What is new in the physiotherapeutic management of chronic pain?
Sibele de Andrade Melo KNAUT, PhD, pht[1]
Who has never suffered from pain? It does not matter if this pain was physical or emotional. Oh God, and how difficult it is to describe it! Many times the people around us do not seem to understand the extent of our pain. And this is legitamate. Each one interprets his/her pain according to his/her own threshold of pain, but also, in relation to previous experiences of pain. These experiences are either from situations we have lived ourselves or from the observation of the suffering of others.
Can you imagine being accompanied by pain day and night, for months, years? Its intensity changes, sometimes milder, sometimes unbearable. If it is not the case, feel happy, because the prevalence of chronic pain has been considerably increasing in the world. Studies show that around 19% of Europeans 1 and 31% of Americans 2 are suffering from chronic pain.
In the last decades, there has been a great reduction in mortality and a consequent increase in survival and morbidity (prevalence of the disease) in the world. The National Academy of Sciences report predicts pain prevalence will rise as chronic illnesses increase 3. Neuropathic and orthopedic pain is expected to rise dramatically due to the increasing prevalence of diabetes and obesity 4.
All over the world, millions of people with chronic pain suffer from the lack of proper and effective treatment. Difficulties in diagnosis and evaluation are some related problems. Again, these problems are linked to the complexity of chronic pain associated with environmental and personal factors.
Existing diagnostic approaches typically fail to incorporate available knowledge regarding the biopsychosocial mechanisms contributing to pain conditions. Thus, classic indicators of health status, such as specific cause mortality rates and morbidity indicators, have become insufficient to assess the welfare, health status and service needs as they do not exactly reflect health and morbidity. For this reason, in 2001, the World Health Organization created the International Classification of Functioning, Disability and Health (ICF). The ICF reflects a new philosophy that shifts the focus from the consequences of the disease to the functionality as an important component of health. It integrates the biopsychosocial model to classify health and health-related domains. As the functioning and disability of an individual occurs in a context, ICF also includes a list of environmental factors that can be considered as facilitators or barriers 5.
The functional diagnosis is one of the main competencies of the Physiotherapists. For this reason, in addition to the individual's signs and symptoms, the search for an ideal diagnosis should include data about which changes in body functions and structures induce the limitation of functional activities and restriction of social participation. Physiotherapy is the science that studies, diagnoses, prevents and recovers individuals with functional movement disorders. A well-conducted clinical-functional assessment can provide a valid explanation of the signs and symptoms in order to guide the best treatment strategies, to give a more accurate prognosis and to monitor the progress of the individual in terms of the treatment received 6.
Setting goals with respect to activity limitations and participation restrictions is also recommended, besides it can also be set in terms of impairment. Goals should be specific, measurable, attainable, realistic and time-bound. Once goals are defined, it is necessary to identify the key impairments or disabilities that are preventing the achievement of goals. Pain is often the main key and focus of physiotherapeutic intervention, at least while this pain is leading to functional limitation. Movements that generate pain should be avoided and the cause of pain should be treated. The movements must be carried out within the tolerance of the individual and according to each situation. Don't poke the bear! If it is already hurting, why do exercises and activities that generate more pain? Sometimes the cause is a mismatch of sensory information with the central nervous system. We should not forget the changes that chronic pain causes in the peripheral and central nervous system – peripheral and central sensitization. With regard to these phenomena already identified in chronic pain, why not focus on increasing the responsiveness of nociceptive neurons in the central nervous system to their normal afferent or sub-threshold input?
Currently the most commonly used measures in Physiotherapy treating patients with chronic pain are acupuncturetherapy, manual therapy (e.g. osteopathic and chiropractic manipulation), therapeutic exercises, somatosensory rehabilitation and, more recently in many countries (Canada, Brazil, etc.) transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS) 7-24. Which of these treatments is best? Until today there is no evidence that a treatment is much better than any other treatment in relation to chronic pain. The causes of chronic pain are diverse and personal and environmental factors directly influence the intensity and behavior of chronic pain. In addition, patients' personal preferences are also related to the success of physiotherapeutic intervention. Thus, the current trend is to implement in clinical practice, the real concept of evidence-based physiotherapy, which includes integrating the best available research, clinical experience, and patient values and circumstances related to patient management and practice management.
Among the interventions mentioned above, the Somatosensory Rehabilitation is gaining more and more my attention and trust. It involves a standardized method of evaluation and conservative treatment of painful disorders of cutaneous vibrotactile sensation 16. After 17 years of studies and clinical application, the somatosensory stimulations (tactile and vibratory), respecting the cutaneous territories 25, seems to increase the pain threshold by reducing spinal, supra-spinal and cortical sensitization 17. With many non-peer-reviewed publications and the high success rate, this method should gain the attention of researchers to confirm its effectiveness.
Another physiotherapeutic intervention for chronic pain that has been gaining the attention of researchers and clinicians around the world, is the use of non-invasive brain stimulation. The possibility of modulating cortical activities by tDCS or rTMS may be valuable therapeutic approaches 26. In fact, the use of transcranial stimulation with sufficient current flow to achieve physiological and functional effects is not a new approach. In 1964, Bindman and colleagues 27 demonstrated an alteration in neural activity and cortical excitability in anesthetized rats by the application of tDCS on the sensorimotor cortex. Recent studies revealed that the use of tDCS or rTMS is probably or possibly effective to reduce pain or to improve the efficacy of conventional medical treatment for chronic pain patients 26-30.
Most studies target transcranial stimulation to the primary motor cortex (M1), mainly contralateral to the pain side 25,29. The potential mechanisms supporting this type of application includes the controls related to excitation of horizontal fibers, modulation of deeper and remote brain structures, and the mediation of various neurotransmitters that are involved in pain relief 31,32. Another application that has been used, is the stimulation of the premotor cortex/dorsolateral prefrontal cortex. With this last application, changes in pain perception and analgesic effects in neuropathic pain after a traumatic spinal cord injury have been demonstrated 33. The analgesic mechanisms of transcranial stimulation to the premotor cortex/dorsolateral prefrontal cortex seem not to be the same as those of M1 stimulation and may include top-down modulation of the medial spinal thalamic system with a preferential effect in the affective and evaluative aspects of pain 34,35,36. Since almost all tissues and cells are sensitive to electrical fields, it is possible that transcranial stimulation may cause changes in non-neuronal tissues in the brain, including endothelial cells, lymphocytes, or glial cells 37.
More recently, the application of transcranial stimulation on somatosensory cortex have been investigated 38,39. Folmli et al.39 applied the tDCS over the somatosensory cortex contralateral to hand dominance aiming to investigate the effects of this stimulation on vibrotactile detection thresholds (VDT). Twenty minutes of 1mA tDCS, during 5 days was responsible for a linear improvement of dominant hand high frequency (200 Hz) VDT. Although the studies that use transcranial stimulation of the somatosensory cortex are rather scarce, they are particularly interesting for the treatment of chronic pain, especially for neuropathic pain. If we take into account basic concepts that (1) neuropathic pain, by definition, originates from some form of injury to the nervous system, (2) somatosensory changes, including tactile hypoesthesia and mechanical allodynia, cause pain, and (3) altered somatosensory perception of all the signs of this area, such as pain can be explained by peripheral sensitization and central sensitization, we can postulate that the modulation of the somatosensory cortex by transcranial stimulation may be a complementary treatment for neuropathic pain. Thus, it would be very interesting to investigate the effects of stimulation of somatosensory cortex with tDCS or rTMS, as a direct modulation of central sensitization in complement to peripheral somatosensory rehabilitation.
Physiotherapy is extremely important for individuals with chronic pain. Physiotherapists should understand the mechanisms of pain, perform a well-standardized assessment to have a functional diagnosis that takes into account the patient's personal and environmental factors, and has a continuing education to be updated with new strategies and knowledge for pain relief.
References
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[1] Physiotherapist, PhD in biomedical sciences - rehabilitation
Professor of the Physical Therapy Program - Universidade Positivo – Campo Comprido - R. Prof. Pedro Viriato Parigot de Souza, 5300 -, Curitiba - PR, 81280-330
President of the Brazilian Association of Neurofunctional Physiotherapy - ABRAFIN
e-mail: sibelemelo@gmail.com
