Dynamics of Motor Network Overactivation After Striatocapsular Stroke. A Longitudinal PET Study Using a Fixed-Performance Paradigm

Abstract

Background and Purpose—Although excessive brain activation during affected hand motion after stroke is well documented, its time course has been rarely studied, and when studied, this has either been with passive movement or with active but cognitively complex task and uncontrolled performance over time, complicating interpretation.

Methods—According to a prospective and longitudinal design, we studied 5 right-handed patients with right-sided hemiparesis due to first-ever left striatocapsular infarction. Three-dimensional PET H2O15 studies were performed twice ( 7 and 31 weeks after stroke [PET1 and PET2, respectively]) during right thumb-to-index tapping executed at the same rate in both studies (1.26 Hz, auditory cued). With SPM96 software, significant group and individual overactivations (P 0.05, corrected for multiple comparisons) were computed by comparison with a group of 7 healthy age-matched right-handed control subjects performing the same task.

Results—Motor recovery was significant from PET1 to PET2. Both the group and individual analyses revealed striking overactivations at PET1, affecting notably the cortical hand area and the whole motor network bilaterally. These overactivations were less prominent at PET2 over both hemispheres, not only in terms of Z score but also in terms of spatial extent (almost reaching statistical significance in the affected hemisphere for the latter, P 0.09). However, new overactivations were found at PET2 in the left prefrontal areas, the putamen, and the premotor cortex.

Conclusions—This study is the first to document that to perform the same simple movement of the paretic fingers, the brain with subcortical infarction shows less overactivations at the late than at the early timepoint, especially on the affected side, suggesting reduced recruitment of affected-hemisphere motor networks. However, unaffected-hemisphere prefrontal, premotor, and putaminal overactivations, observed at PET2 only, may suggest late-appearing compensatory reorganization.