Neurotmesis

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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).

Schema-Nerv.jpg Scheme of an intact nerve
Neurapraxia.jpg Neurapraxia Grade 1: axon and envelope tissue are preserved.
Axonotmesis.svg Axonotmesis Grade 2: The axon is severed, but
the covering tissue is preserved.
Neurotmesis.svg 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.

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