NEURODYNAMIC Flashcards
Periph nerve as MSK soft tissue
- Body presents nervous system with mechanical interface via musculoskeletal system
- With mvt, musculoskeletal system exerts non-uniform stresses & mvt in neural tissues, depending on local anatomical & mechanical characteristics & pattern of body mvt
- This activates array of mechanical & physiological responses in neural tissues, including neural sliding, pressurisation, elongation, tension & changes in intraneural microcirculation, axonal transport & impulse traffic
Structure designed to handle tension
During functional activities, peripheral nervous system needs to be able to accommodate substantial amounts of nerve tension & elongation
Composite limb mvts typically expose peripheral nerves to approximately 5 to 20% strain
Peripheral nerves = heterogeneous structures: although well- organized, multilayered structure of extracellular matrix bears considerable mechanical loads, response of peripheral nerves to mechanical load characterized by their ability to glide, bend & twist
Neuroprotective architectural features, such as unique undulating pattern, offer additional protective strength
Mechanical properties of peripheral nerves not equal along their length, revealing complex tissue ultrastructure
Mechanical interface
Nerves protected by & ‘move‘ through surrounding structures (muscles, bones, ligaments…)
⚠ Mechanical interface – affect nerve properties (nerve entrapment, including radiculopathy)
Nerve morphology
Schema
STRUCTURE DESIGNED TO HANDLE TENSION
- Nerve layer connections structure explain nerve response to stretch: mesoneurium, epineurium, & perineurium coupled via viscoelastic physical connections & interact with loosely coupled perineurium & endoneurium, allowing axons to glide & unravel throughout length of nerve
- Collectively, mechanical features allow nerves to straighten without bearing significant stresses while maintaining functional & structural integrity of delicate axons within
Response to stretch
During stretching, nerve stretches but other components also stretch. There is not only nerve that stretches
Changes in nerve properties
Physiological effects of tensile forces acting on peripheral nerve
- Impact nerve conduction
- Change intraneural blood flow => decreases blood flow as tension increases
After immobilization periods, affecting myelin sheet & fiber diameter - Mobilization causes decreased of capacity to move & to support load or tension
People with Carpal Tunnel syndrome, affecting longitudinal excursion & stiffness
People with lumbar radiculopathy, affecting cross-sectional area
Prolonged stress/overload of nerve (compressive or tensile forces) impact mechanical (gliding) & physiological (intraneural blood flow) nerve properties
≠ nerve injury
- Impaired fascicular gliding
- Edema
- Ischemia
- Impaired axonal transport
- Mechanosensitivity
- Adhesions
Periph nerves & ROM
Joint ROM influenced by peripheral nerves
In stretching position, there is less dorsiflexion than in normal position because sciatic nerve already in tension
Nerve biomechanics
Nerves = viscoelastic tissues & exhibit non-linear viscoelastic responses to tensile loading
Nerves not static structures, presenting:
- Longitudinal & transverse excursion (gliding) - Strain
- Stiffness
- Convergence
- Divergence
- Stress relaxation/Creep
Convergence & divergence concepts
- Joint contraction => nerve gliding toward moving joint => increase tension nerve = CONVERGENCE
- Opposite: decrease tension in nerve => nerve gliding far from moving joint = DIVERGENCE
⚠ Convergence & divergence not dependent of movement but depend on tension (increase tension = convergence & no tension = divergence)
≠ studies in vitro, in animals and on humans & in optimal tension / absent tension
Tableau
Distinct nerve disorders
Schema
Neurodynamic tests
- Neurodynamic tests first described in late 19th century based on abnormal tension concept
- This view changed in examining neural mechanosensitivity (neural tissue provocation tests or neurodynamic tests)
- Nomenclature not used uniformly, leading to misconceptions in medical field
Interpretation of these tests & what constitutes positive test vary greatly in literature: - Partial reproduction of symptoms & structural differentiation = essential criteria for positive test
- Sensitizing maneuvers = crucial for differentiating nerve-related mechanosensitivity from other soft tissue-related mechanosensitivities
Increased mechanosensitivity
How much nerve able to support load or tension
- Examination includes evaluation of increased mechanical sensitivity of nervous system
- Related to increased excitability of small-diameter afferents & sensitization of nociceptors in nervi-nervorum & sinuvertebral nerves
Neurodynamic tests used by physiotherapists in order to identify changes of mechanosensitivity in nervous system, thus assessing gain of function
Positive neurodynamic test criteria
- Partial reproduction of neurogenic pain (“burning” or “lightning-like” pain, tingling sensation, according to dermatome pattern in nerve root pathology) in neck & arm
- Increased/decreased symptoms with structural differentiation
- Differences in painful radiation between right & left sides
