When is bone marrow too dark, and no longer merely represents red-marrow?
The abnormal signal is due to replacement of the small amounts of fat cells normally found in red marrow, such that T1 signal will decrease to or bellow that of signal from disc or muscle. T2 signal is more variable, but will in general increase when compared to muscle.
The majority of the cord, particularly in the cervical region, is significantly expanded and of increased T2 signal. Following administration of contrast, it demonstrates heterogeneous and diffuse enhancement.
Best seen on axial T2 images is marked cervical lymph node enlargement. The bone marrow is diffusely abnormally low in signal on T1 weighted images.