FEATURE STORY/ WHEN THE NERVOUS SYSTEM PANICS
P
ain is complicated. Even
the weakest pain triggers a
complex process. You can
think of pain perception
a bit like a relay race: You
pinch your finger in a door. Nerves in
your finger bolt from the starting line
and carry pain signals — the baton
— to the spinal cord. The next set
of nerves grabs the baton and races
to the thalamus, the central hub of
information in the brain. A third team of
nerves rush the baton to the cerebral
cortex and — ouch! You feel the pinch.
Most patients expect pain to be
always this straightforward. If my arm
hurts, then my arm must be damaged. If
I rated my pain as a 4/10 yesterday and
now it feels like a 6/10, the damage must
be increasing. The brain is expected to
be a reliable narrator of what is going on
in the body. And most of the time it is.
But chiropractors know that the
relationship between perceived pain and
structural damage is not always so clear,
particularly when pain becomes chronic.
The whole system can be thrown off
kilter. Signals go awry.
Many chiropractors have had
patients who experience a vastly
higher level of sustained pain than an
examination would suggest. You may
have wondered, “Why isn’t this patient
feeling better?” These stubborn cases
can be perplexing…and frustrating.
On the other side of the coin, many
practitioners have seen patients with a
complicated set of issues who find relief
for more than just musculoskeletal pain
after receiving care from a chiropractor. A
connection between spinal manipulative
therapy and gastrointestinal issues,
colic and a host of other conditions is
observed in the clinic, but this is not well
documented in the literature. What’s the
missing link?
10
SPRING 2015
The Consequences of Central
Sensitization
D
r. John Srbely, DC, PhD, is a
chiropractor and Assistant
Professor at the University
of Guelph. He is studying central
sensitization — which he likes to call
“C-Sens” for short — and what it can
tell us about the effects of spinal
manipulative therapy and possible
future applications for chiropractic. As
mentioned previously in our article on
osteoarthritis, C-Sens is characterized by
an overall state of heightened perception
of and sensitivity to pain.
Most patients have experienced
peripheral sensitization, but might not
know its formal name. The sensation
of lukewarm shower water feeling
excruciatingly hot on sunburnt skin is a
common example. The peripheral ends
of the pain receptors (nociceptors) in
that skin have become sensitized and are
sending more pain input to the central
nervous system (CNS) than usual. It’s a
protective measure put in place while the
skin heals.
Central sensitization, on the other
hand, is a damaging “neuradaptive
response characterized by an increased
responsiveness to input stimuli of
neurons within the central nervous
system.” People with C-Sens experience
pain which is more intense and lasts
longer than it usually would. They also
have lower pain thresholds, causing
them to experience pain from things that
usually wouldn’t hurt. Yesterday’s pain
rating of 4/10 becomes today’s 6/10. The
CNS continues to alert the brain about
pain even after the input has stopped.
“A comparison of response profiles
from sensitized versus normal dorsal
horn neurons i