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AJNR - American Journal of Neuroradiology

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American Journal of Neuroradiology 24:1276-1282, August 2003
© 2003 American Society of Neuroradiology

SPINE

Polygonal Deformation of the Dural Sac in Lumbar Epidural Lipomatosis: Anatomic Explanation by the Presence of Meningovertebral Ligaments

Caroline Geers^a, Frédéric E. Lecouvet^b, Catherine Behets^a, Jacques Malghem^b, Guy Cosnard^b and Benoít G. Lengelé^a

^a Human Anatomy Research Unit, St. Luc University Hospital, Université Catholique de Louvain, Brussels, Belgium
^b Department of Radiology and Medical Imaging, St. Luc University Hospital, Université Catholique de Louvain, Brussels, Belgium

Address reprint requests to Frédéric E. Lecouvet, MD, PhD, Department of Radiology and Medical Imaging, St. Luc University Hospital, Hippocrate Ave, 0/2942, B-1200 Brussels, Belgium

BACKGROUND AND PURPOSE: In patients with epidural lipomatosis, axial lumbar spine CT and MR images occasionally reveal a geometric, polygonal or stellar, shape of the dural sac. The purpose of this study was to define the anatomic structures responsible for this radiologic appearance. We hypothesized that meningovertebral ligaments could anchor the dura mater to the osteofibrous walls of the spinal canal and account for the geometric deformation of the dural sac.

METHODS: The epidural spaces were examined in 15 adult cadaveric and seven aborted fetal lumbar spines. For macroscopic studies, 70 adult vertebral segments were separated and dissected by removing the extradural fat. For microscopic examination, axial histologic sections were obtained from 35 fetal and five adult undissected vertebral segments.

RESULTS: Meningovertebral ligaments were observed in the median, paramedian, and lateral aspects of the anterior and posterior epidural spaces of both adult and fetal lumbar spines. These ligaments anchor the outer surface of the dura mater to the osteofibrous walls of the lumbar canal. They may form an irregular longitudinal septum partitioning the epidural space. Histologic examination demonstrated the fibroelastic composition of these ligaments and suggested their possible perivascular morphogenetic origin.

CONCLUSION: The morphologic and topographic features of the meningovertebral ligaments explain the polygonal, stellar, or Y-shaped deformation of the dural sac observed on axial CT and MR images in patients with lumbar epidural lipomatosis.