Some terms relating to pain that could be helpful.
Acute pain:
Acute pain has a crucial function for good
health because it is a warning of actual or potential physical harm.
In situations of acute pain the pain usually stops before physical
healing is complete.
A fibres:
A small diameter myelinated afferent axon. These
are divided in subtypes alpha (primary muscle spindle afferents, motor
fibres to motor neurons), beta (touch and pressure afferent fibres in
the skin), gamma (motor fibres to muscle spindles) and delta
(temperature and pain conducting afferent fibres in the skin).
Allodynia:
Pain due to a stimulus that does not normally provoke pain.
B fibres:
Sympathetic preganglionic fibres
Catecholamines:
The different neurotransmitters dopamine,
adrenaline (also known as epinephrine) and noradrenaline (nor
epinephrine) are all catecholamines.
C fibres:
Unmyelinated afferent axons
Chronic pain:
Traditionally chronic pain is considered as
pain that continues for more than 3-6 months or which persists longer
than the time required for healing. More recently the IASP defines it
as being persistent pain that is not amenable to specific remedies and
theorists Loeser and Melzack add that chronic pain is distinguished by
the inability of the body to restore its physiological functions to
normal homeostatic levels.
CRPS:
Chronic Regional Pain Syndrome is divided into two types. Type 1 used to be known as reflex sympathetic dystrophy
does not involve nerve damage. Type 1 pain involves deep diffuse pain
caused initially by minor injury or resulting from infections,
inflammation, surgery, bone fracture, heart attack, stroke, frostbite,
burns or joint disease ((A Wright 2002). Type 2 used to be known as causalgia
does involve nerve injury and often involves the hand or foot. The pain
experienced by either type is often burning or stabbing and can involve
tremor, reduced mobility, oedema, changes in skin blood flow and
surface temperature. Some researchers give three stages with Stage 1
being the acute or warm phase immediately after the pain starts. The
limb is often warm and swollen and there may be increased nail or hair
growth, spontaneous burning pain and allodynia. Stage 2 begins about 3
months after the precipitating event with the pain now occurring in an
extended area with reduced movement in the limb and joint stiffness
becoming significant features. Osteoporosis and muscle wasting are
often evident. Stage 3 can occur around 6 months after the
precipitating event if the condition is untreated. Pain may decrease
and the skin is cool, white cool and has a glossy appearance. Muscle
wastage may not be able to be remedied.
Dorsal Horn:
The dorsal horn refers to the shape of the
central part of the spinal cord and is the key site for receiving and
processing incoming sensory information from the different afferent
fibres.
GABA:
Gamma aminobutyric acid (an inhibitory neurotransmitter)
Pain:
The International Association for the Study of Pain
(IASP) defines pain as ‘An unpleasant sensory and emotional experience
associated with actual or potential tissue damage, or described in
terms of such damage.’
Fascia:
The membrane covering muscles and organs.
Fibromyalgia:
Fibromyalgia is a neuropathic pain syndrome
characterized by widespread muscular aching that affects most of the
body, fatigue and disturbed sleep patterns and may be associated with
depression, irritable bowel syndrome, headaches and Reynaud’s
phenomena. To be diagnosed at least 11 out of 18 possible tender points
need to be painful to finger pressure.
Hyperaesthesia:
Increased sensitivity to stimulation, this excludes the special senses.
Hypothalamus:
The hypothalamus is a midbrain structure
that is strongly implicated in providing responses to emotional changes
and needs. Through efferent pathways to autonomic ganglia in the
brainstem and spinal cord, the hypothalamus controls sympathetic and
parasympathetic functions.
Myofascial pain:
Pain experience that is thought to involve the membranes (fascia) covering the muscles.
Neuroma:
A benign mass of nerve tissue that can form at the end of a nerve that has been damaged or cut.
Neuropathic pain:
Neuropathic pain is any pain condition
where the pain experienced is due to the peripheral or central nervous
system processing somatosensory signals inappropriately. In chronic
neuropathic pain the cause of the injury may have been resolved but
pain continues. Research seems to indicate that the neurons in the
peripheral areas of the body affected by pain can be changed by the
pain experience itself. This also happens to cells in the dorsal horn
of the spinal cord and elsewhere in the central nervous system which
become sensitized and changed structurally.
Neurotransmitter:
A chemical released by the dendrites at
the end of a neuron in response to an impulse and which activates
neighbouring dendrites from nearby neurons.
Nociceptive pain:
Nociceptive pain arises when the
different nerve endings that respond to pressure, touch, heat, irritant
chemicals or pain are stimulated or damaged. This often includes skin,
muscle and joints.
PAG:
The peri aqueductal grey matter surrounds the
cerebral aqueduct of the midbrain and controls functions such as pain
facilitation, analgesia, fear and anxiety, vocalization, sexual
behaviour and cardiovascular control.
Parasympathetic nervous system:
Is that part of the
autonomic nervous system that triggers the relaxation response and
reduces stress reactions. Ideally the sympathetic and parasympathetic
nervous systems balance each others activities in normal life.
Peripheral neuropathy:
A form of neuropathic pain experienced in the hands or feet. It results from conditions such as diabetes.
Post herpetic neuralgia:
A common form of neuropathic pain that persists or recurs 1 month or more following the initial eruption of herpes zoster.
Referred pain:
Pain caused in one part of the musculo skeletal system or in the viscera can be experienced in a different part of the body.
Sympathetic nervous system:
Is that part of the autonomic nervous system that activates the fight flight response and is central in stress reactions.
Thalamus:
The thalamus is a clearing centre for nearly all
sensory and motor information and redirects this information to the
cerebral cortex where the impulse is given meaning.
VAS:
Visual Analogue Scale. Most often this refers to the
score out of 10 reported by a pain patient and indicating their
perception of the severity of their pain.