Pain
Acute versus chronic pain
There is a significant difference between acute pain and chronic (or persistent) pain, even though they may feel the same.
Acute pain is short-term and tends to be associated with tissue damage (see nociceptive pain). For example, an ankle sprain will temporarily hurt, coupled with bruising and swelling. This is acute pain. Acute pain resolves as the tissue heals because the affected part no longer needs protection. Healing typically takes less than three months, even for severe injuries.
Chronic pain lasts longer than acute pain and often does not indicate ongoing damage, even though it may feel like it. In the past it was assumed that this was because the injury had not healed. However, chronic pain is less to do with tissue injury and more to do with the central nervous system. It is like the volume knob on the pain system has been left turned up like a radio stuck on loud. Chronic pain can take over a person’s life.
Chronic pain is complex and different for everyone. It can be associated with surgery, trauma or another condition. Chronic pain can exist without a clear reason. It can be a symptom of disease or it can be a standalone condition. It might show up in a scan or test, or there may be no evidence of its existence. Chronic pain can occur anywhere in the body or at multiple sites. One person can have several forms of pain or just one. It can be daily, or recurrent (such as migraine).
It is important to understand that the pain volume can be turned down again, but takes effort and time. It won’t happen by itself and requires patience in working towards it.
Pain and the brain
When an injury first occurs, acute pain alerts the brain to stop or withdraw the body from danger in order to avoid further damage. Injured tissue sends information through nerves to the brain. The brain then sends signals back to the body to create a change in behaviour. Without acute pain, a person may continue to hurt themselves before healing can take place.
The brain is an important part of pain. Nerves from the body only transmit signals to the brain and report something has occurred. The sensory experience of pain, or how much something hurts, is produced in the brain. The role of the brain is to make a sensible interpretation of all signals being sent from the body. The brain weighs up many aspects of the environment, life factors, stress levels, anxieties, belief systems, whether there has been pain in the past, emotional state, and the future. Only after sorting through these factors does the brain produce pain and create an image of how bad it is.
Nerves can get sensitive
When an injury first occurs and there is tissue damage, it is normal to experience soreness both near the injury and other areas around it. For example, after stubbing a toe, pain may spread to the foot, ankle or calf, beyond areas that were damaged.
In this scenario, the pain volume around that area is turned up. This normal and helpful at first. The increased pain volume is helpful as a reminder to slow down in order to avoid more damage. Typically this pain volume will reduce as tissue healing occurs.
However, in some situations pain can persist longer than is helpful to the body. Nerves can become highly sensitive and signals begin to be sent more frequently in the nervous system. This sets up self-reinforcing feedback loops between the spinal cord and brain.
Nerves do more than send messages around the body. All nerves, including those in the spinal cord and brain, change in response to what takes place in the environment and the person’s perception of it. Nerves continuously change how sensitive they are in response to what is going on around them, like turning the volume up or down on a radio. Sometimes this can result in a change in pain levels without immediately obvious reasons.
Persistent pain and sensitisation
It may feel like persistent pain is due to ongoing or recurrent damage to the body. However, pain that remains after three months has more to do with changes in the nervous system than ongoing tissue damage.
Persistent pain can be described as unhelpful changes in the nervous system. The original injury would have healed as much as possible and, although there may still be signals from stiff joints or poor muscle control, the biggest problem is the increased pain volume. The nervous system has become more sensitive.
While persistent pain feels like acute pain, it acts differently. The nervous system responds to normal messages such as touch, cold, or movement as if they are dangerous. The pain volume stays turned up long after the injury has healed. Minor sensory input can lead to a great deal of pain. Something that may not have hurt initially begins to; or, something that may have only hurt a little starts to hurt a lot. These are signs that the problem is changing from one of physical injury to that of a loud nervous system. This is called sensitisation.
Chronic pain changes the brain
When the nervous system is sensitised, it is common to experience pain with everyday movements such as walking, bending or twisting. In some cases, even thinking about a particular movement or activity can trigger pain.
The brain is made up of different parts, each with different functions. All parts are interconnected and work as a whole. Even seemingly unrelated parts such as smell, movement, or emotions can form connections. When a person repeats a particular movement or activity on a regular basis, the brain creates a pattern of nerve connections. If a movement is painful for long enough, the brain will strengthen that connection between movement and pain. Nerves that fire together, wire together. For example, the brain joins the dots between normal sensations coming from the spine, the movement of bending, the memory of injury, and the experience of pain. This unhelpful pattern can then become turned up in volume once sensitised. Simply preparing to do the movement may be enough to cause the pattern to create the sensation of pain. The body has healed as much as it is going to but the movement still hurts.
Life factors affect pain
Every system that keeps the body running can be involved in producing pain. The way a person experiences pain is influenced by many factors. Humans are social, spiritual, physical, and mental beings. Persistent pain is a whole-of-life problem, therefore effective management needs to take a holistic approach. The way pain is experienced is highly influenced by overall well-being.
Stressful or emotional situations can affect the volume of pain. It might be fatigue, poor sleep, an argument with spouse or child, a rough day at work, anxiety about paying overdue bills, or grief over death of a friend. Thoughts, beliefs and the environment can make the nervous system susceptible to sensitisation.
People with chronic pain tend to be regimented in making sure they get adequate rest, avoid trigger foods, take medications at the correct times, and avoid flare-ups. It is understandable that sometimes they just want to feel normal and eat pizza or stay up late, even if they know they will pay for it later.
People in chronic pain fight daily to be able to understand their bodies and to do things others take for granted. They are often surrounded by a society (even doctors) that does not understand their challenges and therefore cannot provide adequate support.
Begin the upward spiral
Natural chemicals, called neurotransmitters, associated with tiredness, stress, anxiety, and depression are very similar to the chemicals used to communicate danger or damage. In a sensitised nervous system, chemicals released by low moods and feelings can turn up the volume and make pain worse.
Pain then leads to avoiding movement and activity, creating weakness, stiffness, and tiredness, making the experience of pain worse. There is no more damage in the body, but because of this vicious cycle, pain and the ability to cope worsens over time.
Fortunately, it works the other way too. Neurotransmitters associated with happiness, fun or satisfaction act to turn the volume down. This is a powerful system that is likened to a medicine cabinet in the brain.
The first step to understanding chronic pain is that the pain is not causing ongoing damage. Physical well-being, social environment, health beliefs, and mental health all contribute to the experience of pain. Pain is not a conscious decision, but with the right help, consciously addressing all these factors can start to turn the volume down.
Dr Neil Bossenger is currently undertaking a PhD in chronic pain and its associations with the autonomic nervous system. At Spinewave we understand chronic pain and what it takes to support someone experiencing it. For more information, please contact us or call 09 522 0025.