Empty thecal sac sign

Last revised by Mostafa Elfeky on 24 Oct 2021

Citation, DOI, disclosures and article data

Citation:

Millner T, Elfeky M, Nocoń K, et al. Empty thecal sac sign. Reference article, Radiopaedia.org (Accessed on 16 Apr 2024) https://doi.org/10.53347/rID-14052

DOI:

https://doi.org/10.53347/rID-14052

Permalink:

https://radiopaedia.org/articles/14052

rID:

14052

Article created:

19 Jun 2011, Tom Millner

Disclosures:

At the time the article was created Tom Millner had no recorded disclosures.

View Tom Millner's current disclosures

Last revised:

24 Oct 2021, Mostafa Elfeky ◉

Disclosures:

At the time the article was last revised Mostafa Elfeky had no recorded disclosures.

View Mostafa Elfeky's current disclosures

Revisions:

12 times, by 10 contributors - see full revision history and disclosures

Systems:

Central Nervous System, Spine

Sections:

Signs

Tags:

neuroradiology, spine, cases

Synonyms:

Empty sac sign
Empty theca sign

The empty thecal sac sign or empty sac sign is when the thecal sac appears empty on MRI of the lumbar spine, best seen on T2-weighted images. If the empty thecal sac sign is present, a diagnosis of adhesive arachnoiditis can be made.

Radiographic features

MRI

There is usually no gadolinium contrast enhancement. Delamarter et al. ¹ described three categories of MRI appearances consistent with chronic adhesive arachnoiditis. Groups 1 and 2 were mild and group 3 severe. Groups 1 and 2 were consistent with adhesions developing between nerve roots and the parietal arachnoid.

The adherent nerve roots were seen centrally within the CSF in group 1. Whilst in group 2 the nerve roots were adherent peripherally to the theca, which leads to the appearance of an empty thecal sac.