Controlled Cortical Impact Traumatic Brain Injury

The controlled cortical impact (CCI) TBI model was performed, as previously described by our group (Vigil et al., 2019). The CCI model causes a blunt TBI, with the skull remaining intact with minimal hematoma that normalizes 7 days postinjury (Hunt et al., 2009; Ren et al., 2013). This type of brain injury model most closely simulates the TBI experienced during blunt-head injuries from vehicular accidents or falls. Mice were anesthetized with isoflurane (3% induction, 1% maintenance) in 100% O₂. Body temperature of 37°C was maintained using a temperature-controlled heated surgical table. The skull was fixed with ear bars into a stereotaxic frame. A small midline incision was made on the scalp using aseptic surgical techniques. Impact was delivered by a cylindrical probe of 5 mm diameter with an Impact One neurotrauma impactor (Leica Biosystems, IL, Buffalo Grove). A calibrated impact was delivered at 4.5 m/s to a depth of 1 mm and 0.5 s dwell time to the right parietal cortex [+1.8 mm medial–lateral (ML), −2.0 mm anterior–posterior (AP), and −1.0 mm dorsal–ventral (DV)]. Apnea episodes lasted between 10 and 60 s after impact. The scalp was then sutured closed, and mice were placed in a warming recirculation unit and monitored until fully awake and moving freely. Control littermate mice received anesthesia and sham surgery but did not receive impact. For consistency, the left hemisphere of both sham and TBI mice is designated as “contralateral” brain, and the right hemisphere is referred to as “ipsilateral,” despite no impact injury occurring in sham mice.