Ultrastructural study of motoneurons in Werdnig-Hoffmann disease

Ultrastructural studies of the lumbar spinal cord in three children with Werdnig-Hoffmann (W-H) disease type Ia revealed numerous small neurons which appeared both atrophic and immature. We compared these motoneurons with anterior horn cells of a 3-month-old child, a 27-week and a 16-week human fetus, and found (1) that the motoneurons were much smaller in W-H disease, and (2) the Nissl substance was peripherally located and less developed. Signs of motoneuron immaturity as well as secondary degenerative changes suggest that in W-H disease neurons die either because they fail to make adequate peripheral contact or because the neurons are genetically intrinsically defective.