Researchers at the University Medical Center Mainz have discovered that a so-called painful diabetic polyneuropathy is not only caused by damaged nerves, but can also be muscular in origin. Diabetes type 2 patients who had both causes of pain showed higher pain intensity, tolerated it worse, and also had psychological impairment. Based on the new findings they discovered, the research team argues that routine screening should also consider muscular mechanisms. This could lead to better diagnostics as well as a more targeted and thus more successful therapy for many affected individuals.
Pain that occurs in the context of diabetes can have various causes. Scientists at the Department of Neurology at the University Medical Center Mainz have shown this through a comprehensive clinical investigation. In about a quarter of those with so-called painful diabetic polyneuropathy, both nerve pain and muscle-related pain were present. Another important finding was that these patients had significantly more severe physical and psychological impairments than those with only nerve-related pain. The researchers therefore advocate routine screening for muscle-related pain. This could improve diagnostics and therapy for many patients. The study results have now been published in the renowned journal “Diabetes Care” .
“Our findings on the causes of pain in diabetic polyneuropathy are of great importance for those affected. They open up the possibility for causal, personalized therapy options and a more targeted use of both non-drug and drug treatment strategies,” explains Univ.-Prof. Dr. Frank Birklein, Clinical Director and Head of the Peripheral Neurology and Pain Section of the Department of Neurology at Mainz University Medical Center.
Under the direction of Professor Birklein, the working group “Pain – Autonomic Nervous System” of the Clinic and Polyclinic for Neurology of the University Medical Center Mainz examined a total of 69 affected persons with diabetic polyneuropathy caused by diabetes mellitus type 2. This was associated with pain in 41 patients. To assess participants’ individual impairments, the researchers conducted a comprehensive clinical examination that included standardized tests as well as a comprehensive examination of the sensitive phenotype and endogenous pain modulation. Self-report questionnaires for depressive symptoms, anxiety symptoms, and polyneuropathy-related impairments were also used to assess pain.
The result: all 41 patients with painful diabetic polyneuropathy met the criteria for nerve-related (neuropathic) pain. In 22 percent of them, an additional form of pain was identified that has its cause in the musculature: The so-called myofascial pain is characterized by active muscle trigger points. These hardenings in the muscle tissue trigger pain when palpated directly or during physical exertion. In the subjects studied, the painful muscle trigger points were located in the anterior or posterior calf muscles and in the small plantar muscles. They occurred bilaterally in 89 percent of participants. In the majority of cases (78 percent), they were symmetrically expressed.
With regard to the physical and psychological effects of diabetic polyneuropathy, patients with an additional myofascial pain component differed markedly from those with exclusively neuropathic pain: participants with both forms of pain showed higher pain intensity and poorer pain tolerance. In addition, they had higher anxiety and depression scores and reported greater polyneuropathy-related impairments in aspects such as sleep, social relationships, or walking ability.
Diabetes mellitus is the most common metabolic disease in Western countries. In recent years, the number of people with type 2 diabetes mellitus in particular has increased. In Germany, around 500,000 people are newly diagnosed with this type of diabetes every year. About half of all diabetes patients develop polyneuropathy. In about half of those affected, there is damage to the peripheral nervous system, the part of the nervous system that lies outside the brain and spinal cord. In polyneuropathy, the hands and feet are particularly affected by nerve damage. Common symptoms of the disease are sensory disturbances such as tingling and numbness. Up to one-third of diabetes patients with polyneuropathy also experience pain that interferes with many aspects of life, such as work, social activities or sleep. In many cases, this is accompanied by a depressive development.
To date, pain in diabetic polyneuropathy is mostly neuropathically based. That is, the cause of pain is assumed to be damage to the nervous system alone. Therapy and the development of new treatment options for pain in diabetic polyneuropathy is also being done specifically for this form of pain. In contrast, possible further individual components such as causes of pain in the tissue, in the bones or in the muscles have not yet been taken into account as standard. This leads to very heterogeneous and in many cases only moderate therapeutic success.
“Based on our study results, we recommend routine screening for myofascial pain in patients with painful diabetic polyneuropathy, both in individual treatment and in drug trials. This would be easily implemented in practice by adapting the clinical examination. In this way, significantly improved therapeutic successes could be achieved in the future,” emphasizes corresponding author PD Dr. Christian Geber, associate professor at the Clinic and Polyclinic for Neurology at the University Medical Center Mainz and senior physician at the DRK Pain Center Mainz.
Source:
Escolano-Lozano F, et al: Painful diabetic neuropathy – myofascial pain makes the difference. Diabetes Care (2022); DOI: https://doi.org/10.2337/dc22-1023.
