What is the most likely diagnosis?
Nerve sheath tumour (most likely a schwannoma).
A vividly enhancing dumbbell shaped mass extends through the C5/6 neural exit foramen along the C6 nerve root on the left. It is hyperintense on T2 weighted imaging and isointense to cord on T1. The cord is compressed and displaced to the right by the mass.
The bony margins of the foramen are remodelled and expanded.