SIBO: Small intestinal bacterial overgrowth and the Vagus nerve. The problem of nerve compression.

Ross Hauser, MD

Many people with a diagnosis of SIBO or Small intestinal bacterial overgrowth are very familiar with possible causes and treatments as they, you, have heard about many causes of SIBO and they may have tried many treatments.

If you are reading this article it is likely that the treatments you have had have not been effective enough or at all. Over time and as treatments failed, you may have been told the possible cause of your intestinal problem (focused solely on gastrointestinal distress) may not be the actual cause.

There is also a strong chance that your diagnosis of SIBO is only one of many health challenges you are facing. At our center, we see many patients with a myriad of mysterious and simultaneous conditions and symptoms. Typically they also start treatment with us by explaining and showing us the shopping bag full of medications that they are taking for each symptom and the very thick print out of all the tests that they have had performed over the years.

For people with SIBO or other “stomach distress,” this would include rotating, alternating and combinations of antibiotic prescriptions for Neomycin, Levofloxacin, Ciprofloxacin, Metronidazole, and Rifaximin. Some “enlightened,” doctors may suggest the use of probiotics. As you probably know first hand, all these medications are designed to try to address the problems and symptoms of abdominal bloating, cramping, and digestive disorders by reducing the number of bacteria in the intestine. You may be currently on this rotation now or have been on this rotation for years as a kind of “hit and miss,” treatment. As you also probably know, this strong regiment of antibiotics is also usually arrived at when there is an added diagnosis of Irritable Bowel Syndrome and its accompanying problems of diarrhea, constipation, problems of gas, and problems passing stool.

When diet hasn’t helped your Small intestinal bacterial overgrowth

A June 2022 paper in The American journal of gastroenterology (8) discussed the problems of diagnosis and dietary recommendations for SIBO. “. . . The diagnosis of small intestinal bacterial overgrowth is limited by a lack of sensitive and specific tests, with significant knowledge gaps in relation to therapeutic measures to manage and cure small intestinal bacterial overgrowth. Currently, antimicrobials (antibiotic, antifungal, antiparasitics) are the established management option. There have been significant clinical advances in dietary interventions related to the small bowel, but this area is currently a novel (new and evolving)  and advancing field for both patients and clinicians.

Vagus nerve problems or problems of vagal tone

If your symptoms were limited to gastrointestinal distress, you would be in the hands of capable gastroenterologists and you would be managed and likely greatly helped. But what if your problems were bigger? What if SIBO and irritable bowel and possibly Leaky Gut Syndrome and its contributions of chronic diarrhea, constipation, bloating, nutritional deficiencies and even malabsorption, headaches, brain fog, skin problems, and joint pain joined in? What if your story sounded like these people’s that we will discuss below?

In this article, we are going to present one possible explanation for your problems that may not have been explored at this point. This is a connection between your small intestinal bacterial overgrowth, your SIBO, other related digestive problems such as Irritable Bowel Syndrome, Leaky Gut Syndrome, and vagus nerve compression. We are going to present information that these problems are related to Vagus nerve problems or problems of vagal tone.

Before you say I have read about that, or I have tried meditation and other stress-relieving techniques to help improve my vagal tone, that is not what this article is all about. This article is about identifying cervical spine instability, pain in your neck, and vagus nerve compression. This article is about that compression upsetting and impacting the ability of your digestive tract to function properly. This article will also present options on how to possibly fix that.


Cervical spine instability – The many ways cervical instability can cause small intestinal bacteria overgrowth

Possible symptoms related to small intestinal bacteria overgrowth

I believe I am suffering from cervical instability

I believe I am suffering from cervical instability and while my doctors may agree I have neck issues, they are confused and not sure that my neck issues are the cause of all the issues I have. In my neck, I have cracking, stiffness, and severe neck pain. The pain is causing pressure in my head, eye pressure, and vision difficulties. Many times I nearly pass out or faint when I stand. I have migraines, migraines from dizziness, and cognitive decline.

I have dysautonomia, interstitial cystitis, and bladder problems. I have chronic fatigue syndrome / Myalgic encephalomyelitis. My digestive problems include SIBO, constipation, and bowel obstruction. I have a history of years of antibiotic use.

It started with a car accident and a whiplash

I have many symptoms as they relate to my neck. The biggest problem was the whiplash injury I suffered in a car accident. Over time this caused me to have a military neck and loss of the natural curvature of my cervical spine. Some of my providers are suggesting that this whiplash problem is the cause of my SIBO and digestive disorders. I have a very slow GI transit time, sometimes this could approach a week. They have made mention of the vagus nerve and digestive problems and how I may have nerve compression.

It started with a car accident and neck and jaw injury, now my stool does not move.

I was in a car accident almost 8 years ago and fractured my jaw. Since the accident, I have suffered from C1 – Atlantoaxial instability. I have pain, stiffness, loss of range of motion in my neck. Sometimes my neck gets stuck. After the accident, I also started having digestive issues. I have SIBO and a diagnosis of colonic inertia. My colon does not work. I do not make good stools and when I do, my stool does not move. It is stuck.

It got worse after cervical spine surgery.

I started having significant neck pain. It spread into my arms and I was diagnosed with c3-c7 radiculopathy. While this neck pain was worsening I started to have severe gastrointestinal issues. This included new and sudden food intolerances. There was concern about SIBO and bowel transit. I did however start taking better care of my health and watching the foods I eat.

As my neck pain worsened and more symptoms developed, I decided to go ahead with my surgeon’s recommendation for disc replacement surgery. This surgery did not go well for me. Besides the continued problems with cervical radiculopathy, my digestive problems have grown. I have bloating, my stomach “jumps,” like in a spasm. I have a diagnosis of dyspepsia which only means to me that I have a problem with indigestion and I can’t get better with “better,” drugs. I also have problems with bowel transit time, inconsistent stools, and stool transit in my colon. I am just looking to make sense of all this and finally find the right path.

Sphincters, Valves, and Bowel Transit. The answer may be in the Vagus Nerve.

Above I discussed where many people have made a connection between the Vagus Nerve and the problems of digestive disorders including Small Intestinal Bacterial Overgrowth. However, this connection is made usually in the context of someone suffering from stress and anxiety, and its remedies are called for in meditation, stress management, anxiety prescriptions, and medications. This would also include cortisol and adrenaline control and overstimulation of the “fight-flight” response. See our article on Autonomic nervous system dysfunction. But what few discuss or examine is the possibility that cervical spine instability is causing compression on the vagus nerve and this compression is distorting messages from the brain to the digestive tract. In other words, stool traffic is backed up, bacteria is showing up in places it should not, gas is trapped.

What are we seeing in this image?

Cluster headache treatment - cervical ligament instability and the trigeminal and vagus nerves

If you look at the illustration above you will see where the Vagus nerve is closely related to the C1 – C2 – C3 vertebrae. While doctors usually discuss the vagus nerve in the singular sense, there are two vagus nerves, one on each side of the neck and in combination, they are referred to as the vagal nerves. This means that the degenerative damage in your neck can significantly impact the function of one or both vagus nerves. The one on the left side of your body and the one on the right side of your body.

Digestion & the Vagus Nerve: Sphincter function and related symptoms affected by neck instability

Ross Hauser, MD discusses digestion and the vagus nerve as it relates to the sphincter function. In the histories of patients who we see in our center, they often feel like they hit a wall with regard to finding resolution of symptoms or their digestion conditions because the focus has been too narrow. When looking at many digestive symptoms through the aspect of vagus nerve health, many times solutions can be found because the vagus nerve innervates many vital digestive organs. Thus, in our center, we find that patients who have digestive complaints as part of their constellation of symptoms that also point to vagus nerve impairment, that the upper cervical area and cervical curve should be analyzed and examined to see if this could be the cause of the issues.

Vagal dysfunction and small intestinal bacterial overgrowth: The medical hunt for a connection

Digestive inflammation

Jessica Robinson-Papp, MD is a practicing neurologist and clinical researcher at the Department of Neurology, Icahn School of Medicine at Mount Sinai, New York. She specializes in helping people with HIV. In June 2018 she and her colleagues published a paper (1) making a connection between Vagal dysfunction and small intestinal bacterial overgrowth. Here are the learning points:

So one connection is that vagal dysfunction could cause digestive problems which would create inflammation in the digestive tract would worsen the problem it was itself creating. Inflammation is a problem caused by the vagus nerve.

An indicator of nerve inflammation

In 2007, a study was published in the World Journal of Gastroenterology (2) from a research team that wanted “to offer an explanation of one possible cause for functional dyspepsia (indigestion) and irritable bowel syndrome caused by cervical spondylosis.” In this study, the research team used laboratory rats who had surgically induced cervical instability at the C4-C6 levels. As a result, the researchers noted that in both the spinal cord and the stomach, there were elevated inflammatory markers including c-Fos protein, an indicator of nerve inflammation.

Symbiotic intestinal microbiota that presents a risk factor for intestinal inflammation

An interesting study came out of Switzerland in 2018. (3) What makes this study interesting is that it was lead by researchers in the University Hospital of Psychiatry, University of Bern. Specifically the Division of Molecular Psychiatry. Molecular Psychiatry seeks to uncover biological mechanisms underlying psychiatric disorders and their treatment. We see many patients with cervical spine instability who have been recommended to psychiatry. Here the research team presents the biological aspect, not the psychiatric aspect, of gastrointestinal disorders as related to the vagus nerve.

“The gastrointestinal tract is constantly confronted with food antigens, possible pathogens, and symbiotic intestinal microbiota that present a risk factor for intestinal inflammation. It is highly innervated by vagal fibers (vagus nerve) that connect the central nervous system with the intestinal immune system, making (the) vagus (nerve) a major component of the neuroendocrine-immune axis. This axis is involved in coordinated neural, behavioral, and endocrine responses, important for the first-line defense against inflammation.”

Above we see that the vagus nerve is shown responsible for fighting digestive tract inflammation.

Does the SIBO cause small bowel transit time or does the small bowel transit time cause the SIBO?

Dr. Bani Chander Roland, at the time of this study was a researcher affiliated with John Hopkins Medical School and Yale University School of Public Health. He and his colleagues published a paper in the Journal of clinical gastroenterology (4) where they made an interesting post observation.

Here is the interesting observation.

So here we have an observation. A disruption in the normal flow and transit of foods caused the SIBO. Let’s go a step further and continue on with research from Dr. Bani Chander Roland.

SIBO is a problem of stuck valves and excess acid

In the American Journal of Digestive Diseases (5) Dr. Roland Chander Bani continued into this research by making these observations:

Small intestinal bacterial overgrowth (SIBO) is an increasingly recognized clinical syndrome; however, its origin and causes are poorly understood. In this study the researchers hypothesized that loss of gastric acid, a delayed intestinal transit, and ileocecal valve dysfunction may cause the development of SIBO.

Explanatory note: The ileocecal valve is a sphincter muscle where the small intestine and large intestine meet. When the small intestines are done absorbing foods, it passes the remnant product of digested food materials off to the large intestines at the colon.

  • Thirty patients with suspected SIBO were tested for their ability to move food through the intestines, ileocecal junction pressure which is the ability of the ileocecal valve to open and close properly and at the right times), small bowel transit time, and regional gastrointestinal pH. (The measurement for the amounts and potency of gastric acids).
  • Conclusions: Patients with SIBO have significantly lower ileocecal junction pressure (the valve is not opening and closing when it should), prolonged small bowel transit time, and a higher gastrointestinal pH as compared to those without SIBO.

The vagus nerve and the small intestines, inflammation, overgrowing bacteria, stuck valves, and high acid. The road may lead to cervical spine instability and neck pain.

The small intestine’s primary function is to absorb the nutrients from the food we eat. To do this very few bacteria are necessary.  Small Intestinal Bacterial Overgrowth (SIBO) is when an enormous amount of bacteria start residing and growing in the small intestine.

The small intestine is able to do its all-important nutrient absorption job well because there are a series of sphincters and valves and neurological mechanisms that control motility to ensure that when the partially digested food gets to the small intestine it is ready to have the nutrients absorbed.  When a person with SIBO gets on a food allergy elimination diet and good probiotics but symptoms persist it is most likely the SIBO is actually from a structural cause.

Most of the digestive tract from the pharynx to parts of the large intestine are neurologically under the control of the vagus nerve.  When a person has cervical instability that inhibits normal vagus nerve flow, the coordinated integrated processes that are necessary for proper digestion of nutrients break down.

The small intestine has very few bacteria because the bacteria in the food are destroyed by stomach acid and bile both of which are necessary for the proper breakdown of the food we eat.  When there is vagopathy (degeneration or decrease vagus nerve flow) a person can experience gastroparesis and low stomach acid, both of which can cause the chyme (partly digested food that goes from the stomach through the pyloric valve into the duodenum) to prematurely get into the small intestine before the food is digested properly.  In other words, the chyme is not ready yet for the small intestine.  When there is fat in the chyme, the bile produced by the liver and stored in the gallbladder is then released through relaxation of the sphincter of oddi.  Dysfunction of the sphincter of oddi occurs when its neurology is off by decreased vagus nerve flow to it.  Without the normal amount of stomach acid breaking down the food (chyme) and an inadequate amount of bile going into the small intestine, there is a set up for whatever bacteria is in the food (chyme) to multiply and grown.

It normally takes six to eight hours for food to go from a persons stomach through the small intestine when gastrointestinal motility is normal.  Since the vagus nerves communicate with the enteric nervous system, when there is low vagus nerve flow because of cervical instability, as the vagus nerve nodose ganglions sit right in front of the atlas, stomach and small intestine paresis can occur, conditions commonly known as gastroparesis, intestinal dysmotility and intestinal pseudo-obstruction.   Again the longer bacteria sit in the small intestine the greater the chance they will multiply, flourish, and cause SIBO.

Vagus nerve and digestion

In my article Cervical spine instability as a cause of your digestive disorders, I give a detailed overview of the problem. I will summarize that article here:

When a patient comes into our center for cervical spine instability issues and they describe digestive problems, the digestive difficulties are usually one of many symptoms, as I described above. One of the causes of this myriad of symptoms may be found in compression of the vagus nerve. Among the many functions of the vagus nerve is that it provides 75% of the total input for the parasympathetic nervous system, part of the Autonomic nervous system.

Explanatory note: Autonomic nervous system divided into two: sympathetic nervous system  and the parasympathetic nervous system

The vagus nerve is responsible for managing our intestinal activity as well as managing the sphincter muscles in the gastrointestinal tract.

Gastrointestinal symptoms and vagus nerve compression

In this video Ross Hauser, MD. discusses a myriad of gastrointestinal symptoms that may be caused by vagus nerve compression typically found in cervical spine instability.

Below is a summary transcript with explanatory notes:

(0:40) What are we looking for by way of gastrointestinal symptoms?

Some of these people have a long history of gastrointestinal symptoms and cervical spine instability, yet the connection was never made for them. Yet a connection can be obvious.

In the illustration below, the many things the vagus nerve is responsible for are outlined. Highlighting digestive disorders, we see that the vagus nerve:

In this illustration, the many things the vagus nerve is responsible for is outlined. Highlighting digestive disorders, we see that the vagus nerve: Controls throat muscles to assist in swallowing. Regulates insulin secretion and glucose balance (homeostasis) in the liver. Regulates and controls digestion. Provides your brain with the felling of satiation or "I'm full." Helps regulate gastric juices, gut motility (the ability to move food through the digestive tract), and production and regulation of stomach acids.

The vagus nerve, and its important role in digestion that we explained above, runs right in front of the C1 vertebra.

(0:55) The numbers of disrupted nerve cells and how they cause digestive impairment

(1:30) Digestive disorders and stomach acids

(2:25) Intestinal problems, constipation

(3:00) The liver and the spleen, fat absorption, and floating stools.

(4:05) Inflammation and spleen dysfunction

(4:30) Leaky gut syndrome

So how do we treat a patient like this and how do we determine if these problems are from a vagus nerve compression in the neck?

We perform dynamic and upright imaging, including Digital Motion X-ray and cone beam CT scan to assess for the integrity of the cervical curve so as you can see here when the curve is normal we have a normal backward curved or lordosis, your head is sitting on top of your shoulders. In this position, the vagus nerve is properly positioned. We also check what we’ve termed “Neck Vitals” which looks at the size of the vagus nerve in the neck and function by measuring Heart Rate Variability.

We see patients who are losing weight to the point that they should not lose anymore. When we put them in a cervical collar following Prolotherapy injections and we se them four days later they are eating again because “their stomach is working again.”

The vagus nerve isn’t supplying your stomach and your stomach’s not working and you’re severely constipated or your colon is not working and your doctor said he got all these food sensitivities that won’t go away while you might have it where vagus nerve because the impulses to the enteric nervous system aren’t there to get leaky gut that is  causing your autoimmune diseases

Treating cervical ligaments with Prolotherapy  – published research from Caring Medical

Prolotherapy is an injection technique that stimulates the repair of unstable, torn, or damaged ligaments. When the cervical ligaments are unstable, they allow for excessive movement of the vertebrae, which can stress tendons, atrophy muscles, pinch on nerves, such as the vagus nerve,  and cause other symptoms associated with cervical instability including problems of digestion among others.

In 2014, we published a comprehensive review of the problems related to weakened damaged cervical neck ligaments in The Open Orthopaedics Journal. (6) We are honored that this research has been used in at least 6 other medical research papers by different authors exploring our treatments and findings and cited, according to Google Scholar, in more than 40 articles.

In our clinical and research observations, we have documented that Prolotherapy can offer answers for sufferers of cervical instability, as it treats the problem at its source. Prolotherapy to the various structures of the neck eliminates the instability and the sympathetic symptoms without many of the short-term and long-term risks of cervical fusion. We concluded that in many cases of chronic neck pain, the cause may be underlying joint instability and capsular ligament laxity. Furthermore, we contend that the use of comprehensive Prolotherapy appears to be an effective treatment for chronic neck pain and cervical instability, especially when due to ligament laxity. The technique is safe and relatively non-invasive as well as efficacious in relieving chronic neck pain and its associated symptoms.

Get help and information from the Hauser Neck Center at Caring Medical.

1 Robinson-Papp J, Nmashie-Osei A, Pedowitz E, Benn EK, George MC, Sharma S, Murray J, Machac J, Heiba S, Mehandru S, Kim-Schulze S. Vagal dysfunction and small intestinal bacterial overgrowth: novel pathways to chronic inflammation in HIV. AIDS (London, England). 2018 Jun 1;32(9):1147. [Google Scholar]
2 Song XH, Xu XX, Ding LW, Cao L, Sadel A, Wen H. A preliminary study of neck-stomach syndrome. World Journal of Gastroenterology: WJG. 2007 May 14;13(18):2575. [Google Scholar]
3 Breit S, Kupferberg A, Rogler G, Hasler G. Vagus nerve as modulator of the brain-gut axis in psychiatric and inflammatory disorders. Frontiers in psychiatry. 2018 Mar 13;9:44. [Google Scholar]
4 Roland BC, Ciarleglio MM, Clarke JO, Semler JR, Tomakin E, Mullin GE, Pasricha PJ. Small intestinal transit time is delayed in small intestinal bacterial overgrowth. Journal of clinical gastroenterology. 2015 Aug 1;49(7):571-6. [Google Scholar]
5 Roland BC, Mullin GE, Passi M, Zheng X, Salem A, Yolken R, Pasricha PJ. A prospective evaluation of ileocecal valve dysfunction and intestinal motility derangements in small intestinal bacterial overgrowth. Digestive Diseases and Sciences. 2017 Dec 1;62(12):3525-35. [Google Scholar]
6 Steilen D, Hauser R, Woldin B, Sawyer S. Chronic neck pain: making the connection between capsular ligament laxity and cervical instability. The open orthopaedics journal. 2014;8:326. [Google Scholar]
7 Lieske B, Meseeha M. Large Bowel Obstruction. InStatPearls [Internet] 2021 Aug 11. StatPearls Publishing. [Google Scholar]
8 Rej A, Potter MD, Talley NJ, Shah A, Holtmann G, Sanders DS. Evidence-Based and Emerging Diet Recommendations for Small Bowel Disorders. The American Journal of Gastroenterology. 2022 Jun 4;117(6):958-64. [Google Scholar]

This article was update June 29, 2022

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