Abnormal axial diffusivity in the deep gray nuclei and dorsal brain stem in infantile spasm treated with vigabatrin.

We evaluated the DTI changes in the deep gray nuclei and dorsal brain stem, which demonstrated abnormal T2 and/or diffusion signal intensity, in 6 patients with infantile spasm treated with vigabatrin compared with 6 age-matched controls. Regions of interest were placed in the globi pallidi, thalami, and dorsal brain stem; FA, trace, D(‖), and D(⊥) were measured. Patients on vigabatrin had significantly lower FA in both globi pallidi (P = .01) and the dorsal brain stem (P < .01), significantly lower trace in both globi pallidi (P = .01) and the thalami (P = .02 and .01 for right and left, respectively), and significantly lower D(‖) in both globi pallidi (P ≤ .01), the thalami (P < .01), and the dorsal brain stem (P = .03). There were no significant differences in D(⊥) of the globi pallidi, thalami, or dorsal brain stem in patients compared with controls. The findings suggest that axonal changes play a greater role in the observed abnormal signal intensity, with lesser contribution from myelin changes.