The Lee classification is used to classify lumbar spinal canal stenoses into four grades based on the axial T2 sequences in MRI imaging and was published in 2011[^1].

Classification

Lee Grade	Description	Assessment
Grade 0	The anterior cerebrospinal fluid space is not obliterated.	No stenosis
Grade 1	The anterior cerebrospinal fluid space is mildly obliterated, but all cauda equina can be clearly separated from each other	Mild stenosis
Grade 2	The anterior CSF space is moderately obliterated and some of the cauda equina are aggregated (impossible to visually separate)	Moderate stenosis
Grade 3	The anterior CSF space is severely obliterated so as to show marked compression of the dural sac and the cauda equina appears as one bundle (none can be visually separated from each other)	Severe stenosis

Figure