Understanding Epidural Fibrosis: Spinal Nerve Root Scarring

TSpineVertebrae.jpg
Thoracic Spine. creative commons

When you get a back surgery, my guess is that once it's over, the last thing you're anticipating is another problem. Unfortunately, almost any surgery comes with the risk for complications, which in turn may give you pain or other symptoms after the fact. One such complication of spine surgery is epidural fibrosis, or scarring at the surgery site.

What Is Epidural Fibrosis?

Epidural fibrosis is the name given to scarring that occurs after a back surgery.

It is one of several possible causes of a condition known as failed back surgery syndrome (acronym: FBSS.) Epidural fibrosis is perhaps the most common cause of them all; it occurs in up to 91 percent of post-back surgery patients.

But there's good news: Epidural fibrosis does not always result in pain or other symptoms. In fact, for some people, it doesn't affect their daily lives or pain levels at all. A 2015 study published in the journal Insights Imaging found that the question as to whether or not symptoms appear may be related to how widespread the scarring is.

Another 2015 study, this time published in the Asian Spine Journal, found that epidural fibrosis may cause pain in up to 36 percent of people with failed back surgery syndrome. And while 36 percent is a sizable proportion of patients, it's a far cry from 91 percent.

Epidural fibrosis is similar to but a completely different diagnosis than arachnoiditis.

 First, epidural fibrosis affects the outermost covering of the spinal cord (the dura mater,) whereas arachnoiditis goes a layer deeper into the arachnoid membrane. Like the dura mater above it (and the pia mater beneath) the arachnoid surrounds and protects the sensitive nerves that comprise the spinal cord.

Another difference is that epidural fibrosis is caused by a back surgery; but back surgery is only one of a number of possible causes of arachnoiditis. And finally, inflammation can be what causes the scar tissue to form, which then may lead to clumping of the spinal nerves—a very painful and difficult to treat condition.

How Epidural Fibrosis Forms

What actually happens to your spine when you get epidural fibrosis? This answer, generally, is related to an area of your spine called the spinal nerve root.

Most surgeries given for back and leg pain are either a laminectomy (also called decompression surgery) or a discectomy. Both procedures are designed to relieve the pressure on the spinal nerve root as it exits the spinal cord. (Injuries such as herniated disc, as well as degenerative changes in the spine itself can result in various structures—such as fragmented disc pieces or bone spurs pressing on, and irritating, the nerve root.) What this means is that most of the time, a spine surgeon will be working near the area of your nerve root.

Because she'll be focusing on removing things (the disc fragments that don't belong there or the bone spurs that are getting too close to the nerve), she'll necessarily be excising them with a sharp implement. Because of this, a wound will be created as part of your surgery.

Scarring is a natural response to any type of wound that disrupts a body structure, and the area around your spinal nerve root during a surgery is no exception. The process is similar what happens when you scrape a knee; in other words, the development of the epidural fibrosis is comparable to the scab that forms on your knee after the initial injury. The scab, and the epidural fibrosis, are natural healing processes.

Epidural scarring generally happens between 6 and 12 weeks after the surgery.

Epidural Fibrosis: A Deeper Look

Let's dig a little deeper to understand this healing process as it applies to your disectomy or laminectomy. After a back surgery, number of things can happen under the hood, so to speak.

First, one of the three coverings of your spinal cord (the outermost covering which is called the "dura mater") can become compressed. Second, one or more of your nerve roots may become "tethered" (i.e., tied up.) And third, due to either or both of these things, the blood supply to the nerve root and/or cerebral spinal fluid becomes impeded. The cerebrospinal fluid, also known as CSF, is a clear, watery liquid that circulates between the brain and spinal cord at the level between the arachnoid mater and the pia mater. Its job is to cushion and protect the structures of the central nervous system (which is made of only the brain and spinal cord) from impact.

As of 2016, researchers are still debating how, and even if, scarring on or near the spinal nerve root corresponds to pain and other symptoms you might tell your doctor about after your back surgery. The article in the Asian Spine Journal mentioned above found that some study authors say no—the two don't relate at all. But others, the Asian Spine Journal reports, have concluded that widespread scarring in and around the nerve root (as opposed to fibers that are pinpointed in just one area) do have a relationship to symptoms and pain. 

Ether way, once the scars form, there's no genuinely effective treatment. Your surgeon may want to go back in and break up the scars with an endoscope, but this actually can result in more scarring and epidural fibrosis.

For this reason, the best way to treat epidural fibrosis is to prevent it, or at least to reduce the formation of the scar.

The way in which that can be done is currently, as of 2016, being worked out in research studies, mostly on animals rather than humans. These studies test drugs or materials mainly on rats, and then compare the tissues with those of a control group (rats that don't get the drugs or materials applied to them.)

The Degree of Epidural Fibrosis Matters

One thing that science has correlated to symptoms and pain is the degree of the fibrosis. Epidural fibrosis can be graded from 0, which represents normal tissue that has no scarring at all to Grade 3. Grade 3 is a case of severe fibrosis, with scar tissue that takes up more than 2/3 of the area that was operated on (in the case of a laminectomy.) A Grade 3 scar may also extend to the nerve root, whereas Grades 1 and 2 do not. Grade 3 scars correspond to symptoms and pain more than do Grades 1 and 2. 

Grade 1 scars tend to be mild, and made up of thin fibrous bands that are laid down over the dura mater, which is the outermost spinal cord covering described above. Grade 2 scars are moderate, continuous, and they take up less than 2/3 of the laminectomy area. Once a scar has reached Grade 2, it is continuous, meaning few if any individual strands are detectable.

Diagnosis of Epidural Fibrosis

Your doctor may order an MRI to diagnose any epidural fibrosis you may have. The problem is, many times, the scarring cannot be seen with this type of diagnostic imaging test. So if you have symptoms, and the MRI comes back negative, you may also need to get an epiduroscopy.

An epiduroscopy is a test in which a probe, or scope, is inserted into the troubled area to allow your surgeon to see what's going on at your nerve root. It's important to take the diagnostic process this far because your pain may actually be due to another disc herniation, rather than to epidural fibrosis. In this case you'd likely need another surgery; but if the epiduroscopy results shows scarring, and the scarring is what is causing your symptoms, chances are you won't need that 2nd surgery.

Epidural Fibrosis and Nerve Root Scarring Treatment

You may be wondering: If follow up surgery is not likely to relieve your epdiural fibrosis pain, what do you do?

As I mentioned earlier in this article, scientists and doctors have yet to come up with an effective treatment for this particular cause of failed back surgery syndrome. In general, though, medication is given at first—often in conjunction with physical therapy. The medication will likely help with the pain as well as make exercise tolerable. Medications given include Tylenol (acetaminophen,) NSAIDs (non-steroidal anti-inflammatory pain medication,) gabapentinoids, and others.

Physical therapy is designed to keep you mobile and may consist of strengthening, stretching and core exercise. Staying mobile in your joints may help limit the formation of the scar tissue.

As far as surgery goes, one study reports that it generally has only a 30 percent to 35 percent success rate. Not only that, but the same study says that the symptoms of up to 20 percent of patients actually worsen. That said, the two main surgical treatments given for epidural fibrosis are percutaneous adhesiolysis and spinal endoscopy.

So far, percutaneous adhesiolysis has the best evidence behind it. In this procedure, which, by the way, is used for other causes of failed back surgery syndrome as well, medicine, often steroidal medication, is injected into the area by means of an inserted catheter. Also with this procedure, mechanical break up of the scars is not necessary for relief of symptoms.

Percutaneous adhesiolysis is backed by Level I evidence (the highest quality) as to its effectiveness for failed back surgery syndrome symptoms in general, which includes epidural fibrosis.

Another treatment that your doctor may suggest is spinal endoscopy. In this procedure, a scope that allows your doctor to visualize the area is inserted. Sometimes lasers are used to treat the scars while the scope is in there. Spinal endoscopy is rated as Level II and III evidence, and one study has found found it to have "fair" evidence for relieving symptoms.

Source: 

Coskun E., Süzer T., Topuz O., Zencir M., Pakdemirli E., Tahta K. Relationships between epidural fibrosis, pain, disability, and psychological factors after lumbar disc surgery. Eur Spine J. June 2000. https://www.ncbi.nlm.nih.gov/pubmed/10905440

Helm S., Racz G., Gerdesmeyer L., Justiz R., Hayek S., Kaplan E., Terany M., Knezevic N. Percutaneous and Endoscopic Adhesiolysis in Managing Low Back and Lower Extremity Pain: A Systematic Review and Meta-analysis. Pain Physician. Feb. 2016. https://www.ncbi.nlm.nih.gov/pubmed/26815254

Helm S., Hayek S., Colson J., Chopra P., Deer T., Justiz R., Hameed M., Falco F. Spinal endoscopic adhesiolysis in post lumbar surgery syndrome: an update of assessment of the evidence. Pain Physician. April 2013. https://www.ncbi.nlm.nih.gov/pubmed/23615889

Masopust V., Häckel M., Netuka D., Bradác O., Rokyta R., Vrabec M. Postoperative epidural fibrosis. Clin J Pain. Sept. 2009. https://www.ncbi.nlm.nih.gov/pubmed/19692802

Mohi E., Abdel R. Epidural Fibrosis after Lumbar Disc Surgery: Prevention and Outcome Evaluation. Asian Spine J. Jun 2015. https://www.ncbi.nlm.nih.gov/pubmed/26097652

Continue Reading