The fine anatomy of the human spinal meninges

TLDR

The study examined five post‑mortem human spinal cords (ages 15 months–46 years) within 12 h of death, using scanning electron microscopy and light microscopy on transverse, dorsal, and ventral sections to detail meningeal structure. The arachnoid mater was tightly apposed to the dura, an intermediate fenestrated leptomeningeal layer attached to the inner arachnoid formed dorsal septa and became highly fenestrated laterally while remaining distinct from pia and arachnoid, the pia formed a continuous layer coating vessels, dentate ligaments had a collagenous core continuous with subpial tissue and were coated by pia‑arachnoid cells, and overall the spinal meninges’ fine anatomy differs markedly from that of other mammals.

Abstract

✓ The fine anatomy of the human spinal meninges was examined in five postmortem spinal cords taken within 12 hours after death from patients aged 15 months to 46 years. Specimens of spinal cord were viewed in transverse section and from the dorsal and ventral aspects by scanning electron microscopy. Transverse sections of spinal cord and meninges were also examined by light microscopy. The arachnoid mater was seen to be closely applied to the inner aspect of the dura. An intermediate fenestrated leptomeningeal layer was observed attached to the inner aspect of the arachnoid mater and was reflected ventrally to form a series of dorsal septa. As it arborized laterally over the surface of the cord to surround nerves and blood vessels, the intermediate layer became highly fenestrated but remained distinct from the pia and arachnoid mater. The pia mater appeared to form a continuous layer which was reflected off the surface of the cord to coat blood vessels within the subarachnoid space in a manner similar to that described in the leptomeninges over the human cerebral cortex. Each dentate ligament consisted of a collagenous core which was continuous with the subpial connective tissue and was attached at intervals to the dura; pia-arachnoid cells coated the surface of the dentate ligaments. The present study suggests that the fine anatomy of the human spinal meninges differs significantly from that described in other mammals.