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Endometriosis and Central Sensitization | Image Courtesy of Jonathan Borba via Unsplash
Endometriosis and Central Sensitization | Image Courtesy of Jonathan Borba via Unsplash

What's the Link Between Endometriosis and Central Sensitization?

Endometriosis affects roughly about 10% of reproductive-age women, and is characterized by endometrial-like lesions that grow outside of the endometrium (the lining of the uterine wall). Women with endometriosis have symptoms such as: chronic pelvic pain, dysmenorrhea, abdominal pain, infertility, constipation, interstitial cystitis/painful bladder syndrome, and more.

Often endometriosis is treated through hormonal management and/or surgically. However, 18-27% of patients with endometriosis treated via hormonal medications reported no relief from symptoms. About 20% of patients with endometriosis treated through surgical excision or ablation continued to experience chronic pelvic pain and other endometriosis symptoms. Moreover, 70 to 80% of women with chronic pelvic pain with confirmed endometriosis lesions do not have lesions in the areas where they experience symptoms.

How could that be?

We are about to dig in to the science of how chronic pain develops, specifically in endometriosis. More clarification to these terms will be provided below, so hang in there!

Chronic pelvic pain can lead to peripheral and central sensitization via viscerosomatic convergence, which in turn can lead to pain in areas away from the source of the lesion. Central sensitization can also perpetuate pain and decrease the threshold of pain. Endometriosis targeted treatments may not address the pain due to central sensitization and myofascial dysfunction, which can persist even after lesions are removed or managed.

How does central sensitization start?

It starts with an injury or noxious stimulus (a painful insult). As a result, neurons start to fire to signal danger, and inflammatory cells are sent to the site to heal and recover. However, when the noxious stimulus keeps firing, it can lead to peripheral sensitization. Over time, peripheral sensitization leads to central sensitization (read below for more information). 

Peripheral Sensitization

Repeated or prolonged activation of nociceptors (our pain receptors) results in a lower pain threshold known as peripheral sensitization. The lesions can actually innervate (or connect with) nearby blood vessels helping the lesions expand and grow. Due to the lesions, different types of fibers such as C-fibers, sympathetic fibers, tumor necrosis factor-alpha, nerve growth factors, mast cells, etc. are all involved in increasing inflammation, thus causing more pain. 

With peripheral sensitization, neuropeptides are secreted and released into the peripheral tissue after being activated repeatedly. This leads to vasodilation (increasing blood flow), and more immune cells are recruited to these sites. The repetitive firing of nociceptors transmit their signals to the dorsal horn of the spinal cord, and then travel to the brain. Repetitive and prolonged exposure of pain will eventually lead to changes in the central nervous system, initiating the process of central sensitization.

Central Sensitization

Central sensitization is the excessive firing of the nociceptors in the central nervous system and eventually starts to, “amplify and perpetuate the perception of pain long after the initiating pathology resolves.” (Aredo, et al.) Eventually, patients start to experience allodynia (pain from a non-painful stimulus) and/or hyperalgesia (increased pain to a painful stimulus). Three processes may be responsible when it comes to chronic pelvic pain: 

  1. Viscerosomatic convergence: visceral (organ) input to the brain almost always includes nearby muscle and skin input via viscerosomatic convergence. This can lead to referred pain patterns and explains why women experience pain in muscles innervated by the same and neighboring spinal segments as the organ (i.e. source is bladder dysfunction, but we may feel more abdominal muscle pain or low back pain instead)
  2. Viscerosomatic reflex: both visceral and somatic nociceptors connect with interneurons in the spinal cord that can activate alpha and gamma motor neurons that innervate skeletal muscle. Persistent visceral input can increase muscle tone and instigate spasms in the area of the referred patterns. 
  3. Chronic, repeated local pain stimuli may affect the hypothalamic-pituitary-adrenal (HPA) axis leading to decreased cortisol levels and thus exacerbate pain. This can lead to other changes in the brain, such as increased volume in the periaqueductal gray (PAG), which is imperative in pain modulation processes.

Over time, dysfunction in the muscle and surrounding connective tissue via the viscerosomatic processes can lead to myofascial pain and trigger points. Studies have shown that myofascial trigger points are correlated with endometriosis, interstitial cystitis/painful bladder syndrome, vulvodynia, IBS, coccydynia, and urethral syndrome1. Trigger points are small nodules on tight bands of muscles that are thought to be in a sustained state of contracture. Women with confirmed endometriosis often have trigger points in the abdomen and pelvic floor. It is no wonder then, that most women with endometriosis also have pain with sex, constipation, and painful urination (however conditions of these organs can occur concurrently as well).

How do you know if you have central sensitization?

How do you know if you have central sensitization? There is a great outcome measure called the Central Sensitization Inventory or CSI. It has been validated in those with chronic pain conditions to differentiate between centrally sensitized and non-sensitized patients. One study found that specifically for women with endometriosis, a cutoff of 40 on the CSI indicated central sensitization. This study also found that a cutoff of 40 for those with endometriosis was also associated with a younger age onset of symptoms and severity of pain2. 

Physical Therapy and Multidisciplinary Care Program

Once the trigger points are developed, they can be a source of pain on their own, even after the initial insult (endometrial lesions) have been removed or resolved. Physical therapy manual techniques, stretches, joint mobilizations, and exercises/foam rolling can help release trigger points and myofascial pain. In addition, physical therapists can help downregulate the nervous system, train on breathing exercises, and educate on bladder/bowel health. It is important to have a multidisciplinary approach when it comes to central sensitization and may involve other professionals such as counseling/psychotherapy, pain education, and pain/medical management in addition to physical therapy. This is why many endometriosis specialists will sometimes require physical therapy and other complementary alternative therapies before and after endometriosis surgeries to maximize the potential of healing and reducing symptoms. 

Have questions or concerns about endometriosis and central sensitization? Please give our office a call or schedule an appointment through our website.  

 

References:

Abbott J, Hawe J, Hunter D, Holmes M, Finn P, Garry R. Laparoscopic excision of endometriosis: a randomized, placebo-controlled trial. Fertil Steril 2004;82:878-884. 

Aredo JV, Heyrana KJ, Karp BI, et al. Relating Chronic Pelvic Pain and Endometriosis to Signs of Sensitization and Myofascial Pain and Dysfunction. Semin Reprod Med 2017;35(2):88-97. doi:10.1055/s-0036-1597123

Hsu AL, Sinai N, Segars J, Nieman LK, Stratton P. Relating pelvic pain location to surgical findings of endometriosis. Obstet Gynecol 2011; 118(2Pt 1):223-230. 

Orr NL, Wahl KJ, Lisonek M, et al. Central sensitization inventory in endometrial-like tissue and pelvic pain. Pain 2021;163:e234-e245.

Vercellini P, Fedele L, Aimi G, Pietropaolo G, Consonni D, Crosignani PG. Association between endometriosis stage, lesion type, patient characteristics and severity of pelvic pain symptoms: a multivariate analysis of over 1000 patients Hum Reprod 2007; 22(1):266-271. 

Yong PJ, Alsowayan N, Noga H, Williams C, Allaire C, Lisonkova S, Bedaiwy MA. CHC for pelvic pain in women with endometriosis: ineffectiveness or discontinuation due to side-effects. Hum Reprod Open 2020;2020:hoz040.

Zheng P, Zhang W, Leng J, Lang J. Research on central sensitization of endometriosis-associated pain: a systematic review of the literature. J Pain Research 2019;12:1447-1456. 

What Our Patients Have to Say

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Testimonial by Fritzette H.

I went to Heather after the birth of my third child. It was lucky, really, that I was referred to her, because my doctor had referred me to a surgeon for a possible hysterectomy or pelvic wall rebuild. Thankfully, I went to Heather before undergoing either surgery, she was able to fix the problem. She has studied extensively in women's health--even written a book about it--and was able to diagnose my problem, suggest a course of treatment (6 weeks), and then follow through with said treatment. By the end, as she said, I was as good as gold. Boy, was it worth it! Though uncomfortable to talk about, much less write about, it is worth getting the word out there. If you have painful intercourse, especially after birth or other trauma, the treatment may be as simple as Physical Therapy (with Heather, of course). I highly recommend her.

-- Fritzette H., 3/24/16 via Yelp!

Testimonial by A.W., age 32

I wanted to let you know that my pelvic floor held strong and gave me no trouble whatsoever in my trail race this morning (12 miles)! In a way, I felt like I ran better than ever because my core feels so rock solid from all the exercises you have me doing. That was especially valuable on the technical downhill - I just flew down the trail because I had confidence in my balance and form. Thank you for helping me get back to doing what I love.

-- A.W., age 32
(completed Post-partum Renewal Program using the InTone biofeedback/stim unit)

Testimonial by Ann V.

I wish i could give this place 10 stars!! 
I have been suffering from vaginismus for 5 years and never found the cure to it. I had seen an ob/gyn and he diagnosed me with vaginismus and told me i needed a surgery to cure my condition, which i refused to do. He also referred me to a PT that he works with, i had given them multiple calls and they never responded back to me, so i started searching yelp for another PT. I am SO HAPPY I found Heather's office! I was working with Laureen, and with her guidance and techniques i was able to be cured from vaginismus in only 2 1/2 short months!!! I couldn't believe how quickly their program worked for me! I am forever grateful and thankful from Heather, and Laureen! They are the absolute best at what they do!

Read more: Testimonial by Ann V.

Testimonial by Y.L. (mom of 2)

After having my second baby via C-section I searched for months to try to find help for my lower back pain and separated abdominal muscles. I finally came across Heather Jeffcoat via a mommy blog. I reached out to her via email and set my first appointment. My first appointment went amazing … she listened to what my symptoms, check my separation and explained to me in detail what the next steps would be. Not only did my abdominal separation go from 3 to about 1 -1/2 but my back has pain has significantly reduced. I’m personally recommending all my mommy friends to Heather!

Y.L. (mom of 2)

Testimonial by T.C.

While pregnant with my twins, Heather took care with keeping me on my feet and pain free. She saved my back, my sanity and the holidays! I would recommend her to every “mom” looking to stay on her feet during pregnancy and post-partum.

-- T.C.

Testimonial by Carolina J.

I had tried Pelvic Floor Physical Therapy before (with another PT) and I had a really bad (painful) experience. A friend of mine and fellow patient, told me about Heather, Laureen and Femina PT (née Fusion Wellness & Physical Therapy) and I decided to try again. I am so happy I did! Femina PT have, literally, changed my life. I was able to do again things I couldn't do for over 10 years!! Their bedside manners are impeccable, their knowledge and understanding make me feel comfortable to recommend this place to anyone in pain. Specially if you have Endometriosis. 100% recommended!!

-- Carolina J., 12/28/16 via Yelp!

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