Overview of Sympathetic Nerve Block
The sympathetic nervous system, or SNS, is a part of your body that helps handle stress. It can affect both short-term and long-lasting pain. This part of the nervous system can trigger a stress response, raising your body’s resistance to pain through a mixture of nerve and hormone effects.
Given its role in helping tissue grow and managing the immune system, the SNS can also increase inflammation and pain, specifically in the tissues. If this system’s activity in a specific area is reduced, it can relieve pain caused by insufficient blood supply. Also, reducing the activity of this system in a specific region can stop the transmission of pain from internal organs. This is because most of the nerves that carry pain signals from our organs travel along with the nerves of the SNS. In certain conditions, such as complex regional pain syndrome, the SNS might develop into a major source of pain.
Selectively blocking the pathways of the SNS is a common treatment for this type of pain, or pain caused by insufficient blood supply. Most of the large clusters of nerve cells and networks related to the SNS are located separately from the body’s main nerve networks, in the region near the spine. These clusters are easily accessible for non-surgical interruption. If needed, this type of blockade can provide significant pain relief without causing loss of bodily sensation. Blocking the SNS related to our body’s internal organs will shift the balance in that region towards parasympathetic dominance, a part of the nervous system that helps your body to rest and recuperate, meaning it could come with corresponding beneficial effects.
Anatomy and Physiology of Sympathetic Nerve Block
The central sympathetic nuclei, a part of our nervous system that controls automatic bodily functions like heart rate and digestion, are located within the spinal cord, extending from the upper middle (T1) to lower back (L2-L3) areas. The signals from these nuclei travel along nerve fibers, exiting the spinal cord and forming smaller nerves. Some of these nerves form a chain along both sides of the spine called the sympathetic trunk. This trunk is made up of 20 to 24 connected nodes that come together to form the last node known as the ganglion Impar. Other nerves surround major branches of the aorta in the abdomen.
The nerve signals then travel from the ganglion in the form of differently structured nerves and either connect with ordinary nerves or form special nerves related to our internal organs. These special nerves carry sensations of pain and reflex responses from our internal organs back to the spinal cord.
These sensory signals follow a pathway from the organ where they originated, through the corresponding ganglion, and into a mixed spinal nerve. They eventually reach the dorsal root ganglion (DRG), the area of the spinal cord where the nerve cells that sense organ function are located.
This arrangement, with sympathetic and ordinary nerve structures separated, means that doctors can selectively block signals relating to pain from internal organs by using a local anaesthetic. This technique is useful to see if the perceived pain is caused by certain internal organs or tissues.
If a pain-relieving block is shown to be effective, stronger treatment methods, such as chemical neurolysis or ablative therapies (which aim to damage or destroy specific nerve fibers), can be considered for a more long-lasting effect.
When performing these blocks, doctors confirm the correct positioning of the injection needle using imaging techniques. The effectiveness of the block is also evaluated. If significant pain relief is achieved with a low concentration of the anaesthetic, without signs of sensory or motor blockade, it is assumed that the effects occurred due to the sympathetic block.
However, using larger volumes of anesthetic can sometimes affect sensory nerves near the ganglia, potentially creating a false-positive result, meaning the treatment might appear to work when, in fact, it hasn’t really addressed the root cause of the pain.
Why do People Need Sympathetic Nerve Block
Doctors use a technique called diagnostic sympathetic blocks to confirm whether a patient is experiencing pain due to a problem in their sympathetic nervous system – that’s the part of your body that reacts when you’re scared or excited. This technique works by blocking the communication between nerves to confirm whether the blocked nerve is causing the pain. Sometimes, doctors can also use substances that can prevent these nerves from sending pain signals for a longer period. In addition, physical techniques like radiofrequency denervation or cryo-neurolysis may also be used to treat this type of pain.
Sympathetic blocks are used to manage different types of pain like visceral (relating to organs in the body), vascular (relating to your blood vessels), and neuropathic pain (caused by damage to your nerve fibers).
For pain related to organs like the stomach, small intestine, liver, etc., a block is applied to the celiac plexus, a network of nerves near the abdomen. This not only can help reduce pain, but can also help control nausea often seen in patients with organ-related cancers. If this is successful, patients may not need as much pain medication. The effect can last weeks or even months, depending on what is used for blocking.
If you imagine your body as three parts – the foregut and midgut (that includes your stomach, liver, etc.), the hindgut (that includes your lower colon and start of your rectum) and pelvic organs (like your uterus and bladder). The hindgut and pelvic structures are controlled by the superior hypogastric plexus, another network of nerves. Blocking this network can help treat pain in the pelvic and rectal areas that don’t improve with usual treatment measures.
Sympathetic blocks are also used to provide relief from neuropathic pain, which is pain caused by nerve damage. If this type of pain is caused by a condition known as herpes zoster, doctors may use sympathetic blocks to decrease the risk of further nerve pain. However, it’s not entirely clear how well sympathetic blocks work for certain types of nerve pain and research is still ongoing.
The use of sympathetic blocks in treating a condition known as complex regional pain syndrome (CRPS) has been found beneficial. CRPS is a condition where a person experiences pain that is out of proportion to the severity of an initial injury. It can result in prolonged or excessive pain, changes in skin color, temperature, and/or swelling in the affected area.
Lastly, these blocks can help manage pain that comes from problems with the body’s blood vessels. This type of pain happens when your body tissues don’t get enough blood supply. Blocking the signals from the affected area to the brain can help reduce the pain and improve blood flow in the affected part of your body.
Sympathetic blocks also provide temporary relief from a condition called hyperhidrosis where a person sweats excessively.
When a Person Should Avoid Sympathetic Nerve Block
There are certain situations where a medical procedure might not be safe or possible. These include if a person is known to be allergic to any medications that are planned to be used, or if they refuse the procedure or are unable to understand the steps involved.
Another factor that could impact the conductivity of a procedure involves instances where there’s an infection or cancerous area (malignancy) along the path where a needle needs to be inserted. This is because of the risk of spreading the infection or cancer. In situations where someone has a condition that affects their blood’s ability to clot (known as anticoagulation and coagulopathy), it’s important to talk about and address these issues before proceeding with something called a sympathetic block, which is a type of pain management strategy.
Any pre-existing issues with movement (motor deficits) or sensation (sensory deficits) in the area where the block would be applied need to be fully noted down. If possible and if it makes sense, talking about delaying the block until symptoms have improved is also key.
It’s also worth mentioning that people who are on medication to control their blood pressure might have more severe drops in blood pressure – especially those on diuretics, which are medications that help get rid of excess water in your body. There have also been some reports of visual changes after something called a stellate ganglion block, which is why it’s important to have someone around following the procedure. Finally, a celiac block, another type of pain relief, might speed up the movement of food through the digestive tract. This has to be kept in mind for people who are predisposed to blockages or obstructions in the intestine.
Equipment used for Sympathetic Nerve Block
The process of blocking the sympathetic nerves can change the balance in the nervous system within the area that has been numbed. This could lead to some potentially harmful physical effects. For the safety of patients having these procedures, they need to be checked in line with guidelines from the American Society of Anesthesiologists. This means checking the oxygen levels, breathing, and blood flow in the patient’s body.
Having a way to give medication through a vein and the ability to quickly introduce fluids into a patient’s bloodstream is highly recommended if there’s a risk of low blood pressure.
Before blocking any nerves, it’s necessary to look over any images from previous medical tests to check if the patient’s body has any unusual structure. Depending on the method used to guide the procedure, this could involve various equipment such as a portable X-ray machine, ultrasound machine, CT scanner, or MRI scanner.
Other essential items for this procedure include spinal needles of the right size and syringes, special drawing needles with blunt tips, needles for numbing the skin, a mask, hair cover, sterile gloves and drapes, skin cleaning solution, contrast solution (a special dye that helps doctors see certain areas more clearly on medical images), and various medications which can include local anesthetics, neurolytic drugs (medications that block nerve signals), and adjuvant medications (drugs that help enhance the effects of anesthetics).
Who is needed to perform Sympathetic Nerve Block?
A medical doctor who has been specially trained carries out these procedures. This doctor knows about all the potential problems that could happen and the right ways to treat them. A nurse is always there too, helping the doctor throughout the whole procedure. If there’s a need to use special machines to see inside the body (like a fluoroscopy, CT, or MRI), a skilled technician or other staff member will operate that machine. They all work together to make sure the procedure goes as smoothly and safely as possible.
How is Sympathetic Nerve Block performed
A Stellate Ganglion Block is a specific procedure used for certain types of pain. It can help with pain in the upper body and chest area, including a certain type of nerve pain caused by an injury or disease (known as CRPS types I and II). It can also treat pain after radiation treatment, certain types of blood flow problems, and even symptoms from post-traumatic stress disorder. The procedure is sometimes used to treat a rapid and irregular heart rate.
The Stellate Ganglion is a cluster of nerves found in the neck. This procedure works by injecting medication near these nerves to help reduce pain signals. The procedure is usually done at a specific point in the neck, which presents the least risks. The procedure is typically done while the patient is laying down, and monitors are used to check the patient’s heart rate and blood pressure. The injections are usually done under x-ray guidance to make sure the medication is delivered correctly. The procedure involves a needle being placed onto a specific bone in the spine and then slightly withdrawn before the medication is injected.
Stellate Ganglion Block is generally a safe procedure, but it can have some side effects. Commonly, it can cause drooping eyelids, blurry vision, and a stuffy nose on the side where the injection was done. There is also a risk of reaction to the local anesthetic, damage to the nearby blood vessels, and bleeding. Rare but serious complications can include air bubbles in the blood vessels, perforation of the windpipe or food pipe, and even collapse of the lung.
A Splanchnic Nerve Block is another type of procedure used to treat pain, specifically in the upper abdomen and behind the abdominal area, usually due to cancer. The Splanchnic nerves carry signals from different parts of the chest down to the abdominal area. Blocking these nerves can help to reduce pain signals. The procedure is done in a similar way to the Stellate Ganglion Block. The patient lies on their stomach, and the needles are placed near a specific vertebra in the lower back. The tip of the needle and the medication is then injected under x-ray guidance. Despite its advantages, this procedure comes with a higher risk of lung collapse and damage to nearby nerves, limiting its usage.
Possible Complications of Sympathetic Nerve Block
For the potential issues linked with each type of procedure, please refer to the section on ‘Technique’ above.
What Else Should I Know About Sympathetic Nerve Block?
Pain is a complex feeling that can be affected by many things. It is usually sent to our brains by nerves in our skin and muscles. However, pain from our internal organs is sent to the brain through different nerves, which travel together with nerves that control responses like our heart rate and sweating. Interfering with these pathways can give powerful pain relief, especially for diseases of the internal organs like cancer, and decrease the need for strong painkillers such as opioids.
Activity in these controlling nerves can sometimes make some chronic pain conditions worse, such as Complex Regional Pain Syndrome and pain from poor blood flow. Removing these nerves, a process known as sympathetomy, can sometimes effectively relieve this kind of pain. Decreasing the work of these controlling nerves by blocking certain nerve clusters can also be used to treat certain irregular heartbeats, excessive sweating, headaches, Post Traumatic Stress Disorder (PTSD), and a variety of other conditions.
