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Are Epidural Injections Safe?

Epidural Steroid Injections, also known as "ESIs" or "Cortisone Shots" are the most commonly performed back injections in the US. The first ESI was reported in 1901 by two French Physicians who injected a Local Anesthetic into the Epidural Space to help with pain from Sciatica. ESIs became popular in the 1970's after injectable steroids became available. Due to an aging population, reasonable insurance reimbursements, and an increasing number of physicians trained in the procedure, ESIs have nearly doubled between 2000 and 2008. Currently, over 9 Million of these Injections are performed every year.

What is an ESI Injection?

ESIs are performed to reduce the inflammation and pain related to a disease process of the Spine, most commonly Disc Herniations (slipped discs) and Spinal Stenosis (narrowing of the Nerve canal). The Epidural Space contains the Spinal Nerve Roots which are the target of the Injection. After cleaning the Skin over the Spine, a small amount of Local Anesthetic is injected to numb up the Skin. The Epidural Needle is then placed through the numbed area and slowly advanced into the Epidural Space. Ideally this is done with the help of an X-Ray machine called a "fluoroscope". Unlike ordinary X-Ray machines, the fluoroscope can take second-by-second pictures of the Spine. Once the needle is properly placed in the Epidural Space, a small amount of contrast dye is typically injected. This dye can be seen on the X-Ray and helps to verify the correct placement of the Epidural Needle. At this point, the medication to treat the pain and inflammation is injected. Often, this is a mixture of medications, which include the Steroid, a Local Anesthetic and Saline Solution. The Local Anesthetic can help the Sciatica Pain transiently, until the Steroid begins to take effect.

The Image below is a Color MRI Image which shows how an ESI is performed in the low back.

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What are the possible benefits of an ESI Injection?

ESI Injections are ideally done to help with pain from Sciatica related to a Disc Herniation, or Nerve Pain from Spinal Stenosis. In this instance, an ESI injection can help control the pain for an average of 6 to 12 weeks in selected patients. Since the majority of Disc Herniations (approx. 70%) improve over time, ESIs can help control the pain until they resolve on their own. If the Sciatic Pain has been present for over 3 months, the effectiveness of the injection goes down. ESIs are generally most effective when combined with a Spine Rehabilitation program such as targeted Physical Therapy (PT).

What are the possible complications from ESIs?

Statistically, ESIs are reasonable safe when compared to many other invasive procedures, however some of the potential complications can have devastating consequences. Lets take a look at the most common and most serious complications. They are listed from least to most serious:

1. Vagal Reaction

A Vagal Reaction is the feeling of lightheadedness, dizziness and nausea patients experience mostly due to fear or discomfort from a medical procedure. This can occur in up to 8% of patients who have an ESI.

2. Pain from the ESI

Some patients will experience pain at the site where the Epidural Needle was placed through the Skin and Tissue. This pain is usually mild and disappears in a matter of days.

3. Insomnia

Some patients will have difficulty sleeping for the first few nights after the ESI. This is due to the Steroid Medication in the Injection which can make patients somewhat "hyper" and "edgy" for a short period of time.

4. Increase in Sciatic Pain

On rare occasions, patients will initially feel worsening symptoms compared to prior to the Injection. Since the Spinal Nerves are already inflamed and sensitive, they can react to making contact with the injected medication. This can initially lead to an increase in the inflammation until the Steroid can take effect.

5. Allergic Reaction

Patients can be allergic to the injected medications. The most likely one would be an iodine containing contrast dye which is often injected to verify the proper placement of the Epidural Needle.

It is less common to be allergic to the Steroid or Local Anesthetic.

6. Decrease in Immunity

Steroid Medications in general will decrease out body's immunity. This is more pronounced with Oral Steroid Medications, but can also occur with injectable ones. Patients who have a series of ESI injections and those who already have a poor immune system are at higher risks of developing an infection.

7. Adrenal Suppression

The body has many ways to regulate our Hormones. In order to do so, we have "sensors" which constantly measure how much of each Hormone is present in our blood stream. So, when these "sensors" notice that more steroid is circulating in the body, they will tell our own steroid-producing glands to lower the amount of steroid they are producing. This is called "Adrenal Suppression". This is thought to happen in 0.01% (1 in 10,000) of patients and typically resolved in 2-4 weeks after the Injection. Patients who receive very high doses of Steroids or have a large number of ESIs over a short period of time are at a higher risk. For this reason, it is generally not recommended for patients to have more than 3 ESIs per year.

8. Increase in Blood Sugar

This is primarily an issue for diabetic or borderline diabetic patients. Patients with poor Diabetic control and those who receive large doses of Steroids can experience very significant increases in Blood Sugar Readings. In one study, patients experienced an average rise in Blood Sugar from 160 to 285 mg/dL immediately after the Injection. This rise in Blood Sugar typically resolves over 2 days. As a result, Diabetic patients have to take frequent Blood Sugar Readings and potentially adjust their Diabetic Medications following an ESI. Patients should also have a Blood Sugar reading right before the ESI.

9. Postdural Puncture Headache (PDPH)

This type of Headache can happen when the Epidural Needle travels deeper than the Epidural Space and punctures the lining of the Spine Fluid Sac (dura). If some of the Spinal Fluid leaks from the dural sac, a Headache can occur. Statistically a PDPH happens in up to 7% of ESIs. This type of Headache can be very severe and incapacitating. 90% of PDPHs resolve over 10 days. Severe forms of this Headache can be successfully treated and stopped with a procedure called an Epidural Blood Patch.

10. Epidural Hematoma

An Epidural Hematoma is bleeding inside the Epidural Space. Apart from Spinal Nerves and Fat, the Epidural Space also contains Blood Vessels. A puncture of one of these Vessels can potentially lead to bleeding inside the Epidural Space, which can cause compression of the Spinal Nerves or Spinal Cord. While this is an extremely rare occurrence (1 in 200,000 ESIs), patients who are treated with Blood Thinners are at an elevated risk. Considering that many more patients are treated each year with Blood Thinners, the risk of Epidural Hematomas may increase over time.

11. Embolization

Embolization means that a particle travels through the body's Blood Vessels. Typically, embolization happens when blood clots travel within our body. However, some types of Steroids used for ESIs contain particles (methylprednisolone, triamcinolone) which can potentially travel to the Brain and elsewhere in the body and cause Strokes and even Deaths. The risk is higher (1 in 5000) when Steroids containing particles are used for specific Epidural Injections in the Neck (transforaminal ESI).

12. Arachnoiditis

Arachnoiditis is a chronic inflammatory condition of the bundle of Spinal Nerves within the Spinal Fluid Sac (dura). This has been reported when the Steroid is accidentally injected into the Spinal Fluid rather than the Epidural Space. The Spinal Nerves become inflamed which can cause them to "clump together". This can impair the Nerve function and lead to chronic Nerve Pain, numbness and weakness in the Legs.

13. Infection

While infections are rarely associated with ESIs, some types of infections can be devastating. Point in case are the batch of contaminated Steroids which were produced and sold by a compounding pharmacy in Massachusetts in 2012. Approximately 14,000 patients received injections from this batch of Steroids which was contaminated by a Fungus. Tragically, 48 patients died and 720 had to be chronically treated for Fungal Infections.

While this list of potential complications related to ESIs seems daunting, by and large the controversy about ESIs lies in their usefulness to treat pain, rather than the potential complication risks. However, patients must be aware of all the potential complications to allow them to make an informed decision about whether or not to pursue this elective procedure.