Lumbar Disc herniation and nerve root compression with spondylolisthesis: It is rare for a herniated lumbar disc to occur at the level of the listhesis, however the disc may “roll” out as it is uncovered and produce findings on MRI that may resemble a herniated disc which has been termed a “pseudodisc.”
It is more common to see a herniated disc at the level above the listhesis.
If the listhesis does cause nerve root compression, it tends to involve the nerve exiting below the pedicle of the anteriorly subluxed upper vertebra (e.g. if an L4–5 spondylolisthesis causes nerve root compression, it will generally involve the L4 root). The compression is usually due to upward displacement of the superior articular facet of the level below together with disc material, and symptoms typically resemble neurogenic claudication, although true radiculopathy may sometimes occur.
There also may be a contribution from a fibrous/inflammatory mass from the nonunion.
Lumbar degenerative spondylolisthesis (DS) and Lumbar spinal canal stenosis (SPS) were originally described as separate pathoanatomic entities, though both cause narrowing of the spinal canal, compression of the nerve roots, and can lead to neurogenic claudication 1) 2).
Isthmic spondylolisthesis rarely produces central canal stenosis since only the anterior part of the vertebral body shifts forward. May present with radiculopathy or neurogenic claudication from compression in the neural foramen, with the nerve exiting under the pedicle at that level being the most vulnerable. May also present with low back pain. Many cases are asymptomatic.
Progression of spondylolisthesis may occur without surgical intervention, but is more common following surgery 3).
The nerve root compression within the foramina is the main problem in patients with spondylolisthesis who has radicular signs. Especially in patients who have degenerative spondylolisthesis or low-grade dysplastic type spondylolisthesis, foraminal stenosis gets worse in time due to disruption of the disc. The volume of the foraminal space starts to decrease when sliding of vertebra begins, and this decrease gets worse in time with destruction of the disc 5) 6).
Oblique films may demonstrate pars defects. Adding flexion/extension views can assess “dynamic“ in stability.
Degenerative spondylolisthesis with lumbar stenosis is a well-studied pathology and diagnosis is most commonly determined by a combination of magnetic resonance imaging (MRI) and standing plain lumbosacral x-rays. However, routine upright imaging is not universally accepted as standard in all practices.
Routine standing lateral radiographs should be standard practice in order to identify degenerative spondylolisthesis, as nearly 1/3 of cases will be missed on supine MRI. This may have implications on whether or not an arthrodesis is performed on those patients requiring lumbar decompression. Flexion-extension radiographs demonstrated no added value compared to standing lateral xrays for the purposes of diagnosing degenerative spondylolisthesis 8).
The presence of spondylolisthesis in patients with central lumbar spinal stenosis is a risk factor for lack of recovery, but not deterioration. The absence of therapeutic exercise was a risk factor for the progression of the disease 9).