Axonotmesis

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The axonotmesis is a traumatic injury of peripheral nerves with transection of the axon . The myelin sheath made of Schwann cells is also damaged, but it is crucial that the continuity of the nerve envelope structures ( endoneurium , perineurium , epineurium ) is preserved. Since the axon has been disrupted, Waller's degeneration initially takes place. The proximal axon stump forms a growth cone and grows out along the preserved endoneurial sheath. If the regeneration is successful, it is likely that the function will be largely restored.

Demarcation

Axonotmesis is a moderate form of nerve injury. In the division coined by Herbert Seddon , it is differentiated from the lighter neurapraxia and the even more severe neurotmesis

Schema-Nerv.jpg Scheme of an intact nerve
Neurapraxia.jpg Neurapraxia Axon and envelope tissue are preserved.
Axonotmesis.svg Axonotmesis The axon is severed, but
the covering tissue is preserved.
Neurotmesis.svg Neurotmesis Complete severing of the nerve
and its envelope structures

Examination Findings

Neurographically , the excitability of the nerve is lost distal to the lesion site, paresis , muscle atrophy and sensory disturbances occur in the innervation area of ​​the nerve , and vegetative functions are also impaired.

forecast

In axonotmesis, in contrast to neurapraxia, the axon degenerates beyond the point of damage. The prognosis is nevertheless favorable, as the continuity of the surrounding connective tissue and the basement membrane is preserved. Therefore, extensive or even complete regeneration of the nerve function can occur. The sprouting of a new axon takes place at a rate of 0.25 to 3 mm per day. The restitution therefore takes considerably longer than with a pure neurapraxia - depending on the length of the damaged nerve segment in the order of weeks to months. The ability to regenerate remains for years.

literature