JMPT January 1999 Volume 22 Number 1
Dysafferentation: A novel term to describe the neuropathologic
effects of joint complex dysfunctiona look at likely mechanisms of
To the editor:
I would like to thank Drs Seaman and Winterstein for their efforts at
updating neurologic models in which to explain chiropractic subluxation/joint
dysfunction.1 However, I
would like to take issue with Dr Seaman's belief that dysafferentation
from putative joint dysfunction necessarily involves only reduced
mechanoreception but provides joint dysfunction. Dr Seaman provides little
evidence for his opinion, a point he acknowledges. Most of the evidence
cited for the concept of reduced mechanoreception comes from
motor disturbances, vertigo, and so forth, associated with cervical
1,2 Although it is known
that reduction of input from the cervical muscles can cause these symptoms,
it has also been shown that stimulation of mechanoreceptorsmuscle
spindlescan have similar
3,4 For most of the cases
Seaman cites, it is not known whether the symptoms were due to decreased or
It has been suggested that because of their extreme density in the
intervertebral muscles, muscle spindles are an information-gathering system as
complex as vision or
audition. 5 Given this
complexity, any dysfunction that involves these muscles would, most likely,
lead to changes, both increased and decreased, in muscle spindle output
A model that would result in increased mechanoreception could be driven
by nociception, as Dr Seaman proposes. Activation of nociceptors by injury
to a joint generates a reflexive muscle response to guard the
joint6; these are termed
Contraction of extrafusal muscle unloads associated muscle
8,9 Loss of spindle Ia
and II signal causes increased gamma signals to the spindle,
a phenomenon called automatic gain
Once the nocifensive reflex muscle contraction has abatedinjuries
heal and nociception is subject to
increased gamma gain results in significantly
increased spindle Ia and II output. This
phenomenon allows for continued (extrafusal) muscle
and mostly Ia (with some II) spindle
the need for continuing nociceptive input. Experiments in cats have shown
that in sampled Ia fibers, discharge rates after muscle contraction
increased by 60%; a number of these receptors had been silent before the
As Bailey and Dick propose in their model for somatic dysfunction (the
osteopathic equivalent of chiropractic subluxation/joint dysfunction),
perhaps nociceptive reflexes predominate in the acute phase of injury and
mechanoreceptor mechanisms in chronic
phases.20 A review of
PCSD and related phenomenon and a fusimotor model of chronic
subluxation/joint dysfunction have been recently
Although evidence is limited that loss of mechanoreception,
particularly in the cervical spine, causes symptoms, similar symptoms can be
induced by mechanoreceptor stimulation. Intervertebral muscle spindles make
up a complex information-gathering system, dysfunction of which is equally
likely to cause increased as decreased mechanoreception. And finally, joint
dysfunction does cause increased muscle spindle-mechanoreceptor output by
means of the phenomenon of postcontraction sensory discharge. I would suggest
that Seaman's term dysafferentation for
the effects of subluxation/joint dysfunction be moderated to include the
possibility of both reduced and increased mechanoreceptor discharge.
Gary A. Knutson, DC
840 W 17th, Suite 5, Bloomington, IN 47404
1. Seaman DR, Winterstein JF.
Dysafferentation: a novel term to describe the neuropathological effects of
joint complex dysfunction. A look at likely mechanisms of symptom
generation. J Manipulative Physiol Ther 1998;21:26780.
2. Seaman DR. Joint complex dysfunction, a
novel term to replace subluxation/subluxation complex: etiological and
treatment considerations. J Manipulative Physiol Ther
3. Lund S. Postural effects of neck muscle
vibration in man. Experentia 1980;36:1398.
4. Biguer B, Donaldson ML, Hein A, Jeannerod
M. Neck muscle vibration modifies the representation of visual motion and
direction in man. Brain 1988;111:140524.
5. Bakker DA, Richmond FJR. Muscle spindle
complexes in muscles around upper cervical vertebra in the cat. J
6. Slosberg M. Effects of altered afferent
articular input on sensation, proprioception, muscle tone and sympathetic
responses. J Manipulative Physiol Ther 1988;11:4108.
7. Van Buskirk R. Nociceptive reflexes and
the somatic dysfunction: a model. J Am Osteopath Assoc
8. Davidoff RA. Skeletal muscle tone and the
misunderstood stretch reflex. Neurology 1992;42:95163.
9. Hunt CC, Kuffler SW. Stretch receptor
discharges during muscle contraction. J Physiol
10. Matthews PBC. Observations on the
automatic compensation of reflex gain varying the pre-existing level of motor
discharge in man. J Physiol 1986;374:7390.
11. Ruch TC. Pathophysiology of pain. In:
Ruch T, Patton HD, editors. Physiology and biophysics: the brain and neural
function. 2nd ed. Philadelphia: WB Saunders; 1979. p.
12. Smith JL, Hutton RS, Eldred E.
Postcontraction changes in sensitivity of muscle afferents to static and
dynamic stretch. Brain Res 1974;78:193202.
13. Enoka RM, Hutton RS, Eldred E. Changes
in excitability of tendon tap and Hoffman reflexes following voluntary
contractions. Electroencephalogr Clin Neurophysiol
14. Hutton RS, Smith JL, Eldred E.
Persisting changes in sensory and motor activity of a muscle following its
reflexive activation. Pflugers Arch 1975;336:32736.
15. Hagbarth KE, Macefield VG. The fusimotor
system. Adv Exp Med Biol 1995;384:25970.
16. Gregory JE, Mark FR, Morgan DL, Patak A,
Polus B, Proske U. Effects of muscle history on the stretch reflex in cat and
man. J Physiol 1990;424:93107.
17. Hutton RS, Smith JL, Eldred E.
Postcontraction sensory discharge from muscle and its source. J Neurophysiol
18. Hutton RS, Atwater SW. Acute and chronic
adaptations of muscle proprioceptors in response to increased use. Sports Med
19. Baumann TK, Hullinger M. The dependence
of the response of cat spindle Ia afferents to sinusoidal stretch on the
velocity of concomitant movement. J Physiol 1991;439:32550.
20. Bailey M, Dick L. Nociceptive
considerations in treating with counterstrain. J Am Osteopath Assoc
21. Knutson G. Long term postural distortion
and reaction to vectored atlas adjustment: case studies and fusiomotor model
for chronic subluxation. Chiropract Res J. Submitted for