ALS mimic syndrome over the next two years.

Chiari I malformation management in patients with heritable connective tissue disorders

Background

Chiari malformation type I (CMI) is relatively common neurosurgical condition typically treated with posterior fossa decompression. However, the management of CMI in patients with heritable connective tissue disorders (CTDs), such as Ehlers-Danlos Syndrome, Marfan Syndrome, or Osteogenesis Imperfecta, involves a unique set of perioperative challenges.

Objective

This study aims to define the demographic information, comorbidities, and perioperative course of patients with concomitant CMI and CTD.

Methods

Patients with CMI admitted for surgical decompression from 2008 to 2015 were captured using the National Inpatient Sample (NIS). Information was collected based on ICD-9 codes. Descriptive and regression analyses were performed in SPSS (version 26).

Results

38,169 CMI patients, 353 of whom had CTD (0.92%), were identified. CMI patients with CTD were more likely to be female (p < 0.001) and present during teenage (p = 0.033) or young adult years (p < 0.001). They had more chronic issues (p < 0.001): systemic comorbidities include postural orthostatic tachycardia syndrome, cardiac dysrhythmias, and gastroparesis (all p < 0.001). CNS comorbidities include migraine, tethered spinal cord, and epilepsy (all p < 0.001). They have increased joint instability (both p < 0.001), as well as craniocervical instability (CCI). More posterior cervical fusion surgeries and application of cervical halo devices were seen during the same inpatient stay (both p < 0.001).

Conclusions

Patients with concurrent CTD and CMI were more likely to present with complex Chiari and associated CCI. They were also younger, more often female, and had more systemic, CNS, and joint abnormalities. As such, preoperative recognition of an underlying CTD is imperative to achieve optimal outcomes in this patient population.

Relationship between phenotypic features in Loeys-Dietz syndrome and the presence of intracranial aneurysms

OBJECTIVE

Loeys-Dietz syndrome (LDS) is a rare autosomal dominant condition characterized by aneurysms of the aorta, aortic branches, and intracranial arteries; skeletal and cutaneous abnormalities; and craniofacial malformations. Previous authors have reported that higher craniofacial severity index (CFI) scores, which indicate more severe craniofacial abnormalities, correlate with the severity of aortic aneurysm pathology. However, the association between syndromic features and the formation of intracranial aneurysms in LDS patients has yet to be determined. In this study, the authors evaluate the incidence of phenotypic abnormalities, craniofacial features, and Chiari malformation type I (CM-I) in a large LDS cohort and explore possible risk factors for the development of intracranial aneurysms.

METHODS

This was a retrospective cohort study of all patients with LDS who had been seen at the Marfan Syndrome and Aortopathy Center at Washington University School of Medicine in St. Louis in 2010–2022. Medical records were reviewed to obtain demographic, clinical, and radiographic data. The prevalence of craniofacial, skeletal, and cutaneous pathologies was determined. Bivariate logistic regression was performed to identify possible risk factors for the formation of an intracranial aneurysm.

RESULTS

Eighty-one patients with complete medical records and intracranial vascular imaging were included in the analysis, and 18 patients (22.2%) had at least 1 intracranial aneurysm. Patients frequently demonstrated the thin or translucent skin, doughy skin texture, hypertelorism, uvular abnormalities, and joint hypermobility typical of LDS. CM-I was common, occurring in 7.4% of the patients. Importantly, the patients with intracranial aneurysms were more likely to have CM-I (22.2%) than those without intracranial aneurysms (3.2%). The mean CFI score in the cohort with available data was 1.81, with higher means in the patients with the TGFBR1 or TGFBR2 disease-causing variants (2.05 and 3.30, respectively) and lower in the patients with the SMAD3, TGFB2, or TGFB3 pathogenic variants (CFI < 1). No significant CFI difference was observed in patients with or without intracranial aneurysms (2.06 vs 1.74, p = 0.61).

CONCLUSIONS

CM-I, and not the CFI, is significantly associated with the presence of intracranial aneurysms in patients with LDS. Surveillance for intracranial aneurysms is essential in all patients with LDS and should not be limited to those with severe phenotypes. Long-term monitoring studies will be necessary to determine whether a correlation between craniofacial abnormalities and adverse outcomes from intracranial aneurysms (growth, intervention, or rupture) exists.

On the association between Chiari malformation type 1, bone mineral density and bone related genes

Background

Chiari malformation type 1 (C1M) is a neurological disease characterized by herniation of the cerebellar tonsils below the foramen magnum. Cranial bone constriction is suspected to be its main cause. To date, genes related to bone development (e.g. DKK1 or COL1A2) have been associated with C1M, while some bone diseases (e.g. Paget) have been found to cosegregate with C1M. Nevertheless, the association between bone mineral density (BMD) and C1M has not been investigated, yet. Here, we systematically investigate the association between C1M and BMD, and between bone related genes and C1M.

Methods

We have recruited a small cohort of C1M patients (12 unrelated patients) in whom we have performed targeted sequencing of an in-house bone-related gene panel and BMD determination through non-invasive DXA.

Results

In the search for association between the bone related genes and C1M we have found variants in more than one C1M patient in WNT16, CRTAP, MYO7A and NOTCH2. These genes have been either associated with craniofacial development in different ways, or previously associated with C1M (MYO7A). Regarding the potential link between BMD and C1M, we have found three osteoporotic patients and one patient who had high BMD, very close to the HBM phenotype values, although most patients had normal BMD.

Conclusions

Variants in bone related genes have been repeatedly found in some C1M cases. The relationship of bone genes with C1M deserves further study, to get a clearer estimate of their contribution to its etiology. No direct correlation between BMD and C1M was observed.

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We used an in-house bone gene panel to investigate a small cohort of C1M patients.

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Variants in WNT16, CRTAP, MYO7A and NOTCH2 were found in more than one C1M patient.

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No clear relationship was found between C1M and BMD in this small C1M cohort.