An Osteopathic Perspective to Viscerosomatic Reflexes and Enteroceptive Awareness

Sponsored by the ACOFP Foundation, with winners selected by the ACOFP Health & Wellness Committee, the Namey/Burnett Preventive Medicine Writing Award honors the memory of Joseph J. Namey, DO, FACOFP, and John H. Burnett, DO, FACOFP—dedicated advocates for osteopathic medicine—and recognizes the best preventive medicine blog posts submitted by osteopathic family medicine students and residents.

Introduction: Structure and Function are Interrelated 

The third osteopathic tenet is structure and function are interrelated. When taught, this concept is often approached from an engineering mindset. For example, consider the 1940 Tacoma Bridge collapse. A section of the bridge was composed of a solid and stiff truss sandwiched between flexible roadways. The contrast of flexible roadways held together by a stiff truss, led to a loss of flexibility that could not withstand high winds, leading to its collapse (1). The structure was not sound, and the function was sequentially and severely compromised. 

Although usually not to that degree, compromise of the structure of the human body does affect its function. Instead of a solid and stiff truss, perhaps there is a vertebra restricting motion, a muscle blocking vascular flow, or a ligament impinging motility. This can be applied microscopically with cancer cells growing entropically or even erroneous DNA repair affecting the double helix structure with resulting compromise of function. Additionally, visceral organ dysfunction shows the macroscopic and microscopic compromise of function in the organ itself. For example, diverticulosis is caused by a weakened large intestinal wall, typically adjacent to the teniae coli where the vasa recta insert into the circular muscle layer. This change in structure can lead to functional compromise, including bleeding, diverticulitis, and potentially even the need for a colectomy (2). Diverticulosis is common and not typically detected unless inadvertently identified through imaging or a colonoscopy.  

In contrast, diverticulitis typically presents with left lower quadrant pain, fever, nausea, and vomiting (3). However, left lower quadrant pain is not specific for diverticulitis and could indicate a variety of disorders including muscular pain, genitourinary dysfunction, and other gastrointestinal complaints in addition to diverticulitis. Thus, the attending physician must constantly assess potential differential diagnoses when working up a likely visceral complaint. One extra and often overlooked source of information that may be helpful in an assessment and treatment are viscerosomatic reflexes. These reflexes are likely due to structural compromise with ensuing functional deficits of the affected visceral organs that, due to convergence of sensory innervation at the level of the spinal cord, lead to structural changes in somatic tissues (4). 

Enteroceptive Awareness 

Before diving into the interesting topic of viscerosomatic reflexes, it is worth mentioning a concept gaining greater popularity: enteroceptive awareness. As described by Longo, et al. in 2017, enteroceptive awareness is the “ability to perceive the body states…(as) provided by enteroceptors… (that) receive both internal and external stimuli.” Longo describes a study where patients suffering from binge eating disorder were blindfolded during a meal. This led to decreased food intake with the same level of satiation compared to another meal where the patients were not blindfolded. The researchers hypothesized this was due to greater awareness of internal signals (5). Our brains are often not trained to recognize the subtleties of internal organ stimuli beyond a grumbling stomach, hunger, nausea, vomiting, and diarrhea/constipation. We typically do not know exactly when we feel full until we are overfilled, when peristalsis is occurring unless our stomachs are grumbling, when our bladder is filling until it is full, or the exact location of visceral pain. The level of innervation of the viscera pales in comparison to our skin and somatic structures. This is why we know exactly where a painful furuncle is in the skin but when someone presents with appendicitis the pain may be around the umbilicus, in the right lower quadrant, or in the right posterior flank. 

Fortunately, all physicians are taught the basics of being, what I will term, enteroceptively aware of their patients. Providers are taught an abdominal exam which includes how to test for cholecystitis with a Murphy’s sign, how McBurney’s point or Rovsing’s Sign can indicate peritoneal irritation due to appendicitis, checking for constipation, education on the common and varied locations of visceral pain, and finally an in-depth exploration of visceral organ anatomy which further allows for a comprehensive differential when working up acute pain that is likely visceral in origin (6). These physical exam findings detect already present pathology and are largely diagnostic, not preventative or therapeutic. Osteopaths, with their extra training in manipulations and palpation, can take the abdominal exam training to a deeper level through their detection of restricted internal organs and abdominal nervous plexuses. They then can provide a relatively quick and easy myofascial release treatment of any restricted internal structures they find. Additionally, viscerosomatic reflexes are an integral part of Osteopathic training, and awareness of those reflexes, may lead to early detection and potential prevention of visceral problems. 

Viscerosomatic Reflexes 

Viscerosomatic reflexes, as defined in Foundations of Osteopathic Medicine, are “localized visceral stimuli producing patterns of reflex response in segmentally related somatic structures” (7). The brain is thought to influence the viscera via efferent autonomics. The brain receives sensory information from the viscera usually from afferent nerves that typically follow the viscera’s autonomic efferent nerves (4). The parasympathetic system supplies the thoracic viscera and most abdominal viscera via Cranial Nerve 10. The descending colon, sigmoid colon, rectum, lower ureters, and pelvic organs receive parasympathetic innervation from the second to the fourth sacral segment nerves (S2-S4). Additionally, sympathetic innervation of the viscera extends from the first thoracic vertebrae to the second lumbar vertebrae (T1-L2) (8, Table 1). In a viscerosomatic reflex, afferent sensory fibers follow their autonomic efferent nerves to the central nervous system (CNS), where they converge with anterolateral system from the somatic tissues. The brain misunderstands or cannot differentiate where the noxious activity is occurring, whether in the visceral or somatic tissues. This leads to the stimulation of somatic efferents, which causes the tightening of paraspinal tissues at the level of the visceral input. This is commonly referred to as tissue texture changes, asymmetries, range of motion, and tenderness (TART) findings and is found in both acute and chronic viscerosomatic reflexes (4). In the example of acute diverticulitis of the sigmoid colon, noxious stimuli would ascend along afferent nerves from the sigmoid colon that follow the autonomic innervation to the sigmoid colon. This autonomic innervation comes from the least and lumbar splanchnics at the level of T12-L2 (sympathetics) and from the pelvic splanchnic nerves from S2-S4 (parasympathetics) (8). Thus, if a viscerosomatic reflex occurs, examination of the paraspinal tissue may show hypertonicity, bogginess, and potentially vertebral somatic dysfunctions at T12-L2 and S2-S4. 

The existence of viscerosomatic reflexes has been further demonstrated in the following two studies. The first study evaluated correlations between acute myocardial infarctions and musculoskeletal changes at T4. 97 patients were included in the study and those with T4 dysfunctions (soft tissue texture changes or decreased range of motion), had over a 90% positive predictive value for a myocardial infarction. This was a double-blind study where 50% occlusion of a coronary artery was considered positive for a myocardial infarction and two physicians, without knowing the results of the cardiac catheterization, conducted the physical osteopathic exam (9). Another study was interested in delineating the pathogenesis of pain in pancreatitis in rats. Interestingly, the investigators measured the electromyographic (EMG) activity of the acromiotrapezius muscle pre- and post-infusion of Trypsin into the pancreas. When the results were compared to baseline levels, a 190% increase in EMG activity was observed after infusion of Trypsin (10). These studies further support the existence and diagnostic utility of viscerosomatic reflexes. 

As previously explained, a viscerosomatic reflex found in paraspinal tissue can be diagnostic information. Treating the paraspinal tissues and vertebrae may also be therapeutic by normalizing the autonomic input to the viscera (11).  

Key Points 

In summary, providers should keep the following key points in mind. First, structure and function are interrelated, and visceral dysfunction can be evident in a somatic structure through a viscerosomatic reflex. Second, identification of viscerosomatic reflexes increase a physician’s ability to diagnose a visceral pathology and, in my coinage, be more enteroceptively aware of their patients. Third, treatment of the somatic tissues involved in a viscerosomatic reflex improves structure and function of the somatic tissues and facilitates autonomic normalization of the visceral tissues of which benefits are still being elucidated. 

Implementation into Clinical Practice 

Clinical implementation of viscerosomatic reflexes does not need to be arduous or time-consuming. Family doctors listen to the lungs of every patient and a quick palpatory exam of the spine can be logically performed directly after listening to the lungs. Take 6 months to put viscerosomatic reflexes to the test, and observe whether C6, T2, and T6 are dysfunctional in patients with hypertension (12) or if T5-T9 paraspinal tissues are tight in a patient presenting with gastro-esophageal reflux disease. If your observations suggest the reflexes are common, then use the next 6 months to treat the paraspinal tissue and vertebrae. Does the patient need a decreased dose of medication? What does the patient report about their symptoms? If the results are favorable, implement this quick palpatory exam and treatment into your practice. Osteopathic manipulative treatment has been well-documented to increase patient satisfaction (13, 14) and may prove to be a valuable diagnostic and therapeutic component with your patients presenting with visceral complaints.  

References 

1. Petruzzello M. Tacoma Narrows Bridge. Encyclopædia Britannica. Accessed December 14, 2022. https://www.britannica.com/topic/Tacoma-Narrows-Bridge.
2. Pemberton, MD JH. Colonic diverticulosis and diverticular disease: Epidemiology, risk factors, and pathogenesis. Friedman, MD LS, Grover, MD, MPH, AGAF S, eds. Up to Date. Published online April 30, 2021. Accessed December 14, 2022. https://www.uptodate.com/contents/colonic-diverticulosis-and-diverticular-disease-epidemiology-risk-factors-and-pathogenesis?search=diverticulosis&source=search_result&selectedTitle=1~150&usage_type=default&display_rank=1#
3. Pemberton, MD JH. Clinical manifestations and diagnosis of acute diverticulitis in adults. Up to Date. Published July 14, 2022. Accessed December 14, 2022. https://www.uptodate.com/contents/clinical-manifestations-and-diagnosis-of-acute-diverticulitis-in-adults?search=diverticulosis&topicRef=1379&source=see_link#H2
4. Bath M, Owens J. Physiology, Viscerosomatic Reflexes. NCBI Bookshelf. 2022, Accessed December 14, 2022.
5. Longo GM, Falcone J, Martoni RM, Bellodi L, Ogliari A, Erzegovesi S. The role of enteroceptive awareness in eating disorders: A study on a group of binge eaters. Clinical Key. Accessed December 14, 2022. https://www.clinicalkey.com/#!/content/playContent/1-s2.0-S0924933817308118?returnurl=null&referrer=nul
6. Bickley LS, Szilagyi PG, Hoffman RM, Soriano RP. Bates’ Guide to Physical Examination and History Taking. 13th edition. LWW Health Library-Medical Education;Chapter 19: Abdomen. Accessed December 14, 2022. https://meded-lwwhealthlibrary-com.eu1.proxy.openathens.net/content.aspx?sectionid=248759981&bookid=2964#24876048
7. Kuchera ML, Ettlinger H, Seffinger MA. Foundations of Osteopathic Medicine: Philosophy, Science, Clinical Applications, and Research. 4th Edition. Wolters Kluwer; Chapter 31: Assessing Viscerosomatic Reflexes and Somatosomatic Reflexes, Jones Tender Points, Trigger Points, and Chapman Reflexes. Accessed December 14, 2022. https://meded.lwwhealthlibrary.com/content.aspx?sectionid=209548012&bookid=2582
8. Willard, Frank H, Kuchera, William A. Foundations of Osteopathic Medicine: Philosophy, Science, Clinical Applications, and Research. 4th Edition. Wolters Kluwer; Chapter 10: Autonomic Nervous System. Accessed December 14, 2022. https://meded.lwwhealthlibrary.com/content.aspx?sectionid=209540573&bookid=2582#seffinger4-seffinger-4-seffinger-ch010-tbl001
9. Cox, John M, Gorbis, Sherman, Dick, Lorane M, Rogers, Joseph C, Rogers, Felix J. Palpable Musculoskeletal Findings in Coronary Artery Disease: Results of a Double-Blind Study. The Journal of American Osteopathic Association. 1983. Accessed December 29, 2022
10. Hoogerwerf, Willemijntje A, Shenoy, Mohan, Winston, John H, Xiao, Shu-Yuan, He, Zhijun, Pasricha, Pankaj J. Trypsin Mediates Nociception Via the Protienase-Activated Receptor 2: A Potentially Novel Role in Pancreatic Pain. Journal of Gastroenterology. 2004. Accessed December 29, 2022
11. Davis SE, Hendryx J, Bouwer S, et al. Correlation Between Physiologic and Osteopathic Measures of Sympathetic Activity in Women With Polycystic Ovary Syndrome. The Journal of the American Osteopathic Association. 2019;119(1):7. Accessed December 14, 2022.  doi:10.7556/jaoa.2019.00
12. Kelso AF, Johnston WL. The status of a C6-T2-T6 (CT) pattern of segmental somatic dysfunction in research subjects after 3–7 years. J Am Osteopath Assoc. 1989;89(10):1356. Accessed December 14, 2022.
13. Gołyszny MJ, Obuchowicz E, Tramontano M, et al. Outpatient Satisfaction With Osteopathic Manipulative Treatment in a Hospital Center: A Survey. AlternativeTherapies in Health & Medicine. 2018;24(5):44-57. Accessed December 14, 2022. https://search.ebscohost.com/login.aspx?direct=true&AuthType=shib&db=rzh&AN=135988959&site=eds-live
14. Lam MT, Banihashem M, Lam HR, Wan AB, Chow E. Patient experience, satisfaction, perception and expectation of osteopathic manipulative treatment: A systematic review. International Journal of Osteopathic Medicine.2019. Accessed December 14, 2022.  doi:10.1016/j.ijosm.2019.04.00
15. Willard, Frank H. Viscerosomatic and Somatovisceral Integration in Osteopathic Medical Education. AOA OMED 2022 Conference. Accessed December 14, 2022.