Neurology of the Upper Cervical Subluxation

1. Neurology of the Upper Cervical Subluxation

2. 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

3. Subluxation 1934 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 flow of mental impulse supply between brain and body and thus becomes THE CAUSE of all dis-ease. Henderson, C. Subluxation Theory. Lyceum 2000

4. Subluxation ACA 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”. Henderson, C. Subluxation Theory. Lyceum 2000

5. Subluxation “A complex of function and/or structural and/or pathological articular changes that compromise neural integrity and may influence organ system function and general health”. Association of Chiropractic Colleges Owens, E. J Can Chiropr Assoc 2002;46(4)

6. 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 an inch.

7. Neurology of the Upper Cervical 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 of epipial tissue midway between the dorsal and ventral attachments of the nerve roots. • The medial border of the dentate ligaments is continuous with the pia mater of the spinal cord and attaches to the dura mater laterally.

8. Neurology of the Upper Cervical 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

9. Neurology of the Upper Cervical Subluxation • Neurological dysfunction may occur via two mechanisms: • direct mechanical irritation of the nerves of the spinal cord • The collapse of the small veins of the cord producing venous congestion

10. The Spinocerebellar tracts • The spinocerebellar tracts lie along the lateral edge of the spinal cord (the most probable site of maximal mechanicalirritation by the dentate ligaments). • Proprioceptive tracts, which regulates muscle tone and joint position sense. • Irritation of these tracts could lead to muscle tone imbalance of the pelvic girdle resulting in a functional short leg.

11. The Spinothalamic Tracts • Close to the attachment of the dentate ligaments. • Responsible for conveyingpain and temperature into the neuroaxis. • Mechanical irritation and/or ischemic compromise to the spinothalamic tracts possibly explains particular cases ofsevere low back and leg pain being caused by an upper cervical subluxation.

12. MECHANORECEPTIVE DYSAFFERENTATION • Mechanoreceptors are so named because they are activated by mechanical deformation. • The mechanoreceptors are primarily responsible for the body's position sense within the gravity environment. • Provide information orientating the head with respect to the body to maintain equilibrium.

13. 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 cervical muscles. • The most important proprioceptive information required for the maintenance of equilibrium is derived from joint receptors of the neck. Guyton

14. Mechanoreceptors • Type I: provide important information about joint position as they signal the angle of the articulation throughout the range of 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. They are 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.

15. Mechanoreceptors • The cervical spine has more mechanoreceptors, per surface area, than any other region of the spinal column.

16. Model for the receptor activity in the normal, nondysfunctional state (noabnormal vertebral position or particular hypomobility or hypermobility). Normal physiological pressure and tension on fibrous joint capsule Correct anatomical position of vertebra(e) Resting muscle tone; equilibrium between synergists and antagonists Mechanoreceptors and nociceptors are inactive No pain perception

17. Model for receptor activity as a result of vertebral segmental dysfunction (abnormal vertebral position and/or somatic dysfunction with pain and hypomobility, etc.). Irritation of fibrous joint capsule Abnormal position of vertebra(e) Segmental dysfunction Stimulation of mechanoreceptors of type 1 Tonic-reflexogenic influence on motor neurons of neck, limb, jaw, eye muscles (myotendinoses) Additional impulses (mechanical, chemical) Stimulation of Nociceptors Spinothalamic tract Pain perception Spinal Adjustment Correction of segmental dysfunction Stimulation of mechanoreceptors type II; inhibition of afferent fibers; release of enkephalins Less pain, normalization of receptor activity Change toward normal muscle tone

18. The Postural Spondylogenic Reflex Syndrome: Clinical Correlation with Reflexes Linked to Nociceptors and Mechanoreceptors • The clinical symptom of pain in muscles and other soft tissues (spontaneous or elicited by palpatory pressure) has been termed the Spondylogenic Reflex Syndrome by Sutter (1974,1975). • Myotendinoses has been in observe the various systematic response to an articular/somatic dysfunction involving the individual 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 and functional correction of the spinal motion unit, according to Schmorl and Junghanns (1968), can play a significant role, if not the most crucial role in treatment.

19. The Postural Spondylogenic Reflex Syndrome: • The absence of pain does not automatically mean lack of soft-tissue findings. • It is well known that localized palpable muscle bands or systematic myotendinoses 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 and Junghanns (1968). • This could be explained on the basis of the tonic reflexogenic influence 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 may explain the delay with which the individual may perceive his or her pain.

20. The Postural Spondylogenic Reflex Syndrome: • The nociceptive stimulation can be inhibited presynaptically when there is sufficient stimulation of the mechanoreceptors, mainly the type II receptors. • This may occur by release of endorphins: cells in the gelatinous substance of the dorsal horns. • Therefore, it would plausible to propose that these and probably other related neurophysiologic mechanisms may play at least as important a role in manual therapeutic treatment as the pure mechanical correction of one or several segmental dysfunctions.

21. The Postural Spondylogenic Reflex Syndrome:

22. 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

23. Mechanical Forces from the Adjustment • The mechanical force introduced into the vertebral column during a spinal manipulation may directly alter segmental biomechanics by • releasing trapped meniscoids, • releasing adhesions • or by reducing distortion… • …the mechanical input may ultimately reduce nociceptive input from receptive nerve endings in innervated paraspinal tissues. J.G. Pickar / The Spine Journal 2 (2002) 357–371

24. 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 producing mechanisms as well as other physiological systems controlled or 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 in efferent somatomotor and visceromotor activity. J.G. Pickar / The Spine Journal 2 (2002) 357–371

25. UC Subluxation and Neurologic Compromise • Dentate Ligament Cord Distortion “Medullary Lock” Kessinger • Sensory Neurologic Feedback • Central Sensitization

26. Dentate Ligament Cord Distortion “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

27. 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 medulla spinalis and ends in a pointed cul-de-sac at the level of the lower border of the 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 a capillary interval, the subdural cavity, which contains a small quantity of fluid, 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.

28. Dentate Ligament Cord Distortion • the strongest ligaments are in the upper cervical region • short, thick, and pass almost perpendicularly from the pia mater to their attachments on the dura mater.

29. Dentate Ligament Cord Distortion • The upper cervical area is the only area where in the dentate ligaments are perpendicular to the cord. • From full extension and full flexion of the cervical spine the cervical canal length changes about 30 mm. • during extension there is some compression of the cord, during flexion there is stretching of the cord

30. Dentate Ligament Cord Distortion • Based on these observations, it may be a primary role of the upper cervical Dentate ligaments to restrict the downward-pulling axial forces created by the lengthening of the canal when the neck is flexed from being transmitted unattenuated to the brainstem. JD Grostic

31. Dentate Ligament Cord Distortion • In normal flexion the dentate ligaments are strong enough to slightly deform the cord. • Chronic tension on a ligament may produce thickening and strengthening of the ligament, decreasing the ligament's ability to damp the distortive forces before they can deform the cord. Kahn

32. Dentate Ligament Cord Distortion • 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

33. Dentate Ligament Cord Distortion Mechanical irritation to the spinal tracts • The spinocerebellar tracts (proprioception) are located at the site of maximal mechanical irritation. • Spinal cord irritation by dentate ligament traction may cause hypertonicity and spasticity in the muscles of the pelvic girdle and lower extremities.

34. Dentate Ligament Cord Distortion Mechanical irritation to the spinal tracts • Pain in the low back and legs may be caused by mechanical irritation of the spinothalamic tract (pain, temperature, itch and crude touch) in the upper cervical cord due to traction of the dentate ligaments. • The trigeminal nerve spinal nucleus may be tractioned by a lateral deviation and rotation of the atlas.

35. Dentate Ligament Cord Distortion Spinal Cord Ischemia • Dentate ligament may cause mechanical stresses to the cord. • Mechanical obstruction of the veins of the upper cervical cord could cause stasis of blood and ischemia in the portion of the spinal cord drained by these veins. • Venous stasis would tend to first cause ischemia in the lateral columns 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 and increased sensitivity to the effects of mechanical irritation • Jarzem et al. (1992) experimental cord distraction produced a decrease in spinal cord blood flow and concurrent interruption of somatosensory evoked potentials.

36. Dentate Ligament Cord Distortion Tethering the Spinal cord • The UC subluxation causing abnormal motion may cause a disruption of the normal function of the dentate ligaments which would not allow for full motion of the spinal cord during flexion and extension. • Traction of the spinal cord will cause a decrease in the action potentials of spinal neurons. • Mechanical deformation has shown to cause neurologic dysfunction.

37. 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 the nervous system then were sectioned and processed immunohistochemically to identify areas of Fos production in nerve cell bodies. The presence of Fos indicated 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 of stimulation as well as at several spinal cord levels above and below the site of stimulation (on the ipsilateral and the contralateral sides), in sympathetic ganglia at these sites, nerve cell bodies in the combined nucleus cuneatus and gracilis in the medulla oblongata, the vestibular nuclei, and the thalamus. • Stretching a single lateral ligament of the spine produces a barrage of sensory feedback from several spinal cord levels on both sides of the spinal cord. • Information from this study allowed Jaing to trace the relay system of neurological afferent synapse through the CNS. Jiang H. Spine. 22(1):17-25, January 1, 1997

38. Sensory Neurologic Feedback • The “cervico-sympathetic reflex [that can alter heart rate and blood pressure] appears to originate from muscle spindles in the dorsal neck musculature, it is very likely that the suboccipital muscle group is involved in the reflex because these muscles have an extremely high muscle spindle content." • "Additional evidence for the involvement of the suboccipital muscle group 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 suboccipital muscle 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 to neck muscle afferent stimulation, because the NUCLEUS TRACTUS SOLITARIUS is a major integratory area for autonomic control circuits." Ian J. The Journal of Neuroscience August 1, 2007; 27(31); pp. 8324-8333

39. Sensory Neurologic Feedback • A theoretical model showing components that describe the relationships between spinal manipulation, segmental biomechanics, the nervous system and physiology. • The neurophysiological effects of spinal manipulation could be mediated at any of the numbered boxes. J.G. Pickar / The Spine Journal 2 (2002) 357–371

40. 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 stimulation may subsequently lead to increased neuronal responsiveness or central sensitization • These changes cause exaggerated perception of painful stimuli (hyperalgesia), a perception of innocuous stimuli as painful (allodynia) and may be involved in the generation of referred pain and hyperalgesia across multiple spinal segments Mira Meeus & Jo Nijs. Clin Rheumatol (2007) 26:465–473

41. Central Sensitization Diseases Associated with Central Sensitization Syndrome: • Fibromyalgia • Chronic fatigue syndrome • Irritable bowel syndrome • Depression • Insomnia • Abnormal Heart rate variability

42. Central Sensitization • AKA: Central facilitation • The increased excitability or enhanced responsiveness 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. J.G. Pickar / The Spine Journal 2 (2002) 357–371

43. Central Sensitization • 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. J.G. Pickar / The Spine Journal 2 (2002) 357–371

44. Central Sensitization • We currently know that the phenomenon of central facilitation increases the receptive field of central neurons and allows 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 spinal manipulation may be the removal of subthreshold stimuli induced by changes in joint movement or joint play. J.G. Pickar / The Spine Journal 2 (2002) 357–371

45. Central Sensitization • 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. J.G. Pickar / The Spine Journal 2 (2002) 357–371

46. Central Sensitization • Spinal manipulation increased the average pressure/pain threshold of six tender spots in the neck region by approximately 50% (from 2 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. J.G. Pickar / The Spine Journal 2 (2002) 357–371

47. ALTERED SENSORIMOTOR INTEGRATION WITH CERVICALSPINE MANIPULATION • Spinal manipulation of dysfunctional cervical joints may alter specific central corticomotor facilitatory and 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 and restoration of functional ability documented after spinal manipulation. Haavik Taylor, Murphy. J Manipulative Physiol Ther 2008;31:115-126