What Is Chronic Pain

Introduction

One of the most common chronic illnesses known to affect the modern population is chronic pain.¹ It is estimated that about 1 to 6% of the population of England suffer from chronic pain at any given point.² Chronic pain can cause severe primary physical and secondary mental health issues, along with also severely affecting the quality of life of the individual.³ 

How many times have you heard someone around you say that they suffer from chronic pain but never understood what they actually meant or may be going through? Read on to find out more.

Definition of chronic pain

As per the NICE guidelines, chronic pain is defined as:

• Persistent pain that has lasted longer or recurs for over 3 months or more than 12 weeks
• An unpleasant sensory and emotional experience which may or may not be associated with, or the result of, actual or potential tissue damage
• Multifactorial — biological, psychological, and social factors contribute to the pain syndrome.

Headache, joint, and back pain are the most common types of chronic pain. 

The significance of chronic pain

A person’s quality of life can be hugely impacted by chronic pain. It can disrupt your daily activities, including working, sleeping, taking care of yourself, and socialising with friends. Over time, this can cause anxiety and depression, worsening the pain, which may lead to a vicious cycle that can affect an individual's overall ability to function independently.³

The nerves that are linked to chronic pain are also closely associated with the area of the brain that deals with emotion. As a result, emotions closely impact chronic pain, and similarly, chronic pain severely impacts emotions. 

For example - patients suffering from chronic pain may often also suffer from complex emotional states that may worsen or primarily induce anxiety or depression. But inversely, a person suffering from chronic pain over a long period of time may also find their pain worsening when experiencing anxiety or stress. Positive emotions such as happiness may help decrease the pain and, often, cope with it better.⁴ 

How does pain work?

The nerves of the spine and the brain make up our central nervous system. These nerves send signals (sensory information gathered from organs such as the eyes, ears, skin, etc.) from the body to the brain to let the brain know what is going on in the body. The brain sifts through these signals, interprets them, and decides if a response is needed - and if needed, what it should be. 

In cases where there might be actual tissue damage (e.g., a cut or a burn), the sensory information will be interpreted by the brain and cause an individual to feel pain. When this tissue damage is chronic, the unpleasant sensation will also continue, causing chronic pain. 

The pain usually settles in time after the injured area has healed or by medical intervention. However, on some occasions, the nervous system may continue to interpret sensations of pain that are intense, difficult to stop and have no apparent cause.^4,5 

Categories of chronic pain

As per the NICE guidelines, chronic pain can be categorised into two types:

Primary chronic pain

Primary chronic pain is pain that has no known cause. As a result, this type of pain, in particular, can be more emotionally and physically distressing. 

Examples of primary chronic pain include:

• Complex regional pain syndrome
• Fibromyalgia
• Chronic primary headache⁵

Secondary chronic pain

This is chronic pain caused by a known underlying issue. 

The causes of this can be:

• Surgery resulting in chronic post-surgical pain
• Degenerative conditions, such as spondylosis 
• Injury, such as whiplash, causes back or neck pain
• Long-term illnesses can lead to pain, such as cancer or arthritis

It is important to note that primary and secondary pain can occur simultaneously. A person can experience an explainable pain at the same time as experiencing pain with an unknown cause ⁵. 

Types of chronic pain

Chronic cancer pain

This pain is related to an underlying/preexisting cancer that an individual is suffering from, and so the treatment differs from normal pain. 

This pain is either due to the primary tumour or metastases causing pressure/blockage or is a result of cancer treatment (radiotherapy, chemotherapy, surgery, etc.). Chronic cancer pain can either be continuous or intermittent if it is linked to a certain procedure or movement. 

Symptoms can include weakness, nausea, fatigue, difficulty breathing and sleep disturbances. 

Chronic post-traumatic or post-surgical pain

This is pain that is due to trauma or surgical intervention. 

Some major characteristics of this type of chronic pain are:

• It occurs following an injury or surgery and lasts more than 12 weeks after this event
• Inability to be linked to another identifiable cause, such as infection or cancer
• The pain sensation is not the same as the original condition 

Some studies have found a link between chronic post-surgical pain and neuropathic pain.⁶

Chronic visceral pain

Chronic visceral pain can be defined as recurrent or persistent pain that arises from internal organs of the pelvic region, abdominal area, thoracic region, head or neck. 

Symptoms include:

• Intermittent or constant pain
• Sharp or dull pain
• Deep or superficial pain

Research has shown chronic visceral pain to be present in skin or muscle walls that have the same sensory nerves as the original internal organ causing the symptoms. As a result of this, identifying the location of the pain can be difficult.⁷

Chronic musculoskeletal pain

One of the most common types of chronic pain. This pain originates from the bones, ligaments, muscles, nerves, or tendons. 

Symptoms of this chronic musculoskeletal pain include:

• Dull or sharp pain
• Swelling
• Stiffness
• Weakness
• Redness
• Soreness 

Some of the conditions that can cause musculoskeletal pain are:

• Fractures
• Dislocations
• Muscle loss
• Poor posture
• Bone or joint issues  
• Chronic trauma or prolonged use or stress on the muscles^1,8

Nociceptive pain

Nociceptive pain originates from the nociceptors (nervous system receptors present in the skin) and is typically a result of potential or physical damage to the body. Chemicals, inflammation or physical injury can trigger this type of pain. The pain is often described as throbbing, aching or sharp.^1,5

Causes of this pain include:

• Cuts
• Burns 
• Bruises 
• Sprains
• Complex causes may include inflammatory bowel disease, and endometriosis, among others.

Chronic neuropathic pain

A disease or lesion in the somatosensory nervous system can cause neuropathic pain. The pain can be described as:

• Cold or burning
• Tingling or numbness
• Itching
• Pins and needles 

Central neuropathic pain may be found in conditions such as multiple sclerosis, spinal cord injury, and strokes.

Peripheral neuropathic pain may be found in conditions such as: 

• Poisoning by toxins
• Nutritional deficiencies
• Malignancies
• Diabetes
• Herpes zoster virus 

Research has shown neuropathic pain to be more debilitating and more significantly impactful on the person’s quality of life in comparison to nociceptive pain.⁹ 

Diagnosis and tests for chronic pain

Due to pain being subjective, it can be difficult for healthcare professionals to determine the cause or origin of pain.

The most common method of diagnosing chronic pain is through medical history (where doctors may typically ask you for information) and clinical examination.^1-9  

Some questions that might be typically asked during a consultation may be:

• Where do you feel the pain?
• How long have you felt it for and when did it first start? 
• Intensity of the pain on a scale of 1 to 10
• How frequently do you experience this pain?
• The impact it has on your life and work
• If any activity makes it better or worse
• Your physical and mental health history (i.e., any anxiety, stress, or pre-existing medical conditions)
• Medical and surgical history 

Following this, a clinical examination is generally carried out to examine your general fitness, followed by more focus on the area where the pain might be or where it could be related to. 

Healthcare professionals may carry out some of the following tests/investigations to narrow down the cause and the diagnosis of your pain:

• Blood tests (e.g. full blood counts, blood sugar levels, liver and kidney function tests, etc.) 
• X-ray, CT, or MRI scans
• Electromyography to test the activity of muscles
• Nerve conduction studies to test nerve reactions
• Testing the spinal fluid 
• Reflex and balance test
• Urine tests 

Chronic pain treatment

Once the location/cause of pain has been identified, your healthcare professional will be able to treat this. The treatment plan can depend on the type of pain, cause of pain, age, and general health.

Effective treatment typically includes a mixture of methods such as lifestyle alterations, therapies, and medications.

For patients with mental health issues (anxiety and depression) prior to the pain or as a result of the pain, it is crucial that they seek help for this, as these conditions can severely impact pain and recovery.

Some of the following medications are commonly effective in treating pain:

• Non-steroidal anti-inflammatory medication
• Corticosteroids
• Antidepressant medication (used as painkillers)
• Anticonvulsant medication - conventionally used to treat seizures, is now also to found to be useful in treating some cases of chronic pain.
• Muscle relaxants
• Creams or gels applied directly onto the skin
• Sedatives 
• Prescription opioids - these are usually used as a last resort and only in very severe or uncontrolled cases due to tolerance and addictive properties.

Other treatment options may also include:

• Nerve blocks - an anaesthetic is injected close to the site to block the pain
• Epidural steroid injections - a steroid medication is injected around the nerves of the spine to minimise the inflammation or irritation in the spinal nerve roots
• Transcutaneous electrical nerve stimulation (TENS) - small electrical shock pads are placed on the skin to reduce pain. 
• Devices such as mouthguards or oral plates are given to patients with chronic oral musculoskeletal pain. 
• Cognitive behavioural therapy 
• Some preliminary studies have also shown that unconventional methods of treatment such as acupuncture may also be beneficial, however evidence for this is not yet conclusive. 

Treatment for chronic pain is often highly reliant on the individual presentation and the individual themselves, thus your treating clinician’s recommendation here is of significant importance.^1-9 

Summary

Pain lasting more than 3 months or 12 weeks can be defined as chronic pain. Chronic pain is one of the most common illnesses noted within modern populations today, with about 10% of people suffering from it worldwide. Patients with chronic pain may often find it difficult to cope with day-to-day activities and function independently thus affecting their quality of life quite severely. There are several different types of chronic pain based on the underlying cause. Chronic pain is commonly treated using several different methods such as medications, surgical or medical interventions, etc. Treatment choices are often strongly dependent on individual presentation. With appropriate intervention and time, most patients can reduce or even recover from the impact of chronic pain on their overall quality of life.