article archive
April 2007
Vertebral subluxation
and the nervous system
by Dr. Christopher Kent, Esq.
Implications of three new papers
A growing body of literature is developing which may have
significance to the chiropractor. It is evident that the
neurobiological mechanisms in vertebral subluxation may be
far more complex than simple alterations in synaptic transmission.
Three recent papers deserve your attention.
Sensorimotor integration
Haavik‑Taylor and Murphy [1] studied the immediate
sensorimotor effects of high velocity, low amplitude techniques
applied to the cervical spine. The paper noted that the "vertebral
lesion" may be called a "vertebral subluxation" by
chiropractors. Twelve subjects with a history of recurring
neck stiffness and/or neck pain, but no acute symptoms at
the time of the study, participated. Somatosensory evoked
potentials were measured at spinal, brainstem, and cortical
levels. There was a significant decrease in the amplitude
of the cortical components following a single session of "manipulation" compared
to baseline readings.
In reviewing the literature, the authors
noted that spinal manipulation can lead to alterations in
reflex excitability, altered sensory processing, and altered
motor processing. The authors wrote:
*** There is a growing
body of evidence suggesting that the presence of spinal dysfunction
of various kinds has an effect on central neural processing.
For example, several authors have suggested spinal dysfunction
may lead to altered afferent input to the CNS. Altering afferent
input to the CNS is well known to lead to plastic changes in
the way that it responds to any subsequent input.
*** Altered
afferent input from joints can lead to both inhibition and
facilitation of neural input to related muscles.
*** Even painless
experimentally induced joint dysfunction has been shown to
inhibit surrounding muscles.
*** Numerous studies have shown
rapid central plastic changes after injuries and altered sensory
input from the body.
*** Given that spinal dysfunction would
alter the balance of afferent input to the CNS we propose that
this altered afferent input may over time lead to potential
maladaptive neural plastic changes in the CNS.
*** If spinal
manipulation reduces excessive signaling from the involved
intervertebral muscles this altered afferent input to the CNS
may change the way it responds to any subsequent input, such
as the electrical study.
In other words, vertebral subluxations
may, by altering the input to the CNS, change how the nervous
system responds to the environment ‑‑ any subsequent
input. The implications of maladaptive neuroplastic changes
could have profound clinical significance.
Non‑synaptic
messaging
Charles Blum's paper [2] in the Journal of Vertebral
Subluxation Research (JVSR) on non‑synaptic messaging is a quick
and easy introduction to this important subject. Blum discusses
various classes of non‑synaptic interaction, including
chemical and electronic coupling through gap junctions, ephaptic
transmissions, field effect interactions, and fluctuations
in extracellular ions. The paper also reviews glial cell
messaging, and how neural rhythmic pulsations propagated
through the CSF may be a type of nonsynaptic messaging.
Of great
interest is the discussion of piezoelectricity. Mechanical
energy applied to crystalline structures results in electrical
responses. Since connective tissue is crystalline in nature,
biomechanical changes, such as those associated with subluxation,
may elicit electrical responses in bone and other connective
tissues. Such electrical changes may affect, "control
of cell nutrition, local pH control and enzyme activation
or suppression, orientation of intracellular macromolecules,
migratory and proliferative activity of cells, synthetic
capability and specialized function of cells, contractility
and permeability of cell membranes and energy transfer."
This
paper is an excellent primer for those who seek a painless,
clinically relevant discussion of nonsynaptic messaging.
I highly recommend it.
Thinking in the spinal cord?
Investigators at the University
of Copenhagen "have
demonstrated that the spinal cord uses network mechanisms
similar to those used in the brain...Until now, the general
belief was that the spinal networks functioned mechanic;
and completely without random impulses. The new discovery
enables researchers to use the theory on cortical networks
to explore how spinal cords generate movements...How humans
are able to move at all remains a puzzle. Our muscles are
controlled by thousands of nerve cells in the spinal cord.
Entire, complex system must work as a whole in order to successfully
create a single motion. The new research shows that even
if we repeat a certain motion with high accuracy, the involved
nerve cells never repeat their activity patterns. This particular
observation reflects the organization of the nerve cells
of the cerebral cortex." [3]
The study, published in Science
[4], concluded, "Our
study suggests that balanced states of inhibitory and excitatory
synaptic activity did not evolve with higher brain function,
but were already present with functional motor networks in
the spinal cord."
Thus, the spinal cord is far more than a mere conduit for
signal propagation between the brain and the body. It may
actually "think," employing mechanisms previously
thought to operate only in the brain.
References
1. Haavik‑Taylor H, Murphy B: "Cervical spine
manipulation alters sensorimotor integration: A somatosensory
evoked potential study." Clinical Neurophysiology 118
(2007) 391‑402 .
2. Blum CL: "Non‑synaptic messaging: piezoelecticity,
bioelectric fields, neuromelanin and dentocranial implications." J.
Vertebral Subluxation Res. ‑‑ JVSR.com, Jan 30,
2007.
3. Thinking with the spinal cord? Kobenhavns Umversitet
www.ku.dk/english/news/spinal.htm
4. Berg RW, Alaburda A, Hounsgaard
J: "Balanced inhibition
and excitation drive spike activity in spinal half‑centers." Science
2007;315: 390‑393.
(Dr. Christopher Kent, president of
the Council on Chiropractic Practice, is a 1973 graduate of
Palmer College of Chiropractic. The WCA's "Chiropractic Researcher of the Year" in
1994, and recipient of that honor from the ICA in 1991, he
was also named ICA "Chiropractor of the Year" in
1998. He is director of research and a co‑founder of
Chiropractic Leadership Alliance. An attorney as well as
a chiropractor, Dr. Kent is a member of the California bar.
With Dr. Patrick Gentempo, Jr., Dr. Kent produces a monthly
audio series, "On Purpose," covering current events
in science, politics and philosophy of vital interest to
the practicing chiropractor. For subscription information
call 800‑892‑6463.)