Comparison of Brain Morphology for Chiari I Malformation Subjects With and Without Ehlers-Danlos Syndrome


Many patients with Chiari malformation type I (CM) also have Ehlers-Danlos syndrome (EDS). EDS is characterized as a connective tissue disorder with patients diagnosed demonstrating joint hypermobility and recurrent joint dislocations. Our Chiari1000 database shows that 9.4% of the CM subjects also have EDS (CM+EDS).  In addition, 26% score high (>4) on a hypermobility index (Beighton Scale). While there are differences between the biomechanical properties of connective tissue for people with CM+EDS and CM without EDS (CMEDS), it is unclear if this translates to differences between brain morphology for CM+EDS compared to CMEDS.


Midsagittal morphological characteristics of CM+EDS patients were evaluated by comparing 50 morphological measurements (MMs) within the intracranial and craniocervical regions on 245 adult female CM subjects with (n=31) and CMEDS (n=214). Morphological differences were determined using a two-tailed independent t-test and a Mann-Whitney u-test.


Cerebrospinal fluid area (CSF) below the foramen magnum anterior and posterior to the brainstem was 14% and 24% larger respectively in CM+EDS compared to CMEDS (p < 0.001, Cohen’s d > 0.5).  Average tonsillar position was smaller for CM+EDS compared CMEDS (5.3 and 7.8 mm, respectively with p < 0.05, Cohen’s d > 0.47). However, 35 of the 50 MMs showed less than 3% difference between the two groups.

Discussion and Conclusions

While most of the 50 MMs were not different between CM+EDS and CMEDS groups, a trend was observed of reduced crowding in CM+EDS patients within the craniocervical region compared to CM-EDS. Overall, the morphometrics for CM+EDS subjects was not markedly different when compared to CMEDS cases.