Thecal sac indentation
In plain language
A nearby structure presses an outline into the fluid-filled covering around the spinal cord or nerve roots.
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3 things to know first
- The thecal sac is a covering, not the nerve itself. An indentation does not prove nerve damage.
- The cause may be a disc or bone change. The report should identify what presses on it.
- Severity varies. A slight impression is different from substantial canal narrowing.
What it is
The thecal sac is a membrane containing spinal fluid around the cord and nerve roots. Indentation means a nearby structure changes its outline. A disc bulge, herniation, bone spur, or thickened ligament can make an impression.
Why it appears on your report
MRI or CT may show the sac flattened or displaced. The radiologist may say whether the cord or nerves themselves are contacted or compressed; that distinction is more important than the word indentation alone.
How serious is it
A small indentation may be incidental. More marked narrowing, cord compression, or corresponding neurological symptoms call for clinical review.
When to seek care urgently
Seek prompt care for progressive weakness, difficulty walking, saddle numbness, or new bladder or bowel dysfunction.
What usually happens next
- Identify the structure causing the indentation.
- Check whether nerves or cord are actually compressed.
- Compare findings with symptoms and discuss follow-up.
Further reading
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