Types of disc lesions

Image a:

Is an example of the normal lumbar disc, look to its posterior border, it should be concave posteriorly.

Image b:

Is an example of disc bulge, where the disc is protruded posterior along its posterior edge, this mean diffuse bulge and not a focal bulge.

Image c and d:

Is example of disc herniation where there is a tear in the annulus fibrosus resulting in herniation of the nucleus pulposus in a focal manner.

Image e:

Is an example of sequestration, where a part of the herniated disc is separated from the rest.

Disc bulge means that the disc is protruded backward along the length of the posterior surface of the vertebra without tearing of the annulus fibrosus.

While disc herniation, means tear in the annulus fibrosus followed by herniation of the material of the nucleus pulposus through this defect.

While sequestration means that part of the herniated disc is broken and becomes separately.

Normally, the lumbar disc should be concave posteriorly to evaluated as a normal disc.

In case of lumbar disc lesion, you should find the posterior border of the lumbar disc straight or convex posteriorly.

Normally, the disc space between L5-S1 is holding high pressure from the weight of the body, so it is accepted to see the posterior border of the disc convex posteriorly, in this case go to the next slice and see if it is still convex or not, if it is still convex you can diagnose disc lesion, if not consider it normal.

In case of cervical disc, normally you should not see any disc material posterior to the edge of the vertebra, if you see this appearance, you can diagnose cervical disc lesion.

Any way, you should differentiate between disc bulge and disc herniation as mentioned above.