What is Central Pain Syndrome?
Central sensitization of pain is a condition where the nervous system is constantly overly active. This leads to increased sensitivity, making the body react strongly to pain, even when there’s only minor input from the peripheral nervous system, which involves the nerves outside of the spinal cord and brain. This is often referred to as ‘wind-up’ or temporal summation. As a result, patients might feel pain from a touch that is not usually painful, or experiences of pain might feel more severe. Things like cold temperatures or emotional changes can make the pain even worse.
This condition is also called centralized pain or widespread/diffuse pain, and is fairly common. Certain genetic and environmental factors can make some people more susceptible to it. It frequently occurs in individuals with multiple chronic diseases as well as those who have had neurological injuries like a stroke or a spinal cord injury. Therefore, it’s crucial for healthcare providers to identify who is at risk.
Centralized pain can also be linked with memory loss and increased anxiety. Treating this type of pain often involves prescribing antidepressants or anticonvulsants, as conventional pain killers like NSAIDs or opioids usually do not work. This type of pain can turn into a chronic condition that significantly reduces a patient’s quality of life. Research shows that up to one fifth of adults may experience this widespread generalized pain.
What Causes Central Pain Syndrome?
Central pain, sometimes known as neuropathic pain, is believed to occur in the central nervous system. In the past, doctors used to see it as a psychiatric condition occurring after a severe brain injury or as a diagnosis made after all other conditions have been ruled out. The original theory behind central pain was that it was a malfunction of the nervous system, rather than a useful adjustment as seen with pain from muscle or bone injuries. For instance, it’s helpful to pull your hand away from a fire. Pain serves a protective purpose, preventing more damage. However, central pain seemed to operate differently, causing pain without any obvious injury.
It’s not only unhelpful but can become a maladaptive and harmful response. When several system-wide syndromes coincide, pain perception heightens. Some people suffer from conditions like fibromyalgia, chronic fatigue, and somatoform disorders which are known to increase pain sensitivity. These conditions often intersect with regional pain syndromes and psychiatric conditions.
Central pain can appear after events like a stroke or conditions like multiple sclerosis and may also be seen in different chronic rheumatologic and musculoskeletal conditions. When an initial painful injury persists over time, it can result in a state known as centralization, increasing the risk of developing central pain syndrome.
Though patients with chronic pain sometimes believe that their pain is peripheral to the injury site, the reality is that it’s mostly central in nature. The nerve signal intensifies, causing severe sensitivity to pain and even slight touches. For example, in a patient with rheumatoid arthritis, the peripheral (or nociceptive) pain linked to the disease may become centralized over time, resulting in a mixed perception of the pain. Conditions like chronic back pain also exemplify how peripheral pain can become centralized. Risk factors for fibromyalgia, such as trauma, infection, chronic stress, obesity, and depression, are similar to those for central pain syndrome. Brain scans can help in diagnosis.
It’s important to remember that central pain may overlap with other types of pain. All central pain may include some elements of peripheral pain, like peripheral neuropathy. There’s also a significant genetic trait associated with central pain syndrome. Moreover, psychological stresses can worsen symptoms. In many cases, a triggering event due to environmental factors in individuals having genetic susceptibility leads to widespread, centralized pain. It’s thus essential to manage these environmental stressors. Factors like early life trauma, infection, or psychological stress can cause centralized pain in a small portion of people.
The causes for developing centralized pain are considered to be 50% environmental and 50% genetic. The risk of experiencing widespread pain is eight times higher for first-degree relatives compared to the general population. There seems to be no significant difference between males and females, but there’s a stronger connection in families with a history of mood disorders. While a single gene difference hasn’t been identified, there could be a genetic component to the widespread pain experienced by some.
Risk Factors and Frequency for Central Pain Syndrome
Chronic widespread pain, often seen in centralized pain, affects 10 to 40% of people with various types of arthritis such as rheumatoid, psoriatic, or osteoarthritis, as well as spondyloarthritis and lupus. Furthermore, 5 to 15% of the general population also experience centralized pain; most have fibromyalgia. People diagnosed with fibromyalgia often report severe fatigue and are five times more likely to have widespread pain.
- There is a considerable overlap between fibromyalgia and centralized pain.
- People with both central pain syndrome and knee osteoarthritis make up between 10 and 15% of cases.
- This percentage goes up when patients have pain in both knees instead of just one.
In the case of rheumatoid arthritis, 13 to 40% of patients report centralized pain. There is a concern of overtreatment in these cases since increased symptoms might actually be due to centralized pain, not rheumatoid arthritis. These patients usually have lower inflammation markers, but also indicate a lower quality of life compared to those who only have rheumatoid arthritis.
- About 10 to 30% of patients with spondyloarthritis also have centralized pain syndrome.
- From these, 13 to 20% meet the criteria for fibromyalgia as well.
- Patients with widespread pain are more likely to experience severe fatigue and mood disorders.
- Nearly 53% of patients with psoriatic arthritis have centralized pain, a number significantly higher than the general population’s 5%.
- People with this type of pain are more likely to discontinue treatment.
- Centralized pain affects 20 to 40% of lupus or Sjogren syndrome patients and is especially prevalent in those with depression and as chronic diseases progress.
Lastly, over a third of women who suffer from chronic back pain also experience centralized pain. This pain significantly affects their daily activities and could be a possible reason behind their symptoms.
Signs and Symptoms of Central Pain Syndrome
Centralized pain is diagnosed by symptoms of pain that last for at least three months. This pain can be generalized or located in multiple areas of the body. The pain is usually widespread and is triggered by touch or pressure, even if it’s light (this is called “allodynia” or “hyperalgesia”). The pain can also occur without any other apparent cause, such as over a joint or muscle. Centralized pain often comes along with changes in mood, fatigue, trouble with thinking or remembering, disrupted sleep, and feelings of intense worry or sadness.
People with centralized pain may also experience feelings of numbness, burning, tingling, or weird sensations. It’s common for patients to feel pain in several places, have memory problems, and also have major depressive disorder or generalized anxiety disorder. To help identify and keep track of the areas where pain is felt, it can be useful to use a drawing of a human body. This unique type of pain can be triggered by things that don’t usually cause pain, like changes in temperature or loud noises.
When diagnosing centralized pain, it’s important to gather details about the pain. This includes when the pain started, how it feels, where it’s located, whether it spreads to other areas, and how severe it is. If the patient had an injury, details about that should be included, as well as what makes the pain better or worse, how often it occurs, and if there are periods when the pain suddenly gets worse. It’s also important to address other symptoms that might occur with the pain, like muscle spasms or aches, changes in temperature, limited movement, stiffness in the morning, weakness, changes in muscle strength or sensation, and changes in hair, skin, or nails.
A thorough neurological exam and an exam of the area where the pain is felt are also necessary. Evaluating for widespread tender points, like in the condition fibromyalgia, is recommended. For a diagnosis of centralized pain, the pain is usually spread out on both sides of the body and affects the upper and lower parts of the body. Any tenderness over soft tissues or joints should also be noted. If there’s swelling, changes in structure, abnormal neurological findings, or signs of inflamed joints, centralized pain is less likely.
Testing for Central Pain Syndrome
To diagnose a condition known as central pain, doctors usually depend on physical examinations and symptoms, since common lab tests like complete blood counts, inflammation markers, and thyroid function tests may not give positive results. These tests are only requested if the doctor feels they are necessary based on initial findings. Genetic markers that can identify central pain are limited and markers specific to autoimmune diseases aren’t needed unless such a condition is suspected.
To assist in diagnosing central pain, certain screening tools like the central sensitization inventory (CSI) and the painDETECT measure are used. However, differentiating whether the pain originates from central or peripheral nervous system could be challenging.
Imaging methods can help with confirming whether a patient has central pain syndrome. Brain imaging techniques such as MRI and functional MRI (fMRI) can be helpful. The fMRI can show structural and functional changes in the brain of patients suffering from chronic pain disorders. For example, patients with a common central pain disorder known as fibromyalgia show unique brain patterns on their fMRI.
The fMRI can also be used to examine the interactions between different brain regions. Changes observed through this method can be matched with the patient’s level of pain, making it a potential tool for objectively measuring the severity of conditions like fibromyalgia. Interestingly, the brain’s response to pain on an fMRI in patients with fibromyalgia is different from ordinary individuals.
Other imaging techniques such as positron emission tomography and electroencephalography have also shown increased responses to pain in patients with central pain syndrome, which might be useful in diagnosing different pain disorders in the future.
Treatment Options for Central Pain Syndrome
Treatment for centralized pain is often centered around managing the underlying chronic disease that’s associated with the pain. By addressing the root health condition, relief from the pain can be significantly provided. For instance, in knee osteoarthritis, joint replacement improved the symptoms related to central pain.
Drugs used to manage pain in the brain (neuromodulators), drugs used to reduce seizures (antiepileptics), or antidepressants are often more effective at addressing centralized pain than regular painkillers (like NSAIDs) or opioid-based medications.
Getting psychological counseling, such as cognitive-behavioral therapy, is crucial in managing centralized pain. It takes a holistic approach to treat centralized pain as the underlying conditions can involve issues with body structure, immune response, or inflammation.
Physical techniques, guided either by the patient or a professional, can be used for relief. These can include massage, ultrasound therapy, using heat or cold, physical positioning, stretches, and a technique called transcutaneous electrical nerve stimulation (TENS). For women experiencing chronic pelvic pain, myofascial physical therapy (MPT) is beneficial as it eases muscle tension, improves the body’s natural pain-suppression function, reduces sensitivity to pain and provides psychological relief.
Transcutaneous electrical nerve stimulation (TENS) is usually used as a treatment for rheumatoid arthritis and osteoarthritis. It involves applying electrodes over or close to the painful area. However, TENS should be avoided during pregnancy, close to the carotid sinus (a region in the neck), and in patients who have certain types of pacemakers, due to rare instances of hypersensitivity.
Other treatments like motor cortex stimulation (MCS) and deep brain stimulation (DBS) can be effective for patients whose pain does not respond to other treatments. These treatments can help centralized pain and nerve pain.
Occupational therapy can also be especially helpful for patients with chronic pain, including regional chronic pain syndrome, as it helps them to stay active and manage their physical symptoms.
There are a few types of medications recommended for central pain syndrome. These include tricyclic antidepressants, serotonin and norepinephrine reuptake inhibitors (SNRIs), and anticonvulsant drugs. Some examples of these drugs are amitriptyline, duloxetine, and venlafaxine, and the anticonvulsants, pregabalin, and gabapentin. Tramadol or selective serotonin reuptake inhibitors (SSRI) and S-adenosyl-L-methionine (SAMe) are also options, but the evidence supporting their use is not as strong.
What else can Central Pain Syndrome be?
Central pain can be a symptom of many long-term pain conditions such as fibromyalgia, interstitial cystitis (a type of bladder pain), issues with the jaw joint called temporomandibular disease, and irritable bowel syndrome, a disorder that affects the large intestine.
When diagnosing central pain, doctors also need to consider conditions related to the body’s connective tissues and joints, such as polymyalgia rheumatica (pain and stiffness in the shoulders and hips), myopathy (muscle diseases) or myositis (inflammation of the muscles), rheumatoid arthritis, psoriatic arthritis (a type of arthritis affecting some people with psoriasis), or lupus (a long-term autoimmune disease).
Furthermore, centralized pain often goes along with chronic back and neck pain. It can also be linked to injuries, carpal tunnel syndrome (a nerve disorder in the wrist), complex regional pain syndrome (a chronic pain condition affecting an arm or leg), lateral epicondylitis (tennis elbow), osteoarthritis (the most common form of arthritis), and joint hypermobility syndrome (where joints easily move beyond the normal range expected).
Centralized pain can also accompany a stroke or be a result of a neurological disorder like multiple sclerosis. A stroke in a specific part of the brain, known as thalamic stroke, is associated with a particular form of central pain. Lastly, mood disorders such as major depression or generalized anxiety disorder are associated with centralized pain.
What to expect with Central Pain Syndrome
Patients tend to recover more successfully if the cause of their pain can be fixed, managed, or cured. For example, those who have a shoulder replaced because of osteoarthritis usually experience a better outcome. However, people with both osteoarthritis and centralized pain often find ambiguous results. While medications for osteoarthritis can reduce pain, following joint replacement surgery, they may face increased pain complications.
Interestingly, in cases where osteoarthritis and central pain syndrome occur together, the intensity of the patient’s pain isn’t directly linked to the severity of the osteoarthritis seen in medical imaging. In fact, these patients are more prone to experiencing pain in various joints, even when the osteoarthritis is only detected in one joint. Also, these individuals typically have more inflammation and fluid buildup in the knee due to osteoarthritis.
Central sensitization, a phenomenon where the nervous system goes into a persistent state of high reactivity, also significantly influences inflammatory arthritis. This condition is quite common in people with such diseases. Moreover, individuals who have both rheumatoid arthritis and fibromyalgia are found to experience worse pain, poorer mental health, and take more pain medication, including prednisone, while having lower levels of inflammation markers. Those with inflammatory arthritis and central pain syndrome also generally have worse health outcomes. Regardless of whether the arthritis affects their joints’ surfaces or other non-joint areas, these patients suffer from an increased sensitivity to pain.
Possible Complications When Diagnosed with Central Pain Syndrome
Central pain disorder, also known as central pain syndrome, is linked to various conditions, often contributing to more severe symptoms and worse patient outcomes.
In cases of rheumatoid arthritis, the presence of central pain can:
- be tied up with nerve-related symptoms,
- cause higher pain scores without any increase in inflammation markers,
- lead to more negative outcomes,
- result in lower remission rates.
The disorder is also connected to the increased use of painkillers in patients with osteoarthritis, and those suffering from bilateral knee pain are more likely to experience joint pain in other areas within a year. Central pain was found to be related to worse results in the case of spondyloarthritis.
For patients with lupus, having central pain can lead to more significant sleep disturbances and mood changes, and contribute to worse outcomes. Similar effects are observable in patients with chronic back pain and joint hypermobility syndrome.
In patients with carpal tunnel syndrome, the presence of central pain is linked to worse surgical outcomes, while those with lateral epicondylitis will experience more severe pain, prolonged pain duration, and greater risk of treatments failing. Lastly, for those with chronic whiplash injuries, central pain is associated with cognitive disturbances, increased pain, and poorer outcomes.
Additionally, increases in pain levels for fibromyalgia patients before surgery have been correlated with receiving more morphine equivalents post-operation and reduced response to non-steroidal anti-inflammatory drugs (NSAIDs).
Preventing Central Pain Syndrome
Centralized pain is a condition that occurs when your central nervous system becomes more sensitive to pain, causing you to feel pain more easily. This type of pain is fairly common, with up to 20% of those suffering from enduring pain having centralized pain.
People with centralized pain often experience pain when touched lightly or a heightened pain sensation when something painful occurs. This condition is particularly common in individuals who have had persistent conditions related to bones, joints, or muscles (rheumatological and musculoskeletal conditions) for at least three months.
The cause of this heightened pain sensitivity can be both genetic and environmental. You can also experience centralized pain alongside a chronic disease that is causing persistent pain, and this risk increases over time. A diagnostic test using a type of MRI scan could be useful in identifying different pain disorders.
The effects of centralized pain can be severe and can negatively impact the management of chronic diseases, such as osteoarthritis and rheumatoid arthritis. The treatment of centralized pain often requires the collaboration of a pain medicine specialist and a primary care physician. Treating the centralized pain and any related conditions at the same time can help improve a patient’s overall pain levels. Treatments for centralized pain mainly include antidepressants and anticonvulsant medications.
