MR imaging of the sellar spine.

Magnetic resonance images of two cases of sellar spine are reported. The sellar spine is an anatomical variant characterized by an osseous spine that arises in the midline from the dorsum sellae and protrudes into the pituitary fossa. On short repetition time/short echo time (T1-weighted) images the sellar spine is demonstrated as a hypointense structure within the high intensity posterior pituitary. We suggest that the sellar spine is the ossified remnant of the cephalic tip of the notochord.