What further test could be considered to try and differentiate between the two entities suggested by the MRI?
A CT myelogram may be useful.
At the T6 level, there is prominence of the dorsal arachnoid space 6 mm in AP diameter, with pulsation artefact. There is associated deformity of the cord, which is displaced ventrally. The cord is thinned to an AP diameter of 3 mm at this level (normal cord measures 5 mm in AP diameter above this level).
Below the lesion, there is T2 hyperintensity of the cord measuring 7 cm in length, extending to the T8-9 level. No post contrast enhancement to suggest tumour.
Conclusion:
T6 cord deformity with ventral displacement of the cord. Differential includes a dorsal arachnoid web or ventral cord herniation. This is associated with T2 hyperintensity of the cord inferior to this. No evidence of a spinal cord tumour.