What is the meaning of “subcortical retraction” in a description of MRI of a Kearns-Sayre syndrome patient?

Question

I came across the term subcortical retraction and cannot understand its meaning. Does it mean "the withering of the subcortical areas" (shrinking of subcortical white matter)?

From Follow-up of folinic acid supplementation for patients with cerebral folate deficiency and Kearns-Sayre syndrome:

Case 2. Multi Vane T2-Weighted TSE (T2W-MV) disclosed hyperintensity in dorsal brain stem (A), globus pallidus atrophy (B), subcortical retraction and white matter hyperintensity (C).