Empty Thecal Sac Sign
→ It is when the thecal sac appears empty on MRI of the lumbar spine.
→ If it is +nt , a diagnosis of adhesive arachnoiditis can be made.
→ It is best seen on T2-weighted images.
→ MRI findings: It can be present throughout the subarachnoid space.
→ Most easily seen in lumbar region where cauda equina floats in ample CSF.