Anatomy of the extradural compartments of the lumbar spinal canal - Peridural membrane and circumneural sheath

There is a fibrovascular membrane encircling the dura called the peridural membrane which is of importance because hematoma can seep into the area anterior to this membrane and have a very similar appearance on myelography, CT or MRI to an extruded nuclear fragment. Often these patients are subjected to surgery and nothing is found. The reason this is important is that if left alone these hematomata will resolve spontaneously. This membrane divides the anterior extradural area into two potential spaces, the epidural space and the premembranous space. It continues on out through the bony/intervertebral canals as the circumneural sheath encircling the spinal nerves for as much as 10 cm.