Over the past two decades, there has been a paradigm shift in the way healthcare professionals approach pain. This has been more thoroughly discussed in our previous blog on Pain Science. Today, we will be taking a deeper dive into the concept of central sensitization: what it is, why it’s important to understand, and how it can be treated effectively.
During 2021, an estimated 21% of U.S. adults (51.6 million persons) experienced chronic pain, and 6.9% (17.1 million persons) experienced high-impact chronic pain, meaning their pain caused a substantial restriction to daily activities1.
We discussed pain and its definition in our previous blog on Pain Science, but to review, pain is defined as an unpleasant sensory and emotional experience associated with actual or potential tissue damage2. Our nervous system is made up of an extensive network of nerves from our body, as well as our brain and spinal cord. Pain is created and processed by the nervous system when our body perceives a potential threat of harm or injury.
Pain can be acute or chronic. Acute pain comes on suddenly such as with an injury, and typically goes away within three months, or once tissue has healed. Chronic pain is defined as pain that persists longer than three months, or longer than what is considered physiologically normal for most tissue healing. If pain persists beyond the normal healing time frame, and becomes chronic, it can potentially modify the brain and nervous system structurally, functionally, and chemically, causing one to be more sensitive to pain. This phenomenon is referred to as central sensitization, or central pain.
What is Central Sensitization?
Central sensitization occurs when a person’s nervous system is persistently in a high-activity state. This decreases the sensitivity of our body to fire signals to the nervous system that our body is under threat of harm. When this happens, though the peripheral nervous system (nerves from our skin and tissue) provides limited input (i.e. no injury), the central nervous system (brain and spinal cord) responds as if there has been a high level of painful stimuli3. Essentially, painful stimuli or input is lacking or is not severe enough to explain the severe pain experienced by a person.
Pain is typically considered beneficial for our survival – to protect and limit harm. For example, it is beneficial for our brain to tell our body to withdraw one's hand away from an open flame. Central sensitization is thought to be the feeling of pain without fire. Not only is it not protective, but it can actually be maladaptive by providing no apparent protection or healing benefits.3
Central sensitization can occur with pain in any body region and has been studied in instances of chronic low back pain, fibromyalgia, TMJ, migraines, and even osteoarthritis.
As an example, let’s take Jane, a 35-year-old office worker. Jane initially experienced acute low back pain after lifting a heavy box, which was diagnosed as a lumbar strain. Despite resting and taking NSAIDs, her pain persisted and she developed increased sensitivity to pain (hyperalgesia) and pain from normally non-painful stimuli (allodynia). Jane was very fearful of moving, avoiding all bending and lifting due to fear of re-injury, and was avoiding her workout classes. Jane had an aunt who experienced back pain in the past and underwent surgery unsuccessfully, and is worried that she will end up down that path. Over the next six months, her pain became more diffuse, spreading to her upper back and neck, accompanied by fatigue, poor sleep, and mood changes. One year later, Jane's pain had become chronic and widespread, significantly affecting her daily activities. After ruling out other conditions, she was diagnosed with central sensitization.
Causes and Triggers
There are chemicals from the brain that modulate pain signals depending on the situation, whether they amplify or inhibit those signals. Because our brain is neuroplastic, this can lead to our brain persistently amplifying pain signals. Neuroplasticity is the ability of the nervous system to adapt over time. In the case of central sensitization, our nervous system has maladaptively changed to respond to stimuli or triggers that usually wouldn’t cause pain or cause pain to a high level.
Most instances of pain or injury resolve within the normal healing time frame, usually around three months or less. Certain triggers to the development of central sensitization in chronic pain include:
- Early life trauma
- Genetics/ family predisposition
- Infection
- Psychological or emotional stress3
- Diet4
To relate to the example above, Jane experienced significant fear and anxiety around her injury, which perpetuated her anxiety and left her avoiding movement and exercise.
Due to the pain arising from heightened nervous system sensitivity rather than an injury, conventional pain management methods such as medication, injections, and surgery often yield little relief. Furthermore, individuals experiencing central sensitization tend to avoid activities that trigger pain, fearing it signifies additional tissue damage. This avoidance pattern sets off a cascade of problems, wherein individuals refrain from engaging in activities they enjoy, thereby exacerbating psychological distress such as depression, reducing social interactions, and consequently, diminishing social support.
One common misconception is that what shows up on imaging tests like X-rays and MRIs accurately reflects the level of pain someone feels. But the truth is, it's not that simple. Many times, these images reveal things like arthritis, tears, or bulges, even in people who aren't experiencing any pain at all. Our blog on Imaging delves deeper into this issue. We understand that pain is multifaceted, and relying solely on imaging isn't always the best way to diagnose it, except perhaps to rule out serious conditions like nerve compression, fractures or cancer.
Diagnosis and Treatment
Central sensitization may be diagnosed once other medical conditions are ruled out. Typically, central sensitization can be diagnosed through the following signs and symptoms:
- Symptoms that have persisted for more than 3 months.
- Allodynia, which is extreme sensitivity to touch (i.e. a feather touching your skin causes pain).
- Hyperalgesia, which is abnormally increased pain sensitivity. Something that would typically cause someone discomfort or pain causes extreme levels of pain. Pain is not proportionate to injury/ tissue change.
- Cold sensitivity.
- Pain that changes with emotional state.
Due to its complexity, central sensitization often does not respond well to traditional methods of treatment. The treatment approach should be multifaceted, addressing not just the physical, but the overall well being of a person. Treatments that have been studied and applied successfully are as follows:
- Education: A person's understanding of their condition and pain can be incredibly empowering. Our blog on this topic goes into further details on how pain education is a key step in the road to recovery of central sensitization.
- Stress management: Due to the nervous system being in a heightened state, it is important to manage and relieve any other triggers that could exacerbate this, including stress.
- Relaxation techniques, such as diaphragmatic breathing, mindfulness, and progressive muscle relaxation can help to inhibit pathways in the brain that promote pain.
- Graded exercise: Exercise is key to treating central sensitization and pain, but should begin at a low, tolerable level and slowly increase in intensity and duration. Exercise does not only help physically, but can also improve sleep quality and cognitive function.
- Cognitive behavioral therapy (CBT) involves identifying harmful thoughts, emotions, and behaviors and restructuring them into more beneficial ones. Since chronic pain and central sensitization often involve maladaptive behaviors and strategies, CBT can help build more resilient thought patterns and better coping strategies5.
Conclusion
Once other medical conditions have been ruled out, and central sensitization is suspected, it's important to fully understand and weigh your options for treatment. If central sensitization is suspected, often the issue needs more than just a pill or injection to help manage. An Aware Health provider can help guide you further understand your pain, and guide you in the right direction for treatment.
If you are struggling with chronic pain, reach out to getwell@awarehealth.io to see if you are eligible for our program.
If you are a self-funded employer, getting a handle on chronic pain will improve employee health and significantly decrease claims costs. Book a demo to learn more.
Resources
1) Centers for Disease Control and Prevention. (2023). Mental health and substance use disorders among workers: 2020-2021. Morbidity and Mortality Weekly Report, 72(15), 388–394. Retrieved from https://www.cdc.gov/mmwr/volumes/72/wr/pdfs/mm7215a1-H.pdf
2) Raja, S. N., et al. (2020). The revised International Association for the Study of Pain definition of pain: concepts, challenges, and compromises. Pain, 161(9), 1976–1982. https://doi.org/10.1097/j.pain.0000000000001939
3) Dydyk AM, Givler A. Central Pain Syndrome. [Updated 2023 Feb 19]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK553027/
4) Aguilar-Aguilar E, Marcos-Pasero H, Ikonomopoulou MP, Loria-Kohen V. Food Implications in Central Sensitization Syndromes. J Clin Med. 2020 Dec 19;9(12):4106. doi: 10.3390/jcm9124106. PMID: 33352747; PMCID: PMC7766296. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7766296/
5) Central sensitization, chronic pain, and other symptoms: Better understanding, better management. Mary M. Volcheck, Stephanie M. Graham, Kevin C. Fleming, Arya B. Mohabbat, Connie A. Luedtke. Cleveland Clinic Journal of Medicine Apr 2023, 90 (4) 245-254; DOI: 10.3949/ccjm.90a.22019