Lumbar disc herniation – foraminal and extraforaminal
Foraminal and extraforaminal lumbar disc herniations:
are less commonly seen than central/posterolateral disc herniations
contribute to compression of the exiting nerve root at the index level
typically manifest with radiculopathy and focal sensorimotor deficits
Due to dorsal root ganglion compression, the quality of the pain may be different from that seen with central or posterolateral disc herniations; burning, dysesthetic pain sensation. Lower mechanical back pain can also occur when there is a component of segmental instability, which contributes to nerve compression.
Extraforaminal lumbar disc herniations are also referred to as far lateral disc herniations.
The intervertebral disc is built up of a thick collagen-rich annulus fibrosis (AF) containing a gelatinous proteoglycan-rich nucleus pulposus (NP).
Tears or weakening of the AF can result from degenerative changes or trauma and result in bulging or expulsion of NP material, leading to compression of surrounding neural structures.
The consequences of disc herniation will depend on the neural structures at the location of the disc herniation.
Six different types of disc pathologies can be seen:
Bulge (without herniation)
Protrusion (prolapse): the displaced material is less than the base of the displaced material
Contained extrusion: the displaced material is wider than the base of the displaced material, and annular fibers are intact
Uncontained/defect extrusion: materials extrude beyond an annular defect
Sequestration – discontinuous with native disc
Pseudoherniation – the appearance of a bulging disc due to spondylolisthesis. Note that the disc material does not extend posterior to the posterior spinal line.
Protrusion, extrusion, and sequestration are collectively referred to as disc herniations.