Hydrodynamic mechanism of syringomyelia: its relationship to myelocele

Abstract

In a study of congenital malformations of the hindbrain it was concluded that syringomyelia is a mild expression of an embryonic defect which in its severe form results in myelocele. In both conditions the embryonic state is represented by an imperforate and distended neural tube. The degree of distension, embryonically, is related to the permeability of the rhombic roof which in turn depends upon attenuation, the end stage of which is perforation. Delayed attenuation and impaired permeability result in an imperforate rhombic roof persisting into postnatal life. In syringomyelia and myelocele a pathological degree of distension occurs in which overdistension of the forebrain competes with that of the hindbrain. Compensation for the overdistension usually occurs and the infant may appear normal. Imprisoned hydrodynamic stresses, however, will eventually result in syringomyelia. The anatomical evidence gleaned from this study suggests that the cause of synringomyelia be sought in the hindbrain and not in the cord and that myelocele is due to rupture of the neural tube resulting from a degree of overdistension too great for the normal method of compensation.