Central Canal Stenosis¶
Definition¶
Central canal stenosis is a narrowing of the central spinal canal, and can result in in compression of the spinal cord (cervical and thoracic) or the cauda equina (lumbar). It is the most clinically significant form of spinal stenosis and the primary indication for decompressive surgery.
Causes¶
- Disc bulging/herniation — narrows the canal anteriorly
- Ligamentum flavum hypertrophy — narrows the canal posteriorly
- Facet hypertrophy — narrows the canal posterolaterally
- Spondylolisthesis — narrows the canal dynamically as one vertebra slides forward
- Congenitally short pedicles — reduced baseline canal diameter
- OPLL — narrows the canal anteriorly (cervical spine)
- Epidural collections - can result in cord compression
- Tumors/masses - can result in cord compression depending on location
Imaging Findings¶
Measurements¶
| Region | Normal AP Diameter | Relative Stenosis | Absolute Stenosis |
|---|---|---|---|
| Cervical | 14–23 mm | <13 mm | <10 mm |
| Lumbar | 15–27 mm | <12 mm | <10 mm |
| Lumbar cross-sectional area | >100 mm² | 75–100 mm² (moderate) | <75 mm² (severe) |
MRI¶
- Sagittal T2: effacement of the CSF column at the stenotic level; cord compression or cauda equina crowding
- Axial T2: loss of CSF signal around neural elements; trefoil canal shape with combined anterior and posterior compression
- Cord signal change: T2 hyperintensity in the cord indicates myelopathy (cervical/thoracic)
Clinical Pearl
In the lumbar spine, the cross-sectional area of the dural sac on axial MRI is the most reliable measurement for grading central stenosis. AP diameter alone can be misleading because lateral stenosis from facet hypertrophy can significantly reduce the functional canal area without dramatically changing the AP measurement. Always assess the overall canal morphology, not just a single dimension.
Key Points¶
- Central stenosis compresses the cord (cervical/thoracic) or cauda equina (lumbar)
- Usually multifactorial — disc + ligamentum flavum + facets
- Cross-sectional area on axial MRI is the most reliable measurement
- Cord T2 signal change indicates myelopathy and is an important prognostic marker
- Absolute stenosis (<10 mm AP) is almost always clinically significant
References¶
- Schizas C, Theumann N, Burn A, Tansey R, Wardlaw D, Smith FW, Kulik G. Qualitative grading of severity of lumbar spinal stenosis based on the morphology of the dural sac on magnetic resonance images. Spine (Phila Pa 1976). 2010;35(21):1919-1924. PMID: 20671589. https://pubmed.ncbi.nlm.nih.gov/20671589/
- Ko YJ, Lee E, Lee JW, Park CY, Cho J, Kang Y, Ahn JM. Clinical validity of two different grading systems for lumbar central canal stenosis: Schizas and Lee classification systems. PLoS One. 2020;15(5):e0233633. PMID: 32459814. https://pubmed.ncbi.nlm.nih.gov/32459814/
- Seo J, Lee JW. Magnetic Resonance Imaging Grading Systems for Central Canal and Neural Foraminal Stenoses of the Lumbar and Cervical Spines With a Focus on the Lee Grading System. Korean J Radiol. 2023;24(3):224-234. PMCID: PMC9971835. https://pmc.ncbi.nlm.nih.gov/articles/PMC9971835/
- Steurer J, Roner S, Gnannt R, Hodler J. Quantitative radiologic criteria for the diagnosis of lumbar spinal stenosis: a systematic literature review. BMC Musculoskelet Disord. 2011;12:175. PMCID: PMC3161920. https://pmc.ncbi.nlm.nih.gov/articles/PMC3161920/
- Premchandran D, Saralaya VV, Mahale A. Predicting Lumbar Central Canal Stenosis – A Magnetic Resonance Imaging Study. J Clin Diagn Res. 2014;8(11):RC01-RC05. PMCID: PMC4290304. https://pmc.ncbi.nlm.nih.gov/articles/PMC4290304/
- Munakomi S, Cruz R. Lumbar Spinal Stenosis. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; updated 2024. https://www.ncbi.nlm.nih.gov/books/NBK531493/
- Lumbar spinal canal stenosis grading systems by Lee and Schizas. Radiopaedia. https://radiopaedia.org/cases/lumbar-spinal-canal-stenosis-grading-systems-by-lee-and-schizas