Nerve blocks are very useful for many reasons, and there are different types. Sometimes doctors use them to make sure this or that particular nerve is involved in a given type of pain. In other cases, it is a therapeutic procedure to ease the pain in a given area.
One of the differences between diagnostic and therapeutic nerve blocks is that the former contains anesthetics, while the latter uses steroids and other drugs. This steroid is injected in the area to reduce the inflammation and reduce the activation of pain stimuli.
But sometimes, patients report feeling more pain after a nerve block procedure. Why is that? Is it temporary or permanent?
In this article, we’re reviewing the top 7 reasons why pain worsens after a nerve block.
Reason #1. The needle injection came in contact with the nerve
Anatomically, we know the trajectory of nerves. But we can’t be sure about the exact location while performing a live procedure. That leaves us with the uncomfortable possibility of hurting a nerve with the needle injection. A mechanical injury to the nerve causes severe pain and may leave sequelae such as tingling, numbness, and other sensibility issues.
Luckily, injured nerves usually repair after a while, and the chance of ending up with a severe and irreversible injury is almost none. So, in this particular case, pain is expected to subside after a while.
Reason #2. The volume of the injection was not appropriate for the tissue
Steroids should be diluted in a large volume of liquid before administering the injection. Sometimes, the injection volume is too much, or the tissue is very fragile and susceptible to volume changes. In normal cases, the injection liquid spreads in the area. But sometimes the injection is administered in a small space or a closed space.
Joint injections are a likely example. The joint is a closed space, and it is swelling and irritated. When nerve blocks are administered, the tissue stretches and may become more painful for a while. After some time, the pain goes away as the injection liquid spreads, and the steroids do their anti-inflammatory job.
Reason #3. The drug is irritating the area
This reason is closely related to the above. One of the main reasons why inflammation hurts is because it causes an increase in tissue volume. This causes an abnormal stretch of the tissue, which triggers pain-sensitive nerves.
An increase in volume and some drugs contribute temporarily with the stretch and irritation of the area. When they do, the patient feels a type of pain that goes away after a while. In the case of joint nerve block, steroid injections rapidly reduce swelling and improve pain.
Reason #4. Common side effects after a nerve block
Pain is a common side effect of any type of injection, and each one of us has a different pain threshold. An injection causes temporary microscopic trauma to the tissues, and sometimes this causes other symptoms such as bleeding, redness, and limitation of movement. Depending on the technique and the collaboration of the patient, these side effects can be prevented or worsened.
These side effects are self-limiting. In other words, it does not last for a very long time and usually goes away by itself without treatment. However, depending on the case, your doctor may prescribe medications to improve the pain and soothe the area.
Reason #5. A rebound effect as the drug wears off
This is not an immediate type of pain. Quite the contrary, because it takes a while before the injection spreads in the tissue, it starts performing an anti-inflammatory function, and eventually, its effect wears off. After the drug’s effect is gone, there’s always a possibility of having a rebound effect, which depends on the drug’s dosage, the susceptibility of the patient, and his own pain threshold.
In most cases, a rebound effect is perceived as more severe as compared to the original pain. But this is not always the case. The contrast between not feeling pain and experiencing chronic pain once again is very fast and violent, giving rise to a lower pain threshold (a higher susceptibility to feeling pain).
Reason #6. A temporary flare-up before it settles down
The scientific literature often describes temporary flare-ups right after a nerve block as a part of the healing process before settling down, and as the pain starts to go away. This temporary flare-up may be caused by a combination of emotional and physical stress. But in most cases, an obscure combination of the reasons described above contribute to the symptoms.
As noted, this flare-up is temporary. It goes away after a while, and usually by itself without any additional medication. Still, depending on your case, the doctor may decide to use an oral anti-inflammatory or another means to accelerate the recovery from this flare-up.
Reason #7. Muscle spasms
Depending on the injection area and the size of the needle, muscle spasms can be a significant cause of pain after the injection. The needle comes in contact, goes through, and stimulates the muscles. Sometimes it causes a moderate tear of the underlying muscle, leaving it with a higher susceptibility for muscle spasms.
In this case, the type of pain caused by muscle spasms is notably different from that of joint pain, for example. It is also identified with an elementary physical exam. In this particular case, we have medications to reduce muscle spasms and muscle tension if the problem does not go away by itself.
We don’t usually have a single reason for this type of pain after a nerve block. In most cases, it is simply impossible to sort them out and realize which one is causing the symptoms. But we do know it is usually temporary and self-limited. It usually does not require treatment, but it is recommended to stay in contact with your doctor to get proper advice according to your symptoms and your particular case.
Williams, B. A., Bottegal, M. T., Kentor, M. L., Irrgang, J. J., & Williams, J. P. (2007). Rebound pain scores as a function of femoral nerve block duration after anterior cruciate ligament reconstruction: retrospective analysis of a prospective, randomized clinical trial. Regional Anesthesia & Pain Medicine, 32(3), 186-192.
Porzelius, J. (1995). Memory for pain after nerve-block injections. The Clinical journal of pain.