Pain is an essential warning signal for survival. During his life, humans will be subjected to several pain stimuli, of different intensities and from various origins.
Pain, or at least the feeling of it, is a very subjective phenomenon. The same stimulus can be perceived differently depending on each individual or even in one and the same person depending on the environmental context.
We will try to find out here what is happening with neuropathic pain and in particular what link exists between neuropathic pain and stress .
Where does the pain come from?
Pain is the result of stimulation of one or more nerve fibers specialized in pain perception. The stimulus, of mechanical, chemical or thermal origin, will trigger an information transmission mechanism through receptors called nociceptors .
Nociceptors are located in the skin, muscles, joints, etc. They will make it possible to translate a stimulus into a nerve impulse to convey information to the central nervous system.
Chronic pain in a few words
According to Inserm, 30% of adults suffer from chronic pain. This prevalence increases with age and affects women more. Pain is said to be chronic when it lasts for more than 3 months or more than 1 month after resolution of the pathology or injury from which the pain originates. It is a pain that can disappear and reappear over time, for months or sometimes even years.
It is generally associated with a chronic disorder (cancer, arthritis, diabetes or fibromyalgia) or an injury that does not heal. Chronic pain can affect the nervous system. Indeed, nerve fibers and cells are stimulated repeatedly, which causes changes in their structure and makes them more sensitive to new stimulation.
In the case of chronic pain, pain is no longer considered a symptom, it becomes a disease. Pathophysiological mechanisms are then triggered, such as inflammatory pain, neuropathic pain (affecting the central nervous system), mixed pain (which combines an inflammatory and neuropathic component) or nociplastic pain (altered nociception).
What about neuropathic pain?
Neuropathic pain, also called neuralgia, is caused by a failure of the somatosensory system. It was defined in 1994 by the IASP (International Association for the Study of Pain) as “pain initiated or caused by a primary lesion of dysfunction of the nervous system”.
Indeed, this system can present damage or dysfunction due to disease. This dysfunction can cause pain syndromes in the peripheral and central nervous system.
Epidemiological studies have shown that the prevalence of these neuropathic pains varies between 7 and 8% in the general population (1) with a peak between 50 and 64 years. Neuropathic pain affects 20 to 25% of people suffering from chronic pain.
What are the causes of neuropathic pain?
Neuropathic pain can be the repercussion of several pathologies.
Among them, we can cite polyneuropathies in the case of metabolic disorders (such as diabetes), disorders of the blood supply to the extremities (in the case of arterial occlusion disease).
Neuropathic pain can also occur after viral infections (acute shingles), trigeminal neuralgia , in the case of rheumatic pain (such as fibromyalgia), after amputation (this is called phantom pain). Nerve damage due to chronic compression of one or more nerves (carpal tunnel syndrome, sciatica, herniated disc, osteoporosis, etc.) or due to the installation of a tumor , or toxic nerve damage can also cause neuropathic pain .
How to recognize neuropathic pain?
Neuropathic pain can be perceived in different ways. Abnormal, non-painful sensations may occur, such as tingling or numbness. These sensations correspond to a form of paresthesia or dysesthesia.
The manifestation of neuropathic pain may be more pervasive in the case of neurological sensory deficits which induce painful areas and other failures depending on the location of the lesion (motor, cognitive deficits, etc.).
Overall, neuropathic pain is felt by persistent pain (burns), or short, but repetitive (electrical pain, spasms, etc.). Unpleasant sensations, painful hypersensitivity to the slightest contact, and radiating pain.
Can stress be called pain?
Stress is a phenomenon that results in an emotional and physical reaction that allows the body to react quickly to a disturbance in the environment.
It manifests itself differently in each individual, but is mostly perceived as something unpleasant to wear. Stress is often experienced as painful.
In a stressful situation, the body perceives a threat and tries to respond to it by activating the secretion of catecholamines through the sympathetic nervous system (adrenaline and noradrenaline) and neuroendocrine hormones (cortisol). This will cause an increase in heart rate, blood pressure and respiration.
In the short term, this reaction is pro-inflammatory, cytokine production has indeed been observed when the body is under stress (molecules involved in the inflammation process). The secretion of all of these hormones allows the body to react quickly and effectively (at least in theory, it's the law of "fight or flight").
The balance between the sympathetic and parasympathetic nervous systems
On the neurological level, there is a continuum between the functioning of the sympathetic system (fast and immediate action) and the parasympathetic system (allows the functioning of the body at rest, such as the beating of the heart or digestion).
The sympathetic nervous system allows the body to be alert, vigilant and act quickly and efficiently. To do this, it allows the mobilization of energy via the body's glucose reserves (by activating the use of storage pathways or by degrading certain types of tissues).
The parasympathetic nervous system allows the body to function at rest. More specifically, it allows the body to recover at rest. That is to say, to replenish energy stocks, repair damaged tissues and ensure that immunity is maintained.
These two systems must work in balance in the long term. If there is a discontinuity in this balance, the body cannot function optimally.
The effects of cortisol on the body
Cortisol is a so-called catabolic hormone, produced by the adrenal glands. Throughout the day, this hormone helps maintain normal blood sugar levels in order to supply the brain and neuromuscular tissues with energy (more specifically glucose).
Indeed, it is a very powerful anti-inflammatory hormone whose function is to rapidly mobilize energy from the body's glucose reserves. During prolonged stress, there is a dysfunction of cortisol and therefore of the vectors of inflammation.
During a stressful situation, cortisol will be secreted in greater quantities to provide the body with the means to respond quickly and effectively to an environmental disturbance. The glucose that it will mobilize will serve as an energy support for the brain so that it can adapt rapid decision-making, and for the muscles in order to prepare the body to react to the information transcribed by the brain.
The consequences of stress in humans
In humans, stress -induced inflammation is implicated in diseases such as osteoporosis, rheumatoid arthritis, myopathy, fibromyalgia, chronic fatigue syndrome, chronic pelvic pain, joint dysfunction temporomandibular pain, chronic lower back pain, sciatica, etc. (4).
Cortisol, due to chronic stress, causes an inflammatory response and induces oxidative stress . Oxidative stress is defined by the alteration of free radicals of certain molecules accelerating apoptosis (process of cellular degeneration) and therefore aging and systemic degeneration of tissues.
The visible symptoms of chronic stress will be linked to bone and muscle fatigue, depression, physical and mental pain, memory problems, acid-base dysregulation of the body (largely linked to oxidative stress, and which will increase the risk of injury), orthostatic hypotension and alteration of the ocular light reflex. Chronic stress therefore has repercussions in the form of multifactorial events contributing to a large number of inflammatory diseases and a depletion of the immune system.
What is the link between neuropathic pain and stress?
Acute pain can manifest as a spontaneous disturbance in the individual's environment. In this case, pain, by this definition, will therefore be perceived as an environmental stress. Stress is inevitable and necessary in the daily life of Man. But when stress becomes chronic, a hormonal imbalance can be created.
Research has highlighted a possible neuroendocrine alteration caused by cortisol. As explained earlier, cortisol is a hormone secreted during a stressful situation. If this stress is prolonged, or even chronic, cell resistance to cortisol may appear. There will be, what we call, cortisol depletion.
Neuropathic pain causes constant sensory overload of cells due to prolonged pain. Neuropathic pain can therefore be a vector of stress and vice versa, creating a veritable vicious circle that is difficult to get rid of. Finally, we observe here the first link between neuropathic pain and stress.
Who to consult for neuropathic pain?
The most effective solution to get rid of neuropathic pain is to anticipate the onset of this pain. To do this, it is important to take anamnesis (medical history) and diagnose the patient early. This diagnosis must be made on the patient's medical history, a physical and neurological examination and any objective proof provided by electrophysiological procedures or cross-sectional imaging (CT, MRI).
The history generally consists of the following questions: When did the pain appear? Where and when does the pain occur? How often, how intense and at what time of day? How do they express themselves? What accentuates or reduces these pains? Are there other symptoms that accompany this pain? How do they impact your quality of life (work, social, family)?
Then, concerning the medical examination, the general physical state will be analyzed first, followed by the neurological examination. The neurological examination will include control of reflexes, general motor skills and sensitivity to pain, temperature, compression and contact. A measurement of the nerve conduction velocity by electroneurography can also be done in case of neuropathic pain. This diagnosis can be made by your attending physician. He will then refer you to a specialist depending on the origin of the neuropathic pain.
In most cases, he will refer you to a neurologist. But he can also refer you to an orthopedist if the pain comes from a musculoskeletal disease, to a nutritionist in the case of insulin-resistant diabetes, to an immunologist, a toxicologist or doctors specializing in infectious diseases.
How to cure neuropathic pain?
The first treatment that may be prescribed will mainly concern pain treatment, whether medicinal or not. It is essential to treat or relieve pain as quickly as possible. Indeed, during prolonged pain, the body will set up a so-called memory pain, which will lead to painful states that are more difficult to treat. In the case of painful diabetic neuropathy, the appropriate treatment will be prescribed (stabilization of blood sugar). If the pain results from a crushed nerve, surgery can in some cases resolve the problem.
Drug treatments for neuropathic pain and stress
Neuropathic pain generally requires a long treatment. A combination of several drugs is very frequently necessary in order to effectively relieve pain and improve the patient's quality of life. Some pain relievers can be obtained without a prescription, however great care should be taken with self-medication and overdose in these cases. To combat pain effectively, prescription antidepressants , antiepileptics and opioid analgesics can be prescribed. These are sometimes added together in a treatment.
Non-drug treatments for neuropathic pain and stress
It is sometimes possible to avoid taking medicinal substances. Physical therapies can limit the pain and improve the comfort of life.
These therapies include thermal treatments (relaxing, spasmolytic), cryotherapy (for acute inflammatory pain), balneotherapy or physiotherapy (physiotherapy, massage). Some use acupuncture in addition to medication to relieve symptoms of neuropathy. There are treatments using transcutaneous electrical nerve stimulation (TENS). These are analgesic methods using electrodes applied to the skin, at the painful area. This method makes it possible to target pain and inhibit nociceptive receptors (involved in pain transmission).
Other patients manage to improve their comfort of life and reduce pain thanks to certain exercises such as relaxation , meditation , hypnosis or even a method called biofeedback . They do not cure neuropathic pain, but they help make the pain more bearable.
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Bibliographic references:
- Bouhassira, D. (2018). Neuropathic pain: Definition, assessment and epidemiology . Neurological Review . 1 – 10.
- Ralf Baron; Andreas Binder; Gunnar Wasner (2010). Natural and Neuropathic pain: diagnosis, pathophysiological mechanisms, and treatment . Lancet Neurology , 9(8), 807–819.
- Macone, Amanda; Otis, James (2018). Neuropathic Pain . Seminars in Neurology, 38(6), 644–653.
- Kara E. Hannibal and Mark D. Bishop. (2014). Chronic Stress, Cortisol Dysfunction, and Pain: A Psychoneuroendocrine Rationale for Stress Management in Pain Rehabilitation . Physical Therapy . 94: 1816-1825.
