What is physiological pain?
- Obvious tissue injury or illness
- Activation of the 'normal' pain pathways
- Protective function
Description
–Sharp ± dull
–Well localised
Physiological pain can be further classified into:
- Nociceptive pain
- Early warning protective system in response to damage/noxious stimuli
- Inflammatory pain
- Inflammation after tissue injury results in increased sensitivity of pain pathways leading to a further protective function
Reference: Woof CJ. What is this thing called pain? J Clin Invest 2010; 120 (11): 3742-4
What is pathological pain?
- Abnormal processing of pain signal
- May be due to nervous system damage or dysfunction
- Needs to be treated differently
- Not 'useful'
- No protective function
Examples
Nerve trauma, diabetic pain (damage)
Fibromyalgia, chronic tension headache (dysfunction)
Mechanisms of pathological pain
- Increased numbers of pain receptors
- Abnormal sensitisation of nerves
- Peripheral sensitisation
- Increased sensitivity (excitability) of peripheral nociceptors
- Central Sensitisation
- Increased sensitivity (excitability) of nerves within the central nervous system. Normal inputs begin to produce abnormal responses, e.g. spread of pain sensitivity beyond an area of tissue damage.
- Chemical changes in the dorsal horn
- Loss of normal inhibitory modulation
NB: Peripheral sensitisation after, eg. injury, is physiological and useful, whereas prolonged central sensitisation is pathological and not useful
Description
- Burning / Shooting / "Pins and needles" / "Numb" / Poorly localised
Other Definitions
Allodynia - Pain due to a stimulus that does not normally cause pain (e.g. light touch)
Hyperalgesia - Increased pain in response to a stimulus that normally causes pain
Pathological Pain can be further classified into:
- Neuropathic pain
- e.g. damage to nervous system
- Dysfunctional pain
- e.g. chronic pain after prolonged poorly treated acute pain...?due to persistent central sensitisation
Reference: Woof CJ. What is this thing called pain? J Clin Invest 2010; 120 (11): 3742-4
