Microscopic studies in newborns and animal models indicate impaired myelination after premature birth, particularly for cortical myelination; however, it remains unclear whether such myelination impairments last into adulthood and – if so – are relevant for impaired cognitive performance. It has been suggested that the ratio of T1w and T2w MRI signal intensity (T1w/T2w ratio) is a proxy for myelin content. We hypothesized altered grey matter (GM) T1w/T2w ratio in premature-born adults, which is associated with lower cognitive performance after premature birth.
Methods
We analyzed GM T1w/T2w ratio in 101 very premature-born adults (<32 weeks of gestation and/or birthweight <1500g, VP/VLBW) and 109 full-term controls at 26 years of age, controlled for voxel-wise volume alterations. Cognitive performance was assessed by verbal, performance, and full-scale intelligence quotient (IQ) using the Wechsler Adult Intelligence Scale.
Results
Significantly higher T1w/T2w ratio in VP/VLBW subjects was found bilaterally in widespread cortical areas, particularly in frontal, parietal and temporal cortices, and in putamen and pallidum. In these areas, T1w/T2w ratio was not related to birth variables such as gestational age, or IQ scores. In contrast, significantly lower T1w/T2w ratio in VP/VLBW subjects was found in bilateral clusters in superior temporal gyrus which was associated with birth weight in the VP/VLBW group. Furthermore, lower T1w/T2w ratio in left superior temporal gyrus was associated with lower full-scale and verbal IQ.
Conclusions
Results demonstrate GM T1w/T2w ratio alterations in premature-born adults and suggest altered GM myelination development after premature birth with lasting and functionally relevant effects into early adulthood.
Schmitz-Koep, B., Menegaux, A., Gaser, C., Brandes, E., Schinz, D., Thalhammer, M., Daamen, M., Boecker, H., Zimmer, C., Priller, J., Wolke, D., Bartmann, P., Sorg, C., & Hedderich, D. M. (2022 online journal pre-proof). Altered grey matter cortical and subcortical T1-weighted/T2-weighted ratio in premature-born adults. Biol Psychiatry Cogn Neurosci Neuroimaging. https://doi.org/10.1016/j.bpsc.2022.02.013