Epidural Steroid Injections | Selective Nerve Root Blocks

Injections in the cervical and lumbar spines have long been used to both diagnose and treat nerve irritation, canal stenosis and disc pain. These injections can be very helpful even in the long term to yield spine and extremity pain relief. Below, a detailed discussion is offered on epidural injections and selective nerve root blocks–diagnostic and therapeutic.

Difference between epidural steroid injections (ESI) and selective nerve root blocks (SNRB)

The difference between epidural steroid injections (ESI) and selective nerve root blocks (SNRB) requires going back to anatomy. The dura is the membrane inside the spinal canal which makes up the long tube from the brain to the tailbone. This dural sac contains the nerves and the cerebrospinal fluid or CSF. The nerves then branch out from this sac like tree branches (one on each side) at every level to exit the spinal canal (see the anatomy section).

The Latin term “epi” means “above” so an epidural injection is an injection above the dura. This injection is normally placed around the center of the neck or back and the medication is deposited on top of the dura. The SNRB puts medication at the nerve root branch from the spine in the area called the foramen. With a small volume, only the exiting nerve root can be targeted. With a larger volume, the medication will enter the canal and cover more than one nerve root.

How Do You Choose Which One?

The choice of injection location depends upon the problem area suspected of causing pain. If the canal is stenotic (narrowed), a central injection or ESI would be used. If a nerve is suspected of causing pain, a SNRB would be used in the foramen that the nerve exits. Now to confuse the issue, you can introduce medication into the central canal through the foramen if you use enough volume. This would be called a trans-foraminal epidural steroid injection (TFESI). If disc pain is suspected, either route (ESI or TFESI) would be acceptable.

Diagnostic vs. Therapeutic?

Epidural injections and selective nerve root blocks–diagnostic and therapeutic–which one to choose? There are two medications injected at the same time. One is a numbing agent and the other is a steroid. With both medications injected at the same time, the injection is called “diagnostic and therapeutic”. If just the numbing medication is injected, it would be called a diagnostic test. If only the steroid was injected- obviously the injection would be called a therapeutic injection.

The part of the test named “diagnostic” involves numbing the structure or structures thought to be involved in the pain generation. This can be a nerve root, a disc or the entire canal. This is just like a trip to the dentist. An injection into the jaw anesthetizes the sensory nerve and makes the jaw feel “numb and swollen”. After three hours, the feeling or sensation returns.

The same concept is used with the diagnostic injection into the structure thought to cause the pain. The first three hours after the injection will numb that area. If the region that is numbed is causing the symptoms, there should be relief of pain for about two to three hours while repeating the activity that causes pain (sitting, standing, walking bending or whatever action induces the pain). This of course means that if sedation is used during the injection-it must have worn off in a short period of time. If you are sedated for three hours and lie in the recovery room, the diagnostic portion of the injection will be lost and the injection will have to be repeated.

Pain Diary

The most important thing post injection is to get up and repeat the activity that causes the pain in the three hour diagnostic “golden window”. Do not just sit around after the injection! A pain diary needs to be kept both prior to the injection and after the injection. Please see the section on providing a pain diary to understand how to fill one out.

Steroids

The therapeutic portion of the injection is the steroid. The steroid medication is wonderful for nerve inflammation. Someone should develop a bumper sticker “Nerves Love Steroids”. These steroids are corticosteroids and not the anabolic type that body builders use to look like a puffed up balloon. The body manufactures about 8-10 mg/day of this in the adrenal glands.

There are multiple actions of steroids that benefit nerves. The main action of the steroid is to prevent the chemical cascade that causes inflammation. A cascade is an amplification system to get a small matter big attention. For example- a small inflammatory source (a cut or abrasion) will cause multiple amplifications in a cascade. The first step magnifies the response 100 times; the next step multiplies that step 100 more times and so on. There may be 7-8 steps for this cascade to continue. Breaking this cascade is the specialty of the steroid.

What the steroid prevents is swelling, breakdown and tissue destruction of the injured area (which is what inflammation really is). Normally the chemical cascade “calls” in white blood cells (WBCs) to do their work. When the white blood cells (WBCs) migrate to this area, they release their contents which cause more swelling and even some tissue destruction (normally designed to “clean up” the injured area but in this case, causes more nerve injury). Swelling occurs when the under the influence of the chemical mediators of inflammation- small blood vessel walls in the vicinity become more “leaky” and tissue fluid floods into the area. The WBCs literally dissolve and eat (phagocytize) the dead and dying tissue. This is great for healing a tendon or skin abrasion but not so good for the nerve root.

The steroid also seems to “toughen” the nerve root. The lack of swelling and irritation reduces the size of the herniation but also probably makes the root less susceptible to compression. Remember that the disc herniation material is toxic to nerves. The steroid stabilizes the membrane that surrounds the root itself- making it less susceptible to chemical contamination.

Of course, there are potential risks of steroids and they need to be discussed with your physician but the global benefits of the steroid injection cannot be underestimated. Many times, it is the only substance that can give such immediate relief and continue that relief for a longer period of time. Steroid should be thought of as a management tool for the spinal generated pain. The procedure should be simple for a skilled and meticulous physician.

Dr. Donald Corenman is committed to meeting the needs of patients in Colorado and throughout the US. For more information on epidural injections and selective nerve root blocks (diagnostic and therapeudic), please contact Dr. Donald Corenman at 888-888-5310.

(Click to Enlarge Image) The black arrow points to the needle placed into the epidural space at the L5-S1 level.

(Click to Enlarge Image) The black arrow points to the x-ray dye that fills the left side of the canal and confirms the placement of the needle tip and the ability to spread the medication in the correct location.

(Click to Enlarge Image) The black arrows point to the location of the needle tips for this selective nerve root block (SNRB) of both the L4 and L5 nerve roots.

(Click to Enlarge Image) The dye pattern illuminates the path of both nerves. This is called a “neurogram” and confirms that the medication to be injected will be delivered in the correct location. Notice that the dye only enters the spinal canal to the origin of each nerve from the dural sac. These are perfectly placed needles.

Donald Corenman, MD, DC

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81 reviews

Eric S

Sep 26, 2021

by Eric S on Donald Corenman, MD, DC

Successful pars repair at 46 years old

Back in November of 2018 (at 46 years old) I came from Vancouver BC to have a pars repair done with Dr. Donald Corenman at the Steadman Clinic in Vail Colorado. I'm finally posting this review nearly three years later in late 2021. The reason I waited so long was I wanted to know the final result before I posted my review. Unfortunately in that time Dr. Corenman has retired. Nevertheless, I want to post this review of Dr. Corenman and his staff at the Steadman Clinic in their excellent treatment of my L5 pars interarticularis.

I fractured my pars at age 42 back in 2014 when rolling on the gym floor, and was denied treatment by the Canadian healthcare system, probably due to my age. First my GP told me there was no surgical option for a pars defect, which was quite incorrect! I tried to live with it, but the symptoms worsened (periodic random spine slippage and weeks of resultant pain after just bending over to tie my shoe, so I eventually learned to mostly squat and hardly bend). When I finally consulted with Canadian spine surgeons, I was told they believed my pars defect had been congenital (since birth). This was absurd, considering I had done extreme martial arts (including jiu jitsu) for years prior, as well as 5 years of reinforcing steel full time in my 20s, probably the hardest job on the back you can find. No pars defect like mine would possibly have allowed this--ergo it was impossible that I had had the defect since birth. I did however have an asymptomatic congenital spina bifida occulta that made me more susceptible to a pars fracture. In 2014 in one instant, I went from having the strongest back people I knew said they'd ever seen, to being unable to safely bend over and tie my shoe without a non-negligible risk of my spine slipping randomly (which would lead to weeks of pain after each occurrence). This was due to the unilateral L5 pars defect, otherwise known as spondylolysis. It was when lying in pain on the floor 4 years later after maybe the 6th spine slippage event post injury, that I had had enough, and resolved to have surgery. If Canada's "universal health care" said no, I would make lemonade from lemons, and find the very best surgeon in the world at pars repairs. That was Dr. Donald Corenman. Dr. Corenman back in 2018 ran a website https://neckandback.com/ that dedicated many pages to the science of every aspect of pars repairs, from eligibility (good discs on MRI), to best surgical techniques (minimal open compared to minimally invasive), best imaging to use (i.e., O-Arm with Stealth imaging vs. older fluoroscopy), the ideal amount of BMP to use and why not use too much or too little, and much more, all to do with pars repairs, pages upon pages of his site just on the pars, with scientific references and his own extensive expert opinion. As a health research statistician, I was very impressed with this. It was in stark contrast to the websites of other spine surgeons which barely gave the pars a word or two, focusing almost exclusively on fusions. I had found the best surgeon in the world for pars repairs, and so after Dr. Corenman personally screened my MRI to ensure my discs were healthy, I booked the surgery.

Being 46 years old at the time of surgery in 2018, with a 4-year-old pars fracture from 2014 combined with a congenital SBO meant my pars fragment was somewhat atrophied, but it was "very solid", said Dr. Corenman in the operative report. Nevertheless, it was challenging with two things to fix, the pars and SBO, and OR time was around 4 hours. Recovery over the following months was guided by a very clear "Spine binder" from the Steadman Clinic with strict rules of "no BLT" (no bending, lifting or twisting), and illustrated physiotherapy guidelines. They even warned patients to avoid fish oil supplements, which could excessively dampen inflammation and hence slow bone healing. They answered many questions I had during months of recovery, with responses coming from the very supportive Lori Fugate (then director of Dr. Corenman's practice), and Ehrich Bean (then physician's assistant at the practice), as well as a couple calls with Dr. Corenman himself after two of the CT scans. Ehrich Bean offered great advice for taking the spine binder conservatively due to the nature of pars repairs vs. fusions. The final post-op CT scan I had was a couple weeks ago at 34 months post-op, and Dr. Corenman had retired, but I got a very positive and informative call from Eric Strauch (current PA at the Steadman Clinic under Dr. Corenman's replacement there, and who had also worked with Dr. Corenman previously). The staff at the Steadman Clinic were extremely supportive all the way through the process. I should mention, the local Canadian spine surgeon did offer me very good post-operative support including antibiotics as needed to deal with a mild surface incision-site infection early on, booking numerous x-rays when I felt something was amiss, as well as booking all four of my post-op CT scans. I am very grateful for that support also.

My final result shows plenty of solid bone across the pars and a healed SBO, with my vertebral body now a solid bone ring instead of being broken at two places as it was pre-op. Does my spine hold up in the real world? You bet! I have recently dug and moved several yards of dirt and sand and gravel by myself (shovel and wheelbarrow!) to fix our water main, pulled roots from the yard, moved several "portable" (these are HUGE) air conditioners up several flights of stairs my myself, and lifted weights. I now run 2 miles (3.2 KM) several times weekly with a hard 100 meter dash in the middle. I bend deeply before each run I go on, with no spine slippage. My spine feels amazing. I can bend over to do exercise, or real word tasks, with no risk of spine slippage.

My sincere thanks to God, Dr. Donald Corenman, Lori Fugate, Ehrich Bean, Eric Strauch, and the Steadman Clinic, as well as the Canadian spine surgeon who offered me excellent post-operative care back in Canada. You have all given me a new lease on life.

Sincerely,
Eric S

Robert S

May 11, 2021

by Robert S on Donald Corenman, MD, DC

Back Fusion Surgery

I had my entire lumbar spine fused in November of 2018. I had scoliosis , with pinched nerves that were so painful I could hardly walk - and standing for more than a few minutes was impossible. Even sitting was painful.
The fusion surgery produced immediate relief! And the recovery was much easier than I expected.
To this day I can do all the activities I love from hiking, to standing in a stream fly fishing to riding my bike long distances - or just walking down the street with my wife.
Kudos to Dr. Corenman and his staff, (including the two Erics) for taking such good care of me!

Leslie R

Jul 9, 2020

by Leslie R on Donald Corenman, MD, DC

TLIF

I had my TLIF surgery on 6/24/2020 by Dr. Corenman, I can not say enough good things about the Dr or his staff. I was always treated with respect and explained everything throughly, that made it easy for everyone to understand. I highly recommend Dr. Corenman and the Steadman Clinic.

Epidural Injections and Selective Nerve Root Blocks- Diagnostic and Therapeutic

Difference between epidural steroid injections (ESI) and selective nerve root blocks (SNRB)

How Do You Choose Which One?

Diagnostic vs. Therapeutic?

Pain Diary

Steroids

About the Author: Donald Corenman, MD, DC

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