Lumbar foraminal stenosis
Lumbar foraminal stenosis or lumbar neuroforaminal stenosis is a common cause of back pain and/or radiculopathy, and is assessed for as part of the routine evaluation of lumbar MRI studies to determine what impact, if any, the surrounding structures have on the exiting nerve root.
Anatomy
In the lumbar spine, the structures surrounding the exiting nerve root and adjacent perineural epidural fat are:
- anterior: intervertebral disc and vertebral endplates/vertebral body
- posterior: ligamentum flavum and facet joint
- superior and inferior: pedicles
Grading
Most commonly, lumbar neuroforminal stenosis is graded as mild, moderate, severe, or normal (no stenosis). This, however, is not an arbitrary application of one's judgment but follows the guidelines below, initially published by Lee, et al as a modification of the Kunogi and Hasue classification .
- grade 0 (normal): fat surrounds the nerve root circumferentially
- grade 1 (mild): absence of perineural fat visualization in one dimension, either vertically or horizontally
- anteroposterior narrowing from ligamentum flavum thickening/buckling
- superoinferior narrowing from disc and/or osteophyte encroachment or disc height loss
- grade 2 (moderate): absence of perineural fat visualization circumferentially but without compression of the nerve root
- multidirectional enchroachment from degenerative facet hypertrophy, ligamentum flavum thickening/buckling, disc and/or osteophyte enchroachment, and/or disc hight loss
- grade 3: (severe): absence of perineural fat visualization with compression (morphologic change) of the nerve root
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