miR-21 exerts neuroprotective effects in models of cerebral ischemia, subarachnoid hemorrhage (SAH), and traumatic brain injury (TBI), primarily by targeting p53, PTEN, or Rab11a and modulating the PI3K/AKT and Bcl-2/Bax pathways, thereby suppressing neuronal apoptosis and oxidative stress [19,48,49]. The gene discussed is AKT1; the disease is subarachnoid hemorrhage.