Can Disc Herniations Actually Be Worse Than The MRI Shows? Part II

Friday, July 8th, 2016
disc herniation

I want to preface this week’s entry by saying that I’ve had discussions on this topic with different medical radiologists before. My question, as stated in Part I of this series, was, “If a low back (or lumbar) disc is 4 mm herniated while laying down in an MRI tube, what happens when the patient then sits up and becomes weight-bearing? Will the herniation increase or be affected at all?”

All of them stated that they supposed it’s possible but not likely considering the strength of the disc itself. But, in my opinion, if the disc is thinned, degenerated, or weakened by injury or all of the above, then why wouldn’t extra pressure on the disc accentuate or increase the bulge or herniation?

That’s when I started searching PubMed for papers on this topic.

Continuing with Part II of this discussion, we’ll start with this study by DS Choy called “Magnetic resonance imaging of the lumbosacral spine under compression.

Why They Did It

Evidently sitting MRI imaging exists at Harvard and Zurich. Since most MRI machines can’t accomplish this sort of imaging, the author of the paper wanted to see if, in a regular machine, compression could be dependably added to the spine in order to duplicate the pressures found in the low back discs while people are in the seated position.

How They Did It

The author created a plywood compression frame that was able to be used in a standard MRI machine. When applied, the patient lying in the MRI machine would be subject to similar compression forces as those experienced when seated.

What They Found

They could reproduce the symptoms in 50% of the patients through the compression. Here’s the finding that led me to include this study in this discussion: the author was able to also reproduce “augmentation” or accentuate the disc herniation from applying the compression.

Wrap It Up

The compression applied allowed the author to reproduce the forces experienced when a person sits, it reproduced the symptomatology in half of the subjects, and the compression caused the disc to herniate further.

Choy DS, “Magnetic resonance imaging of the lumbosacral spine under compression.” J Clin Laser Med Surg. 1997;15(2):71-3.
http://www.ncbi.nlm.nih.gov/m/pubmed/9612180/?i=20&from=sitting%20disc%20herniation%20mri

Continuing with the second paper: it’s by Nowicki, et. al. called, “Occult lumbar lateral spinal stenosis in neural foramina subjected to physiologic loading,” from 1996.

Why They Did It

These authors were interested in how different positioning of the trunk affects the relationships of the bones and discs in regards to the neural structures in the same anatomic region. They also wanted to find out how disc degeneration responds to loading.

How They Did It

  • The authors used cadavers for this study and looked at each vertebral segment (L1 on L2 or S1 on L5 for example) via CT or MRI scans.
  • The study were done “loaded, frozen in situ, reexamined with CT, and sectioned with a cryomicrotome.”
  • The neural foramina (holes the spinal nerves run through) were classified as follows
    1. No evident stenosis
    2. Having stenosis
    3. Having occult stenosis
    4. Showing resolved stenosis
  • Also studied was “the effect of spinal level, disc type, and load type on the prevalence of stenosis.”

What They Found

The average finding in the paper were that extension, flexion, lateral bending, and rotation show contact or compression of the spinal nerve by the ligamentum flavum or disc in 18% of the neural foramina. Extension loading produced the most cases of nerve root contact. Disc degeneration significantly increased the prevalence of pain stenosis.

Wrap It Up

The authors concluded, “The study supports the concept of dynamic spinal stenosis; that is, intermittent stenosis of the neural foramina. Flexion, extension, lateral bending, and axial rotation significantly changed the anatomic relationships of the ligamentum flavum and intervertebral disc to the spinal nerve roots.”

Nowicki BH, et al., “Occult lumbar lateral spinal stenosis in neural foramina subjected to physiologic loading.” AJNR Am J Neuroradiol. 1996 Oct;17(9):1605-14.
http://www.ncbi.nlm.nih.gov/m/pubmed/8896609/?i=20&from=axial%20loaded%20disc%20MRI

So, we’re starting to understand that positioning and weight-bearing does indeed have an affect on the discs, the ligamentum flavum, and the neural structures present at each level. Here’s the last one we’ll cover this week in Part II called The diagnostic effect from axial loading of the lumbar spine during computed tomography and magnetic resonance imaging in patients with degenerative disorders. This one was published in the prestigious Spine journal.

Why They Did It

While imaging through CT or MRI scans is becoming more popular these days, they’re still done in the supine, or unloaded, position. Basically, people are lying down in a tube rather than sitting. The authors stated goal in this paper were to find out if there was any real value in imaging patients that had axial loads (simulated weight-bearing) applied in cases of degenerative spines.

How They Did It

  • Device was used to induce a load on the low back before imaging.
  • 172 patients were examined with compression applied.
  • 50 of those were imaged with CTs.
  • 122 of those subjects were imaged with MRIs.
  • Any changes in the major anatomy of the regions was noted.

What They Found

“Additional valuable information was found” in 50 of the original 172 participants. “A narrowing of the lateral recess causing compression of the nerve root was found at 42 levels in 35 patients at axial loading.”

Wrap It Up

There is certainly and frequently additional information that can be gathered for diagnostic purposes when the imaging is done with weigh-bearing loads applied. This included those with neurogenic claudication as a result of stenosis but also sciatica.

Willén J. et al., “The diagnostic effect from axial loading of the lumbar spine during computed tomography and magnetic resonance imaging in patients with degenerative disorders.” Spine (Phila Pa 1976). 2001 Dec 1;26(23):2607-14.
http://www.ncbi.nlm.nih.gov/m/pubmed/11725243/?i=14&from=axial%20loaded%20disc%20MRI

We’re starting to see a bit of a trend here I believe. We still have Part III and Part IV coming up in this series so make sure you don’t miss it.