[Catalyst 2019]

IT'S ALL IN YOUR BRAIN
THE NEURAL NETWORK OF CHRONIC PAIN
By Tammita Phongmekhin
A
medical maxim goes: “The extent of
pain one feels is directly proportional
to the severity of the physical injury.”
Through decades of research, this idea
has largely been debunked by the scientific
community. However, much of the general
population still believes in this common
misconception.
This idea of pain being proportional to
the amount of tissue damage ties into
the subject of chronic pain. Chronic pain
is defined as pain that persists for longer
than three months. Those that suffer from
chronic pain conditions often feel a degree
of pain that exceeds the extent of physical
injury, if such an injury even exists. Chronic
pain can make even the most basic tasks
unbearable; additionally, these conditions
can be especially hard to treat, as they often
do not present visible symptoms. As Dr.
Leslie J. Crawford, Vanderbilt University’s
rheumatology research director, states:
“[chronic pain is] perhaps the symptom that
brings more patients into our practices than
any other, but also the symptom most likely
to make us feel helpless as healers.” 1
Chronic pain is an artifact of the brain. Just
as learning and repetition rewire the brain,
prolonged pain can alter the brain’s neural
networks, causing a heightened sensitivity
to pain which further amplify the effects it
has on emotional and cognitive abilities.
As such, chronic pain modifies the central
nervous system, induces mental disorders,
and negatively affects a person’s lifestyle. 1
Therefore, healthcare professionals consider
it to be both a physical disability and a
neurological disease.
A Negative Remolding of the Brain
There are multiple physical symptoms and
alterations that are observed in chronic pain
patients, and they are largely centralized
in the brain and the nervous system of the
body.
One symptom involves a decrease in gray
matter, which results in a decreased ability
to perform tasks involving muscle control,
sensory perceptions, and memory. Patients
may also experience shrinkage of their
prefrontal cortex, leading to difficulties
controlling the brain’s executive functions
like decision-making. Reduced hippocampus
size has also been observed in chronic pain
patients--a physiological change which
causes increased likelihood of developing
anxiety and depression. 2
“
Chronic pain can make
even the most basic
tasks unbearable. These
conditions can be
especially hard to treat, as
they often do not present
visible symptoms.
”
Additionally, studies confirm that chronic
pain patients who undergo these changes
in brain structures have cognitive and
emotional modulation of pain. As patient
conditions worsen and emerge as chronic
pain, brain activity shifts from traditional
pain-related areas of the brain to those
areas associated with emotions. 3 These
findings not only explain why many
chronic pain patients develop anxiety
and depression, but also why those who
experienced periods of high stress prior to
injury are more prone to develop chronic
pain once they are injured.
Heightened Sensitivity
In addition to physical changes in the brain,
prolonged pain affects the state of the
nervous system, resulting in heightened
sensitivity to pain and emotional difficulties.
Central sensitization is the condition in
which the nervous system experiences a
constant state of high reactivity, effectively
lowering the threshold for pain and causing
pain to last even when the initial injury may
have healed. Central sensitization is also
associated with emotional distress since the
nervous system’s high reactivity state causes
a person to be in a state of nervousness.
When patients acquire an injury or
illness, predisposing factors play roles
in determining whether or not they will
develop chronic pain. For example, a
history of stress corresponds to a more
reactive nervous system, thereby making a
16 | CATALYST