Fig. 2.

Thalamic injury identified by structural MR1 and thalamic chronic inflammation by [¹⁸F]-FEPPA-PET in chronic post-trauma rats. (A-B) Structural MRI (multi-echo gradient echo, isotropic 160μm³) 5 months post-LFPI and typical location of the thalamic calcifications and iron (both hypointense here, open arrow in A; B shows magnified view). In the LFP1 model, the calcifications are known to form within VPM and VPL nuclei (approximately outlined in B) that project to the S1 barrel field. Thalamic injury leads to deafferentation of projection neurons. Despite the high spatial resolution of the MRI, the shape deformation of ipsilateral thalamus hinders the analysis of any specific nuclei. The damage in reticular nuclei (Rt, red dotted arc) along the lateral border of the thalami facing the capsula interna (ic) is thus difficult to assess. (C-D) A PET marker of reactive microglia (18kDa Translocator protein (TSPO) radiotracer [¹⁸F]-FEPPA) shows prominent, sustained inflammation in ipsilateral thalamus (black asterisk in C). This representative animal was scanned 1 month post-LFPI and shows only negligible TSPO expression in injured cortex (dashed oval in PET image; white asterisk depicts the primary contusion location in corresponding T2-wt image). Courtesy of R.Immonen unpublished, University of Eastern Finland.