Abstract
Purpose: Researchers have sought to better understand Chiari type I malformation (CMI) through morphometric measurements beyond tonsillar position (TP). Soft tissue and bone structures within the brain and craniocervical junction have been shown to be different for CMI patients compared to healthy controls. Yet, several morphological characteristics have not been consistently associated with CMI. CMI is also associated with different prevalent conditions (PCs) such as syringomyelia, pseudotumor, Ehlers-Danlos syndrome (EDS), scoliosis, and craniocervical instability. The goal of this study was two-fold: (1) to identify unique morphological characteristics of PCs, and (2) to better explain inconsistent results from case-control comparisons of CMI.Methods: Image, demographic, and PC information was obtained through the Chiari1000, a self-report web-accessed database. Twenty-eight morphometric measurements (MMs) were performed on the cranial MR images of 236 pre-surgery adult female CMI participants and 140 female healthy control participants. Custom software was used to measure 28 structures within the posterior cranial fossa (PCF) compartment, craniocervical junction, oral cavity, and intracranial area on midsagittal MR images for each participant.Results: Morphometric analysis of adult females indicated a smaller McRae line length in CMI participants with syringomyelia compared to those without syringomyelia. TP was reduced in CMI participants with EDS than those without EDS. Basion to posterior axial line was significantly longer in CMI participants with scoliosis compared to those without scoliosis. No additional MMs were found to differ between CMI participants with and without a specific PC. Four morphometric differences were found to be consistently different between CMI participants and healthy controls regardless of PC: larger TP and a smaller clivus length, fastigium, and corpus callosum height in CMI participants.Conclusion: Syringomyelia, EDS, and scoliosis were the only PCs that showed significant morphometric differences between CMI participants. Additionally, four midsagittal MR-based MMs were found to be significantly different between healthy controls and CMI participants regardless of the presence of one or more PCs. This study suggests that the prevalence of comorbid conditions are not strongly related to CMI morphology, and that inconsistent findings in the radiographic literature cannot be explained by varying prevalence of comorbid conditions in CMI study samples.
Highlights
Chiari type I malformation (CMI) is a complex neurological malformation within the brain that is diagnosed by a tonsillar position (TP) of at least five millimeters below the foramen magnum (FM), known as tonsillar ectopia (TE), in conjunction with a myriad of symptoms, including headache, paresthesia, gait disturbance, and sleep apnea amongst others
None of the related conditions (RCs) demonstrated group differences for posterior cranial fossa (PCF) height or area, or for any of the intracranial measurements when compared to controls
In an analysis of sub-groupings of CMI participants similar to those described by Milhorat et al (2010), we found that classical CMI participants demonstrated a significantly smaller clivus length compared to controls, a finding that replicates Milhorat et al (2010)
Summary
Chiari type I malformation (CMI) is a complex neurological malformation within the brain that is diagnosed by a tonsillar position (TP) of at least five millimeters below the foramen magnum (FM), known as tonsillar ectopia (TE), in conjunction with a myriad of symptoms, including headache, paresthesia, gait disturbance, and sleep apnea amongst others. Previous studies have found associations with CMI and bone structures of the posterior cranial fossa/skull base, and the craniocervical region such as basilar invagination, small posterior cranial fossa (PCF), abnormal segmentation of the odontoid process, and a short clivus bone (Sahuquillo et al, 1994; Nishikawa et al, 1997; Milhorat et al, 1999, 2010; Besachio et al, 2015; Houston et al, 2017) These differences in soft tissue and bony structures within the PCF and upper cervical spinal canal have been suggested to result in symptoms related to lower brainstem and upper cervical cord compression (Sinclair et al, 2002)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
