Why Endo Hurts: the Body, the Nervous System, and Nociplastic Pain

As we all know too well, Endometriosis is a chronic and debilitating condition that affects an estimated 1 in 9 people assigned female at birth. Our understanding of Endo is still emerging, but the modern definitions have thankfully moved away from it being considered a purely gynaecological or menstrual disease, and now identify endo as a chronic inflammatory whole body disease involving the immune, endocrine, nervous and musculoskeletal systems! Complex! Tissue similar to the lining of the uterus grows outside the uterus (often in the pelvis but has also been found elsewhere). These lesions can have their own blood supply, are sensitive to our hormones and can also produce their own, and as foreign tissue they incite the immune system (which can become trigger happy and overactive!) to produce inflammation, which then can lead to swelling, tissue changes and pain.  It has been stated that Endometriosis is considered to be in the top 20 of the most painful conditions known to humans…   it’s the pain that can be the most debilitating aspect of Endo, and the one that patients commonly seek treatment to change. It even has its own classification in the International Association of the Study of Pain (IASP) called Endometriosis Associated Pain Syndrome. On the surface, it would appear that to manage endo associated pain, we need to focus on the lesions (ie excision surgery). And this is true… excision surgery can lead to good reductions in pain… but this is not always the case. Oftentimes, pain that persists after surgery is not necessarily an indication that surgery has ‘failed’, but more that the lesions themselves were only one part of the big picture when it comes to our pain experience. Pain is a complex beast, and it’s not just what’s happening locally in the tissues that needs to be addressed for effective pain management. This blog will focus on the different drivers of Endometriosis Associated Pain. When we understand endo pain, we can start to change our mindset and work to address the multidimensional aspects of pain to help us achieve the best outcomes for symptom reduction

1.Pain drivers in the tissues 

Endometriosis pain stems from a variety of physical factors. Lesions themselves produce cytokines initiating inflammation, as well as specialised factors to build their own blood and nerve supply. A person’s unique distribution of lesions in the body will impact different organs and nerves. Lesions can bleed throughout the menstrual cycle (not just with your period), and this promotes the formation of adhesions, which can cause a ‘stickiness’ and restrict movement between the tissues and organs. The adhesions can impact the way the organ functions (eg bowel endo can impact constipation or pain with opening bowels) and the stretch sensations on movement from this stickiness may further contribute to pain perception. Interestingly, the extent of disease as described by the stage 1-4 system that surgeons use, doesn’t actually correlate to the extent of pain experienced. So someone with stage 3 endo could actually experience less pain than someone with stage 1, even though through the lens of surgery they have more significant disease. So we know there is much more going on that influences our pain experience. it is not just the type and extent of lesions present. 

The experience of pain can impact our posture and our muscle tension patterns. We all know the feeling of muscles tensing or bracing in the face of pain, as a reflexive form of protection, or curling up in a ball and not seeking out much movement as a way to try and cope. Over time however, changes in muscle activation, especially our pelvic floor, can become another driver of pelvic pain and pelvic dysfunction, including pain or difficulty with our bladder, bowel and sexual functioning. When a muscle guards and contracts it can create compression in the blood vessels that can decrease oxygen supply to those tissues. This can lead to a build up in lactic acid that can cause irritation and inflammation, and contribute to greater pain production. The muscle tension can also create compression on local nerves (the sciatic nerve and the pudental nerve are common culprits in pelvic pain), which then alters sensation and creates that frustrating buzzing, burning and numbness that nerve pain can cause. Pain from muscle tension (known as tension myalgia), can also influence pain perception in tissues nearby. We’ll talk about this process of cross sensitisation in the next section...

2. Pain Drivers in the peripheral nervous system and cross sensitisation 

There are many known changes to nerves local to the pelvic organs in endometriosis, and this phenomenon is called peripheral sensitisation. We see an increase in nerve growth factors (like fertiliser for nerve growth) within the lesions and in the peritoneal fluid, that basically increases the density of nerves in the region, which means more pathways for sensation to be taken to the spinal cord and up to the brain. Yup, just like more lanes on a highway means more cars can get where they are going… more nerve density means more sensation gets sent up to the central nervous system for processing. In addition to this, the threshold these nerves have for firing off messages can also be reduced, so it takes less input (eg a change in temperature, stretch or chemical change) for a message to be sent up. So a whisper of sensation can be heard like a scream. Endo lesions can also sneakily arise along nerve pathways, which may restrict how that nerve can move within it’s surrounding tissues and change how it communicates sensation.  

Cross sensitisation is a term that describes when messages from an affected organ or muscle get mixed up at the spinal cord and are perceived as messages from an unaffected organ. For example, what we may perceive as pain in the bladder, may in fact be pain stemming from a tense pelvic floor, but the messages got mixed up. We know that the pelvic organs and muscles are pretty incredible at how they coordinate and communicate to ensure our bladder, bowel and sexual functioning can all work together, not against each other.  It’s thanks to this communication that we don’t wee during sex for example! However it is thought that this close communication also sets the stage for these sensation mix ups. So this is why a person could experience bladder pain, without necessarily having endo around the bladder or a UTI. Or we might experience our pain as ‘spreading’, and worry that it may be endo lesions spreading, when in fact it could be this process of cross sensitisation. 

3. Pain Drivers in the Central Nervous System

Last but not least, we need to discuss the fascinating role of the BRAIN in our pain processing. One important pain science fact is that we don’t actually have ‘pain’ receptors in the body. Instead it’s just sensory neurons that pick up different sensations, and send that information up to the brain for processing. They can pick up mechanical sensations (ie pressure or stretch), thermal sensation (ie changes in temperature) and chemical change (like lactic acid build up or inflammation). It’s then the brain’s job to take these sensations and combine it with other information from the environment around us, and from our inner landscape of memories, thoughts, feelings and beliefs, to decide whether or not these sensations represent something important. Do they represent a threat to our survival in this moment? If yes, then they warrant our attention and a fast response or reaction, and pain will be the brain’s output to make us start protecting ourselves however we can. Or do these sensations represent something neutral, boring, or not at all implicated in our survival? Then they don’t warrant the same kind of attention or response, so less pain or no pain will be the brain’s output. So you can see here that our mindset around the meaning of pain, as well as our past experiences of pain, can have a big impact on our present moment pain experience. 

Nociplastic pain, also known as central sensitisation, refers to pain that arises from changes in our brain’s processing of pain, rather than tissue damage or inflammation. Norman Doidge in his book ‘The Brain that Changes Itself” refers to persistent pain as “the dark side of neuroplasticity”, in that we know our brains are plastic, changeable, and adaptable to our experiences - whether that be our sensations, thoughts, feelings, or environment. In endometriosis, the combination of ongoing pain, with the common experience of delayed diagnosis (aka years of feeling misunderstood, invalidated, gaslit, and anxious around not understanding what is happening in your body…) drives plastic changes in the brain. The years of not knowing what our pain was about, engender a strong threat response in our nervous system in response to sensation and pain. This is our brain’s way of trying to protect us, but it actually has the effect of zooming in our focus on the pain sites and turning up our pain volume switch - our brain wanting to keep a very close ‘eye’ on what’s happening in this very special area of the body. 

Our emotional and psychological health can’t be forgotten when we talk about pain. As if it was dancing a tango with pain, sometimes the pain is taking the lead, pushing our mood around or driving anxiety up. Yet sometimes our negative thoughts or fearful feelings can take the lead, and unfortunately this can lead to nervous system dysregulation that pushes our pain up. We will all feel revved up in our stress response at times, and feel especially triggered by certain events or sensations, but our body’s ability to recover from that stress, feel safe and recalibrate back into our relaxation response, is essential for optimal health. When pain and disease is chronic, managing our nervous system is nuanced and challenging. How can we move our system out of fear and protection, and into safety, when we have lived a life waiting for pain to come back? Not an easy feat. But when working on a nervous system regulation plan with our clients, it always comes back to how we can attune to and regulate our moment to moment experience. Our mind will often move to focus on negative past experience and future worries - it’s an evolutionary strategy to try and predict the future and keep us safe from harm. But will often feed into dysregulation and turn pain up. Bringing the mind into the present and using a blend of body-based and cognitive strategies to connect to safety and calm, can really help to turn down tension and pain. It can’t be your only strategy, but it is often one of the missing links in pain management. And one that is essential to start to progressively rewiring your brain to feel less pain.  

So taking into consideration these key elements of pain, it’s no wonder that we need a multifaceted approach to get symptom reduction! Medical and surgical management is very important, however pelvic physiotherapy, mindful movement and exercise, nutrition and supplementation, meditation and nervous system regulation, prioritising quality sleep and mental health support all play a part in changing your pain experience. 

What component of pain were you least familiar with?

What are the therapies above that you have never considered as helpful for pain management?

We take a deep dive into pain science and practical strategies to implement at home in our Evolve 8-week course that is set to launch in May 2023. Please sign up for our newsletter to hear the launch date first!

In the meantime, follow along on insta for more education, tips and tricks for managing your Endo, your way. 

x Felicity & Jess