thecal sac: meaning, definition, pronunciation and examples
Very Low (Specialist/Technical)Highly Technical/Specialist Medical
Quick answer
What does “thecal sac” mean?
The protective, fluid-filled membranous sheath that surrounds and encloses the spinal cord and spinal nerve roots.
Audio
Pronunciation
Definition
Meaning and Definition
The protective, fluid-filled membranous sheath that surrounds and encloses the spinal cord and spinal nerve roots.
A key anatomical structure in the spine; in medical imaging (especially myelograms and MRIs), its shape and the flow of cerebrospinal fluid within it are crucial for diagnosing spinal cord compression, stenosis, or other pathologies.
Dialectal Variation
British vs American Usage
Differences
No difference in meaning or usage. Spelling and pronunciation are consistent.
Connotations
Purely technical, anatomical term with no regional connotations.
Frequency
Identically low frequency, confined strictly to medical contexts (neurology, neurosurgery, radiology, orthopaedics).
Grammar
How to Use “thecal sac” in a Sentence
The thecal sac [verb: terminates/extends/is compressed] at L1/L2.MRI shows [adjective: effacement/compression] of the thecal sac.The [noun: nerve roots] lie within the thecal sac.Vocabulary
Collocations
Examples
Examples of “thecal sac” in a Sentence
adjective
British English
- the thecal sac impression was noted on the scan.
American English
- The thecal sac compression was evident at L4-L5.
Usage
Meaning in Context
Business
Not used.
Academic
Exclusively in medical and anatomical textbooks, lectures, and research papers.
Everyday
Virtually never used. A patient might hear it in a detailed consultation with a specialist.
Technical
The primary domain. Used in MRI/CT radiology reports, surgical notes, neurological assessments, and myelogram interpretations.
Vocabulary
Synonyms of “thecal sac”
Neutral
Weak
Vocabulary
Antonyms of “thecal sac”
Watch out
Common Mistakes When Using “thecal sac”
- Mispronouncing 'thecal' as /ˈθɛkəl/ (like 'technical' without the 'ni').
- Using it outside of a spinal/anatomical context.
- Confusing it with the 'dural mater' (the thecal sac is *formed by* the dura mater).
FAQ
Frequently Asked Questions
No. The thecal sac is the protective sheath *containing* the spinal cord, nerve roots, and cerebrospinal fluid.
Not directly. However, compression, inflammation, or distortion of the thecal sac can affect the nerves within it, leading to pain, tingling, or weakness (e.g., sciatica).
It is a radiological term meaning the normal contour of the fluid-filled sac is being flattened or indented, usually by a nearby structure like a herniated disc or bone spur, indicating potential pressure on the spinal contents.
In adults, it typically terminates at the level of the second sacral vertebra (S2), well below the end of the spinal cord proper (which ends around L1/L2).
The protective, fluid-filled membranous sheath that surrounds and encloses the spinal cord and spinal nerve roots.
Thecal sac is usually highly technical/specialist medical in register.
Thecal sac: in British English it is pronounced /ˈθiːkəl sæk/, and in American English it is pronounced /ˈθiːkəl sæk/. Tap the audio buttons above to hear it.
Learning
Memory Aids
Mnemonic
Think: 'The-Cal' sounds like 'The Call' – imagine the spinal cord getting 'the call' safely inside its protective sac.
Conceptual Metaphor
PROTECTIVE TUBE / FLUID-FILLED CONTAINER
Practice
Quiz
In which professional context are you most likely to encounter the term 'thecal sac'?