Developmentally, vertebrae form from the
sclerotome portions of the somites, which are derived from paraxial mesoderm.
It is likely, however, that the development of the IAF and double (pseudo) lamina occur following the
sclerotome stage, after sclerotomal mesenchymal cells migrate dorsally from the ventral portion of the somite to surround the neural tube, contributing to the formation of the pedicles, laminae, and spinous process of the neural arch, while lateral
sclerotomes contribute to the formation of the transverse processes.
The developing somite then forms the dermomyotome, myotome, and
sclerotome. The cells in the dermomyotome express the paired box transcription factors Pax3 and Pax7 [4-7].
In 1979, Murray and McCredie [14] suggested that an early embryonic abnormality of a spinal sensory nerve affecting a single
sclerotome resulted in bony overgrowth.
Each vertebra embryologically formed from combination of caudal half of one
sclerotome and the cranial half of succeeding
sclerotome regulated by HOX genes.
When Shh is synthesized by the notochordal cells, it not only controls cell fate of neurons in the neural tube, ventral location so that they can be identified as motor neurons, but also participates in determining the
sclerotome and pattern formation of somites (Bumcrot & McMahon, 1995; Munsterberg & Lassar, 2005; Lassar & Munsterberg, 1996).
Vertebral body formation occurs during the fourth week of embryonic development as mesenchymal
sclerotome cells migrate to surround the notochord.
Then a closed incision was made 3.5 mm from the corneal limbus by a
sclerotome which was connected with an infusion tube at the 7-o'clock position.
The characteristic feature of the condition is that the anatomical location of the abnormality corresponds closely with the zone of innervation by the
sclerotome.1 Involvement of the 2nd and 3rd digits of the hands and feet is common, corresponding to the median and the medial plantar nerve supply in the upper and lower limbs respectively; but 5th digit involvement is rare.
As the somites mature later in development, their ventral-medial cells (the
sclerotome) undergo EMT, lose their epithelial contacts, and revert to a mesenchymal state.
The basal support for the hindbrain is provided by parachordals that are formed from the
sclerotome portion of anterior somites.