Diseased Filum Terminale as a Cause of Tethered Cord Syndrome in Ehlers-Danlos Syndrome: Histopathology, Biomechanics, Clinical Presentation, and Outcome of Filum Excision

Petra M Klinge; Vikas Srivastava; Abigail McElroy; Owen P Leary; Zahra Ahmed; John E Donahue; Thomas Brinker; Philippe De Vloo; Ziya L Gokaslan

doi:10.1016/j.wneu.2022.03.038

Diseased Filum Terminale as a Cause of Tethered Cord Syndrome in Ehlers-Danlos Syndrome: Histopathology, Biomechanics, Clinical Presentation, and Outcome of Filum Excision

World Neurosurg. 2022 Jun:162:e492-e502. doi: 10.1016/j.wneu.2022.03.038. Epub 2022 Mar 17.

Authors

Petra M Klinge¹, Vikas Srivastava², Abigail McElroy³, Owen P Leary³, Zahra Ahmed², John E Donahue⁴, Thomas Brinker⁵, Philippe De Vloo⁶, Ziya L Gokaslan³

Affiliations

¹ Department of Neurosurgery, Rhode Island Hospital, The Warren Alpert Medical School of Brown University, Providence, Rhode Island, USA. Electronic address: petra_klinge@brown.edu.
² Center for Biomedical Engineering and School of Engineering, Brown University, Providence, Rhode Island, USA.
³ Department of Neurosurgery, Rhode Island Hospital, The Warren Alpert Medical School of Brown University, Providence, Rhode Island, USA.
⁴ Department of Neuropathology, Rhode Island Hospital, The Warren Alpert Medical School of Brown University, Providence, Rhode Island, USA.
⁵ Department of Neurosurgery, Medical School Hannover, Hannover, Germany.
⁶ Department of Neurosurgery, University Hospitals Leuven, Leuven, Belgium.

PMID: 35307588
DOI: 10.1016/j.wneu.2022.03.038

Abstract

Background: Patients with hypermobile Ehlers-Danlos syndrome (hEDS), a heritable connective tissue disorder, present frequently with symptoms of tethered cord syndrome (TCS) but without a low-lying conus. Currently, surgical treatment of such cases is controversial. Because connective tissue disorder affects fibrous structures, we hypothesized that a diseased filum terminale (FT) might cause TCS in hEDS, justifying surgical transection for treatment.

Methods: We investigated FT pathology, FT biomechanics, clinical presentation, and outcome following FT excision in 78 radiologically occult hEDS-TCS cases and for comparison in 38 typical TCS cases with low-lying conus and/or fatty FT infiltration but without hEDS.

Results: In hEDS-TCS, electron microscopy revealed inherited collagen fibril abnormalities and acquired fibril damage. Biomechanical tension tests revealed elastic properties of the FT in both study groups, but they were impaired in the hEDS TCS. Follow-up examinations at 3 and 12 months after FT excision showed statistically significant improvement of urinary, bowel, and neurologic symptoms in both study groups; intergroup comparison revealed no differences in outcome except more pronounced neurologic improvement in the hEDS-TCS group.

Conclusions: Both morphologic findings and biomechanical tests indicate limited elastic properties of the FT in hEDS, which is no more able to dampen but still transmitting spine movement-related stretch forces. That mechanism exposes the conus medullaris to unphysiologic stretch forces, causing TCS, especially when considering the hypermobile spine in hEDS. This notion is supported by the observed clinical improvement following FT resection in hEDS-TCS cases without a low-lying conus.

Keywords: Biomechanical analysis; Connective tissue disorder; Ehlers-Danlos syndrome; Filum terminale pathology; Surgical outcome; Tethered cord syndrome.

MeSH terms

Biomechanical Phenomena
Cauda Equina* / diagnostic imaging
Cauda Equina* / pathology
Cauda Equina* / surgery
Ehlers-Danlos Syndrome* / complications
Ehlers-Danlos Syndrome* / surgery
Humans
Neural Tube Defects* / diagnostic imaging
Neural Tube Defects* / etiology
Neural Tube Defects* / surgery

Supplementary concepts

Ehlers-Danlos syndrome type 3