Pain is an unpleasant sensation and emotional experience linked with actual or potential tissue damage. Its purpose is to allow the body to react and prevent further tissue damage.
Also, it protects a damaged body part while it heals and protects to avoid similar experiences in the future.
Chronic pain is a pain which persists after healing is expected to have taken place, or which exists in the absence of tissue damage. Psychosocial complaints almost always accompany long-term pain.
It is considered as chronic when it lasts or recurs for more than 3 months.
It affects roughly 20% of the worldwide population.
The International Association for the Study of Pain (IASP) has drew up a helpful classification of chronic pain.
7 main groups were identified:
It is a pain present in 1 or more anatomical region associated with significant emotional distress or significant functional disability in the daily activities which cannot be explained by another chronic pain condition. Within this group Fibromyalgia is included.
It includes pain caused by the cancer itself and pain that is caused by the cancer treatment.
It is a pain that persists beyond normal healing, is frequent after surgery and traumatic injuries. Logically should have been already excluded all other possible causes of related pain.
Chronic neuropathic pain is caused by a lesion or disease of the somatosensory nervous system.
The somatosensory nervous system provides information about the body including skin, musculoskeletal, and visceral organs.
Depending on where the lesion of the nervous system is, we can have peripheral or central neuropathic pain.
Neuropathic pain may be spontaneous or evoked, as an increased response to a painful stimulus (hyperalgesia) or a painful response to a normally nonpainful stimulus (allodynia).
The diagnosis of neuropathic pain requires a history of nervous system injury and a neuroanatomically plausible distribution of the pain.
Chronic headache and chronic orofacial pain are defined as headaches or orofacial pains that occur on at least 50% of the days during at least 3 months.
Chronic visceral pain is persistent or recurrent pain that originates from the internal organs. It is perceived in areas that receive the same sensory innervation as the internal organ at the origin of the symptom (referred visceral pain).
An example is the intestine which shares the sensory innervation with the lower back area.
In this area is often present hyperalgesia, the intensity of the symptom may be no related with the extent of the internal damage to the viscera.
It is defined as persistent or recurrent pain that arises as part of a disease process directly affecting bone(s), joint(s), muscle(s), or related soft tissue.
Examples are: chronic low back pain, chronic neck pain, chronic knee pain, chronic shoulder pain.
What are the current treatments for chronic pain?
Chronic pain is not only a physiological problem but as well the psychosocial part
plays a big role.
Anxiety, depression, stress, anger, insomnia, suicide, loss of financial independence, disability, family instability, job satisfaction , cultural and social environment are closely associated with long-term pain.
The neuromatrix theory suggests that in the absence of overt physical damage, it is the psychological factors of emotion and cognition that contribute most to the experience of pain.
Biopsychosocial treatments model
It involves several healthcare professionals that collaborates in a multidisciplinary team to try to address the different components of the chronic pain.
It will involve:
- Physiotherapy: aims to decrease the pain perceived and to maintain the max functional ability, it will use a range of aerobic and anaerobic exercises to do so, avoiding any major increase in the pain.
- Occupational therapy: helps planning and satisfactory perform daily activities understanding that rest is not a good way to deal with chronic pain.
- Pain specialist nursing: can help with understanding why some medications has been prescribed and the best modalities to assume them and to reduce the side effects.
- Clinical psychology: It takes care of how the pain is impacting on the mental health and well-being of the person. Also explains the role of non-physiological factors in the maintenance of pain symptoms. Therefore, helps the person with understanding that is essential the way to react and cope with physical pain and the related emotional sufferance.
- Cognitive–behavioural therapy (CBT): explains the connections between thoughts, feelings, and behaviours. Negative thoughts and feelings about the pain generate maladaptive behaviours and exacerbation of symptoms.
A person is in the middle of the therapy and must collaborate with the therapist to reconceptualised thoughts, beliefs, behaviours and the pain symptoms itself.
- Acceptance and commitment therapy (ACT): Differently of CBT approach, ACT focuses on the RESPONSE to negative thought, beliefs and behaviours regarding the condition and the pain. Moving the attention from the pain condition to what their life goals are.
BIOMEDICAL TREATMENT MODEL
Analgesic medication for pain:
- Non‑steroidal anti‑inflammatory drugs(paracetamol and non-steroidal anti-inflammatory drugs (NSAIDs).
- Weak and strong opioids:(opioids, codeine and dihydrocodeine.)
- Topical analgesics: lipophilic opioids, fentanyl and buprenorphine, and Lidocaine.
- Adjuvants(medication to reduce and fear and anxiety):anxiolytics, hypnotics, muscle relaxants
Interventional pain management:
Spinal cord stimulation
It aims to interrupt the nerve transmission and therefore the transmission of the pain using electrical stimulation.
The stimulation is delivered by electrodes placed next to the spinal nerves in the dorsal epidural space. It is recommended by NICE in the UK for use in chronic pain of neuropathic origin.
Deep brain stimulation (DBS)
Consist in the implantation of electrodes to stimulate brain structures involved in the transmission and regulation of the pain. It is a highly invasive and risky treatment method that is used in only some carefully selected patients.
Repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS)
Are Non-invasive brain stimulation techniques which have some evidence in reducing the pain. The stimulation it is applied over the motor cortex, it usually requires several sessions to be effective.
Transcutaneous electrical nerve stimulation (TENS) and percutaneous electrical nerve stimulation (PENS)
Electrical nerve stimulation via electrodes placed onto the skin (transcutaneous) or inserted into the skin (percutaneous),both of them have shown a certain efficacy in pain reduction.
Regarding TENS application Nash and colleagues reported that should be used at least 30min twice a day.
Repeated applications or high concentrations of capsaicin can provoke a loss of normal function of the nerve cell and a persistent desensitisation to the painful stimuli.
Superficial application of heat or cold in a different way may provide an immediate, short-term relief from pain. They are widely available, simple to use and cost effective.