Seeing the peripheral nerves in the cadavers, we were able to answer many questions from students in the course regarding palpation of the nerves and differentiation of healthy nerves, unhealthy nerves and scar tissue. An "un-healthy" nerve is inflamed and round due to the intraneural edema, whereas a healthy nerve is relatively flat! We often compare spaghetti to linguine to help students understand.
But what effect does this edema have on the nerve? Why does it occur? and how can WE HELP?
The peripheral nerves are supplied with blood from the vasa nervorum, these blood vessels are impermeable to macromolecules in the circulation, forming the blood-nerve barrier. Also, please note that the absence of lymphatics, the combination of these two physiologic factors isolates the endoneurial space from the systemic circulation and extraneural interstitium.
Within all nervous tissue there is a high positive endoneurial fluid pressure (EFP), as most other tissues display a negative interstitial fluid pressure. The mechanism by which typically positive fluid pressure is maintained has yet to be fully understood however, many factors, such as the blood-nerve barrier and lack of lymphatic drainage, are thought to contribute to this.
To date, many mechanisms for endoneurial edema have been identified, each of them associated with an increased EFP. These mechanisms include compression/crush injuries and chemical injury from nearby inflammation. This occurs through altered permeability of the vascular endothelium, causing fluid to enter the endoneurial compartment.
This increase in EFP causes a decrease in nerve blood flow, disruption of endoneurial electrolytes, hypoxia and ischemia because the vasa nervorum is not resistant to these changes in pressure. Thus, leading to a disruption of normal nerve function and conduction.
The importance of this is not just in compression or related nerve injuries. It involves every injury or performance issue. With anything we deal with, if you treat the nervous system you get better results.
Neurodynamic techniques are methods that focus on mobilizing peripheral nerves or adopting positions in joints that unload the nervous system. This facilitates movement between the nerve tissue and surrounding structures, and reduces the mechanical load on the nervous system to tolerate the compression, friction, and traction forces associated with sport and daily activities. These techniques include manual therapy or therapeutic exercises. Interestingly, in a recent 2022 meta-analysis, neurodynamic techniques were shown to improve the dispersion of intraneural edema [2]. With many years of clinical practice, we believe some of the best techniques for improving these environments are acupuncture and specifically Micro-Conditioning TM soft tissue techniques.
The importance of this study lies heavily in the analysis and not in the term "neurodynamic technique". In reality, a neurodynamic technique is a catch-all term for therapy! Whatever your method is, you are promoting the mobilization of tissues and encouraging joints to adopt a more functional position.
Personally, I like to use electro-acupuncture, manual therapy (Neurofucntional Micro-Conditioning TM) and exercise with my patients. Electro-acupuncture has a direct effect on the nervous system by stimulating peripheral nerves. In addition, it modulates the sympathetic nervous system, which controls the dilation and constriction of the vasa nervorum. Another prominent effect is increased perfusion, encouraging all tissues' metabolic health, allowing joints to adopt these favourable positions and offload the nerves.
However, if you want great results from treating the nervous system, you need an equally great ASSESSMENT.
Practitioners need a way to assess that is different from an orthopedic assessment. You need a therapy-based model that gives you treatment targets and outcome measures, as well as allows you to design a step-by-step plan for your patients.
References
1.Powell, H.C., Myers, R.R. (1989). The Blood-Nerve Barrier and the Pathologic Significance of Nerve Edema. In: Neuwelt, E.A. (eds) Implications of the Blood-Brain Barrier and Its Manipulation. Springer, Boston, MA. https://doi.org/10.1007/978-1-
2. Nuñez de Arenas-Arroyo S, Martínez-Vizcaíno V, Cavero-Redondo I, Álvarez-Bueno C, Reina-Gutierrez S, Torres-Costoso A. The Effect of Neurodynamic Techniques on the Dispersion of Intraneural Edema: A Systematic Review with Meta-Analysis. Int J Environ Res Public Health. 2022 Nov 4;19(21):14472. doi: 10.3390/ijerph192114472. PMID: 36361353; PMCID: PMC9655711.
3. Amenta, Francesco et al. “The autonomic innervation of the vasa nervorum.” Journal of Neural Transmission 58 (2005): 291-297.
4. Mizisin AP, Kalichman MW, Myers RR, Powell HC. Role of the blood-nerve barrier in experimental nerve edema. Toxicol Pathol. 1990;18(1 Pt 2):170-85. doi: 10.1177/019262339001800123. PMID: 2195637.
5. Olmarker, Kjell MD, PhD, and; Rydevik, Björn MD, PhD. Selective Inhibition of Tumor Necrosis Factor-α Prevents Nucleus Pulposus-Induced Thrombus Formation, Intraneural Edema, and Reduction of Nerve Conduction Velocity: Possible Implications for Future Pharmacologic Treatment Strategies of Sciatica. Spine 26(8):p 863-869, April 15, 2001.
6. Lundborg, G. Structure and function of the intraneural microvessels as related to trauma, edema formation, and nerve function. The Journal of Bone & Joint Surgery 57(7):p 938-948, October 1975.
7. Schmid, Annina B., et al. "Effect of splinting and exercise on intraneural edema of the median nerve in carpal tunnel syndrome—an MRI study to reveal therapeutic mechanisms." Journal of Orthopedic Research 30.8 (2012): 1343-1350.
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