Neural substrates of the oculomotor vergence network for concussion-related convergence insufficiency within the CONCUSS study

Concussion-related convergence insufficiency (CONC-CI) participants were compared to binocularly normal controls (BNC) using an fMRI stimulus-induced vergence oculomotor task to assess group-level differences in neural substrates. The hypothesis tested was whether the CONC-CI and BNC groups would show significant differences in the vergence oculomotor neural substrates, providing comparative data for the CONCUSS randomized clinical trial or future therapeutic longitudinal studies. A pediatrician diagnosed concussions, and an optometrist diagnosed convergence insufficiency. The CONC-CI group experienced their last concussion between one and six months since the last injury and had persisting post-concussion symptoms. A total of 46 BNC and 59 CONC-CI participants underwent a sensory-motor vision exam and had datasets from the fMRI experiment that passed a priori criteria for motion artifacts. The BNC group exhibited activation within the parietal eye field (PEF), supplemental eye field (SEF), frontal eye field (FEF), visual cortex, and cerebellum. Activation in these regions was present but significantly reduced in the PEF, cerebellum, and visual cortex for the CONC-CI group compared to BNC (FWE p ' 0.05). The CONC-CI group had greater activation in the precuneus than the BNC group (FWE p ' 0.05). Significant differences in the correlation between the near point of convergence and the convergence insufficiency symptom survey (CISS) with the functional activity of the PEF and the PFt region of the inferior parietal cortex were observed across groups (BNC versus CONC-CI) (p ' 0.001). Together, these findings demonstrate how functional activity is affected by CONC-CI, particularly in individuals with persisting post-concussion symptoms. Future therapeutic intervention studies are discussed.