About a year ago Melissa was involved in a car accident where she sustained a moderate whiplash injury. She had pretty serious pain in her neck for several weeks, but then it subsided. Recently she’s been having a very similar pain sensation, although she has not had any recent injury that would appear to aggravate the pre-existing condition. At times, the pain can get quite intense and it is significantly limiting her activities.
This kind of scenario is increasingly common for clients seeking the help of a massage therapist. However, it poses a serious challenge for the practitioner, as there is no apparent dysfunction or pathology presents that would account for the level of pain she is experiencing. This makes identifying the primary tissues at fault far more challenging. In cases like these, it is likely that central sensitization is playing a part in the pain condition and additional exploration of this option will be very helpful in finding a successful resolution.
What is Central Sensitization?
To fully understand central sensitization and how it works, we must first look at some basic principles of current pain science. The primary theory of pain transmission in the body that existed for quite some time was a simple mechanistic stimulus-response model. According to this model pain receptors on the periphery of the body were stimulated by some noxious signal such as tissue damage or inflammation. Once the threshold was reached, the pain signal traveled along specific pain pathways directly to the brain where the pain sensation was registered.
This simplistic understanding of pain transmission lasted for quite some time but did not fully explain numerous facets of pain that were observed clinically. In the mid-1960s the gate theory of pain was proposed in the classic paper by Melzack and Wall. According to the gate theory, certain pain sensations could be inhibited or encouraged depending on whether certain neurological “gates” were open of closed. For example, an accident could cause an injury to the neck and shoulder. However, more information may be temporarily coming in from peripheral proprioceptors while a person moves their body out of immediate danger. The proprioceptive information essentially ‘gates’ or limits how much information comes in from the nociceptive fibers and pain is limited while this gate is closed.
While the gate theory has not been disproven, it has shown some limitations in explaining current pain phenomenon. Some of these phenomena are more accurately explained through the concept of central sensitization.
Sensitization refers to an increase in sensitivity to certain neurological stimuli. For example, combat veterans who have been exposed to serious traumatic explosions are sensitized to loud noises like car backfiring or fireworks. It could even be as simple as a door loudly closing. This sensory stimulus does not need to be extreme in order to set off the nervous system once it has become sensitized. It appears that the process of sensitization involves adaptations by the central nervous system. Consequently, it has come to be known as central sensitization.
For many years clinicians have heard complaints from patients about pain sensations they were having that did not fully fit the existing models of pain transmission. Unfortunately, it led many to classify the patients as malingerers or as people that were simply trying to take advantage of the medical system. They were frequently told that the pain was in their head (imagined) or in many cases that they had some type of psychiatric disorder. We now recognize this was a serious error because sensitization of neural pathways can cause the exact symptoms that many of these people were experiencing.
There are several key characteristics of central sensitization1,2:
- Perception of pain where something appears painful that ordinarily should not (this is called allodynia).
- Hyperalgesia: An increased sense of pain that is out of proportion to the stimulus or pain that is very strong from a stimulus that should only evoke a weak pain sensation.
- An exaggerated pain response to some type of noxious stimuli well after the stimuli has ceased.
- Spreading of the increased sensitivity to otherwise normal tissues that do not appear injured or damaged at all.
A client reporting pain that appears out of portion to apparent tissue damage, or pain that occurs without a direct cause that is immediately apparent could be experiencing some degree of central sensitization. In this case alterations in the processing of the sensory stimuli by the central nervous system are causing pain sensations to be felt when they most likely shouldn’t be.
There are a number of common musculoskeletal conditions where central sensitization is frequently reported. They include: rheumatoid arthritis, osteoarthritis, temporomandibular disorders, fibromyalgia, various musculoskeletal disorders, headache, whiplash, neurological injuries such as carpal tunnel syndrome, and postsurgical pain.1,2
Massage therapy is used to treat all these conditions commonly so it is helpful to consider how our approach might impact and potentially address central sensitization. In many cases of tissue injury like a ligament sprain or muscle strain there is a clear correlation between specific tissue damage and the pain sensations reported. Yet, in some soft-tissue pain complaints there is exaggerated soft-tissue pain without a clear indication of where it is coming from or why.
There does not yet exist a solid base of research evidence supporting the use of massage for addressing central sensitization, simply because it has not been adequately studied yet. However, we can take what we know about the physiology of massage and apply it to the concepts of central sensitization to come up with general guidelines and ideas about how massage could benefit people experiencing these exaggerated pain sensations.
It appears that in many cases sensitization occurs as a result of overstimulation of the nervous system. We also know that massage has numerous beneficial effects on decreasing excitability of nervous system responses and encouraging a decrease in sympathetic nervous system activity. Consequently, general massage applications, especially those with a very soothing focus, could be very beneficial in helping to regulate proper neurological reporting to help decrease excitability of the nervous system. There are not necessarily specific techniques that need to be used. However, overall soothing approaches such as effleurage, light skin drag methods (dermoneuromodulcation or what is often called myofascial release) are likely to provide some of the best results for decreasing this neural excitability.
- Woolf CJ. Central sensitization: implications for the diagnosis and treatment of pain. Pain. 2011;152(3 Suppl):S2-S15. doi:10.1016/j.pain.2010.09.030.
- Latremoliere A, Woolf CJ. Central sensitization: a generator of pain hypersensitivity by central neural plasticity. J Pain. 2009;10(9):895-926. doi:10.1016/j.jpain.2009.06.012.