Stikkordarkiv: tunnel syndromes

Palmitoylethanolamide, a neutraceutical, in nerve compression syndromes: efficacy and safety in sciatic pain and carpal tunnel syndrome

av

Gjennomgang av studier på PEA mot smerter som følge av nerver i klem. Ved 600mg daglig har man best og raskest effekt, men 300mg daglig gir også noe. Det tar bare lenger tid.

Fra abstract:

In total, eight clinical trials have been published in such entrapment syndromes, and 1,366 patients have been included in these trials. PEA proved to be effective and safe in nerve compression syndromes. In one pivotal, double blind, placebo controlled trial in 636 sciatic pain patients, the number needed to treat to reach 50% pain reduction compared to baseline was 1.5 after 3 weeks of treatment. Furthermore, no drug interactions or troublesome side effects have been described so far.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4631430/

 

 

Peripheral Nerve Entrapment and Injury in the Upper Extremity

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Denne beskriver flere innklemningsnevropatier som kan oppstå i skuldre og armer.

Spesielt to prinsipper er smarte å ha med:

1: ved smerte eller svakhet i å løfte armen over hodet: suprascapular nerven

2: ved smerte eller svakhet i å skru inn en skrue: carpal tunnel eller pronator syndrom (median nerven)

http://www.aafp.org/afp/2010/0115/p147.html

The trigger point strikes … out!

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En blog av Quinter som bedre forklarer det nevrologiske utgangspunktet for triggerpunkter, eller mer korrekt: ømme punkter og stramme muskler.

Basert på deres nye forklaringsmodell vil et problem (f.eks. betennelse) lenger inn på en sensorisk nerve sender betennelse (nevrogen betennelse) ut til muskelen, i tillegg til at motoriske og sympatiske (stress) signaler fra ryggmargen sendes ut til muskelen og gir en muskelspenning og twitchrespons vi kan se og kjenne med fingrene.

Ang. nevrogen betennelse så nevner wikipedia en studie på mus som viser at magnesium mangel, selv det som er innenfor «normalen» kan bidra til økt utskillelse av SP, som er en nevrogen betennelsesfaktor. http://en.wikipedia.org/wiki/Neurogenic_inflammation

***

But when I met the late Bob Elvey, he completely changed my way of thinking about these clinical problems. Bob’s mantra was that “muscles protect nerves.” He introduced me to the dynamics of the nervous system and I came to understand that peripheral nerves of the upper limb had evolved to be able to adapt to the various changes in limb position and length and that they were vulnerable at certain anatomical points along their course.

***

In brief, Geoff’s studies have had two major impacts on how we think about pain felt in muscles or other deep structures.

Firstly, he confirmed the presence of nociceptors with multiple receptive fields that branch within the nerve sheaths and extend to other deep tissues (nervi nervorum) [7]. The implication of this finding is that activity in a receptor in one structure such as the nerve sheath, could be perceived in another, such as the muscle.

Secondly, he showed that inflammation of nerves has profound effects on these same axons, the nociceptors to deep structures. These effects include ongoing activity and abnormal mechanical sensitivity [8, and others]. The implication of this finding is that this activity will be perceived by the brain in the area of the receptive fields mapped for the deep structure nociceptors, not in the area of the problem.

***

Figure 1. Proposed hypothesis for the development of focal muscle sensitivity and possible alteration in muscle texture with a proximal neural cause. Inflammation affecting a peripheral nerve (red spot) results in spontaneous and mechanically evoked afferent and efferent action potentials in small caliber sensory neurons innervating non-cutaneous structures, and decreased sympathetic discharge (-). These processes may cause reflex motor discharge sufficient to cause a palpable contraction (?), which combined with clinical phenomena associated with neurogenic inflammation (+), could explain the clinical phenomenon that has become known as a “trigger point.”

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Structure and Biomechanics of Peripheral Nerves: Nerve Responses to Physical Stresses and Implications for Physical Therapist Practice

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Nevner det aller meste om perifere nerver og hvordan de får plager av «normale» sitasjoner, som f.eks. musearm.

http://www.ncbi.nlm.nih.gov/pubmed/16386065

http://ptjournal.apta.org/content/86/1/92.long

Abstract

The structural organization of peripheral nerves enables them to function while tolerating and adapting to stresses placed upon them by postures and movements of the trunk, head, and limbs. They are exposed to combinations of tensile, shear, and compressive stresses that result in nerve excursion, strain, and transverse contraction. The purpose of this appraisal is to review the structural and biomechanical modifications seen in peripheral nerves exposed to various levels of physical stress. We have followed the primary tenet of the Physical Stress Theory presented by Mueller and Maluf (2002), specifically, that the level of physical stress placed upon biological tissue determines the adaptive response of the tissue. A thorough understanding of the biomechanical properties of normal and injured nerves and the stresses placed upon them in daily activities will help guide physical therapists in making diagnoses and decisions regarding interventions.

Figure 1.

Structural components of peripheral nerves. In the endoneurial compartment (En), a single Schwann cell envelops several unmyelinated axons, and another Schwann cell provides multiple wrappings of plasma membrane forming the myelin sheath of a myelinated axon. The portion of a myelinated axon myelinated by a single Schwann cell is called the internode, and internodes are separated by nodes of Ranvier. Schwann cells associated with both unmyelinated and myelinated axons are covered with a continuous basal lamina (BL). Capillaries (Cap) are present within the endoneurial compartment, and collagen fibers (Col) run primarily longitudinally between the axons. The axons, Schwann cells, collagen, and endoneurial fluid are bundled into a fascicle by the perineurium (Pe). The perineurium consists of several layers of flattened perineurial cells connected by tight junctions and covered internally and externally by a basal lamina. The layers of perineurial cells are separated by collagen fibers (Col) oriented obliquely. Several fascicles are bundled together by the epineurium (Ep) to form a nerve. The epineurium consists primarily of fibroblasts, collagen fibers (Col), and elastic fibers. The epineurium between fascicles is termed the interfascicular epineurium, and that encompassing all of the fascicles is termed the epifascicular epineurium. Arterioles (A) and veins are oriented primarily longitudinally within the epineurium.

Blood supply

The blood supply to nerves is provided by coiled segmental arteries that enter the epineurium periodically along the length of the nerve and form the vasa nervorum. Arteries divide into epineurial arterioles that form an anastomotic network running primarily longitudinally within the epifascicular epineurium and the interfascicular epineurium (Fig. 3). Epineurial arterioles are supplied with a perivascular plexus of serotoninergic, adrenergic, and peptidergic nerves.17,18 Perforating arterioles cross the perineurium at oblique angles and carry a short sleeve of perineurial cells into the fascicle.3,19 Perineurial arterioles have poorly developed smooth muscle and thus have limited ability to regulate intrafascicular blood flow.20 Within the endoneurium, arterioles immediately turn into large-diameter, longitudinally oriented capillaries that allow blood flow in either direction (Fig. 3).21 The endothelial cells of endoneurial capillaries are connected by tight junctions, thus forming the tight blood-nerve barrier.7 Venules return blood to the venous system. Of note, lymphatic capillaries are present only within the epineurium; there is no lymphatic drainage from the intrafascicular or endoneurial space.22

Biomechanical properties

Under normal physiological conditions imposed by posture and movement, nerves are exposed to various mechanical stresses. Stress is defined as force divided by the area over which it acts9,23–25 and can be applied to a nerve as tensile, compressive, or shear stress or as a combination of stresses (Fig. 4). Tensile stress may be applied to tissues either parallel or perpendicular to the length of the nerve, causing respective longitudinal or transverse stress in the nerve. When joint motion causes elongation of the nerve bed, the nerve is inherently placed under tensile stress and accommodates the stress by both elongating and gliding.15 The deformation or change in nerve length induced by longitudinal tensile stress is called strain and is expressed typically as percent elongation.23,26–28 Displacement or gliding of a nerve relative to the surrounding nerve bed is called excursion.29–31 The direction of excursion may be longitudinal or transverse, or both, relative to the nerve tract31,32 and is measured in millimeters.

Figure 4.

Physical stresses placed on peripheral nerve. Tensile stress applied longitudinally to peripheral nerve creates an elongation of the nerve (an increase in strain). The transverse contraction that occurs during this elongation is greatest at the middle of the section undergoing tensile stress.

When the nerve bed is elongated, the nerve is placed under increased tensile stress. With the elongation of the nerve bed, the nerve glides toward the moving joint,1,33,34 a movement termed convergence.1 Conversely, if the nerve bed tension is relieved during joint motion, the nerve will realign along the shortened nerve bed by gliding away from the moving joint, a movement termed divergence.33 Convergence in the median nerve may be demonstrated during elbow extension (Fig. 5). The motion elongates the bed of the median nerve, causing the nerve segment in the arm to glide distally toward the elbow and the nerve segment in the forearm to glide proxi mally toward the elbow. In contrast, elbow extension relieves the tensile stresses in the ulnar nerve bed, causing the ulnar nerve to diverge away from the elbow (Fig. 5).

Figure 5.

Excursion of the median nerve (solid line) and the ulnar nerve (dotted line) during elbow extension followed by wrist extension. The concepts of nerve convergence toward and divergence away from a moving joint are illustrated in measurements of excursion taken at each site indicated. All measurements are reported in millimeters of proximal (P) or distal (D) excursion. The direction of excursion is also represented by solid arrows for median nerve excursion and open arrows for ulnar nerve excursion. (A) With elbow extension from 90° of flexion to 0° of flexion, the median nerve bed lengthens and the median nerve glides toward the elbow (converges). With the same joint motion, the ulnar nerve bed shortens and the ulnar nerve glides away from the elbow (diverges). (B) With wrist extension from 0° of extension to 60° of extension, both nerve beds lengthen; thus, both nerves converge toward the wrist. The magnitude of excursion is greatest closest to the moving joint. Data were obtained from: aDilley et al,29 bWright et al,27 and cWright et al.33 Measurements of nerve excursion at the wrist and elbow in panel A were extrapolated from studies of nerve excursion during elbow flexion from 0° to 90°.27

Nerve Stiffness

First, a recent study43 measured greater nerve compliance in nerve segments that cross joints than in segments that do not cross joints.

Second, nerve stiffness is greater in long nerve sections and in nerve sections with numerous branches.15 Severing nerve branches or vessels but leaving the nerve in situ results in increased compliance and decreased stiffness.15

Third, nerve stiffness is greater when a nerve is elongated rapidly rather than slowly. In addition, the ultimate strain at the point of failure appears to be dependent on the rate of elongation.

When a nerve is placed under tension and maintained at that new fixed length over time, there is a reduction in the tension in the nerve or the force required to maintain the fixed length. The observed reduction in tension may be plotted in a stress-relaxation curve (Fig.8).25,44 The majority of relaxation occurs in the first 20 minutes of fixed elongation.25,44Stress relaxation in nerves that are stretched slowly is greater than in nerves that are stretched rapidly.25,37,44–46 This phenomenon was observed when comparisons were made for rabbit tibial nerves stretched at different rates to lengths 6% longer than their resting lengths. Over the 60-minute relaxation time, there was a 57% reduction in stress in nerves elongated at 0.08% per second,45 but only a 34% reduction in stress in nerves elongated at 3.0% per second.44

Figure 8.

Stress-relaxation curve demonstrating viscoelastic properties of peripheral nerve. When a nerve is elongated and the new length is kept constant, there is a rapid reduction in the stress within the nerve, expressed as percent reduced relaxation. Most of the relaxation occurs in the first 20 minutes. The degree of elongation affects the amount of stress relaxation that will occur. The dotted line represents a nerve that has been elongated to 6% above its resting length. The solid line represents nerves that have been elongated to 9% and 12% above their resting lengths. Greater stress relaxation was documented in nerves that underwent less elongation.25,44 Modified from Kwan MK, Wall EJ, Massie J, Garfin SR. Strain, stress, and stretch of peripheral nerve: rabbit experiments in vitro and in vivo. Acta Orthop Scand. 1992;63:267–272, with permission of Taylor and Francis AS.

However, a nerve stretched repetitively to 8% or 10% strain exhibits a reduced slope of the stress-strain curve, indicating that that nerve undergoes less stress with successive elongations because of increased compliance and decreased stiffness.

Compression of nerve

In addition to tensile stress, nerves are exposed statically and dynamically to compressive stresses. As mentioned previously, the laws of physics dictate that the cross-sectional area of a cylindrical object is reduced as the cylinder is elongated. As a nerve is elongated under tensile force, the nerve undergoes transverse contraction, which is resisted by the fluid and nerve tissue contained within the connective tissue sheath.15,39The magnitude of the transverse contraction stress is greatest at the center of the elongating segment15 (Fig. 4). Nerves also may be compressed externally by approximation to adjacent tissues, such as muscle, tendon, or bone, or by pressure increases in the extraneural environment. Compression of a nerve segment causes displacement of its internal contents in transverse and longitudinal directions. As shown in rat nerve, extraneural compression causes an immediate displacement of endoneurial fluid to the edges of a compressive cuff over 5 to 10 minutes and a much slower displacement of axonal cytoplasm over the course of hours.48 The damage to axons and myelin is greatest at the edges of the compressed zone,48,49 where the shear forces are highest.50

At the edges of the cuff, however, myelin retraction with resultant widening of nodes and paranodal demyelination occurred. These structural alterations in myelin may be expected to result minimally in impaired impulse conduction or maximally in demyelination and a conduction block.

In response to biomechanical stresses placed on a nerve as an individual assumes a posture or movement, the nerve follows the path of least resistance.29 Combinations of tensile, shear, and compressive stresses result in combinations of nerve excursion, strain, and transverse contraction. Because the biomechanical forces on the nerve are so intricately linked, the sequencing and range of joint movement affect the magnitude and direction of excursion,27,29 the magnitude of nerve strain,27,29,35 and the degree of transverse contraction at different sites along the nerve.27

Simultaneous nerve excursion, strain, and transverse contraction may be seen in the ulnar nerve as an example of responses to physical stresses imposed during movements of the upper limb. When the upper limb is maintained in a position of 90 degrees of shoulder abduction and 90 degrees of shoulder external rotation with the wrist neutral, and when the elbow is moved from 90 degrees of flexion to full extension, the ulnar nerve bed is shortened and the tensile stress on the nerve is decreased. With this motion, there is divergence of the ulnar nerve away from the elbow (Fig. 5), decreased nerve strain, especially at the elbow (Fig. 6), and decreased compression within the cubital tunnel.27,29,33 When the wrist then is extended from neutral to full extension, the ulnar nerve bed is lengthened, resulting in convergence of the nerve toward the wrist (Fig. 5), an increase in nerve strain (Fig. 6), and transverse contraction greatest in the nerve segment across the carpal bones and at the tunnel of Guyon.27,29,33 The magnitude of nerve strain and excursion will be greatest near the wrist, and the fascicles will rearrange as the nerve assumes a flattened oval shape. Because the nerve does not lie directly on the rotational axis of joint motion, the fascicles farthest from the axis will undergo greater strain than those closer to the center of rotation51

Figure 6.

Strain of the median nerve (solid line) and the ulnar nerve (dotted line) during elbow extension followed by wrist extension. Measurements at the sites indicated are reported as percent increase (↑) or percent decrease (↓) in strain. (A) With elbow extension from 90° of flexion to 0° of flexion, median nerve strain increases because of elongation of the nerve bed. Conversely, ulnar nerve strain decreases as the ulnar nerve bed shortens. (B) With wrist extension from 0° of extension to 60° of extension, the strain at the sites measured increases in both nerves as both nerve beds elongate. The magnitude of the strain is greatest closest to the moving joint. Data were obtained from: aWright et al27and bWright et al.33 Measurements of nerve excursion at the wrist and elbow in panel A were extrapolated from studies of nerve excursion during elbow flexion from 0° to 90°.27

Continuum of physical stress states

First, levels of physical stress lower than the levels required for tissue maintenance (low stress) result in a reduced ability of the tissue to tolerate subsequent stress and are consistent with tissue plasticity and response to functional demand.

Second, levels of physical stress in the range required for tissue maintenance (normal stress) result in no tissue adaptations and are considered to maintain a state of equilibrium.

Third, physical stress levels that exceed the range required for tissue maintenance (high stress) result in an increase in the tolerance of the tissue for stress in an effort to meet the mechanical demand.

Fourth, physical stress levels that exceed the capacity of some components of the tissue (excessive stress) result in tissue injury.

Fifth, levels of physical stress that are extreme (extreme stress) result in tissue death.

Finally, it is important to note that the physical stress level is a composite value with variable components of magnitude, time, and direction or type of stress.

 In the functional zone, the physical stresses on the nerve are sufficient to maintain a state of equilibrium and normal physiological function. In the dysfunctional zone, various levels of physical stress have altered the ability of the nerve to tolerate subsequent stress.

Figure 9.

Continuum of physical stress states. The white area represents the functional zone in which the physical stresses on the nerve are sufficient to maintain a state of equilibrium and normal physiological function. The shaded areas represent dysfunctional zones resulting from various levels of physical stress placed on the nerve tissue. Under conditions of prolonged low stress, the functional zone will shrink in width and shift to the left, reducing the ability of the tissue to tolerate subsequent stresses even of previously normal levels. Under conditions of high stress, the functional zone may expand and shift to the right, improving the ability of the tissue to tolerate subsequent physical stress. If the nerve is exposed to prolonged or repeated excessive stress, the functional zone will shrink in width. Although scarring of damaged tissue may enable the nerve to tolerate subsequent physical stresses, the physiological function of the nerve will be reduced. Exposure to extreme stress will result in disruption of axon continuity or neural cell death and significantly reduced physiological function.

Immobilization Stresses

Under conditions of immobilization, such as casting, splinting, and bracing, peripheral nerves are exposed to levels of physical stress that are lower than those necessary to maintain the nerves in a state of equilibrium or in a functional zone (Fig. 9). According to the Physical Stress Theory, nerve will undergo predictable physiological and structural modifications proportional to the levels of reduced stress and the duration of immobilization.2 Immobilization induces cell biological changes in axons and axon terminals52–54 and structural changes in myelin and nerve connective tissue layers that likely alter the ability of nerves to tolerate subsequent physical stress.

We hypothesize that after a period of immobilization, the width of the functional zone on the continuum of physical stress states will shrink and shift toward the left (Fig. 9).

Lengthening Stresses

Nerves are exposed to various levels of longitudinal tensile stress during limb-lengthening procedures, such as distraction osteogenesis (Ilizarov procedures), traction injuries, and stretching maneuvers. The tissue response is dependent upon the magnitude and duration of the tensile stress. The extant data indicate that lengthening of 6% to 8% for a short duration causes transient physiological changes that appear to be within the normal stress tolerance of the tissue, whereas acute strains of 11% and greater cause long-term damage and may be considered to be excessive or extreme stress states.

In cadavers, positioning in shoulder depression, 90 degrees of shoulder abduction, 90 degrees of shoulder external rotation, 70 degrees of forearm supination, 60 degrees of wrist extension, full finger extension, and full elbow extension resulted in 7.6%±8.2% (X̄±SD) strain in the median nerve measured just proximal to the wrist.28 Adults who were healthy and who were placed in this same position lacked 12±13 degrees (X̄±SD) of elbow extension because of substantial discomfort in the limb.61 The subjects reported pain of 5.1±1.9 (X̄±SD) on a 10-point visual analog scale, and 36% of the subjects reported paresthesia in the upper limb. Taken together, these findings suggest that many people are unable to tolerate levels of strain below the theoretical 11% threshold.

Compression Stresses

Compression on a nerve may be the result of extraneural force or may occur as transverse contraction secondary to increased longitudinal strain (Fig. 4). Compression stress of a low magnitude and a short duration may result in reversible physiological and minor structural changes. Compressive stress of a high magnitude, however, may result in structural alterations in myelin sheaths and even disruption of axons. Low-magnitude compressive stress applied over a long period of time may cause significant structural changes in the nerve secondary to impairment of blood flow and sequelae of ischemia.

As with strain-induced injury, a threshold for compression-induced nerve injury is difficult to determine. Common functional positions may result in compression pressures that approach or exceed the 20 to 30 mm Hg demonstrated to impair nerve blood flow.75 The carpal tunnel is a site well known for compressive damage to the median nerve and thus has been well studied. Carpal tunnel pressure in subjects who were healthy was measured at 3 to 5 mm Hg with the wrist in a neutral position.76–78 Simply placing the hand on a computer mouse was shown to increase the tunnel pressure from the resting 5 mm Hg to 16 to 21 mm Hg,79 and actively using the mouse to point and click increased the tunnel pressure to 28 to 33 mm Hg, a pressure high enough to reduce nerve blood flow.

In subjects with carpal tunnel syndrome, pressure in the carpal tunnel was 32 mm Hg with the wrist in a neutral position and rose to a mean of 110 mm Hg with full wrist extension in subjects with carpal tunnel syndrome.76 These tunnel pressures exceed the threshold of 20 to 30 mm Hg for vascular perfusion even at rest. Taken together, these findings suggest that even functional positions, such as the use of a computer keyboard and mouse, place the wrist in a position of increased carpal tunnel pressure, compromising nerve blood flow and placing people at risk for median nerve injury.

Direct damage to myelin and axons has been shown to occur with extraneural compression of as low as 50 mm Hg maintained for 2 minutes,48 and the percentage of damaged fibers increases with increasing force. Ten days after the application of compressive stress at 50 mm Hg, 30% of the axons in the region under the compressive cuff showed evidence of demyelination, focal myelin thickening, remyelination, and axonal degeneration or regeneration.48

The pathological consequences of prolonged compression include subperineurial edema; inflammation; deposition of fibrin; activation of endoneurial fibroblasts, mast cells, and macrophages; demyelination; axon degeneration; and fibrosis.83 Compression of a very long duration has been modeled in animals with loose ligatures,88 Silastic* tubes,89,90and pressure balloons placed within an anatomical tunnel.91 The pathological findings are thought to result from both inflammatory and cellular phenomena and include changes in the blood-nerve barrier, thickening of the perineurium and epineurium, thinning of myelin, demyelination and degeneration of axons in the fascicle periphery, and slowed nerve conduction velocity.

In the case of chronic compression, decompression is paramount. Physical therapy intervention should focus on reduction of inflammation, improvement in blood flow, and enhancement of the capacity of the nerve for strain and excursion along its full length in an effort to reduce the physical stress on the compressed region.

Repetitive Stresses

Vibration constitutes one form of repetitive stress. We know from studies of humans who use hand-held vibrating tools that vibration stresses can cause reductions in tactile sensation, as well as other sensory disturbances96 and reduced grip force.97,98Furthermore, myelin breakdown and fibrosis have been seen in the dorsal interosseous nerve at the wrist in people with vibration-induced neuropathy.99 Long-term exposure to vibration stresses has been shown to result in the grouping of muscle fiber types in muscle biopsies, indicative of denervation and reinnervation.98

Repetitive movements, such as those that occur in work-related musculoskeletal disorders, were discussed in detail recently by Barr and Barbe.102 The stresses placed upon the tissues may be variable in terms of type, magnitude, frequency, and duration, and the combination of these factors may place nerves in normal to extreme levels of physical stress. The chronic inflammation associated with repetitive movements places nerves under constantly higher hydrostatic compressive stress, which may increase further with contraction of the surrounding muscles. Chronic inflammation elicits within the nerves a remodeling response that seeks to add mechanical stability.103 The most common outcome is the deposition of collagen in the connective tissue layers, which leads to decreased compliance of the nerves to elongation. As with chronic compression, the approach for assessment and treatment of injuries attributable to repetitive movements must address the chronic inflammatory state and connective tissue changes. Of primary importance in interventions for all stress-induced injuries are the identification and characterization of physical stresses and the modification of their components, magnitude, time, and direction, as outlined in the physical stress theory.2

Summary

This assessment should guide treatment interventions to normalize the stresses on the nerves, be they rest, soft tissue or neurodynamic mobilization, stretching, modalities, exercise, or patient education. Treatment rationale should be based on an educated understanding of the biomechanical properties of normal and pathological nerves. The concept of a continuum of low-normal-high-excessive-extreme stresses may be used as a training tool for patient education, pointing out examples of daily activities that fall under the different categories.

Structure and Biomechanics of Peripheral Nerves: Nerve Responses to Physical Stresses and Implications for Physical Therapist Practice

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Denne sier mye om nervenes blodgjennomstrømmning. Spesielt interessant er avnittet om hvor lite trykk som skal til før blodgjennomstrømningen stopper. Om trykket opprettholdes i 8 timer vil det skje en skade i nerven. Så lite som 20 mm Hg er nok til at blodsirkluasjonen blir dårligere.

http://ptjournal.apta.org/content/86/1/92.full

Simply placing the hand on a computer mouse was shown to increase the tunnel pressure from the resting 5 mm Hg to 16 to 21 mm Hg,79 and actively using the mouse to point and click increased the tunnel pressure to 28 to 33 mm Hg, a pressure high enough to reduce nerve blood flow.

In subjects with carpal tunnel syndrome, pressure in the carpal tunnel was 32 mm Hg with the wrist in a neutral position and rose to a mean of 110 mm Hg with full wrist extension in subjects with carpal tunnel syndrome.76 These tunnel pressures exceed the threshold of 20 to 30 mm Hg for vascular perfusion even at rest. Taken together, these findings suggest that even functional positions, such as the use of a computer keyboard and mouse, place the wrist in a position of increased carpal tunnel pressure, compromising nerve blood flow and placing people at risk for median nerve injury.

Arterial and endoneurial capillary blood flows were stopped at pressures of 50 to 70 mm Hg67 and 80 mm Hg,75 respectively. Interestingly, in humans, intraneural blood flow and sensory responses are blocked at extraneural tissue pressures 45 mm Hg below the mean arterial pressure.82 A compressive stress of only 30 mm Hg, if maintained for 2 hours, results in endoneurial edema,83 and, if maintained for 8 hours, results in endoneurial pressure high enough to subsequently impair blood flow.84 The endoneurial edema is thought to result from ischemic damage to endoneurial capillary endothelial cells and an alteration in the blood-nerve barrier. The same compressive stress of 30 mm Hg applied for 8 hours is sufficient to impair both anterograde axonal transport and retrograde axonal transport.85,86Increasing pressure results in greater tissue damage, as a compressive force of 150 mm Hg maintained for 30 minutes was shown to induce a degeneration of 30% of the distal fibers,48 and compressive forces of 200 and 400 mm Hg maintained for 2 hours were shown to block axonal transport for 1 and 3 days, respectively.87

The pathological consequences of prolonged compression include subperineurial edema; inflammation; deposition of fibrin; activation of endoneurial fibroblasts, mast cells, and macrophages; demyelination; axon degeneration; and fibrosis.83 Compression of a very long duration has been modeled in animals with loose ligatures,88 Silastic* tubes,89,90and pressure balloons placed within an anatomical tunnel.91 The pathological findings are thought to result from both inflammatory and cellular phenomena and include changes in the blood-nerve barrier, thickening of the perineurium and epineurium, thinning of myelin, demyelination and degeneration of axons in the fascicle periphery, and slowed nerve conduction velocity.

The Mechanisms of Manual Therapy in the Treatment of Musculoskeletal Pain: A Comprehensive Model

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Nevner det meste rundt behandling av muskel og skjelett problemer, både usikkerheter, manglende diagnostisk spesifisitet, dårlig forhold mellom forklaringsmodelle og realitet, og foreslår nevrosentriske forklaringsmodeller. Viser til at spesifikk behandling ikke har bedre effekt enn uspesifikk behandling. Og til at den mekaniske teknikken setter igang en kaskade av nevrologiske effekter som resulterer i en behandlingeffekt.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2775050/

Abstract

Prior studies suggest manual therapy (MT) as effective in the treatment of musculoskeletal pain; however, the mechanisms through which MT exerts its effects are not established. In this paper we present a comprehensive model to direct future studies in MT. This model provides visualization of potential individual mechanisms of MT that the current literature suggests as pertinent and provides a framework for the consideration of the potential interaction between these individual mechanisms. Specifically, this model suggests that a mechanical force from MT initiates a cascade of neurophysiological responses from the peripheral and central nervous system which are then responsible for the clinical outcomes. This model provides clear direction so that future studies may provide appropriate methodology to account for multiple potential pertinent mechanisms.

Mechanical Stimulus 

First, only transient biomechanical effects are supported by studies which quantify motion (Colloca et al., 2006;Gal et al., 1997;Coppieters & Butler, 2007;Coppieters & Alshami, 2007) but not a lasting positional change (Tullberg et al., 1998;Hsieh et al., 2002). Second, biomechanical assessment is not reliable. Palpation for position and movement faults has demonstrated poor reliability (Seffinger et al., 2004;Troyanovich et al., 1998) suggesting an inability to accurately determine a specific area requiring MT.  Third, MT techniques lack precision as nerve biased techniques are not specific to a single nerve (Kleinrensink et al., 2000) and joint biased technique forces are dissipated over a large area (Herzog et al., 2001;Ross et al., 2004).

Finally, studies have reported improvements in signs and symptoms away from the site of application such as treating cervical pain with MT directed to the thoracic spine (Cleland et al., 2005;Cleland et al., 2007) and lateral epicondylitis with MT directed to the cervical spine (Vicenzino et al., 1996).

Subsequently, we suggest, that as illustrated by the model, a mechanical force is necessary to initiate a chain of neurophysiological responses which produce the outcomes associated with MT. 

Neurophysiological Mechanism 

Studies have measured associated responses of hypoalgesia and sympathetic activity following MT to suggest a mechanism of action mediated by the periaquaductal gray (Wright, 1995) and lessening of temporal summation following MT to suggest a mechanism mediated by the dorsal horn of the spinal cord (George et al., 2006) The model makes use of directly measurable associated responses to imply specific neurophysiological mechanisms when direct observations are not possible. The model categorizes neurophysiological mechanisms as those likely originating from a peripheral mechanism, spinal cord mechanisms, and/or supraspinal mechanisms.

Peripheral mechanism 

Musculoskeletal injuries induce an inflammatory response in the periphery which initiates the healing process and influences pain processing. Inflammatory mediators and peripheral nociceptors interact in response to injury and MT may directly affect this process. For example, (Teodorczyk-Injeyan et al., 2006) observed a significant reduction of blood and serum level cytokines in individuals receiving joint biased MT which was not observed in those receiving sham MT or in a control group. Additionally, changes of blood levels of β-endorphin, anandamide, N-palmitoylethanolamide, serotonin, (Degenhardt et al., 2007) and endogenous cannabinoids (McPartland et al., 2005) have been observed following MT. Finally, soft tissue biased MT has been shown to alter acute inflammation in response to exercise (Smith et al., 1994) and substance P levels in individuals with fibromyalgia (Field et al., 2002). Collectively, these studies suggest a potential mechanism of action of MT on musculoskeletal pain mediated by the peripheral nervous system for which mechanistic studies may wish to account. 

Spinal mechanisms 

MT may exert an effect on the spinal cord. For example, MT has been suggested to act as a counter irritant to modulate pain (Boal & Gillette, 2004) and joint biased MT is speculated to “bombard the central nervous system with sensory input from the muscle proprioceptors (Pickar & Wheeler, 2001).”Subsequently, a spinal cord mediated mechanism of MT must be considered and is accounted for in the model. Direct evidence for such an effect comes from a study (Malisza et al., 2003b) in which joint biased MT was applied to the lower extremity of rats following capsaicin injection. A spinal cord response was quantified by functional MRI during light touch to the hind paw. A trend was noted towards decreased activation of the dorsal horn of the spinal cord following the MT. The model uses associated neuromuscular responses following MT to provide indirect evidence for a spinal cord mediated mechanism. For example, MT is associated with hypoalgesia (George et al., 2006;Mohammadian et al., 2004;Vicenzino et al., 2001), afferent discharge (Colloca et al., 2000;Colloca et al., 2003), motoneuron pool activity (Bulbulian et al., 2002;Dishman & Burke, 2003), and changes in muscle activity (Herzog et al., 1999;Symons et al., 2000) all of which may indirectly implicate a spinal cord mediated effect.

Supraspinal mechanisms 

Finally, the pain literature suggests the influence of specific supraspinal structures in response to pain. Structures such as the anterior cingular cortex (ACC), amygdala, periaqueductal gray (PAG), and rostral ventromedial medulla (RVM) are considered instrumental in the pain experience.(Peyron et al., 2000;Vogt et al., 1996;Derbyshire et al., 1997;Iadarola et al., 1998;Hsieh et al., 1995;Oshiro et al., 2007;Moulton et al., 2005;Staud et al., 2007;Bee & Dickenson, 2007;Guo et al., 2006). Subsequently, the model considers potential supraspinal mechanisms of MT. Direct support for a supraspinal mechanism of action of MT comes from (Malisza et al., 2003a) who applied joint biased MT to the lower extremity of rats following capsaicin injection. Functional MRI of the supraspinal region quantified the response of the hind paw to light touch following the injection. A trend was noted towards decreased activation of the supraspinal regions responsible for central pain processing. The model accounts for direct measures of supraspinal activity along with associated responses such as autonomic responses (Moulson & Watson, 2006;Sterling et al., 2001;Vicenzino et al., 1998) (Delaney et al., 2002;Zhang et al., 2006), and opiod responses (Vernon et al., 1986) (Kaada & Torsteinbo, 1989) to indirectly imply a supraspinal mechanism. Additionally, variables such as placebo, expectation, and psychosocial factors may be pertinent in the mechanisms of MT (Ernst, 2000;Kaptchuk, 2002). For example expectation for the effectiveness of MT is associated with functional outcomes (Kalauokalani et al., 2001) and a recent systematic review of the literature has noted that joint biased MT is associated with improved psychological outcomes (Williams et al., 2007). For this paper we categorize such factors as neurophysiological effects related to supraspinal descending inhibition due to associated changes in the opioid system (Sauro & Greenberg, 2005), dopamine production (Fuente-Fernandez et al., 2006), and central nervous system (Petrovic et al., 2002;Wager et al., 2004;Matre et al., 2006) which have been observed in studies unrelated to MT.

Figure 3 Pathway considering both a spinal cord and supraspinal mediated effect from Bialosky et al (2008)

Tensjon i nervesystemet opprettholdes i hofta

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Dette klippet nevner forskningen til den svenske nevrokirurgen Alfred Breig og viser til at det er hofteleddet som bestemmer det meste i nervesystemets tensjon (strekk). Utoverrotasjon og lett abduksjon gir minst strekk i nervesystemet.

«Tension in the nervous system has the same effect as compression» – Barret Dorko

Magnesium attenuates chronic hypersensitivity and spinal cord NMDA receptor phosphorylation in a rat model of diabetic neuropathic pain

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Magnesium gjør at nervesystemet blir mindre sensitivt i studie på rotter med nevropati. Dosen er beregnet til å være ca 147 mg pr dag (24t), som er veldig mye relativt til kroppsvekten på en mus på 10-20g. Om vi regner det om til menneskevekt blir det megadoser.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3002451/

Neuropathic pain is a common diabetic complication affecting 8–16% of diabetic patients. It is characterized by aberrant symptoms of spontaneous and stimulus-evoked pain including hyperalgesia and allodynia. Magnesium (Mg) deficiency has been proposed as a factor in the pathogenesis of diabetes-related complications, including neuropathy. In the central nervous system, Mg is also a voltage-dependant blocker of the N-methyl-d-aspartate receptor channels involved in abnormal processing of sensory information. We hypothesized that Mg deficiency might contribute to the development of neuropathic pain and the worsening of clinical and biological signs of diabetes and consequently, that Mg administration could prevent or improve its complications. We examined the effects of oral Mg supplementation (296 mg l−1 in drinking water for 3 weeks) on the development of neuropathic pain and on biological and clinical parameters of diabetes in streptozocin (STZ)-induced diabetic rats. STZ administration induced typical symptoms of type 1 diabetes. The diabetic rats also displayed mechanical hypersensitivity and tactile and thermal allodynia. The level of phosphorylated NMDA receptor NR1 subunit (pNR1) was higher in the spinal dorsal horn of diabetic hyperalgesic/allodynic rats. Magnesium supplementation failed to reduce hyperglycaemia, polyphagia and hypermagnesiuria, or to restore intracellular Mg levels and body growth, but increased insulinaemia and reduced polydipsia. Moreover, it abolished thermal and tactile allodynia, delayed the development of mechanical hypersensitivity, and prevented the increase in spinal cord dorsal horn pNR1. Thus, neuropathic pain symptoms can be attenuated by targeting the Mg-mediated blockade of NMDA receptors, offering new therapeutic opportunities for the management of chronic neuropathic pain.

Diabetes is also the most common pathological state in which secondary magnesium (Mg) deficiency occurs. Indeed, Mg deficiency has been described in 25–30% and 13.5–47.7% of type 1 and type 2 diabetic patients, respectively (Garland, 1992; Tossielo, 1996; Corsonelloet al. 2000; Engelen et al. 2000; Rodriguez-Moran & Guerrero-Romero, 2003; Pham et al.2007) and its incidence is correlated to diabetes complications (De Leeuw, 2001). Mg is an ATPase allosteric effector involved in inositol transport (Grafton et al. 1992) and the impaired Na+/K+-ATPase activity in peripheral nerves of diabetic animals (Garland, 1992) plays a role in the pathophysiology of diabetic neuropathy (Li et al. 2005).

In the central nervous system, Mg has voltage-dependent blocking properties that play an important role in pain processing at the N-methyl-d-aspartate (NMDA) receptor channel complex (Mayer et al. 1984; Xiao & Bennett, 1994; Begon et al. 2000). In vitro, this blockade operates at extracellular Mg concentrations of less than 1 mm (Mayer et al. 1984), i.e. within the ranges found in human and animal cerebrospinal fluid and plasma (Morris, 1992). The excess release of glutamate from central nociceptor terminals due to nerve damage releases Mg blockade and activates NMDA receptors known to trigger painful sensations (hyperalgesia, allodynia) and alter the sensitivity of postsynaptic cells, resulting in central sensitization (Bennett, 2000). This central sensitization involving the NMDA receptor can be induced in rats in vivo by Mg depletion (Alloui et al. 2003). Several studies suggest that phosphorylation of the NMDA receptor NR1 subunit is correlated to the presence of signs of neuropathy and to persistent pain following nerve injury (Gao et al.2005; Ultenius et al. 2006; Gao et al. 2007; Roh et al. 2008).

One week after STZ or distilled water injection, the animals were assigned to the following three experimental groups:

  • MgSO4-supplemented STZ-D group: STZ-D rats receiving MgSO4 (296 mg l−1 of Mg) in drinking water for 3 weeks,
  • Non-supplemented STZ-D group: STZ-D rats given tap water,
  • Control non-diabetic group: rats given tap water.

Water intake was 10-fold and sixfold higher in non-supplemented and MgSO4-supplemented STZ-D rats, respectively, compared with non-diabetic rats. Water intake was significantly lower in MgSO4-supplemented STZ-D rats than non-supplemented STZ-D rats (Table 1). Consequently, urine excretion was 24-fold higher in non-supplemented STZ-D rats than non-diabetic rats. The MgSO4-supplemented STZ-D rats also developed polyuria corresponding to a 15-fold increase in urine excretion compared with non-diabetic rats, but which was nevertheless lower than the increase in non-supplemented STZ-D rats (Table 1). Polyuria in STZ-D rats was significantly correlated to water intake (P < 0.001).

Parameter Non-diabetic Non-suppl. STZ-D MgSO4-suppl. STZ-D
Water intake (ml (24 h)−1) 35.22 ± 2.36 376.6 ± 32.87*** 214.4 ± 30.87***,###
Urine excretion (ml (24 h)−1) 12.45 ± 1.51 300.1 ± 24.16*** 184.4 ± 25.23***,##
Food intake (g (24 h)−1) 30.7 ± 1.83 54.66 ± 3.67** 42.06 ± 6.21
Total Mg intake (mg (24 h)−1) 61.40 ± 3.66 109.32 ± 7.34*** 147.58 ± 1.58***,###

Figure 4: Time course of mechanical sensitivity measured by paw pressure-induced vocalization threshold (VT) variations in non-diabetic (Non-D), non-supplemented STZ-diabetic (Non-suppl. STZ-D) and MgSO4-supplemented (MgSO4-suppl. STZ-D) rats

Parameter Non-diabetic Non-suppl. STZ-D MgSO4-suppl. STZ-D
Tactile hypersensitivity
Week 2 0/10 3/10 0/10#
Week 4 0/10 6/10* 0/10#
Thermal hypersensitivity
Week 2 0/10 6/10* 0/10#
Week 4 0/10 6/10* 0/10#

This study clearly showed that Mg supplementation prevents tactile and thermal allodynia and attenuates and delays mechanical hyperalgesia in STZ-D rats. This effect was mediated, at least in part, by the prevention of NMDA receptor NR1 subunit phosphorylation in STZ-D rats. However, the study also showed that Mg supplementation did not improve most of the biological and clinical signs of diabetes despite restoration of normal insulin secretion.