What other finding confirms that the larger part is made of fatty material on T2 weighted sagittal image?
Chemical shift artifact (black line anterior and white line posterior to the mass).
Explain chemical shift artifact.
Chemical shift is due to the differences between resonance frequencies between fat and water. It occurs in the frequency encoding direction where a shift in the detected anatomy occurs because fat resonates at a slightly lower frequency than water. It results in a bright line on one side and a black line on the other side of a fatty mass (see annotated images which follow).
What two main components to this mass can you identify?
A fatty component (which saturates on fat attenuated sequences) and a central solid enhancing component.
What is the differential?
One should consider a spinal lipoma, although they should not have a solid component. A mature spinal teratoma could appear very similar, but they are rarely diagnosed in patients older than two years of age.
An intradural extramedullary mass having mixed fat and solid enhancing components, displacing and compressing the cord anteriorly.