What is a thecal sac?

Question

I just recieved my MRI report and it says, L4-5, Large right paracentral disk protrusion present INDENTING the thecal sac.This DOES compromise the anterior posterior dimension of the thecal sac.

L5-S1, Moderate to Large left paracentral disk protrusion. This DOES efface the left S1 nerve root.

What is the thecal sac and is it bad that it's being indented and compromised? Also, what does it mean to "efface" the left S1 nerve root?

Thanks!

Answer 1

Hi Kevin. The thecal sac is the connective tissue that surrounds the spinal cord. The report is saying that you have some compression of this outer part of the cord.

Effacement means 'touching', so the large disk protrusion at L5-S1 is touching the S1 nerve root.

Each of these findings indicates a significant problem. How significant the problem is depends entirely on your symptoms and the findings of a thorough physical examination - including a proper spinal examination, clinical orthopedic tests and clinical neurologic tests.

Best wishes and good luck.