Familial Chiari malformation: case series

A genetic component in Chiari I malformation: Chiari 1 malformation in all five family members

Under certain classifications, a Chiari type I (CMI) malformation can be characterized as a herniation of the cerebellar tonsils greater than 3 mm. Patients with CMI often have a smaller posterior fossa volume, which results in a smaller amount of space for the cerebellum, leading to the herniation of the cerebellar tonsils through the foramen magnum. Although inheritable factors such as posterior fossa volume can be traced to specific genes, there has not been a gene that can be attributed to directly causing CMI. However, several cases of CMI have exhibited a familial inheritance pattern. There are mixed findings regarding the exact nature of its inheritance, with some papers arguing in favor of an autosomal dominant pattern. In this case series, we detail a mother, father, and all 3 of their children diagnosed with CMI. Previous literature has not included both a mother and father with CMI.

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.

Arnold-Chiari Malformation Type I Evident After a Streptococcal Throat Infection in a Young Female: A Rare Case

Arnold-Chiari malformation (ACM) is a rare neurological developmental disorder that presents at birth. No such cases have been reported in support of microbial infections causing Chiari malformation, yet there is evidence of how microorganisms can lead to brain abscess, brain empyema, and meningoencephalitis. We present a 23-year-old young woman with progressive back and leg pain after a streptococcal throat infection, followed by a single episode of syncope. Radiographs of the spine revealed a mild reversal of cervical spine curvature and minimal levocurvature of the lumbar spine. Magnetic resonance imaging of the brain showed herniation of the cerebral tonsils into the foramen magnum, which suggested the diagnosis of ACM type I. Neurosurgery was recommended for posterior fossa decompression, but the patient was reluctant to undergo the procedure. This is a rare case of ACM symptomology that became evident only after a streptococcal throat infection in a young adult female.

Case Report: Pansynostosis, Chiari I Malformation and Syringomyelia in a Child With Frontometaphyseal Dysplasia 1

Frontometaphyseal dysplasia 1 (FMD1) is a rare otopalatodigital spectrum disorder (OPDSD) that is inherited as an X-linked trait and it is caused by gain-of-function mutations in the FLNA. It is characterized by generalized skeletal dysplasia, and craniofacial abnormalities including facial dysmorphism (supraorbital hyperostosis, hypertelorism, and down-slanting palpebral fissures). The involvement of the central nervous system in patients with OPDSD is rare. Herein, we present the case of a 12-year-old boy with facial dysmorphism, multiple joint contractures, sensorineural hearing loss, scoliosis, craniosynostosis, and irregular sclerosis with hyperostosis of the skull. Brain and whole-spine magnetic resonance imaging revealed Chiari I malformation with extensive hydrosyringomyelia from the C1 to T12 levels. Targeted next-generation sequencing identified a hemizygous pathologic variant (c.3557C>T/p.Ser1186Leu) in the FLNA, confirming the diagnosis of FMD1. This is the first report of a rare case of OPDSD with pansynostosis and Chiari I malformation accompanied by extensive syringomyelia.

Correlation of a new hydrodynamic index with other effective indexes in Chiari I malformation patients with different associations

This study aimed to find a new CSF hydrodynamic index to assess Chiari type I malformation (CM-I) patients’ conditions and examine the relationship of this new index with morphometric and volumetric changes in these patients and their clinical symptoms. To this end, 58 CM-I patients in four groups and 20 healthy subjects underwent PC-MRI. Ten morphometric and three volumetric parameters were calculated. The CSF hydrodynamic parameters were also analyzed through computational fluid dynamic (CFD) simulation. The maximum CSF pressure was identified as a new hydrodynamic parameter to assess the CM-I patients’ conditions. This parameter was similar in patients with the same symptoms regardless of the group to which they belonged. The result showed a weak correlation between the maximum CSF pressure and the morphometric parameters in the patients. Among the volumetric parameters, PCF volume had the highest correlation with the maximum CSF pressure, which its value being higher in patients with CM-I/SM/scoliosis (R² = 65.6%, P = 0.0022) than in the other patients. PCF volume was the more relevant volumetric parameter to assess the patients’ symptoms. The values of PCF volume were greater in patients that headache symptom was more obvious than other symptoms, as compared to the other patients.

Chiari type 1-a malformation or a syndrome? A critical review

OBJECTIVE

As the understanding of pathophysiology behind Chiari malformation still is limited, the treatment of Chiari malformation type 1 remains rather empirical. This may result in suboptimal treatment strategy and outcome in many cases. In this review, we critically address whether the condition known today as Chiari malformation type I should rather be denoted Chiari syndrome.

METHODS

The current knowledge of Chiari malformation type 1 is summarized from the historical, etymological, genetic, clinical, and in particular pathophysiological perspectives.

RESULTS

There are several lines of evidence that Chiari malformation type 1 represents a condition significantly different from types 2 to 4. Unlike the other types, the type 1 should rather be considered a syndrome, thus supporting the reasons to reappraise the traditional classification of Chiari malformations.

CONCLUSION

We propose that Chiari malformation type 1 should rather be denoted Chiari syndrome, while the notation malformation is maintained for types 2-4.

Neuroanatomic Correlates for the Neuropsychological Manifestations of Chiari Malformation Type I

Chiari malformation comprises a spectrum of congenital malformations characterized by a herniation of the cerebellar tonsils below the foramen magnum. Chiari malformation type I (CM-I) is the most prevalent subtype seen in clinical practice. This condition variably compresses the cerebellum and medulla-spinal cord junction secondary to malformation of the posterior fossa. Most neurologists and neurosurgeons recognize the sensorimotor and lower brainstem manifestations that result in the clinical picture of CM-I. The effects of CM-I on cognitive functioning, however, and their impact on neuropsychological performance are poorly understood, despite having long been recognized. This article reviews neuropsychological deficits demonstrated by individuals with CM-I, and explores cerebellocortical neuroanatomic pathways to provide possible rationale for the neurocognitive impairments present in affected individuals.

Central Hypothyroidism and Novel Clinical Phenotypes in Hemizygous Truncation of TBL1X

Transducin β-like 1 X-linked (TBL1X) gene encodes a subunit of the nuclear corepressor-silencing mediator for retinoid and thyroid hormone receptor complex (NCoR-SMRT) involved in repression of thyroid hormone action in the pituitary and hypothalamus. TBL1X defects were recently associated with central hypothyroidism and hearing loss. The current study aims to describe the clinical and genetic characterization of a male diagnosed with central hypothyroidism through thyroid hormone profiling, TRH test, brain MRI, audiometry, and psychological evaluation. Next-generation sequencing of known genes involved in thyroid disorders was implemented. The 6-year-old boy was diagnosed with central hypothyroidism [free T4: 10.42 pmol/L (normal: 12 to 22 pmol/L); TSH: 1.57 mIU/L (normal: 0.7 to 5.7 mIU/L)], with a mildly reduced TSH response to TRH. He was further diagnosed with attention-deficit/hyperactivity disorder (ADHD) at 7 years, alternating episodes of encopresis and constipation, and frequent headaches. MRI showed a normal pituitary but detected a Chiari malformation type I (CMI). At 10 years, audiometry identified poor hearing threshold at high frequencies. Sequencing revealed a nonsense hemizygous mutation in TBL1X [c.1015C>T; p.(Arg339Ter)] largely truncating its WD-40 repeat domain involved in nuclear protein-protein interactions. In conclusion, to our knowledge, we identified the first severely truncating TBL1X mutation in a patient with central hypothyroidism, hypoacusia, and novel clinical features like ADHD, gastrointestinal dysmotility, and CMI. Given the relevance of TBL1X and NCoR-SMRT for the regulation of transcriptional programs at different tissues (pituitary, cochlea, brain, fossa posterior, and cerebellum), severe mutations in TBL1X may lead to a distinct syndrome with a phenotypic spectrum wider than previously reported.

Familial Chiari Type 1: A Molecular Karyotyping Study in a Turkish Family and Review of the Literature

BACKGROUND

The etiology of Chiari I malformation (CMI) has not been fully elucidated. Therefore, we performed a genetic study of a Turkish family in which 3 sisters had a diagnosis of CMI with or without syringomyelia.

METHODS

In a family with 7 children, 4 daughters complained of occipital headaches. In 2 of these daughters, CMI had been diagnosed during their 30s, and CMI plus syrinx had been diagnosed in the other daughter in her 40s. Cranial magnetic resonance imaging of the fourth daughter who had developed headaches during her 30s showed normal findings. Because the other siblings in the family were asymptomatic, radiological examinations were not performed. The family had a history of distant consanguineous marriage between parents. Additionally, the father had died, and the mother was asymptomatic, with radiologically normal findings. Array comparative genome hybridization studies were performed for 12 persons from 3 generations of this family.

RESULTS

None of the 12 cases examined harbored copy number variations.

CONCLUSIONS

This family with 3 sisters having CMI suggested a possible autosomal recessive single-gene etiology. Cases of familial CMI are unusual but important to study because they could reveal the specific genes involved in posterior fossa/foramen magnum structure and function and provide insights into the cause of sporadic cases.

Population-based description of familial clustering of Chiari malformation Type I

OBJECTIVE

A population-based genealogical resource with linked medical data was used to define the observed familial clustering of Chiari malformation Type I (CM-I).

METHODS

All patients with CM-I were identified from the 2 largest health care providers in Utah; those patients with linked genealogical data were used to test hypotheses regarding familial clustering. Relative risks (RRs) in first-, second-, and third-degree relatives were estimated using internal cohort-specific CM-I rates; the Genealogical Index of Familiality (GIF) test was used to test for an excess of relationships between all patients with CM-I compared with the expected distribution of relationships for matched control sets randomly selected from the resource. Pedigrees with significantly more patients with CM-I than expected (p < 0.05) based on internal rates were identified.

RESULTS

A total of 2871 patients with CM-I with at least 3 generations of genealogical data were identified. Significantly increased RRs were observed for first- and third-degree relatives (RR 4.54, p < 0.001, and RR 1.36, p < 0.001, respectively); the RR for second-degree relatives was elevated, but not significantly (RR 1.20, p = 0.13). Significant excess pairwise relatedness was observed among the patients with CM-I (p < 0.001), and borderline significant excess pairwise relatedness was observed when all relationships closer than first cousins were ignored (p = 0.051). Multiple extended high-risk CM-I pedigrees with closely and distantly related members were identified.

CONCLUSIONS

This population-based description of the familial clustering of 2871 patients with CM-I provided strong evidence for a genetic contribution to a predisposition to CM-I.

Chiari 1 deformity in children: etiopathogenesis and radiologic diagnosis

The metamerically associated normal hindbrain and normal posterior fossa are programmed to grow together in such a way that the tonsils are located above the foramen magnum and surrounded by the cerebrospinal fluid (CSF) of the cisterna magna. This allows the pulsating CSF to move freely up and down across the craniovertebral junction (CVJ). A developmental mismatch between the rates of growth of the neural tissue and of the bony posterior fossa may result in the cerebellar tonsils being dislocated across the foramen magnum. The cause of this may be, rarely, an overgrowth of the cerebellum. More commonly, it is due to an insufficient development of the posterior fossa, possibly associated with a malformation of the craniocervical joint. When it is not due to a remediable cause, such a herniation is called a Chiari 1 deformity. This definition is anatomic (descent of the tonsils below the plane of the foramen magnum) and not clinical: many patients with the deformity are and will remain asymptomatic. Most authors consider that a descent of 5 mm or more is clinically significant but other factors, such as the diameter of the foramen magnum and the degree of tapering of the upper cervical "funnel," are likely to be as important. Morphologic markers of severity on magnetic resonance imaging are, beside the degree of descent, the peg-like deformity of the tonsils, the obstruction of the surrounding CSF spaces (at the craniocervical junction and in the whole posterior fossa), a compression of the cord, an abnormal signal of the cord, and a syringomyelia, typically cervicothoracic. The syringomyelia is assumed to be explained by the "Venturi effect" that is associated with the increased velocity of the CSF across the restricted CSF spaces. Radiologically, the etiopathogenic assessment should address the size and morphology of the posterior fossa, and the functional status of the craniocervical flexion joint. The posterior fossa is best evaluated on sagittal cuts by the posterior fossa pentagon proportionality associated with the line of Chamberlain, and on coronal cuts, by showing a possible shallowness of the posterior fossa. The functional status of the craniocervical joint is altered in case of a proatlantal hypoplasia, as this condition results in a cranial shift of the joint that brings the tip of the dens and of the flexion axis in front of the medulla, that is, in a situation of osteoneural conflict. Less commonly, similar conflicts may also occur when an abnormal craniocervical segmentation results in an instability of the joint.

Potential damaging mutation in LRP5 from genome sequencing of the first reported chimpanzee with the Chiari malformation

The genus Pan is the closest related to humans (Homo sapiens) and it includes two species: Pan troglodytes (chimpanzees) and Pan paniscus (bonobos). Different characteristics, some of biomedical aspect, separate them from us. For instance, some common human medical conditions are rare in chimpanzees (menopause, Alzheimer disease) although it is unclear to which extent longevity plays an active role in these differences. However, both humans and chimpanzees present similar pathologies, thus, understanding traits in chimpanzees can help unravel the molecular basis of human conditions. Here, we sequenced the genome of Nico, a central chimpanzee diagnosed with a particular biomedical condition, the Chiari malformation. We performed a variant calling analysis comparing his genome to 25 whole genomes from healthy individuals (bonobos and chimpanzees), and after predicting the effects of the genetic variants, we looked for genes within the OMIM database. We found a novel, private, predicted as damaging mutation in Nico in LRP5, a gene related to bone density alteration pathologies, and we suggest a link between this mutation and his Chiari malformation as previously shown in humans. Our results reinforce the idea that a comparison between humans and chimpanzees can be established in this genetic frame of common diseases.

Inheritance of Chiari-Like Malformation: Can a Mixed Breeding Reduce the Risk of Syringomyelia?

Canine Chiari-like malformation (CM) is a complex abnormality of the skull and craniocervical junction associated with miniaturization and brachycephaly which can result in the spinal cord disease syringomyelia (SM). This study investigated the inheritance of CM in a Griffon Bruxellois (GB) family and feasibility of crossbreeding a brachycephalic CM affected GB with a mesaticephalic normal Australian terrier and then backcrossing to produce individuals free of the malformation and regain GB breed characteristics. The study family cohort (n = 27) included five founder dogs from a previous baseline study of 155 GB which defined CM as a global malformation of the cranium and craniocervical junction with a shortened skull base and increased proximity of the cervical vertebrae to the skull. T1-weighted sagittal DICOM images of the brain and craniocervical junction were analysed for five significant traits (two angles, three lines) identified from the previous study and subsequent Qualitative Trait Loci analysis. Mean measurements for mixed breed, pure-breed and baseline study groups were compared. Results indicated that mixed breed traits posed less risk for CM and SM and were useful to distinguish the phenotype. Moreover on the MR images, the filial relationships displayed by the traits exhibited segregation and those presenting the greatest risk for CM appeared additive towards the severity of the condition. The external phenotypes revealed that by outcrossing breed types and with careful selection of appropriate conformation characteristics in the first generation, it is possible to regain the GB breed standard and reduce the degree of CM. The four GB affected with SM in the study all exhibited reduced caudal skull development compared to their relatives. The craniocervical traits may be useful for quantifying CM and assessing the possibility of SM thus assisting breeders with mate selection. However, such a system requires validation to ensure appropriateness for all breeds at risk.

Chiari malformation type III: Case report and review of the literature

Chiari malformation type III is an extremely rare anomaly characterized by a small posterior fossa and a low occipital/high cervical encephalocele with herniation of the posterior fossa contents (that is, the cerebellum and/or the brainstem, occipital lobe, and fourth ventricle). We report a case of Chiari malformation type III in a neonate, discuss the etiopathogenetic and radiological features, and review the pertinent literature.

[Idiopathic intracranial hypertension in a patient with Chiari I malformation]

CASE REPORT

The case involves a 22-year-old woman who presented with headache and decreased vision. She showed asymmetric papilledema, and a 6-mm tonsillar descent was observed in the image tests. She was diagnosed with secondary intracranial hypertension coinciding with the symptoms of a Chiari malformation (MC).

DISCUSSION

Chiari malformation type I is the most common in this group of malformations, and is characterized by a greater than 5mm descent of the tonsils, being able to cause increased intracranial pressure and papilledema by blocking the flow of the cerebrospinal fluid. In this case, the MC was not the responsible for triggering the secondary intracranial hypertension, but a mere coincidence of both processes.

Chiari malformation I and autism spectrum disorder: an underrecognized coexistence

OBJECT

Patients with symptomatic Chiari malformation Type I (CM-I) frequently present with headaches, neck pain, difficulty swallowing, and balance disturbances. In children with autism spectrum disorder (ASD), diagnosing CM-I can be a challenging task. Moreover, even if symptomatic, some patients do not undergo further evaluation or management, as their presentations are attributed to autism and its myriad symptoms. Therefore, cranial MRI findings were reviewed after evaluating and treating patients with coexisting ASD and CM-I. In this paper, the authors report on 5 children with ASD and symptomatic CM-I, including their clinical presentation, imaging studies, management, and outcomes, and discuss the likely underrecognized coexistence of these conditions.

METHODS

All pediatric patients with ASD and cranial MRI conducted for any reason in the period from 1999 to 2013 were considered for analysis. All cases with concomitant symptomatic CM-I were eligible for this retrospective analysis.

RESULTS

One hundred twenty-five pediatric patients diagnosed with ASD had undergone MRI, and 9 of them had evidence of cerebellar tonsillar herniation. Five patients were symptomatic and underwent suboccipital craniectomy, a C-1 or a C-1 and C-2 laminectomy, and duraplasty with bovine pericardium or Type I collagen allograft. There were no intraoperative complications. All patients showed symptom improvement and/or resolution of presenting symptoms, which included headache, dysphasia, speech, and irritability.

CONCLUSIONS

There is no identified cause of autism. Children with ASD can be difficult to assess specifically in a neurological examination. Thus, cranial MRI considered when completing a comprehensive diagnostic evaluation. While cranial MRI is not a routine part of ASD evaluation, this study demonstrates that CM-I and ASD may coexist and be underrecognized. The study reinforces the importance of a comprehensive medical evaluation designed to elucidate neurological findings in children with impaired communication abilities and suggests the judicious use of neuroimaging.

Distribution of cerebellar tonsil position: implications for understanding Chiari malformation

OBJECT

Prior attempts to define normal cerebellar tonsil position have been limited by small numbers of patients precluding analysis of normal distribution by age group. The authors' objective in the present study was to analyze cerebellar tonsil location in every age range.

METHODS

Two thousand four hundred patients were randomly selected from a database of 62,533 consecutive patients undergoing MRI and were organized into 8 age groups. Magnetic resonance images were directly examined for tonsil location, morphology, and other features. Patients with a history or imaging findings of posterior fossa abnormalities unrelated to Chiari malformation (CM) were excluded from analysis. The caudal extent of the cerebellar tonsils was measured at the midsagittal and lowest parasagittal positions.

RESULTS

The mean tonsil height decreased slightly with advancing age into young adulthood and increased with advancing age in the adult age range. An increasing age in the adult age range was associated with a decreased likelihood of a tonsil position 5 mm or more below the foramen magnum (p = 0.0004). In general, the lowest tonsil position in each age group was normally distributed. Patients with pegged morphology were more likely to have a tonsil location at least 5 mm below the foramen magnum (85%), as compared with those having intermediate (38%) or rounded (2%) morphology (p < 0.0001). Female sex was associated with a lower mean tonsil position (p < 0.0001). Patients with a lower tonsil position also tended to have an asymmetrical tonsil position, usually lower on the right (p < 0.0001).

CONCLUSIONS

Cerebellar tonsil position follows an essentially normal distribution and varies significantly by age. This finding has implications for advancing our understanding of CM.

Stratified whole genome linkage analysis of Chiari type I malformation implicates known Klippel-Feil syndrome genes as putative disease candidates

Chiari Type I Malformation (CMI) is characterized by displacement of the cerebellar tonsils below the base of the skull, resulting in significant neurologic morbidity. Although multiple lines of evidence support a genetic contribution to disease, no genes have been identified. We therefore conducted the largest whole genome linkage screen to date using 367 individuals from 66 families with at least two individuals presenting with nonsyndromic CMI with or without syringomyelia. Initial findings across all 66 families showed minimal evidence for linkage due to suspected genetic heterogeneity. In order to improve power to localize susceptibility genes, stratified linkage analyses were performed using clinical criteria to differentiate families based on etiologic factors. Families were stratified on the presence or absence of clinical features associated with connective tissue disorders (CTDs) since CMI and CTDs frequently co-occur and it has been proposed that CMI patients with CTDs represent a distinct class of patients with a different underlying disease mechanism. Stratified linkage analyses resulted in a marked increase in evidence of linkage to multiple genomic regions consistent with reduced genetic heterogeneity. Of particular interest were two regions (Chr8, Max LOD = 3.04; Chr12, Max LOD = 2.09) identified within the subset of "CTD-negative" families, both of which harbor growth differentiation factors (GDF6, GDF3) implicated in the development of Klippel-Feil syndrome (KFS). Interestingly, roughly 3-5% of CMI patients are diagnosed with KFS. In order to investigate the possibility that CMI and KFS are allelic, GDF3 and GDF6 were sequenced leading to the identification of a previously known KFS missense mutation and potential regulatory variants in GDF6. This study has demonstrated the value of reducing genetic heterogeneity by clinical stratification implicating several convincing biological candidates and further supporting the hypothesis that multiple, distinct mechanisms are responsible for CMI.

Chiari malformation type I: a case-control association study of 58 developmental genes

Chiari malformation type I (CMI) is a disorder characterized by hindbrain overcrowding into an underdeveloped posterior cranial fossa (PCF), often causing progressive neurological symptoms. The etiology of CMI remains unclear and is most likely multifactorial. A putative genetic contribution to CMI is suggested by familial aggregation and twin studies. Experimental models and human morphometric studies have suggested an underlying paraxial mesoderm insufficiency. We performed a case-control association study of 303 tag single nucleotide polymorphisms (SNP) across 58 candidate genes involved in early paraxial mesoderm development in a sample of 415 CMI patients and 524 sex-matched controls. A subgroup of patients diagnosed with classical, small-PCF CMI by means of MRI-based PCF morphometry (n = 186), underwent additional analysis. The genes selected are involved in signalling gradients occurring during segmental patterning of the occipital somites (FGF8, Wnt, and retinoic acid pathways and from bone morphogenetic proteins or BMP, Notch, Cdx and Hox pathways) or in placental angiogenesis, sclerotome development or CMI-associated syndromes. Single-marker analysis identified nominal associations with 18 SNPs in 14 genes (CDX1, FLT1, RARG, NKD2, MSGN1, RBPJ1, FGFR1, RDH10, NOG, RARA, LFNG, KDR, ALDH1A2, BMPR1A) considering the whole CMI sample. None of these overcame corrections for multiple comparisons, in contrast with four SNPs in CDX1, FLT1 and ALDH1A2 in the classical CMI group. Multiple marker analysis identified a risk haplotype for classical CMI in ALDH1A2 and CDX1. Furthermore, we analyzed the possible contributions of the most significantly associated SNPs to different PCF morphometric traits. These findings suggest that common variants in genes involved in somitogenesis and fetal vascular development may confer susceptibility to CMI.