Wallerian Degeneration: Difference between revisions
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== Clinically Relevant Anatomy == | == Clinically Relevant Anatomy == | ||
[[File:Neuron Part 1.png|right|frameless]] | [[File:Neuron Part 1.png|right|frameless]] | ||
Wallerian degeneration is an active process of retrograde degeneration of the distal end of an [[Axons|axon]] that is a result of a [[Nerve Injury Rehabilitation|nerve lesion]]. It occurs between 7 to 21 days after the lesion occurs. After the 21st day, acute | Wallerian degeneration is an active process of retrograde degeneration of the distal end of an [[Axons|axon]] that is a result of a [[Nerve Injury Rehabilitation|nerve lesion]]. It occurs between 7 to 21 days after the lesion occurs. After the 21st day, acute nerve degeneration will show on the electromyograph. | ||
Within a [[Neurone|nerve]], each axon is surrounded by a layer of connective tissue called the endoneurium. The axons are bundled together into groups called fascicles, and each fascicle is wrapped in a layer of connective tissue called the perineurium. Finally, the entire nerve is wrapped in a layer of connective tissue called the epineurium.<ref>Purves D, Augustine GJ, Fitzpatrick D, Hall WC, LaMantia AS, McNamara JO, White LE.[https://archive.org/details/neuroscienceissu00purv ''Neuroscience''] (4 ed.). Sinauer Associates. 2008 pp. [https://archive.org/details/neuroscienceissu00purv/page/n36 11]–20. </ref> | Within a [[Neurone|nerve]], each axon is surrounded by a layer of connective tissue called the endoneurium. The axons are bundled together into groups called fascicles, and each fascicle is wrapped in a layer of connective tissue called the perineurium. Finally, the entire nerve is wrapped in a layer of connective tissue called the epineurium.<ref>Purves D, Augustine GJ, Fitzpatrick D, Hall WC, LaMantia AS, McNamara JO, White LE.[https://archive.org/details/neuroscienceissu00purv ''Neuroscience''] (4 ed.). Sinauer Associates. 2008 pp. [https://archive.org/details/neuroscienceissu00purv/page/n36 11]–20. </ref> | ||
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'''Axon Degeneration''' | '''Axon Degeneration''' | ||
Within approximately 30 minutes of injury, there is a separation of the proximal and distal ends of the nerve. After a short latency period | Within approximately 30 minutes of injury, there is a separation of the proximal and distal ends of the nerve. After a short latency period, the transected membranes are sealed until degeneration which is marked by the formation of axonal sprouts. This occurs in less than a day and allows for nerve renervation and regeneration | ||
'''Myelin Clearance''' | '''Myelin Clearance''' | ||
This occurs by the 7th day when macrophages are signaled by the Schwann cells to clean up axonal and myelin debris.<ref>Gaudet AD, Popovich PG &Ramer MS. Wallerian degeneration: Gaining perspective on inflammatory events after peripheral nerve injury.Journal of Neuroinflammation.2011 Available from.https://jneuroinflammation.biomedcentral.com/articles/10.1186/1742-2094-8-110 (accessed on 06/04/2021)</ref> Usually, the rate of clearance is slower in the [[Introduction to Neuroanatomy|Central Nervous System]] than the | This occurs by the 7th day when macrophages are signaled by the Schwann cells to clean up axonal and myelin debris.<ref>Gaudet AD, Popovich PG &Ramer MS. Wallerian degeneration: Gaining perspective on inflammatory events after peripheral nerve injury.Journal of Neuroinflammation.2011 Available from.https://jneuroinflammation.biomedcentral.com/articles/10.1186/1742-2094-8-110 (accessed on 06/04/2021)</ref> Usually, the rate of clearance is slower in the [[Introduction to Neuroanatomy|Central Nervous System]](CNS) than in the Peripheral Nervous System (PNS) due to the clearance rate of myelin. Another reason for the different rates is the change in permeability of the blood-tissue barrier in the two systems. In PNS, the permeability increases throughout the distal stump, but the barrier disruption in CNS is limited to just the site of injury. Also in the CNS, [[Glial Cells|oligodendrocytes]] inhibit regeneration. | ||
'''Regeneration''' | '''Regeneration''' | ||
Revision as of 15:00, 20 May 2021
Top Contributors - Anthonia Abraham, Kim Jackson, Cindy John-Chu and Lucinda hampton
Clinically Relevant Anatomy[edit | edit source]
Wallerian degeneration is an active process of retrograde degeneration of the distal end of an axon that is a result of a nerve lesion. It occurs between 7 to 21 days after the lesion occurs. After the 21st day, acute nerve degeneration will show on the electromyograph.
Within a nerve, each axon is surrounded by a layer of connective tissue called the endoneurium. The axons are bundled together into groups called fascicles, and each fascicle is wrapped in a layer of connective tissue called the perineurium. Finally, the entire nerve is wrapped in a layer of connective tissue called the epineurium.[1]
Mechanism of Injury[edit | edit source]
The pathological process of Wallerian degeneration is in 3 stages;
Axon Degeneration
Within approximately 30 minutes of injury, there is a separation of the proximal and distal ends of the nerve. After a short latency period, the transected membranes are sealed until degeneration which is marked by the formation of axonal sprouts. This occurs in less than a day and allows for nerve renervation and regeneration
Myelin Clearance
This occurs by the 7th day when macrophages are signaled by the Schwann cells to clean up axonal and myelin debris.[2] Usually, the rate of clearance is slower in the Central Nervous System(CNS) than in the Peripheral Nervous System (PNS) due to the clearance rate of myelin. Another reason for the different rates is the change in permeability of the blood-tissue barrier in the two systems. In PNS, the permeability increases throughout the distal stump, but the barrier disruption in CNS is limited to just the site of injury. Also in the CNS, oligodendrocytes inhibit regeneration.
Regeneration
If soma/ cell body is damaged neuron can not regenerate, However, if the injury is at the end of the axon, at a growth of 1mm per day., the distal segment undergoes granular disintegration over several days to weeks. After the macrophages clear axonal and myelin debris, Schwann cells multiply to fill are previously occupied by former segment completed by leaving the endometrial tube and Swann calls. In regeneration cytoplasmic elements begin to accumulate.[3]
Clinical Presentation[edit | edit source]
Most patients have presentations of nerve damage.
These presentations may include,
- Paralysis of associated structures to denervated nerves
- Gradual onset of numbness, prickling, or tingling in your feet or hands, which can spread upward into your legs and arms
- Sharp, jabbing, throbbing, freezing, or burning pain
- Extreme sensitivity to touch
- Lack of coordination and falling
- Muscle weakness or paralysis if motor nerves are affected
- Neuromatous or causalgia pain
Diagnostic Procedures[edit | edit source]
- Electromyography
- Nerve Conduction Studies
- Sensation deficit and skin condition
- Muscle strength/loss
- Functional deficits
Outcome Measures[edit | edit source]
Depends on various criteria including pain and psychosocial skills but could include:
- Oxford scale
- Visual analogue scale
- Short form McGill pain questionnaire
(see Outcome Measures Database)
Management / Interventions[edit | edit source]
See Nerve Injury Rehabilitation
Wallerian Degeneration can instigate a nerve repair mechanism. Managing nerve damage can include the use of Cryotherapy[6], Exercise, Neurorehabilitation, and Surgery.
References[edit | edit source]
- ↑ Purves D, Augustine GJ, Fitzpatrick D, Hall WC, LaMantia AS, McNamara JO, White LE.Neuroscience (4 ed.). Sinauer Associates. 2008 pp. 11–20.
- ↑ Gaudet AD, Popovich PG &Ramer MS. Wallerian degeneration: Gaining perspective on inflammatory events after peripheral nerve injury.Journal of Neuroinflammation.2011 Available from.https://jneuroinflammation.biomedcentral.com/articles/10.1186/1742-2094-8-110 (accessed on 06/04/2021)
- ↑ Coleman MP, Conforti L, Buckmaster EA, Tarlton A, Ewing RM, Brown MC, Lyon MF, Perry VH (August 1998). "An 85-kb tandem triplication in the slow Wallerian degeneration (Wlds) mouse". Proceedings of the National Academy of Sciences of the United States of America. 95 (17): 9985–90. Bibcode:1998PNAS...95.9985C. doi:10.1073/pnas.95.17.9985. PMC 21448. PMID 9707587.
- ↑ Medical & Exercise Physiology School.Wallerian degeneration/ regeneration process of nerve fiber/axon cut and progressive response. Available from https://www.youtube.com/watch?v=kbzYML05Vac (last accessed 5 March 2021)
- ↑ The Young Orthopod. Nerve Regeneration. Available from https://www.https://www.youtube.com/watch?v=P02ea4jf50g&t=192s (last accessed 6 March 2021)
- ↑ Hsu M,and Stevenson FF.Wallerian Degeneration and Recovery of Motor Nerves after Multiple Focused Cold Therapies. US National Library of Medicine.National Institutes of Health.2015 ; 51(2): 268–275.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4315870/ (accessed on 6/04/2021)
