A morphometric study of the atlanto-occipital joint in adult patients with Chiari malformation type I

Wan, Ming Young Simon; Zong, Rui; Tong, Huaiyu; Zhang, Zhizhong; Zhao, Bo; Yu, Xinguang

doi:10.1080/02688697.2020.1823940

Cited by 7 publications

(5 citation statements)

References 23 publications

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“…Specifically, Wan et al used thin sliced CT to calculate the depth to length ratio of the convex surfaces of the atlas in 47 adult CMI patients as compared to age and gender-matched controls and found that the ratio was significantly reduced in the CMI group. This flattening is similar to morphometric studies in Down syndrome patients with clinically identified AO joint instability [ 15 ]. Wan et al also used thin CT slices to examine the occipital condyles of 73 adult CMI patients compared to matched controls and found the average length, width, and height of the condyles in the CMI group were significantly smaller [ 16 ].…”

Section: Hypothesissupporting

confidence: 85%

“…In a morphometric study of the AO joint, Wan et al used high-resolution computerized tomography (CT) to show that symptomatic CMI patients have smaller than normal occipital condyles and shallower facets on the atlas [ 15 - 16 ]. This finding, combined with a study that showed the stabilizing transverse and alar ligaments are also abnormal in CMI patients [ 17 ], led Wan et al to postulate that AO joint instability plays a role in CMI.…”

Section: Symptomatic CMI Theoriesmentioning

confidence: 99%

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A new hypothesis for the pathophysiology of symptomatic adult Chiari malformation Type I

Labuda¹,

Nwotchouang

Ibrahimy

et al. 2022

Medical Hypotheses

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Chiari malformation Type I (CMI) is characterized by herniation of the cerebellar tonsils through the foramen magnum. The pathophysiology of CMI is not well elucidated; however, the prevailing theory focuses on the underdevelopment of the posterior cranial fossa which results in tonsillar herniation. Symptoms are believed to be due to the herniation causing resistance to the natural flow of cerebrospinal fluid (CSF) and exerting a mass effect on nearby neural tissue. However, asymptomatic cases vastly outnumber symptomatic ones and it is not known why some people become symptomatic. Recently, it has been proposed that CMI symptoms are primarily due to instability of either the atlanto-axial (AA) or the atlanto-occipital (AO) joint and the cerebellar tonsils herniate to prevent mechanical pinching. However, only a small percentage of patients exhibit clinical instability and these theories do not account for asymptomatic herniations. We propose that the pathophysiology of adult CMI involves a combination of craniocervical abnormalities which leads to tonsillar herniation and reduced compliance of the cervical spinal canal. Specifically, abnormal AO and/or AA joint morphology leads to chronic cervical instability, often subclinical, in a large portion of CMI patients. This in turn causes overwork of the suboccipital muscles as they try to compensate for the instability. Over time, the repeated, involuntary activation of these muscles leads to mechanical overload of the myodural bridge complex, altering the mechanical properties of the dura it merges with. As a result, the dura becomes stiffer, reducing the overall compliance of the cervical region. This lower compliance, combined with CSF resistance at the same level, leads to intracranial pressure peaks during the cardiac cycle (pulse pressure) that are amplified during activities such as coughing, sneezing, and physical exertion. This increase in pulse pressure reduces the compliance of the cervical subarachnoid space which increases the CSF wave speed in the spinal canal, and further increases pulse pressure in a feedback loop. Finally, the abnormal pressure environment induces greater neural tissue motion and strain, causing microstructural damage to the cerebellum, brainstem, and cervical spinal cord, and leading to symptoms. This hypothesis explains how the combination of craniocervical bony abnormalities, anatomic CSF restriction, and reduced compliance leads to symptoms in adult CMI.

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Section: Hypothesissupporting

confidence: 85%

Section: Symptomatic CMI Theoriesmentioning

confidence: 99%

A new hypothesis for the pathophysiology of symptomatic adult Chiari malformation Type I

Labuda¹,

Nwotchouang

Ibrahimy

et al. 2022

Medical Hypotheses

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“…After systematic measurement, the length and height of C0 and the curvature of AOJ in normal subjects were within the previously reported range. [19][20][21][22] On the other hand, most patients with CM alone have deformities, including clivus dysplasia, a short supraoccipital bone, and flat AOJ (type II-AOJ), although a ball-and-socket joint was still identified. However, when CM coexisted with type II-BI, the degree of CVJ deformity was significantly aggravated, which was reflected in the flat articular surface of the AOJ (type III-AOJ).…”

Section: Discussionmentioning

confidence: 99%

“…The proportion of female patients in the control group, CM group, and CM + II-BI group was 48.8%, 63.5%, and 59.5%, respectively (χ 2 , P = . 19). The mean age of patients in the control group, CM group, and CM + II-BI group was 45.0 ± 13.3, 43.1 ± 11.8, and 41.0 ± 12.7 years, respectively (Wilcoxon rank-sum test, P = .26).…”

Section: Baseline Characteristicsmentioning

confidence: 99%

Exploring the Pathogenesis of Atlanto-Occipital Instability in Chiari Malformation With Type II Basilar Invagination: A Systematic Morphological Study

et al. 2022

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BACKGROUND:Our previous study suggested that atlanto-occipital instability (AOI) is common in patients with type II basilar invagination (II-BI).OBJECTIVE:To further understand the pathogenesis of AOI in Chiari malformations (CM) and CM + II-BI through systematic measurements of the bone structure surrounding the craniocervical junction.METHODS:Computed tomography data from 185 adults (80 controls, 63 CM, and 42 CM + II-BI) were collected, and geometric models were established for parameter measurement. Canonical correlation analysis was used to evaluate the morphological and positional relationships of the atlanto-occipital joint (AOJ).RESULTS:Among the 3 groups, the length and height of the condyle and superior portion of the lateral masses of the atlas (C1-LM) were smallest in CM + II-BI cases; the AOJ had the shallowest depth and the lowest curvature in the same group. AOJs were divided into 3 morphological types: type I, the typical ball-and-socket joint, mainly in the control group (100%); type II, the shallower joint, mainly in the CM group (92.9%); and type III, the abnormal flat-tilt joint, mainly in the CM + II-BI group (89.3%). Kinematic computed tomography revealed AOI in all III-AOJs (100%) and some II-AOJs (1.5%) but not in type I-AOJs (0%). Morphological parameters of the superior portion of C1-LM positively correlated with those of C0 and the clivus and significantly correlated with AOI.CONCLUSION:Dysplasia of the condyle and superior portion of C1-LM exists in both CM and II-BI cases yet is more obvious in type II-BI. Unstable movement caused by AOJ deformation is another pathogenic factor in patients with CM + II-BI.

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“…However, this theory does not address the question of asymptomatic cases or significant morphological evidence of changes in PCF (posterior fossa). Wan et al [ 41 ] believed that atlantooccipital instability caused the decline of cerebellar tonsils and contributed to nerve damage. However, the study did not explain the physiological link.…”

Section: Discussionmentioning

confidence: 99%

A Clinical Study on the Treatment of Recurrent Chiari (Type I) Malformation with Syringomyelia Based on the Dynamics of Cerebrospinal Fluid

Lou

Yang

et al. 2022

BioMed Research International

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Objective. Combining the dynamics of cerebrospinal fluid, our study investigates the clinical effects of syringomyelia after the combination of fourth ventricle-subarachnoid shunt (FVSS) for recurrent Chiari (type I) malformations after cranial fossa decompression (foramen magnum decompression (FMD)). Methods. From December 2018 to December 2020, 15 patients with recurrent syringomyelia following posterior fossa decompression had FVSS surgery. Before and after the procedure, the clinical and imaging data of these individuals were retrospectively examined. Results. Following FVSS, none of the 15 patients experienced infection, nerve injury, shunt loss, or obstruction. 13 patients improved dramatically after surgery, while 2 patients improved significantly in the early postoperative period, but the primary symptoms returned 2 months later. The Japanese Orthopedic Association (JOA) score was 12.67 ± 3.95 , which was considerably better than preoperatively ( t = 3.69 , P 0.001). The MRI results revealed that the cavities in 13 patients were reduced by at least 50% compared to the cavities measured preoperatively. The shrinkage rate of syringomyelia was 86.67% (13/15). One patient’s cavities nearly vanished following syringomyelia. The size of the cavity in the patient remain unchanged, and the cavity’s maximal diameter was significantly smaller than the size measured preoperatively ( P < 0.001 ) PC-MRI results indicated that the peak flow rate of cerebrospinal fluid at the central segment of the midbrain aqueduct and the foramen magnum in patients during systole and diastole were significantly reduced after surgery ( P < 0.05 ). Conclusion. After posterior fossa decompression, FVSS can effectively restore the smooth circulation of cerebrospinal fluid and alleviate clinical symptoms in patients with recurrent Chiari (type I) malformation and syringomyelia. It is a highly effective way of treatment.

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A morphometric study of the atlanto-occipital joint in adult patients with Chiari malformation type I

Cited by 7 publications

References 23 publications

A new hypothesis for the pathophysiology of symptomatic adult Chiari malformation Type I

A new hypothesis for the pathophysiology of symptomatic adult Chiari malformation Type I

Exploring the Pathogenesis of Atlanto-Occipital Instability in Chiari Malformation With Type II Basilar Invagination: A Systematic Morphological Study

A Clinical Study on the Treatment of Recurrent Chiari (Type I) Malformation with Syringomyelia Based on the Dynamics of Cerebrospinal Fluid

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