The Pain – Causes, Symptoms, Diagnosis, Treatment

The Pain is an unpleasant sensation that can range from mild, localized discomfort to agony. Pain has both physical and emotional components. The physical part of pain results from nerve stimulation. Pain may be contained to a discrete area, as in an injury, or it can be more diffuse, as in disorders like fibromyalgia. Pain is mediated by specific nerve fibers that carry the pain impulses to the brain where their conscious appreciation may be modified by many factors.

According to the  pattern of pain there are three classes of pain

• Nociceptive pain,
• Inflammatory pain which is associated with tissue damage and the infiltration of immune cells, and
• Pathological pain is a disease state caused by damage to the nervous system or by its abnormal function (e.g. fibromyalgia, peripheral neuropathy, tension-type headache, etc.)

According to the severity three main categories of pain

• Acute pain – lasts for a short time and occurs following surgery or trauma or other condition. It acts as a warning to the body to seek help. Although it usually improves as the body heals, in some cases, it may not.
• Chronic pain – lasts beyond the time expected for healing following surgery, trauma or other condition. It can also exist without a clear reason at all. Although chronic pain can be a symptom of another disease, it can also be a disease in its own right, characterized by changes within the central nervous system.

A brief explanation of classes of pain is thus useful clinically to assist in the management of pain as a symptom and possible diagnosis of the underlying condition.

• Acute pain – At the site of local tissue injury, the activation of nociceptive transducers contributes to this form of pain. The local injury environment may further alter the characteristics of nociceptors, central connections, and the autonomic nervous system.[rx][rx][rx][rx]
• Chronic pain – Persistent pain is frequently related to conditions (e.g., diabetes mellitus, arthritis, and tumor growth) which potentiates chronic tissue inflammation or alteration of the properties of peripheral nerves (neuropathic). Given the unrelenting nature of chronic pain, expectations are that external factors such as stress, emotions, and the environment may produce a summative effect with the damaged tissue to enhance the intensity and persistence of the pain. [1-4]
• Somatic pain – This form of pain may be acute or chronic and is pain activated by the nociceptors in the cutaneous or deep tissues. In the case of cutaneous somatic pain, for instance, in the case of a skin cut, it is described as sharp or burning and is well localized. In the case of somatic pain arising from the deep tissues, such as in the joints, tendons, and bones, it is described as more throbbing or aching and is less localized.[rx][rx][rx][rx][rx]
• Visceral pain – This pain arises mainly from the viscera and deep somatic structures (e.g., pain from the gastrointestinal tract). Visceral pain that is not distinctly localized is carried by the C fibers from the deep structures to the spinal cord.[rx]
• Neuropathic – This persistent pain is often a consequence of damage to these nerve fibers, leading to increased spontaneous firing or alterations in their conduction or neurotransmitter properties.[rx]
• Allodynia – Pain resulting from a typically harmless stimulus is referred to as allodynia. Though the mechanism is not fully understood, it is thought to potentially arise from 1) sensitization of the skin, leading to a decreased threshold of silent nociceptors or 2) damage to peripheral neurons inducing structural changes leading touch-sensitive fibers to reroute and form synapses in areas of the spinal cord that normally receive pain input.[rx]
• Hyperalgesia – Occurs when noxious stimuli generate an exaggerated pain response. Similar mechanisms as proposed in the case of allodynia, with patients demonstrating amplification of pain or hyperalgesia, as well as a lengthened persistence of the pain.[rx]
• Referred pain – When there is pain perception at a location other than the site of the painful stimulus, it is known as referred pain. The classical example of referred pain involves pain brought down the neck, shoulders, and back following myocardial infarction. There is no current consensus regarding the true mechanisms behind referred pain, and there are several theories.  Referred pain may be visceral or somatic, with the former describing pain from an organ and the latter describing pain from the deep tissues such as muscles or joints. [rx][rx][rx][rx]

Acute pain can last a moment; rarely does it become chronic pain. Chronic pain persists for long periods.

According to the treatment pattern, pain is following

• Chronic Pain – Learn about how chronic pain occurs, and why chronic pain sometimes lingers.
• Nerve Pain – When nerve fibers get damaged, the result can be chronic pain. Read about the very common causes of neuropathic pain, like diabetes.
• Psychogenic Pain – Depression, anxiety, and other emotional problems can cause pain — or make existing pain worse.
• Musculoskeletal Pain – Musculoskeletal pain is pain that affects the muscles, ligaments and tendons, and bones. Learn about the causes, symptoms, and treatments.
• Chronic Muscle Pain – Use your muscles incorrectly, too much, too little — and you’ve got muscle pain. Learn the subtle differences of muscle injuries and pain.
• Abdominal Pain – Learn common causes of abdominal pain and when to contact your doctor.
• Joint Pain – See the causes of joint pain and how to treat it with both home remedies and prescribed medication.
• Central Pain Syndrome – A stroke, multiple sclerosis, or spinal cord injuries can result in chronic pain and burning syndromes from damage to brain regions. Read this brief overview.
• Complex Regional Pain Syndrome – It’s a baffling, intensely painful disorder that can develop from a seemingly minor injury, yet is believed to result from high levels of nerve impulses being sent to the affected disorder. Learn more about this disorder.
• Diabetes-Related Nerve Pain (Neuropathy) – If you have diabetes, nerve damage can be a serious complication. This nerve complication can cause severe burning pain especially at night. Learn more about diabetic neuropathy.
• Shingles Pain (Postherpetic Neuralgia) – Shingle is a painful condition that arises from varicella-zoster, the same virus that causes chickenpox. Learn more about the symptoms and risk factors.
• Trigeminal Neuralgia – It’s considered one of the most painful conditions in medicine. The face pain it causes can be treated. Learn more about what causes trigeminal neuralgia and treatments for face pain caused by it.
•  Phantom pain – Phantom pain is pain felt in a part of the body that has been amputated, or from which the brain no longer receives signals. It is a type of neuropathic pain. The prevalence of phantom pain in upper limb amputees is nearly 82%, and in lower limb amputees is 54%. One study found that eight days after amputation, 72% of patients had phantom limb pain, and six months later, 67% reported it. Some amputees experience continuous pain that varies in intensity or quality; others experience several bouts of pain per day, or it may reoccur less often.
• Nociceptive – Nociceptive pain is caused by stimulation of sensory nerve fibers that respond to stimuli approaching or exceeding harmful intensity (nociceptors), and maybe classified according to the mode of noxious stimulation. The most common categories are “thermal” (e.g. heat or cold), “mechanical” (e.g. crushing, tearing, shearing, etc.), and “chemical” (e.g. iodine in a cut or chemicals released during inflammation). Some nociceptors respond to more than one of these modalities and are consequently designated polymodal.
• Breakthrough  –  Breakthrough pain is transitory acute pain that comes on suddenly and is not alleviated by the patient’s regular pain management. It is common in cancer patients who often have background pain that is generally well-controlled by medications, but who also sometimes experience bouts of severe pain that from time to time “breaks through” the medication. The characteristics of breakthrough cancer pain vary from person to person and according to the cause.
• Neuropathic -Neuropathic pain is caused by damage or disease affecting any part of the nervous system involved in bodily feelings (the somatosensory system). Peripheral neuropathic pain is often described as “burning”, “tingling”, “electrical”, “stabbing”, or “pins and needles”.Bumping the “funny bone” elicits acute peripheral neuropathic pain.
• Allodynia – Allodynia is pain experienced in response to a normally painless stimulus. It has no biological function and is classified by stimuli into dynamic mechanical, punctate and static. In osteoarthritis, NGF has been identified as being involved in allodynia. The extent and intensity of sensation can be assessed through locating trigger points and the region of sensation, as well as utilizing phantom maps.

The suggested ICD-11 chronic pain classification suggests 7 categories for chronic pain

• Chronic primary pain: defined by 3 months of persistent pain in one or more anatomical regions that is unexplainable by another pain condition.
• Chronic cancer pain: defined as cancer or treatment-related visceral, musculoskeletal, or bony pain.
• Chronic posttraumatic pain: pain lasting 3 months post-trauma or surgery, excluding infectious or preexisting conditions.
• Chronic neuropathic pain: pain caused by damage to the somatosensory nervous system damage.
• Chronic headache and orofacial pain: pain that originates in the head or face, and occurs for 50% or more days over a 3 months period.
• Chronic visceral pain: pain originating in an internal organ.
• Chronic musculoskeletal pain: pain originating in the bones, muscles, joints, or connective tissue.

Causes of Pain

Common causes of musculoskeletal pain include:

• Chronic exertional compartment syndrome
• Chronic fatigue syndrome
• Claudication
• Dermatomyositis
• Dystonia
• Fibromyalgia
• Hypothyroidism (underactive thyroid)
• Influenza (flu) and other viral illness (influenza-like illness)
• Lyme disease
• Medications, especially the cholesterol medications known as statins
• Muscle cramp
• Myofascial pain syndrome
• Polymyalgia rheumatica
• Polymyositis (an inflammatory disease that causes muscle weakness)
• Repetitive strain injuries
• Rheumatoid arthritis (inflammatory joint disease)
• Rocky Mountain spotted fever
• Sprains and strains
• Years of poor posture
• Improper lifting and carrying of heavy objects
• Being overweight, which puts excess strain on the back and knees
• A congenital condition such as curvature of the spine
• Traumatic injury
• Wearing high heels
• Sleeping on a poor mattress
• No obvious physical cause
• Ordinary aging of the spine (degenerative changes)
• Cervical sprain and strain
• Cervical myofascial pain
• Cervical disc disease
• Cervical fracture
• Chronic pain syndrome
• Fibromyalgia
• Adhesive capsulitis
• Brachial plexopathy
• Thoracic outlet syndrome
• Carpal tunnel syndrome
• Cubital tunnel syndrome
• Parsonage-Turner syndrome
• Multiple sclerosis
• Vitamin B12 deficiency
• Amyotrophic lateral sclerosis
• Guillain-Barre syndrome
• Vertebral metastasis
• Discitis/osteomyelitis

Diagnosis of Pain

Treatment of Pain

The list of nonpharmacological therapies for chronic pain is extensive. Nonpharmacological options include

• heat and cold therapy,
• cognitive behavioral therapy,
• relaxation therapy,
• biofeedback,
• group counseling,
• ultrasound stimulation,
• acupuncture,
• aerobic exercise,
• chiropractic,
• physical therapy,
• osteopathic manipulative medicine,
• occupational therapy, and TENS units.
• Spinal cord stimulation, epidural steroid injections,
• radiofrequency nerve ablations,
• nerve blocks,
• trigger point injections and intrathecal pain pumps are some of the procedures and techniques commonly used to combat chronic pain. The efficacy of TENS units has been variable, and the results of TENS units for chronic pain management are inconclusive.[rx] Deep brain stimulation is for post-stroke and facial pain as well as severe, intractable pain where other treatments have failed.[rx]

Medications

Several types of medications are available that can help treat chronic pain. Here are a few examples:

• NSAIDs –  over-the-counter pain relievers, including acetaminophen (Tylenol) or nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin (Bufferin) or ibuprofen (Advil). opioid pain relievers, including morphine (MS Contin), codeine, and hydrocodone(Tussigon) adjuvant analgesics, such as antidepressants and anticonvulsants. Acute pain is usually managed with medications such as analgesics and anesthetics. Caffeine when added to pain medications such as ibuprofen, may provide some additional benefit. Ketamine can be used instead of opioids for short-term pain. Management of chronic pain, however, is more difficult and may require the coordinated efforts of a pain management team, which typically includes medical practitioners, clinical pharmacists, clinical psychologists, physiotherapists, occupational therapists, physician assistants, and nurse practitioners.
• The initial treatment of neuropathic – is often with gabapentin or pregabalin. These are calcium channel alpha 2-delta ligands. They are indicated for postherpetic neuralgia, diabetic neuropathy, and mixed neuropathy.[rx] There is limited evidence in the use of other antiepileptic medications to treat chronic pain, where many of these, such as lamotrigine, have a more significant side effect profile. The exception is carbamazepine in the treatment of trigeminal neuralgia and other types of chronic neuropathic pain.[rx][rx]
• Antidepressants – such as dual reuptake inhibitors of serotonin and norepinephrine (SNRI) or tricyclic antidepressants (TCA) can is an option. Antidepressants are beneficial in the treatment of neuropathic pain, central pain syndromes, and chronic musculoskeletal pain. For neuropathic pain, antidepressants have demonstrated a 50 percent reduction of pain relief. Fifty percent is a significant reduction, considering the average decrease in pain from various pain treatments is 30%.[rx][rx]
• The serotonin-norepinephrine reuptake inhibitor (SNRI) – duloxetine is useful in treating chronic pain, osteoarthritis, and the treatment of fibromyalgia.[rx] Furthermore, the efficacy of duloxetine in the treatment of comorbid depression is comparable to other antidepressants.[rx][rx] Venlafaxine is an effective treatment for neuropathic pain, as well.[rx] A TCA can also be utilized, such as nortriptyline. TCA medications may require six to eight weeks to achieve its desired effect.[rx]
• Topical NSAIDs – Adjunctive topical agents such as topical lidocaine are a useful treatment for neuropathic pain and allodynia as in postherpetic neuralgia.[rx][rx] Topical NSAIDs have been shown to improve acute musculoskeletal pain, such as a strain, but are less effective in chronic pain. Yet, topical NSAIDs are more effective than controls in the treatment of pain related to knee osteoarthritis.[rx][rx] Separately, topical capsaicin cream is an option for chronic neuropathic or musculoskeletal pain unresponsive to other treatments.[rx] Botulinum toxin has also demonstrated effectiveness in the treatment of postherpetic neuralgia.[rx] The use of cannabis is also an area of interest in pain research. There is some evidence that medical marijuana can be an effective treatment of neuropathic pain, while the evidence is currently limited in treating other types of chronic pain.[rx]
• Sugar (sucrose) – when taken by mouth reduces pain in newborn babies undergoing some medical procedures (lancing of the heel, venipuncture, and intramuscular injections). Sugar does not remove pain from circumcision, and it is unknown if sugar reduces pain for other procedures. Sugar did not affect pain-related electrical activity in the brains of newborns one second after the heel lance procedure. Sweet liquid by mouth moderately reduces the rate and duration of crying caused by immunization injection in children between one and twelve months of age.
• Psychological – Individuals with more social support experience less cancer pain, take less pain medication, report less labor pain, and are less likely to use epidural anesthesia during childbirth, or suffer from chest pain after coronary artery bypass surgery.
• Cognitive-behavioral therapy (CBT) – has been shown effective for improving quality of life in those with chronic pain but the reduction in suffering is modest, and the CBT method was not shown to have any effect on the outcome. Acceptance and Commitment Therapy(ACT) may also effective in the treatment of chronic pain.

Medical procedures for pain

Certain medical procedures can also provide relief from chronic pain. An example of a few are:

• electrical stimulation, which reduces pain by sending mild electric shocks into your muscles
• nerve block, which is an injection that prevents nerves from sending pain signals to your brain
• acupuncture, which involves lightly pricking your skin with needles to alleviate pain
• surgery, which corrects injuries that may have healed improperly and that may be contributing to the pain

Additionally, various lifestyle remedies are available to help ease chronic pain. Examples include:

• Physiotherapy
• Yoga
• Acupuncture
• Cognitive behavior therapy
• Art and music therapy
• Chiropractic 
• Psychotherapy
• Massage
• Meditation

References