Pain

What is pain?

Pain is a general term that describes uncomfortable or unpleasant sensations in the body. Pain stems from activation of the nervous system and, while unpleasant, it can let us know when something is wrong.

People generally feel pain when a pain receptor picks up a stimulus and relays the message through nerve fibres to the brain for interpretation.
The experience of pain is different between every individual, and, as such, there are various ways to feel and describe pain. People also respond to pain, with varying degrees of tolerance. Pain can range from just annoying to outright debilitating, and it can feel like a sharp stabbing or a dull ache, or it can be described as throbbing, stinging, crushing, sore or pinching, amongst others.
For this reason, pain is highly subjective and can be very challenging to define, diagnose and treat.

Additionally, pain can occur acutely or develop gradually over time, lasting for a short period, or over a very long period (described as chronic pain). Pain can also be localised, affecting only a specific area of your body, like with an injury, or it can be general; for example, the overall body aches associated with influenza infection.

Knowing how to describe pain can help your doctor provide a more specific diagnosis to provide you with effective treatment.

What causes pain?

You generally feel pain when specific nerve receptors (pain receptors), called nociceptors, detect tissue damage and transmit information about the damage along nerves to the spinal cord, and from there to the brain.
Nociceptors are sensory neurons (special nerve cells) found widely in the skin, the deep tissues beneath the skin (muscle and joints) and in visceral organs.

Most nociceptor activation stimulates a reflex arc.
For example, if you step on a sharp needle, a message, in the form of an electrical impulse in your nerves, is relayed to the spinal cord, that, in turn, sends electrical impulses to your periphery, in this case, the muscles in your leg to contract and withdraw from the pain-causing stimulus (the needle).

This reflex occurs very quickly; so quickly in fact, that the message has not even had time to be relayed to the brain yet. However, the pain message will eventually reach the brain which will interpret the experience as unpleasant, or painful.

The brain’s interpretation of “pain” signals, and how effective the communication between the nociceptors and the brain is, dictates how you experience pain. The brain may also release feel-good chemicals, called endorphins (such as dopamine), to try and counter the unpleasant effects of pain; thereby modulating your experience of the painful sensation.

What are the different types of pain?

Pain is generally classified more broadly as either acute or chronic.

Acute Pain:

This type of pain, while generally intense, is short-lived. It is how the body tends to alert you to an injury or localised tissue damage. Therefore, treating the underlying injury usually resolves acute pain.

Acute pain also triggers the body’s sympathetic response, or fight-or-flight mechanism, often resulting in a faster heartbeat and breathing rate.

There are different types of acute pain, including:

• Somatic pain: This is the most common type of pain you experience. You may feel superficial pain on the skin or in the soft tissues just below the skin from a minor injury or localised tissue damage.
• Visceral pain: This pain originates in the internal organs or cavities in your body, such as with the stomach pain associated with peptic ulcer disease.
• Referred pain: A person feels referred pain at a location other than the damaged or injured site. For example, people often experience shoulder or jaw pain during a heart attack.

Chronic Pain:

According to a 2014 study on the global burden of chronic pain, at least 10 % of the global population is affected by a chronic pain condition, with an additional 1 in 10 people developing chronic pain every year.

Chronic pain is a type of pain that lasts longer than acute pain, usually defined as pain lasting longer than 12 weeks.

Chronic pain can be mild or severe and there is usually no one treatment for complete relief of this type of pain. It can also be either continuous, such as with chronic pain syndromes, as with fibromyalgia and the musculoskeletal pain of arthritis, or intermittent, as with headache pain like associated with migraine.
Intermittent pain occurs on repeated occasions but stops in between flare-ups, such as with angina of coronary artery disease or the pain caused by gastritis and gastroesophageal reflux disease (GERD).

If acute pain occurs very often, it can generate an accumulation of electrical signals that can overstimulate nerve fibres and the spinal cord or the brain, causing the experience of chronic pain.
This effect is known as “wind-up,” like the build-up of electrical signals in a windup toy. For example, winding a toy with more intensity leads to the toy running faster or for longer. Chronic pain works in the same way, which is why a person may feel pain long after the event that first caused it has ended.

Chronic pain is a disabling condition that negatively impacts an affected person’s quality of life.

As reported by the Lancet in 2011, “chronic pain affects every aspect of a patient’s life, contributing to a loss of both physical and emotional function, affecting a patient’s levels of activity (ability to work at home and job and engage in social and recreational pursuits).” Furthermore, the authors note that the economic consequences of this condition for the sufferers is severe, as a result of the healthcare expenses and the potential loss of financial income.

The recent Global Burden of Disease highlights “the high prominence of pain, and diseases associated with pain, as a global cause of disability in both developed and developing countries,” with chronic lower backpain as the single greatest cause of years lost due to disability.

There are more specialised ways of describing chronic pain, including by cause, such as:

• Neuropathic pain: This pain occurs following direct injury or damage to the peripheral nerves (the nerves that connect the periphery of the body to the spinal cord and brain). Neuropathic pain is often described as electric shocks, extreme tenderness,  numbness or tingling.
  Neuropathic pain is a common complication of long-term, poorly managed diabetes, diabetic neuropathy .
• Phantom pain: Phantom pain refers to the pain experienced after the amputation of a limb or digit. The painful sensations often feel as though they are coming from the missing part of the body.
• Central pain: This type of pain usually occurs due to infarction, abscesses, tumours and bleeding that occur in the brain or spinal cord. Central pain can range from mild to extremely painful. People with central pain report burning, aching and pressing pain sensations.

You are at greater risk of experiencing chronic pain if:

• You have suffered an injury
• Have had recent surgery
• Have underlying medical conditions like cancer or diabetes
• Are female
• Are overweight or obese.

How is pain diagnosed?

Your subjective description of the pain will help your doctor make a diagnosis.
To do this, your doctor will take a pain history and ask you questions to elicit information about:

• The character of the pain – usually described as burning, stinging, crushing or stabbing.
• The site and quality of the pain and where it radiates to– meaning where you feel the pain, what it feels like and how far it seems to spread.
• Factors that may aggravate or relieve the pain.
• The specific times in the day when the pain occurs.
• The effect of the pain on your daily functioning and mood.
• Your meaning and understanding of the pain; in other words, what you think is causing the pain.

Therefore, to elicit all of this information correctly for an accurate diagnosis, it is important that you communicate as clearly and openly as possible with your doctor.

Your doctor may also ask you to grade your pain, typically based on one of the below methods:

• Numerical rating scales: Your doctor will ask you to measure your pain on a scale of 0–10, where 0 means no pain at all, and 10 represents the worst possible pain. This measurement is also useful for checking how your pain levels may change in response to treatment.
• Verbal descriptor scale: This scale is usually used by doctors to help them measure pain levels in children or in those with cognitive impairments or the elderly. Instead of using numbers, your doctor will ask different descriptive questions about your pain.
• Faces scale: Here, your doctor will show you a range of expressions on faces, ranging from very distressed to very happy. This method is mainly used with children.
• Brief pain inventory: This is more detailed written questionnaire that can help doctors gauge the effect of your pain on your mood, daily activity, sleep patterns and interpersonal relationships. It also charts the timeline of the pain to detect any recognisable patterns.
• McGill Pain Questionnaire (MPQ): The MPQ encourages people to choose words from a group of 20 to get an in-depth understanding of how the pain feels. Group 6, for example, is “tugging, pulling, wrenching,” while group 9 is “dull, sore, hurting, aching, heavy.”

Other indicators of pain:

A person in pain may also display the following:

• Crying
• Restlessness
• Moaning and groaning
• Grimacing
• Resistance to movement
• Withdrawal from socialising
• Loss of appetite and not eating
• Problems sleeping.

What treatment is available for the management of pain?

Treatment of pain is based on what type of pain you have and what is causing it. A treatment that is effective against one type of pain may not relieve another.

Your doctor can often identify and treat an underlying condition that may be causing your pain; for example, if a bacterial infection is causing a sore throat or a sore ear, your doctor will prescribe antibiotics to clear the infection.

However, treating pain also often involves taking medications called analgesics (pain relievers), such as:

• Nonsteroidal anti-inflammatories (NSAIDs): These medications can reduce inflammation that causes pain.
  Some NSAIDs, like aspirin and ibuprofen, are available over-the-counter to purchase, while others are only available on your doctor’s prescription at a range of higher strengths. NSAIDs are suitable for minor acute pains, such as headaches, light bruises or sprains, backache or musculoskeletal pain from arthritis.
  NSAIDs can cause stomach, cardiovascular and bleeding problems, as well as liver and kidney damage – so take care to use these medications correctly and only as indicated. NSAID gels (such as diclofenac) can be applied to the skin over an arthritic joint, for example, and, in such a way, may cause fewer side-effects and be more effective at relieving pain than some oral NSAIDs.
• Opioids: Doctors prescribe these types of medications for the most extreme forms of acute pains, such as those that result from surgery, burns, cancer or bone fractures.
  Opioids are highly addictive, can cause withdrawal symptoms and they tend to lose effectiveness over time. Therefore, your doctor has to give you a prescription to use an opioid. In situations involving severe trauma and pain, your doctor may want to carefully manage and administer the dosage themselves, gradually reducing the amount to minimise withdrawal symptoms.
  You should discuss all medication options carefully with your doctor and disclose any health conditions and current medication usage, as opioids may significantly affect the progression of several chronic diseases, including:
  • Chronic obstructive pulmonary disorder (COPD)
  • Kidney disease 
  • Liver disease
  • Previous substance use disorders
  • Dementia.

A range of non-drug therapies can help relieve pain, especially when it comes to chronic pain which can be difficult to treat. These therapies can include:

• Acupuncture: This is a part of Chinese Traditional Medicine that involves inserting very fine needles at specific pressure points in the body to reduce pain.
• Nerve blocks: These injections can numb a whole group of nerves that act as a source of pain for a specific limb or body part.
• Psychotherapy: This type of therapy can help with the emotional stress and anxiety of experiencing ongoing pain. Chronic pain often affects your enjoyment of everyday activities and reduces your ability to be fully productive at work or in school. A psychotherapist can help enhance your understanding of pain and ensure you implement lifestyle changes to build coping skills to deal with the pain.
• Transcutaneous electrical nerve stimulation (TENS): TENS aims to stimulate your brain’s own opioid system, providing positive modulation of pain.
• Surgery: This can include on nerves, the spine or possibly the brain (such as rhizotomy), decompression and electrical deep brain and spinal cord stimulation procedures.
• Relaxation therapies: These include a wide range of controlled relaxation techniques and exercises, including hypnosis, yoga, meditation and massage therapy, amongst others, that may help to relieve pain.
• Physical therapy: A physiotherapist or chiropractor can sometimes help relieve pain by manipulating the tension in muscles or joints, especially as related to backpain.
• Heat and cold: Using hot and cold packs can help relieve inflammation, thereby reducing pain.
• Rest: If pain occurs due injury or overwork, rest may be the best option to relieve the pain and to allow injuries to heal and inflammation to subside.

Recently, studies of cannabidiol (CBD), an isolate of the hemp plant, have shown benefits in relieving hard to treat chronic pain.