‘Snake eyes’ appearance within the spinal cord

Q.---All are true regarding degenerative changes of spine except

a.  The commonest site of protrusion is located  posterioriorly

b. type 1 reactive changes yield high signal on T1W and high on

 T2W

c. Ossification of OPLL involves the mid- and lower cervical region in over 90 % cases

d. Retro-odontal pseudotumour  refers to thickened transverse

 ligament of the atlas and associated ligaments

e. ‘snake eyes’ appearance within the spinal cord  on axial images

 is seen in   cervical spondylotic myelopathy

ANS.---b

Modic described three types of reactive changes in the cancellous bone adjacent to the vertebral end-plates: (type 1) in the acute stage of disc disease there is invasion of the cancellous spaces by fibrovascular reactive tissue; in time this leads to (type 2) fatty replacement of red marrow; eventually this leads to (type 3) bony sclerosis. These changes are exquisitely shown by MRI: (A) type 1 changes yield low signal on T1W and high on T2W; (B) type 2 changes yield high signal on T1W and T2W (unless fat suppressed, when they will yield low signal); (C) type 3 changes yield low signal on all sequences.