Nerve sensitization: chronic headaches, back pain, digestive issues


Sensitization syndromes represent a whole group of disorders that are commonly stress-induced and worsened with stress. Interestingly, there is a sensitization syndrome for many systems in the body! Everyone’s body communicates with them differently. Some get headaches, some get stomach pain, some get back pain, and some just get mad!


Some of the most common sensitization syndromes are listed below.


Body System                        Sensitization syndrome

Joints/muscles                    chronic back pain and neck pain

                                                   chronic muscle pain (myofascial pain syndrome)

                                                   fibromyalgia

                                                   tempromandibular joint disorder


Digestive                               chronic heartburn, stomach pain

                                                   irritable bowel syndrome


Neurologic                            migraine headaches

                                                   tension-type headaches

                                          

Urinary                                  chronic bladder pain (i.e. interstitial cystitis)


Reproductive                      chronic pelvic pain


This group of stress-related disorders is referred to collectively as central sensitization syndromes (CSS). According to some estimates, sensitization syndromes are likely to be the most common reason for patient visits to an outpatient clinic. An estimate of upwards of 30 million adults in the USA suffers from one or more sensitization syndromes (Yunus, 2015). They are referred to as central sensitization syndromes because they can all have nerve sensitization that affects the symptoms. Nerve sensitization makes the nerves more sensitive and more reactive. It actually amplifies the pain level. The pain literally feels worse. 

 

Central sensitization is the result of dysfunction in the nervous system.

There is dysfunction in how pain signals are processed, transmitted, and perceived. Technically speaking, it is the result of disordered sensory processing in the brain and spinal cord (Nij 2021). More practically, when sensitization is present, it changes how a person experiences pain. The nerves are over-sensitive and over-reactive. So, they send more pain signals, more often. They are like a tattletale, constantly telling the brain something is wrong. The brain then tells the person something serious is really wrong! It is a maladaptive biologic process, but it is real and causes a lot of suffering. 

Sensitization is associated with the development and maintenance of pain. The over-sensitivity lowers the threshold for feeling pain. Where a day full of house cleaning normally leads to some mild soreness in the back may now result in feeling severe pain and needing to rest for two days. Naturally, this is going to lead someone to think they have a more serious injury. Understanding it and managing it is a process that takes time. 

 

When sensitization is present, it changes how a person experiences pain. They feel it more intensely, more easily, and in more places

1) There is increased sensitivity to painful things. For example, if you lift something too heavy instead of feeling a mild pull in your back that is “3 out of 10” on a pain scale, it feels like a “7”! It literally hurts more. The nerves are telling the brain it hurts more. 

2) Pain in response to things that aren’t normally painful. For instance, feeling pain with just a light touch or mild pressure on the back. Normally, light pressure on the back muscles doesn’t cause discomfort outside of an injury.

3) The pain spreads to a larger area and may include more parts of the body. For instance, with a pinched nerve in the back instead of feeling pain in the area of the irritated nerve the entire leg may hurt.  

 

The symptoms from central sensitization syndromes can cause non-pain symptoms too.

These symptoms include fatigue, poor sleep, and difficulty concentrating. They associate with mental health conditions including depression and anxiety; each one worsening the other. The disorder increases the risk of depression and anxiety. Anxiety and depression enhance pain perception. It is a bidirectional relationship.

 

The list of conditions that fall under central sensitization syndromes was the most common group of stress-related disorders that I saw in the clinic. For the people not responding to standard therapy, like physical therapy, or anti-inflammatory medications, typically stress or sensitization was the important factor that hadn’t been addressed.