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

Axial CT scan at the L5-Sl level in a 66-year-old patient with epidural lipomatosis shows low-attenuation fat surrounding the dural sac in the spinal canal; the sac shows Y-shaped or inverted triangular deformation (arrows). Disk bulge (anteriorly) and ligamenta flava (posterolaterally) lie peripheral to the fat.

MR imaging appearance of epidural lipomatosis in a 70-year-old patient. Axial T1-weighted MR image at the L4 level shows high-signal-intensity fat surrounding the dural sac in the spinal canal; the sac shows polygonal (stellar) deformation with spiculated contours (arrows).

MR imaging appearance of epidural lipomatosis in another 66-year-old patient. Axial T1-weighted MR image at the L5-S1 level shows high-signal-intensity fat surrounding the dural sac in the spinal canal; the sac shows Y-shaped or triangular deformation (arrows).

Macroscopic study in an adult spine.

A-C, Transverse sections of the lumbar spinal canal show median (arrow in A), bilateral paramedian (arrows in B), and lateral (arrows in C) locations of the meningovertebral ligaments in the anterior epidural space. The thecal sac (S) is collapsed by drawing the dura mater posteriorly with a thread.

Macroscopic study in an adult spine. Transverse sections of the lumbar spinal canal show different locations of the meningovertebral ligaments in the posterior epidural space.

A, Paramedian (arrow) and median (arrowhead) locations of meningovertebral ligaments. The thecal sac (S) is collapsed by drawing the dura mater forward with a thread.

B and C, Paramedian (arrow) and lateral (arrowheads) locations of meningovertebral ligaments. The thecal sac (S) is collapsed centrally.

Macroscopic study in an adult spine shows lateral location (arrow) of meningovertebral ligaments in the lateral epidural space (the dura mater is drawn laterally).

Distribution of the meningovertebral ligaments in the transverse plane in the 70 adult dissected lumbar vertebrae, with corresponding frequencies (numbers are percentages).

Microscopic study in a 27-week fetal spine shows relation of meningovertebral ligaments to dura mater and to spinal canal walls.

A, Photomicrograph (Goldner trichrome stain; original magnification, ×12) of a fetal spinal canal at the L1 level. Meningovertebral ligaments extend from the outer surface of the dura mater to the osteofibrous walls of the spinal canal in the lateral areas, representing perivascular bands (arrowheads), and in the median area of the posterior epidural space (arrow). The large box outlines the region of the epidural space that is magnified in B. The small box outlines the region that is magnified in C.

B, Magnified view (immunohistochemical stain for type I collagen) of the large box in A. The meningovertebral ligament anchors the dura mater (curved arrow) to the spinal canal (arrow) and surrounds small vascular structures (arrowhead).

C, Magnified view (immunohistochemical stain for type I collagen) of the small box in A. The meningovertebral ligament (arrowhead), mainly composed of type I collagen, is connected to the outer surface of the dura mater (arrow).

Microscopic study of meningovertebral ligament content in fetal spine. Photomicrograph (Goldner trichrome stain; original magnification, ×20) at the L1 level of a 27-week fetal spinal canal. The meningovertebral ligament (arrowhead) contains small vessels (arrow) (same observation as in adult spine in Fig 11).