This is a prospective observational cohort study of adult patients admitted to the Neurosciences Intensive Care Unit (NSICU) at UT Southwestern Medical Center. The study acquires multimodal neuromonitoring data - including SedLine quantitative EEG (qEEG) from standard-of-care monitoring, Brain4Care (B4C) noninvasive intracranial dynamics monitoring, and near-infrared spectroscopy (NIRS)-derived cerebral autoregulation (CA) indices where NIRS is already in clinical use - and links these data to bedside physiologic, medication, diagnostic, and clinical outcome variables during standard care. No alteration of clinical management occurs. The study prioritizes aneurysmal subarachnoid hemorrhage (aSAH) patients to characterize the natural history of noninvasive CA parameter evolution through the delayed cerebral ischemia (DCI) window (admission through Day 14) and provides preliminary data for subsequent interventional study design.