This is a Chapter 2 summary of “Clinical Neurodynamics” by Michael Shacklock.
Specific neurodynamics include local effects of body movements on the nervous system. So today we will go through each body region discussing these.
Here are some interesting tidbits regarding the spine and neurodynamics.
- When we flex the spine, the spinal canal elongates by about 9 cm.
- Neck flexion creates significant tension to the lumbosacral nerve roots.
- Neural structures slide relative to the bony interface differently depending on the location and the movement used.
- Flexion increases tension, but reduces compression. Extension adds compression, but reduces tension.
- Lateral flexion increases tension on the convex/contralateral side of the spine. This situation occurs by interface and neural tissue elongation and increased distance between the spine and periphery.
- Rotation closes on the ipsilateral side and opens on the contralateral side.
The spinal cord tends to move towards various specific segments. These areas are termed zones of convergence, and these areas include C5-6 and L4-5. For example, tissues above C5-6 will slide toward this zone, as will tissues below this segment. The midpoint at which tissues diverge is at T6. At this point, tissues below T6 will converge towards L4-5, and tissues above T-6 will converge to C5-6.
Gravity can also play a role in neurodynamics. For example, if you perform a SLR in sidelying, the downward side usually has less mobility. This difference occurs because the neural contents are convex on the downward side and convex on the upper side, increasing tension in the lower leg.
Here are some tidbits on the upper quarter
The cervical spine:
- In the cervical spine, contralateral sidebending usually increases symptoms with median and radial neurodynamic tests.
- Ipsilateral sidebending usually reduces symptoms, but is not useful in structural differentiation because peripheral nerve tension may not be sufficient.
The scapula and shoulder:
- Scapular depression consistently produces increased symptoms with upper limb neurodynamic tests.
- Shoulder abduction creates distal sliding of the nerves proximal to the shoulder and proximal sliding of nerves distal to the shoulder, such that they converge to the shoulder.
- Shoulder external rotation responses vary.
- Horizontal extension can increase tension, but is inconsistent and not essential.
- Shoulder internal rotation increases tension along the radial nerve.
- Elbow extension increases median nerve bed length by 20%, with convergence towards the elbow.
- Elbow flexion decreases median nerve tension and increases ulnar nerve tension up to 23%.
- Pronation and supination create small effects in the nervous system, but can be meaningful at making end-range changes.
- Radial and ulnar deviation produces small changes in the nervous system, similar to pronation and supination.
- When radial deviation occurs, strain in the median nerve increases at the elbow and decreases at the wrist.
- Ulnar deviation increases strain at eh elbow and wrist.
- Flexion decreases median nerve tension, and extension increases it.
The Lower Limb
Here are some tidbits on the lower limb
- Hip flexion increases hamstring tension and posterior pelvic tilt as early as 10 degrees.
- Nerves converge towards the hip joint with the straight leg raise.
- Internal rotation increases tension in the lumbosacral plexus and its related nerve roots and also in the sciatic nerve.
- Adduction increases responses in the SLR.
- Extension accounts for 49% of sciatic nerve bed elongation.
- Flexion increases femoral nerve tension, but the standard prone knee bend test is usually not indicative of neural issues.
The foot and ankle:
- Dorsiflexion increases tibial nerve tension; and if done at the end of the SLR, can produce movement at the lumbosacral nerve roots.
- Eversion increases tension of the posterior tibial nerve.
- Dorsiflexion/inversion tenses the Sural nerve.
- Plantarflexion/inversion tenses the superficial fibular nerve. Can also implicate piriformis syndrome for those who have a high sciatic nerve division.