Central Stenosis is narrowing of the spinal canal around the thecal sac that contains the cauda equina. This is caused by facet joint problems (arthrosis or hypertrophy), thickening of the LF, bulging of the disk, and spondylolisthesis.
Lateral Stenosis is encroachment of the spinal nerve on the lateral side of the spinal canal. This can be cause by facet hypertrophy, loss of disk height, disk bulging, or spondylolisthesis.
Foraminal stenosis is narrowing of the foramen in which the nerve root exits and enters the spinal cord.