The thecal sac, enclosing the spinal cord and cauda equina, sits within a protective ring of bone consisting of the vertebral body anteriorly, and the pedicles, lamina, and spinous process posteriorly. The latter three structures form what is collectively referred to as the posterior arch.

Where is the thecal sac located?

Thecal sac is the outer covering of the spinal cord. This means there are bone spurs on the back of the spinal bones, putting pressure on or affecting the front part of the outer layer of the (neck) cervical spinal cord.

Where does the thecal sac begin?

It is the space within the thecal sac which extends from below the end of the spinal cord (the conus medularis), typically at the level of the first to second lumbar vertebrae down to tapering of the dura at the level of the second sacral vertebra.