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De novo chromatin remodelling variants in sporadic Chiari 1 malformation.

Chiari 1 malformation (CM1) is the most common congenital malformation of the human hindbrain. Although prior studies have implicated chromatin-remodeling genes in CM1, the de novo genetic architecture and underlying neurodevelopmental mechanisms remain incompletely defined. To investigate the molecular genetics of a novel familial form of CM1 linked with syringomyelia and tethered cord and determine whether rare, damaging de novo variants (DNVs) contribute to sporadic CM1 risk with gene- and pathway-level resolution, we performed whole-exome sequencing in an ultra-rare multigenerational family with CM1 and associated spinal pathology, and in the largest assembled trio-based cohort to date, comprising 1,585 proband-parent trios with sporadic, idiopathic CM1 (2017-2025). The comparison cohort included 1,798 unaffected control siblings. Clinical phenotyping was by systematic medical record review. Structural domain mapping, in silico modeling, and integration with single-cell transcriptomic data from developing human cerebellum was conducted to assess biological plausibility. A heterozygous loss-of-function variant in CHD3 segregated with CM1 and syringomyelia in a multigenerational family. In the trio-based cohort, rare protein-altering DNVs were significantly enriched across multiple chromodomain helicase DNA-binding (CHD) genes, including CHD1, CHD3, CHD4, and CHD8, exceeding gene-specific mutation expectations (protein-damaging variants: P = 1.3 × 10-9; predicted loss-of-function variants: P = 8.6 × 10-5). CHD1 contained two pathogenic DNVs (p.A999D and p.E984K). CHD4 (p.D744N, p.T1813P, and p.I1102T) and CHD8 (p.R1402X, p.R1472X, and p.R2035X) each contained three new DNVs. Variants clustered within conserved ATPase, helicase, and chromodomain regions essential for chromatin remodeling, and these patients frequently had comorbid developmental delay and related neurodevelopmental features. Single-cell transcriptomic analyses demonstrated enrichment in Purkinje cells and inhibitory neurons of midgestational cerebellum, where CHD gene products form a coherent chromatin-regulatory network. Rare, large-effect DNVs that disrupt chromatin-remodeling programs contribute to sporadic CM1, implicating genetically encoded dysregulation of cerebellar development as a central disease mechanism. Exome sequencing may complement surgical evaluation of children with sporadic CM1, particularly when accompanied by neurodevelopmental concerns, informing prognosis and family counseling.

de novo variants

Size of posterior fossa in Chiari type 1 malformation in adults.

The clinical and neuroradiological findings in five patients with Chiari Type 1 malformation presenting symptoms in adult life are presented. New posterior fossa ratio methods have been applied to this material. The posterior cranial fossae are demonstrated to be small, and the most significant deviation from normal gave the ratio h/Tw: posterior fossa height in proportion to Twining's line. The implications of these findings are discussed in relation to the static and dynamic factors that are operating in the development of neurological symptoms in Chiari type 1 malformation. A final discussion is given comparing the Chiari type 1 malformations to meningo-myelocele. The findings using posterior fossa ratio methods may strengthen the indications for suboccipital craniectomy in these patients.

Adult

The adult Chiari malformation.

The adult or type 1 Chiari malformation is a hindbrain anomaly in which the cerebellar tonsils, but not the vermis, are chronically dispalced into the foramen magnum (1). Syringomyelia or syringobulbia are frequently associated with the anomaly (2-4). Seventeen cases of surgically verified adult Chiari malformations with or without a syrinx were recently diagnosed at the Neuropsychiatric Institute. University of California at Los Angeles. A review of these patients confirmed this anomaly has protean manifestations. Recognition of paroxysmal complaints induced by a variation of the Valslava maneuver, especially in the presence of nystagmus, might lead to early neurodiagnostic procedures and surgical intervention, with reduced morbidity.

Age Factors

[The basilar impression and the Arnold-Chiari malformation. Techno-surgical considerations apropos of 13 cases].

The surgical technic for decompression of the posterior fossa in cases of basilar impression and malformation of Arnold-Chiari mainly based in (1) endotracheal intubation without any flexion of the head, (2) position of the head without anterior flexion during the surgery, (3) plastic of the posterior fossa with dura-mater of cadaver conserved in glicerina, was emploied in 13 patients. The plastic was made to create space at the craniocervical joint in order to avoid cerebrospinal fluid fistula and to restore the integrity of the dura. Infection was not observed.

Adolescent

Respiratory obstruction and apnea in infants with bilateral abductor vocal cord paralysis, meningomyelocele, hydrocephalus, and Arnold-Chiari malformation.

This report describes 21 infants and children with bilateral abductor vocal cord paralysis and associated meningomyelocele, Arnold-Chiari malformation, and hydrocephalus. Two life-threatening forms of respiratory distress are distinguished: (1) upper airway obstruction due to bilateral abductor cord paralysis and (2) apnea. Clinically significant episodes of apnea were documented in 13 infants. Ten infants had evidence of aspiration and dysphagia. Vocal cord paralysis, apnea, aspiration, and dysphagia were frequently temporally related to increased intracranial pressure.

Airway Obstruction

Transitional forms of Arnold-Chiari and Dandy-Walker malformations.

The morphological findings in 12 cases of Arnold-Chiari and 3 cases of Dandy-Walker malformations are described and compared to those in 2 cases of congenital hydrocephalus of unknown origin, 1 case of isolated meningo-myelocele and 2 cases of normal newborn brains. Lesions common to both types of malformation indicate a same time-related embryogenetic defect of the roofplate of the rhombencephalon, that does not allow the inferior vermis and the choroid plexus to turn inward into the fourth ventricle.

Arnold-Chiari Malformation

[Neuroradiological studies in syringomyelia].

In the years 1973--1975 20 patients with syringomyelia were treated surgically. The surgical interventions were preceded by careful radiological examinations which was often indispensable for confirmation of diagnosis, establishing of indications to operation and choice of surgical method. On plain radiograms in 16 cases cervicothoracic scoliosis was found, in 11 cases the vertebral canal was dilated in its cervical part, in 6 cases atlanto-occipital malformations were disclosed. The basic diagnostic examination was ascending myelography which was performed in 17 cases. In 3 cases the contrast medium failed to pass to the atlanto-occipital junction because of marked dilatation of the spinal cord in the cervical part. In 9 out of the remaining 14 cases radiological findings were compatible with the diagnosis of Arnold-Chiari syndrome which was confirmed during the operation. In 1 case positive contrast central pneumoencephalography was performed demonstrating a communication between the 4 th ventricle and the cavity in the spinal cord. Early detailed neuroradiological diagnosis is indispensable in syringomyelia for early surgical treatment.

Adolescent

Myelomeningocele before birth.

The authors report a study of 92 human embryos and four fetuses with myeloschisis. The characteristics of embryonic myeloschisis compared with spina bifida cystica in infants are: 1) the lesion is often more diffuse, involving the whole spinal cord (12 embryos); 2) the cervical cord is frequently affected (23 of the remaining 80 embryos); 3) holoprosencephaly is frequently associated (18 embryos); 4) meningocele is not found; and 5) hydrocephalus and Arnold-Chiari malformation are not yet developed. Hydrocephalus and Arnold-Chiari malformation are found in myeloschistic fetuses. Almost all embryos with diffuse and cervical myeloschisis or with holoprosencephaly are extruded before birth by spontaneous abortion. Absence of meningocele in the embryonic period implies that its appearance is deferred to the fetal period. The development of hydrocephalus and Arnold-Chiari malformation also seems to be delayed until the fetal period. Our observation implies that myelomeningocele is induced by non-closure of the neural tube, not by rupture once it was closed. "Neural overgrowth" and disturbed "recanalization process" are discussed in relation to the pathogenesis of myelomeningocele.

Abnormalities, Multiple

Familial communicating syringomyelia.

Calssical cervical syringomyelia was found in 3 members of one family. All 3 underwent air myelogram, and a Chiari malformation type I and postural collapse of the spinal cord was found in each case. An affected 7-year-old boy was discovered after a clinical and radiological survey of 8 first-degree relatives on the basis of mild scoliosis, pyramidal tract signs in the lower limbs and enlarged sagittal diameter of the cervical canal. One other member had basilar impression of the skull but no neurological abnormalities. No positive correlation was found between either the size of the cystic cord enlargement or descent of the ectopic tonsils with the duration or severity of the neurological findings. Suboccipital decompressive craniotomy and upper cervical laminectomy in one case was followed by improvement in strength and sensation 1 year later. Progression in familial syringomyelia appears to occur through a mechanism identical to that in the sporadic form and surgery is therefore also indicated. In affected families, routine survey of close relatives for abnormal neurological signs, and radiological evidence of scoliotic deformity of the spine, enlarged cervical canal and bone abnormalities at the craniovertebral junction may prove valuable for early detection. A dominantly inherited, genetically determined malformation seems to be the probable mechanism of inheritance in this family.

Adolescent