2 Neurology of the UC Subluxation

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Neurology of the Upper

Cervical Subluxation



Subluxation sub = Less Than

Luxatio = Dislocation

“less than a dislocation”

Medical use of the term traced back to 1688 by

Holme. “a dislocation” or “putting out of

joint”

Henderson, C. Subluxation Theory. Lyceum 2000



Subluxation1934 Subluxation Specific, BJ Palmer

A vertebral subluxation is any vertebra out of

normal alignment, out of apposition to its co-respondents above and below, wherein it does

occlude a foreman, either spinal or intervertebral,

which does produce pressure upon nerves, thereby

interfering and interrupting the normal quantity flowof mental impulse supply between brain and body

and thus becomes THE CAUSE of all dis-ease.




SubluxationACA and ICA adopted definition:

“ A motion segment in which alignment,

movement integrity, and/or physiologic function are altered although contact between

the joint surfaces remains intact ”.




Subluxation“ A complex of function and/or structural and/or

pathological articular changes that

compromise neural integrity and mayinfluence organ system function and general

health”.

Association of Chiropractic Colleges

Owens, E. J Can Chiropr Assoc 2002;46(4)



Neurology of the Upper Cervical

Subluxation It has been shown that the average occipito-

atlantal misalignment in the frontal plane is

almost 3°, which equates to about 1/8 of an

inch of linear movement.

This is significant because the upper cervical

spinal cord has a diameter of about half aninch.




Subluxation The upper cervical spinal cord is directly attached to:

the circumference of the foramen magnum,

the second and third cervical vertebrae,

posterior longitudinal ligament

The dentate ligaments are 21 paired lateral bands ofepipial tissue midway between the dorsal and ventralattachments of the nerve roots.

The medial border of the dentate ligaments iscontinuous with the pia mater of the spinal cord andattaches to the dura mater laterally.




Subluxation The rectus capitis posterior minor muscle

attaches to the dura mater of the upper

cervical spinal cord. Attachment have also been found to the spinal

cord via:

the ligamentum nuchae epidural ligaments




Subluxation Neurological dysfunction may occur via two

mechanisms:

direct mechanical irritation of the nerves of thespinal cord

The collapse of the small veins of the cord

producing venous congestion



The Spinocerebellar tracts The spinocerebellar tracts lie

along the lateral edge of thespinal cord (the most probablesite of maximal mechanical

irritation by the dentateligaments).

Proprioceptive tracts, whichregulates muscle tone and joint

position sense.

Irritation of these tracts could

lead to muscle tone imbalance ofthe pelvic girdle resulting in afunctional short leg.



The Spinothalamic Tracts Close to the attachment of the

dentate ligaments.

Responsible for conveying pain and temperature into the

neuroaxis. Mechanical irritation and/or

ischemic compromise to thespinothalamic tracts possibly

explains particular cases of

severe low back and leg pain being caused by an upper

cervical subluxation.



MECHANORECEPTIVE

DYSAFFERENTATION

Mechanoreceptors are so named because they

are activated by mechanical deformation.

The mechanoreceptors are primarilyresponsible for the body's position sense

within the gravity environment.

Provide information orientating the head withrespect to the body to maintain equilibrium.



The vestibular apparatus (VA)

Informs the brain of the head's position and

works to keep it perpendicular with the

ground by altering the tone of the cervicalmuscles.

The most important proprioceptive

information required for the maintenance ofequilibrium is derived from joint receptors of

the neck. Guyton



Mechanoreceptors Type I: provide important information about joint position as

they signal the angle of the articulation throughout the rangeof motion.

Type II: Have a low threshold and rapidly adapt to a stimulus.Detect rate of movement at the articulation.

Type III: High threshold and slowly adapting receptors. Theyare stimulated only at the extremes of joint movement.Structurally similar to the Golgi tendon organ of the muscular

system Type IV: Nociceptors; have a high threshold and do not

adapt. These pain receptors tend to be free nerve endings.



Mechanoreceptors

The cervical spine has more

mechanoreceptors, per surface area, than any

other region of the spinal column.



Model for the receptor activity in the normal,nondysfunctional state (no abnormal vertebral position

or particular hypomobility or hypermobility).

Correct anatomical

position of vertebra(e)

Normal physiological pressure

and tension on fibrous joint capsule

Mechanoreceptors and

nociceptors are inactive

Resting muscle tone; equilibrium

between synergists and antagonists

No pain perception



Model for receptor activity as a result of vertebral segmental dysfunction

(abnormal vertebral position and/or somatic dysfunction with pain and

hypomobility, etc.).

Abnormal position

of vertebra(e)

Segmental dysfunction

Irritation of fibrous

joint capsule

Tonic-reflexogenic influence

on motor neurons of neck,

limb, jaw, eye muscles

(myotendinoses)

Pain perception

Correction of segmental

dysfunction

Less pain, normalization

of receptor activity Changetoward normal muscle tone

Stimulation of

mechanoreceptors

of type 1

Spinothalamic tract

Stimulation of mechanoreceptors

type II; inhibition of afferent

fibers; release of enkephalins

Stimulation of

NociceptorsAdditional impulses

(mechanical, chemical)

Spinal Adjustment



The Postural Spondylogenic Reflex Syndrome: Clinical

Correlation with Reflexes Linked to Nociceptors and

Mechanoreceptors

The clinical symptom of pain in muscles and other softtissues (spontaneous or elicited by palpatory pressure) has

been termed the Spondylogenic Reflex Syndrome by Sutter(1974,1975).

Myotendinoses has been in observe the various systematicresponse to an articular/somatic dysfunction involving theindividual apophyseal, occipito-atlanto-axial, and sacroiliac

joints.

“Many systematic myotendinoses improve during the course

of therapeutic intervention in the individual patients”. It was therefore assumed that, in addition to other helpful

physical and therapeutic procedures, the mechanical andfunctional correction of the spinal motion unit, according toSchmorl and Junghanns (1968), can play a significant role, if

not the most crucial role in treatment.



The Postural Spondylogenic Reflex

Syndrome:

The absence of pain does not automatically mean lack of soft-tissuefindings.

It is well known that localized palpable muscle bands or systematicmyotendinoses can be elicited upon careful palpation in many

individuals who have no subjective pain complaints. This situation is to be considered pathologic and correlates with the

latent state of intervertebral insufficiency according to Schmorl andJunghanns (1968).

This could be explained on the basis of the tonic reflexogenicinfluence of the type 1 mechanoreceptors upon the motor neurons

of the axial or peripheral musculature. It has been shown that pain-inducing nociceptors have significantly

higher thresholds than pain-inhibiting mechanoreceptors. This mayexplain the delay with which the individual may perceive his or her

pain.



The Postural Spondylogenic Reflex

Syndrome:

The nociceptive stimulation can be inhibited presynaptically when there is sufficient stimulationof the mechanoreceptors, mainly the type IIreceptors. This may occur by release of endorphins: cells in the

gelatinous substance of the dorsal horns.

Therefore, it would plausible to propose that theseand probably other related neurophysiologic

mechanisms may play at least as important a role inmanual therapeutic treatment as the pure mechanicalcorrection of one or several segmental dysfunctions.



The Postural Spondylogenic Reflex Syndrome:Irritation Zone Spondylogenic Myotendinosis

Changes Skin, subcutaneous tissues, tendons,

muscles, joint capsule

Muscles, ligaments

localization In area of the disturbed spinal segment,

topographically defined in region

around spinous or articular processes

Muscles, ligaments (referred pain?)

Time course (latency) Immediate reaction to a segmental

dysfunction

Apparent after a certain latent period

Qualitative palpatory

findings

Decreased ease of skin displacement,

increased tissue tension, localized pain

Increased resistance, less resiliency,

tender upon pressure with radiation

(trigger points?)

Quantitative palpatory

findings

Related to the degree of abnormal

segmental function

Dependent on the duration of

segmental dysfunction

Changes observed with

successful treatment

Immediate decrease in quality and

quantity

May disappear after a certain latency

period (possibly reflexively)



Force of the UC Adjustment

Depending upon the type of cervical manipulative

technique used, preload forces range from 0 to

approximately 50 N, and peak impulse forces range

from approximately 40 N to approximately 120 N.

The forces delivered during cervical manipulations

develop faster than during manipulation of the thoracic

spine and sacroiliac joint.

Impulse duration lasts from approximately 30 ms to

approximately 120 ms.

J.G. Pickar / The Spine Journal 2 (2002) 357 –371



Mechanical Forces from the Adjustment

The mechanical force introduced into thevertebral column during a spinal manipulationmay directly alter segmental biomechanics by

releasing trapped meniscoids,

releasing adhesions

or by reducing distortion…

…the mechanical input may ultimately reducenociceptive input from receptive nerve endingsin innervated paraspinal tissues.




Neurology of the Chiropractic

Adjustment The mechanical thrust could either stimulate or silence non-

nociceptive, mechano-sensitive receptive nerve endings in paraspinal tissues, including skin, muscle, tendons, ligaments,facet joints and intervertebral disc.

These neural inputs may influence pain producingmechanisms as well as other physiological systems controlledor influenced by the nervous system.

These changes in sensory input are thought to modify neural

integration either by directly affecting reflex activity and/or by affecting central neural integration within motor,nociceptive and possibly autonomic neuronal pools.

Either of these changes in sensory input may elicit changes inefferent somatomotor and visceromotor activity.




UC Subluxation and Neurologic

Compromise

Dentate Ligament Cord Distortion

“Medullary Lock” Kessinger

Sensory Neurologic Feedback

Central Sensitization




“Medullary Lock”

The upper cervical spinal cord is directly

attached to:

the circumference of the foramen magnum, the second and third cervical vertebrae,

posterior longitudinal ligament



Dentate Ligament Cord Distortion The dura mater is a strong, fibrous membrane which forms a wide,

tubular sheath; this sheath extends below the termination of the medullaspinalis and ends in a pointed cul-de-sac at the level of the lower border ofthe second sacral vertebra.

The dura mater is separated from the wall of the vertebral canal by the

epidural cavity, which contains a quantity of loose areolar tissue and a plexus of veins; between the dura mater and the subjacent arachnoid is acapillary interval, the subdural cavity, which contains a small quantity offluid, probably of the nature of lymph.

The arachnoid is a thin, transparent sheath, separated from the pia mater by a comparatively wide interval, the subarachnoid cavity, which is

filled with cerebrospinal fluid. The pia mater closely invests the medulla spinalis and sends delicate

septa into its substance; a narrow band, the ligamentum denticulatum, extends along each of its lateral surfaces and is attached by a series of

pointed processes to the inner surface of the dura mater.




the strongest ligaments

are in the upper

cervical region

short, thick, and pass

almost perpendicularly

from the pia mater to

their attachments onthe dura mater.




The upper cervical area is the only area wherein the dentate ligaments are perpendicular tothe cord.

From full extension and full flexion of thecervical spine the cervical canal lengthchanges about 30 mm.

during extension there is some compression ofthe cord, during flexion there is stretching ofthe cord




Based on these observations, it may be a

primary role of the upper cervical Dentate

ligaments to restrict the downward-pullingaxial forces created by the lengthening of the

canal when the neck is flexed from being

transmitted unattenuated to the brainstem.

JD Grostic




In normal flexion the dentate ligaments are

strong enough to slightly deform the cord.

Chronic tension on a ligament may producethickening and strengthening of the ligament,

decreasing the ligament's ability to damp the

distortive forces before they can deform thecord. Kahn




Tension on the dentate ligaments may cause

distortion to the spinal dura causing:

Mechanical irritation to the spinal tracts Spinal Cord Ischemia

Tethering the Spinal cord




Mechanical irritation to the spinal tracts

The spinocerebellar tracts (proprioception) are

located at the site of maximal mechanicalirritation.

Spinal cord irritation by dentate ligament

traction may cause hypertonicity andspasticity in the muscles of the pelvic girdle

and lower extremities.




Mechanical irritation to the spinal tracts

Pain in the low back and legs may be caused

by mechanical irritation of the spinothalamictract (pain, temperature, itch and crude touch)in the upper cervical cord due to traction ofthe dentate ligaments.

The trigeminal nerve spinal nucleus may betractioned by a lateral deviation and rotationof the atlas.




Spinal Cord Ischemia Dentate ligament may cause mechanical stresses to the cord.

Mechanical obstruction of the veins of the upper cervical cordcould cause stasis of blood and ischemia in the portion of thespinal cord drained by these veins.

Venous stasis would tend to first cause ischemia in the lateralcolumns of the cord

These veins operate at such low pressures and are easily occluded by compressive forces.

Ischemia may first increases the irritability of nerves andincreased sensitivity to the effects of mechanical irritation

Jarzem et al. (1992) experimental cord distraction produced adecrease in spinal cord blood flow and concurrent interruption ofsomatosensory evoked potentials.




Tethering the Spinal cord

The UC subluxation causing abnormal motion maycause a disruption of the normal function of the

dentate ligaments which would not allow for fullmotion of the spinal cord during flexion andextension.

Traction of the spinal cord will cause a decrease in

the action potentials of spinal neurons. Mechanical deformation has shown to cause

neurologic dysfunction.



Sensory Neurologic Feedback After the intertransverse ligament at T3-T4 in 4-week-old chickens was

stretched mechanically and repeatedly for 60 minutes. Various areas of thenervous system then were sectioned and processed immunohistochemicallyto identify areas of Fos production in nerve cell bodies. The presence of Fosindicated neurons that had been stimulated by the stretching the ligament,

including interneurons along the feedback pathway. The Fos protein was identified in: nerve cell bodies in the dorsal root

ganglia and intermediate gray matter of the spinal cord at the level ofstimulation as well as at several spinal cord levels above and below the siteof stimulation (on the ipsilateral and the contralateral sides), in sympatheticganglia at these sites, nerve cell bodies in the combined nucleus cuneatusand gracilis in the medulla oblongata, the vestibular nuclei, and thethalamus.

Stretching a single lateral ligament of the spine produces a barrage ofsensory feedback from several spinal cord levels on both sides of the spinalcord.

Information from this study allowed Jaing to trace the relay system ofneurological afferent synapse through the CNS.

Jiang H. Spine. 22(1):17-25, January 1, 1997



Sensory Neurologic Feedback The “cervico-sympathetic reflex [that can alter heart rate and blood

pressure] appears to originate from muscle spindles in the dorsal neckmusculature, it is very likely that the suboccipital muscle group isinvolved in the reflex because these muscles have an extremely highmuscle spindle content."

"Additional evidence for the involvement of the suboccipital musclegroup in the cervico-sympathetic reflex comes from changes in blood

pressure associated with chiropractic manipulations of the C1 vertebrae,which would result in altering the length of fibers in the suboccipitalmuscle group."

"The projection from the INTERMEDIATE NUCLEUS to the

NUCLEUS TRACTUS SOLITARIUS identified in this study therefore places it in an ideal position to mediate cardiorespiratory changes toneck muscle afferent stimulation, because the NUCLEUS TRACTUSSOLITARIUS is a major integratory area for autonomic controlcircuits."

Ian J. The Journal of Neuroscience August 1, 2007; 27(31); pp. 8324-8333



Sensory Neurologic Feedback A theoretical model

showing components thatdescribe the relationships

between spinal

manipulation, segmental biomechanics, the nervoussystem and physiology.

The neurophysiological

effects of spinalmanipulation could bemediated at any of thenumbered boxes.

J.G. Pickar / The Spine Journal 2 (2002) 357 – 371



Central sensitization debilitating fatigue, the majority of patients with

chronic fatigue syndrome (CFS)

Prolonged or strong activity of dorsal horn neurons

caused by repeated or sustained noxious stimulationmay subsequently lead to increased neuronalresponsiveness or central sensitization

These changes cause exaggerated perception of painful stimuli (hyperalgesia), a perception of

innocuous stimuli as painful (allodynia) and may beinvolved in the generation of referred pain andhyperalgesia across multiple spinal segments

Mira Meeus & Jo Nijs. Clin Rheumatol (2007) 26:465 – 473




Diseases Associated with Central SensitizationSyndrome:

Fibromyalgia

Chronic fatigue syndrome

Irritable bowel syndrome

Depression

Insomnia

Abnormal Heart rate variability




AKA: Central facilitation

The increased excitability or enhancedresponsiveness of dorsal horn neurons to an afferent

input. Central facilitation can be manifested by

increased spontaneous central neural activity,

by enhanced discharge of central neurons to an afferent

input by a change in the receptive field properties of central

neurons.





Motoneurons could be held in a facilitated

state because of sensory bombardment from

segmentally related paraspinal structures. The motor reflex thresholds also correlated

with pain thresholds, further suggesting that

some sensory pathways were also sensitized

or facilitated in the abnormal segment.




Central Sensitization We currently know that the phenomenon of central

facilitation increases the receptive field of central neurons andallows innocuous mechanical stimuli access to central pain

pathways.

In other words, subthreshold mechanical stimuli may initiate pain, because central neurons have become sensitized.

Removal of these subthreshold stimuli should be clinically beneficial.

One mechanism underlying the clinical effects of spinalmanipulation may be the removal of subthreshold stimuliinduced by changes in joint movement or joint play.

J.G. Pickar / The Spine Journal 2 (2002) 357 –

371




The dorsal horn is not simply a passive relay

station for sensory messages but can modulate

the messages as well. Natural activation of A-a and A-b fibers (like

the spinal adjustment) has been shown to

reduce chronic pain and increase pain

threshold levels.





Spinal manipulation increased the average

pressure/pain threshold of six tender spots in

the neck region by approximately 50% (from2 kg/cm2 to 2.9 kg/cm2)

The effect of spinal manipulation on pain

could also be mediated by the neuroendocrine

system. The endogenous opiate system is

known to modify pain processes.




ALTERED SENSORIMOTOR INTEGRATION WITH

CERVICALSPINE MANIPULATION

Spinal manipulation of dysfunctional cervical jointsmay alter specific central corticomotor facilitatoryand inhibitory neural processing and cortical motor

control. This suggests that spinal manipulation may alter

sensorimotor integration.

These findings may help elucidate the mechanisms

responsible for the effective relief of pain andrestoration of functional ability documented afterspinal manipulation.

2 Neurology of the UC Subluxation

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