Tall vertebrae at birth: a radiographic finding in flaccid infants.

It has been well documented that children with severe neuromuscular disorders have tall vertebrae, presumably a consequence of altered mechanical forces. This finding was present in four neonates who were born with severe "floppy" hypotonia due to Werdnig-Hoffmann disease (two cases), nonspecific neonatal myopathy, and congenital muscular dystrophy. Fetal vertebral development is normally modified by intrauterine muscle tension and fetal activity.