The notochord represents the earliest fetal axial skeleton, extending from the Rathke pouch to the coccyx. It is a primitive cell line from which the skull base and vertebral column develop. The notochord is cylindrical and is replaced by sclerotomes that produce cartilage, and subsequently bone. Remnants of the notochord usually remain near the midline and are entrapped in bone. Chordomas are a malignant tumor that can develop from the notochord remnants.
The nucleus pulposus of the intervertebral discs represent residual notochord.
Vestigial non-neoplastic notochordal remnants are seen in up to 2% of cadavers, usually in the midline. They are located:
- spheno-occipital synchondrosis
- sacrococcygeal regions
- smaller scattered foci in the spine (especially C2 and lumbar spine)
- benign notochordal cell tumor
- Thornwaldt cysts
- ecchordosis physaliphora
- large craniopharyngeal canal
- Inferior median clival canal