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
Neurodynamic as treatment: def sliders & tensioner
SLIDERS
Nerve elongation at one end while releasing tension at other end
TENSIONER
Nerve elongation at both ends
Peripheral nerve assessment: functional neural mechanosensitivity testing
- Elevation of shoulder: reduce of tension of brachial plexus & peripheral nerve originates in plexus
- Lateral flexion of neck toward affected side
=> reduce tension in nerve
Guideline to perform neurodynamic testing
- Instruct patient & ask him to actively perform mvt
- Follow logic sequence of mvts
- Consider testing first non affected side
- Bilateral comparison
- Maintain each movement before adding new one
- Take time & ask for constant feedback
- Perform structural differentiation
≠ tests of neuro dynamic
Straight leg raise
Sensitizing maneuver
Differentiation mvt
Diagnostic accuracy for sciatica
Diagnostic accuracy for cervical radiculopathy
STRAIGHT LEG RAISE description
- Assess to radiculopathy & lumbosacral neural structures
- To test movement & mechanical sensitivity of lumbosacral neural structures & their distal extensions
- Gradually add components of maneuver to progressively load nerve
- SLR = hip flexion > knee extension > sensitizing maneuver > differentiation movement
If nerve involved in tension => pain increase If nerve not involved => pain does not change
SENSITIZING MANEUVER description
- Sciatic nerve: ankle eversion & inversion - Additional mvts that increase load in specific neural structures
- Hip adduction / medial rotation: stress more common peroneal nerve
- Overload specific nerve
- Nerve impact ROM of people
- Affective nerve => decrease in ROM
DIFFERENTIATION MVT
- Adding mvts distant to location of symptoms that affect neural structures in limb without affecting non-neural tissue local to area of symptoms
- Cervical flexion, as differentiator, between somatic pain (fascia or muscle-tendon units) & neural pain
DIAGNOSTIC ACCURACY FOR SCIATICA description
Increase validity, high Sp & Sn
- SLR: reliability moderate when testing included structural differentiation (ankle dorsiflexion)
- Extended SLR (ESLR): by adding location-specific structural differentiation mvts (hip internal rotation or ankle dorsiflexion) better differentiate neural symptoms from musculoskeletal compared to traditional SLR
ESLR showed high validity in detecting neural symptoms & strongly associated with pathology seen in MRI when judged positive. ESLR showed 0.85 Sn & 0.45 Sp for Lumbar Disc Herniation & 0.75 Sn & 0.50 Sp for Nerve Root Compression
- In isolation, diagnostic performance of most physical tests poor
- SLUMP: test performed slightly better, but number of studies too small for strong conclusion
DIAGNOSTIC ACCURACY FOR CERVICAL RADICULOPATHY description
4 tests for UL:
- 2 for median nerve (higher Sn) - 1 for ulnar (higher Sp)
- 1 for radial(higher Sn)
Combined ULNTs have Sn = 0.97 & Sp = 0.69 - ULNT3 (ulnar) = highest Sp = 0.88
- ULNT1 (median) = highest Sn = 0.83
