Lumbar Stenosis - Canal and Foraminal Stenosis Grading



How do we tell if the nerves have enough room? We look at the space around them. For the canal, it is CSF- if there's enough room, extra space will be filled by CSF.  For foramina, it is fat—extra room is filled by fat.



Lumbar Canal Stenosis:

 • For mild canal stenosis, there is mild attenuation of the CSF space, but there is still plenty of CSF around.

 • For moderate canal stenosis, the canal starts closing in, so there is less CSF around and the nerve roots appear aggregated.

 • For severe canal stenosis, the canal doesn’t just hug up to the nerve roots, it compresses them.



Lumbar Foraminal Stenosis - For foraminal narrowing, the nerve inside the foramen has fat around it on four sides that can be attenuated as the space gets tighter. How many sides are attenuated determines how severe the stenosis is.

 • Mild stenosis is where you have loss of the fat on 2 sides.  Because the fat is preserved on the other two sides, so you still have lots of space.

 • For moderate stenosis, you lose the space on all four sides, but the nerve itself is not compressed or deformed.

 • For severe stenosis, the fat isn’t just gone, the nerve is compressed and deformed.



By Lea Alhilali, MD @teachplaygrub



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