Abnormal spinal cord motion at the craniocervical junction in hypermobile Ehlers-Danlos patients

Abstract

OBJECTIVE The craniocervical junction (CCJ) is anatomically complex and comprises multiple joints that allow for wide head and neck movements. The thecal sac must adjust to such movements. Accordingly, the thecal sac is not rigidly attached to the bony spinal canal but instead tethered by fibrous suspension ligaments, including myodural bridges (MDBs). The authors hypothesized that pathological spinal cord motion is due to the laxity of such suspension bands in patients with connective tissue disorders, e.g., hypermobile Ehlers-Danlos syndrome (EDS). METHODS The ultrastructure of MDBs that were intraoperatively harvested from patients with Chiari malformation was investigated with transmission electron microscopy, and 8 patients with EDS were compared with 8 patients without EDS. MRI was used to exclude patients with EDS and craniocervical instability (CCI). Real-time ultrasound was used to compare the spinal cord at C1–2 of 20 patients with EDS with those of 18 healthy control participants. RESULTS The ultrastructural damage of the collagen fibrils of the MDBs was distinct in patients with EDS, indicating a pathological mechanical laxity. In patients with EDS, ultrasound revealed increased cardiac pulsatory motion and irregular displacement of the spinal cord during head movements. CONCLUSIONS Laxity of spinal cord suspension ligaments and the associated spinal cord motion disorder are possible pathogenic factors for chronic neck pain and headache in patients with EDS but without radiologically proven CCI.

The relationship between compensatory hyperplasia of the myodural bridge complex and reduced compliance of the various structures within the cranio‐cervical junction

“…Their hypothesis suggests that the suboccipital muscles contract excessively and involuntarily to compensate for atlanto‐axial or atlanto‐occipital joint instability in some patients with CMI. These contractions of the suboccipital muscles would lead to mechanical overload of MDBC and further cause failure of the MDBC to function normally (Klinge et al, 2021 ). Therefore, the mechanical properties of the SDM would be changed such as with increased stiffening and decreased compliance, which would alter CSF circulation over time.…”

Craniocervical Instability in Ehlers-Danlos Syndrome—A Systematic Review of Diagnostic and Surgical Treatment Criteria

“…36 Distinct observations were made by Klinge et al, who identified laxity of spinal cord suspension ligaments and associated spinal cord motion disorder as possible pathogenic factors for chronic neck pain and headache in patients with EDS, however, without radiologically proven CCI. 37 Even though 4 of the included case series state a clear improvement of the patient's symptoms after cervical instrumentation, a definite clinico-anatomical association is pending. Furthermore, there has been no method described to date which allows pre-operative assessment of the most probable neurological outcome response after the surgery.…”

“… 36 Distinct observations were made by Klinge et al, who identified laxity of spinal cord suspension ligaments and associated spinal cord motion disorder as possible pathogenic factors for chronic neck pain and headache in patients with EDS, however, without radiologically proven CCI. 37 …”

Presentation and physical therapy management of upper cervical instability in patients with symptomatic generalized joint hypermobility: International expert consensus recommendations

“…There are multiple comorbidities and differential diagnoses with signs and symptoms that overlap those of UCI ( Table 10 ). Some may be more common in people with S-GJH due to excessive motion or abnormal tissue characteristics (e.g., Chiari malformation, dysfunctional myodural bridges, tethered cord) ( 45 , 46 ). Prevalence of Low, Moderate, and High Irritability UCI is unknown.…”