PCL 2- Types and causes of pain

Types and causes of pain...

Nociceptive Pain
- divided into somatic and visceral pain
- Arises from the stimulation of specific pain receptors which can respond to
heat, cold, vibration, stretch and chemical stimuli released from damaged
cells.
- can be experienced as sharp, dull, or aching

Non-nociceptive pain
- divided into neuropathic and sympathetic
- arises from within the peripheral and central nervous system
- specific receptors do not exist here, with pain being generated by nerve
cell dysfunction.

Somatic pain
Source : tissues such as skin, muscles, joints, bones, and ligaments - often known as musculo-skeletal pain.

Receptors activated : specific receptors (nociceptors) for heat, cold, vibration,
stretch muscles), inflammation and oxygen starvation
(ischaemic muscle cramps)

Characteristics : often sharp and well localised, and can often be reproduced by touching or moving the area or tissue involved.

Visceral pain
Source : internal organs of the main body cavities. There are three main cavities - thorax heart and lungs), abdomen (liver, kidneys, spleen and bowels), pelvis (bladder, womb, and ovaries).

Receptors activated : specific receptors (nociceptors) for stretch, inflammation, and oxygen starvation (ischaemia).

Characteristics : often poorly localised, and may feel like a vague deep ache, sometimes being cramping or colicky in nature. It frequently produces referred pain to the back, with pelvic pain referring pain to the lower back, abdominal pain referring pain to the mid- back, and thoracic pain referring pain to the upper back.

Neuropathic pain
Source : from within the nervous system itself - also known as pinched nerve, trapped nerve. The pain may originate from the peripheral nervous system (the nerves between the tissues and the spinal cord), or from the central nervous system (the nerves between the spinal cord and the brain)

Causes :
1. Nerve Degeneration - multiple sclerosis, stroke, brain haemorrhage, oxygen starvation
2. Nerve Pressure - trapped nerve
3. Nerve Inflammation - torn or slipped dis
4. Nerve Infection - shingles and other viral infections
5. Peripheral neuropathy
6. Phantom limb pain

Receptors activated : the nervous system does not have specific receptors for pain (non nocicpetive). Instead, when a nerve becomes injured by one of the processes named above, it becomes electrically unstable, firing off signals in a completely inappropriate, random, and disordered fashion.

Characteristics : These signals are then interpreted by the brain as pain, and can be associated with signs of nerve malfunction such as hypersensitivity (touch, vibration, hot and cold), tingling, numbness, and weakness. There is often referred pain to an area here that nerve would normally supply. Spinal nerve root pain is also often associated with intense itching in the distribution of a particular dermatome. People often describe nerve pain is often
described as lancinating, shooting, burning, and hypersensitive. Sometimes patients do not describe the sensation as being "painful" but rather as feeling unpleasantly strange or
tingly

Sympathetic Pain
Source : due to possible over-activity sympathetic nervous system, and central /peripheral nervous system mechanisms.

Causes : occurs more commonly after fractures and soft tissue injuries of the arms and legs, and these injuries may lead to Complex Regional Pain Syndrome (CRPS).

Receptors activated : like nerve pain there are no specific pain receptors (non nociceptive).

Characteristics : presents as extreme hypersensitivity in the skin around the injury and also peripherally in the limb (allodynia), and is associated with abnormalities of sweating and temperature control in the area. The limb is usually so painful, that the sufferer refuses to
use it, causing secondary problems after a period of time with muscle wasting, joint contractures, and osteoporosis of the bones. It is possible that the syndrome is initiated by trauma to small
peripheral nerves close to the injury.

Mixed Pain
- nociceptive and non-nociceptive pain mechanisms are involved
- For instance in cancer pain, the pain can be due to the tumour causing inflammation of tissue around the tumour (nociceptive) and causing entrapment of a nerve (non-nociceptive)

Acute pain
- Pain that is usually temporary and results from something specific, such as a surgery, an injury, or an infection.
- may be mild and last just a moment, or it may be severe and last for weeks or months
- may be accompanied by anxiety or emotional distress
- cause of acute pain can usually be diagnosed and treated, and the pain is self-limiting
- In most cases, acute pain does not last longer than six months and it disappears when the underlying cause of pain has been treated or has healed
- Unrelieved acute pain, however, may lead to chronic pain.
- Physiologic responses to acute pain include tachycardia, tachypnea, and sweating due to discharge in the sympathetic nervous system

Chronic pain
- pain that lasts longer than six months.
- Chronic pain can be mild or excruciating, episodic or continuous, merely inconvenient or totally incapacitating.
- With chronic pain, signals of pain remain active in the nervous system for weeks, months, or even years. This can take both a physical and emotional toll on a person.
- There may have been an initial mishap -- sprained back, serious infection, or there may be an ongoing cause of pain -- arthritis, cancer, ear infection, but some people suffer chronic pain in the absence of any past injury or evidence of body damage.
- The emotional toll of chronic pain also can make pain worse
- Anxiety, stress, depression, anger, and fatigue interact in complex ways with chronic pain and may decrease the body's production of natural painkillers
- There is considerable evidence that unrelenting pain can suppress the immune system.
- Symptoms :

 Mild to severe pain that does not go away
 Pain that may be described as shooting, burning, aching, or electrical
 Feeling of discomfort, soreness, tightness, or stiffness

- Associated symptoms :

o Fatigue
o Sleeplessness
o Withdrawal from activity and increased need to rest
o Weakened immune system
o Changes in mood including hopelessness, fear, depression, irritability, anxiety, and stress
o Disability