Reciprocity of the neural growth in the Arnold-Chiari malformation

It has been suggested (1) that nerves grow as plants grow. Extensive development of one nerve tends to retard its neighbours, lack of development tends to excite them to more active growth. This is a widespread neurobiologic phenomenon which may be traced up also in the pathomechanism of the Arnold-Chiari malformation: Impairment of the neural growth at the level of a lumbosacral meningomyelocele results in overgrowth of the cranio-cervical nerves associated with shortening of the cervical cord segments. A similar reciprocity, normal and pathologic, seems to work also between the nerve roots of the cauda equina and the lumbosacral segments of the spinal cord.