Neurotmesis
The Neurotmesis is a traumatic injury of a peripheral nerve , adjacent to the at Axon ( axonotmesis ) the myelin sheath and the accompanying connective tissue structures ( perineurium , epineurium ) are more or less separated. The axon disintegrates distal to the lesion site in the sense of Waller's degeneration , while the proximal axon stump forms a growth cone and tries to grow back into the innervation area.
Demarcation
From the neurotmesis, a distinction is made between the lighter forms of lesion neurapraxia and axonotmesis according to the classification coined by Herbert Seddon (1903–1977).
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Scheme of an intact nerve | |||
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Neurapraxia | Grade 1: axon and envelope tissue are preserved. | ||
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Axonotmesis | Grade 2: The axon is severed, but the covering tissue is preserved. |
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Neurotmesis | Grade 3: axon and endoneurium are destroyed, perineurium and epineurium are intact | Grade 4: axon, endo- and perineurium are destroyed, epineurium is intact | Grade 5: All structures of the nerve are destroyed (entire nerve severed) |
Note: The axons are surrounded by an endoneurium and combined to form a fascicle. Several fascicles are grouped together by the perineurium to form the actual nerve. The nerve itself is surrounded by an epineurium.
The targeted surgical transection of a nerve is called a neurotomy (without loss of substance) or neurectomy (with loss of substance).
forecast
The prognosis depends on the degree of damage. While a neurapraxia usually heals without consequences after a few weeks, with the axonotmesis regeneration only occurs after a few months, which is usually complete (restitutio ad integrum). In grade 3 neuronotmesis, there is incomplete regeneration, which takes place at a rate of approx. 1-3 mm / day. In the case of higher-grade damage (such as grade 4 and 5) scar tissue forms (continuity neuroma ), which allows no or only very poor regeneration. There is therefore an indication for surgery. Especially with grade 5 (i.e. the complete severing of all nerve structures) only one nerve suture can offer a prospect of improvement in nerve function. If the nerve stumps can no longer be approached, a nerve interposer can be inserted. H. nerve fibers from another nerve are transplanted into the gap, so the defect is bridged.
literature
- Marco Mumenthaler , Manfred Stöhr, Hermann Müller-Vahl: Lesions of peripheral nerves and radicular syndromes. 8th edition. Thieme Stuttgart, 2003. ISBN 3-13-380208-9 .