Axonal retraction

Diffuse axonal injury Cytotoxic edema, myelin vacuolization, or axonal retraction balls... 

Halpem et al. (1991) and Sink and Whitington (1991a) have observed that the RP motor axons in Drosophila extend over a number of inappropriate muscles in addition to their appropriate targets and retract these branches later in embryogenesis. 

This model predicts that the formation or retraction of an axonal branch by a neuron on a particular substrate does not result primarily from competition with other neurons occupying that substrate. Rather, neurons behave autonomously, with competition taking place between different branches of an individual neuron. Indeed, target-deprived motoneurons in the Drosophila embryo form and maintain connections with adjacent nontarget muscles, even though such muscles continue to receive innervation from their appropriate motoneurons (Cash et al., 1992). 

Gao, W.-Q. and Macagno, E.R. (1987a) Extension and retraction of axonal projections by some developing neurons in the leech depends upon the existence of neighbouring homologues. 1. The HA cells. J. Neurobiol. 18 43-59. 

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