The American Academy of Pain Medicine (AAPM)
defines pain as – “An unpleasant sensation
and emotional response to that sensation”.
The Web version of the Encyclopedia
Britannica defines pain as – “A complex
experience consisting of a physiological
(bodily) response to a noxious stimulus
followed by an affective (emotional)
response to that event. Pain is a warning
mechanism that helps to protect an organism
by influencing it to withdraw from harmful
stimuli. It is primarily associated with
injury or the threat of injury, to bodily
Pain is an individual sensation that can be
described or defined by the person having
it. It may cause distress and discomfort, it
is usually described as: aching, pinching,
throbbing or stabbing. We may distinguish
between two basic types of pain -
acute and chronic.
Acute pain lasts a relatively short
time. It is a signal that body tissue is
being injured. The pain generally disappears
when the injury heals. Acute pain results
from disease, inflammation or tissue injury.
It may appear suddenly, such as after
surgery trauma and may be accompanied by
emotional or anxiety distress. The cause of
acute pain can usually be diagnosed and
treated accordingly. In certain cases it may
Chronic pain may range from mild to
severe and lasts usually for long periods of
time, more than three months. It is
associated with the disease itself. Chronic
pain may get worse by psychological or
The cause of chronic pain is not always
evident. In certain cases, it may be
associated with chronic conditions such as:
arthritis, fibromyalgia or lupus with
symptoms such as: swollen joints,
unexplained fever, extreme fatigue, sleep
problems or red skin rash. Chronic pain
syndromes, in particular, are complex and
their effective treatment often involves
coordinated, multidisciplinary consultation.
In contrast to acute pain, chronic pain can
be mysterious, intractable and is often very
expensive to treat. The complexity of
chronic pain stems from the fact that it is
a bio-psycho-social condition, which occurs
in various forms.
Since pain is a bio-psycho-social condition,
all aspects of the condition must be
treated. Assuming that a condition is “all
in the patient’s head” makes the mistake of
overlooking possible real pain.
On the other hand, failure to assess the
psycho-social factor can also lead to longer
recovery. The complex nature of chronic pain
disorders makes it impossible for a single
professional to treat it successfully.
We may distinguish between peripheral
and central pain.
Peripheral pain originates in
the peripheral nerves or in muscles, usually
Central pain arises from Central
Nervous System (CNS) pathology or
dysfunction. This is primarily due to
structural changes in the CNS, such as:
spinal cord injury, multiple sclerosis,
stroke and epilepsy.
Inhibition of pain is important and needed
especially when our safety is more
important, like when we are running away
from dangerous situation. The purpose of
pain is to tell us via our brain when
something needs to be done about a damaged
area. The brain will assist us whether to
pay attention to the painful area or ignore
This information is transmitted by the brain
and travels to the spinal cord or brainstem
via electrical impulses in fibers of spinal
or certain cranial nerves. Those signals
pass electrically to higher CNS levels.
Therefore, monitoring those signals in real
time may be used as essential
parameters in our effort for detecting and
Pain and Gender
Recent studies using Positron Emission Tomography (PET) brain scans of patients
during pain stimuli showed different brain responses between men and women.
Several areas of male and female brains responded differently
to the same pain stimuli. Female's brain showed more activity in emotion related
centers where males responded in the cognitive or analytical regions. Those
differences may relate to our evolution process and the different social tasks
of males and females.
Women often have high pain experience levels but lower pain tolerance. Their
sensitivity to pain is affected by many factors such as biological, inherited
conditions and hormone levels.
Pain and Animals
The presence of pain is by the observation of change from normal behavior.
Pain may be evident as a limp or a change in gait, withdrawal or protection of
an injured part, abnormal postures, licking, rubbing or scratching at an area.
Signs of pain and distress particular to rodents include eating too much,
chewing toes and feet.
Signs of pain may be subtle such as a change in respiration, reluctance to move,
apprehension, sudden aggression, inability to rest or sleep normally, or a
worried or anxious expression.