Wallerian degeneration

As Wallerian degeneration or Wallerian degeneration of the complex molecular processes are called that occur after an injury to a nerve in the peripheral nervous system ( PNS) or of fiber tracts of the central nervous system (CNS) and lead lying on the sinking of the distal ( below) the damage to nerves share.

This degeneration of the axon with " collapse" and " disintegration " follows here in PNS and CNS a similar time course. The myelin sheath itself is broken down more slowly in the CNS, however, because there are hardly phagocytic macrophages there.

Possible causes are traumatic discontinuity as sharp transection ( axotomy ) or contusion, ischemia, hemorrhage, inflammation, viral or toxic damage.

Histologically, leave the resolution of the myelin sheath and the axon and phagocytosis prove.

Clinically, this can result in the originally innervated areas to a flaccid motor paralysis including a possible bladder and bowel disorder and / or a loss of sensation. The evidence of failure is dependent on the type and number of affected axons.

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Such damage in the PNS have different effects in the CNS:

Peripheral Nervous System

If the myelin sheath of the axon of a peripheral nerve obtained which Axonstumpf above ( proximal to ) the damage lies can in the denervated myelin sheath grow at a rate of 1 mm per day and reinnervieren the target organ, thus restoring the function (regeneration) is possible. Find the proximal axon sprouting with his so-called growth cones, the myelin sheath as a lead not this Sprouting axon can aimlessly proliferate and form a traumatic or Amputationsneurom as Hyperregenerat of the peripheral nerve.

Central Nervous System

Already 100 years ago was starting to be shown from the transplantation experiments Ramon y Cajal that damaged CNS fiber tracts do not regenerate in contrast. If namely the proximal end, a piece of optic nerve - which is attributable to the CNS as cranial nerve and its nerve sheath is formed by oligodendrocytes - added, the proximal end of the axon did not grow into this lead structure.

Augustus Volney Waller (1816-1870), was an English physiologist in Birmingham, who in his histological preparations described this degenerating nerve fibers in 1850 for the first time.