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.

BACKGROUND: Patients admitted to the NSICU undergo rapid physiologic changes related to primary neurologic injury, secondary brain injury, sedation, mechanical ventilation, and evolving systemic illness. Cerebral autoregulation (CA) - the brain's intrinsic mechanism for maintaining stable perfusion across a range of systemic arterial pressures - is measurably impaired in aSAH, traumatic brain injury (TBI), intracerebral hemorrhage (ICH), and acute ischemic stroke. In aSAH, CA impairment during the 4-14 day post-rupture window is independently associated with delayed cerebral ischemia (DCI), the leading cause of preventable death and disability in survivors. Approximately 75% of aSAH patients require an external ventricular drain (EVD), which prevents standard ICP-based CA monitoring. B4C extensometry and NIRS-derived CA indices offer EVD-independent monitoring approaches whose feasibility and signal characteristics in aSAH have not been prospectively described.

DESIGN: Single-center prospective observational cohort study at the UT Southwestern NSICU. Eligible subjects may undergo B4C extensometry monitoring (the sole research-specific device under this protocol) and/or have research data recorded from existing standard-of-care clinical monitoring including SedLine qEEG, full-montage long-term monitoring EEG (where clinically ordered), NIRS, invasive ICP/CPP from EVD monitors, transcranial Doppler (TCD; standard of care for aSAH at UT Southwestern), and NeurOptics NPi automated pupillometry. The Moberg Clinical Platform (Moberg Analytics; FDA-cleared) serves as the primary data acquisition hub in the NSICU, aggregating synchronized high-resolution physiologic waveforms from existing bedside monitors without placing any additional research devices.

MONITORING MODALITIES:

Research device placed specifically for research purposes under this protocol:

- Brain4Care (B4C) extensometry: skull-mounted noninvasive sensor recording cranial compliance-related waveform morphology (P2/P1 ratio, Time to Peak), from which surrogate CA indices (nPRx, nCPPopt, nMx) are derived.

Standard-of-care clinical data recorded for research purposes (no additional devices placed):

• SedLine qEEG: clinically placed forehead sensor used for sedation monitoring as standard of care; provides Patient State Index, Spectral Edge Frequency, and raw EDF waveforms.
• Full-montage long-term monitoring EEG: from clinically ordered continuous EEG electrodes for seizure and ADR monitoring where applicable.
• NIRS (near-infrared spectroscopy): regional cerebral oxygenation; CA indices computed include cerebral oximetry index (COx) and total oxygenation reactivity index (TOxA).
• Clinical ICP/CPP waveform data from EVD transducer where present.
• TCD vasospasm surveillance (daily studies as standard of care for aSAH; peak and mean velocities, Lindegaard ratio).
• NeurOptics NPi pupillometry: NPi, constriction velocity, latency, amplitude.
• Moberg Clinical Platform: synchronized arterial blood pressure, ICP, ECG/HRV, SpO2, EtCO2, CVP, ventilator parameters, NIRS.

ASAH PRIORITY ENROLLMENT: For aSAH patients, the protocol prioritizes monitoring through ICU Day 14 to characterize the natural history of B4C-derived and NIRS-derived CA index evolution through the DCI window. An optional 90-day follow-up captures functional and neurological outcomes beyond hospital discharge.

DATA MANAGEMENT: Subjects are assigned unique study identifiers. Direct identifiers are removed from analytic datasets. De-identified data may be shared with qualified external collaborators under executed data use agreements and with applicable IRB approval. De-identified data from this study may be combined with data from the companion NSICU Autonomic Modulation Study for analyses within the approved scope of both protocols.

Inclusion Criteria:

• Age 18 years or older
• Admitted to the NSICU at UT Southwestern Medical Center
• Informed consent obtained from subject or legally authorized representative (as defined under Texas Health and Safety Code Section 166.039), or consent process underway per institutional policy
• At least one study monitoring modality feasible (SedLine qEEG and/or Brain4Care extensometry); NIRS data collected where already in standard clinical use

Exclusion Criteria:

• Age younger than 18 years
• Prisoner status
• Active declination of participation by subject or legally authorized representative
• Absence of both subject and legally authorized representative consent when required
• Clinical condition preventing safe placement of any study monitor (e.g., extensive facial or scalp injury, surgical dressings or hardware at all possible sensor sites, open wounds at sensor locations, severe uncontrolled agitation)
• Anticipated clinical data capture insufficient for meaningful analysis
• Urgent clinical priorities making research monitor placement inappropriate at time of approach
• Inability to provide informed consent in English; study consent materials are available in English only

Adult patients age 18 years or older admitted to the Neurosciences Intensive Care Unit (NSICU) at UT Southwestern Medical Center. The population is intentionally broad to support observational analyses across common neurocritical care diagnoses. aSAH patients are a priority enrollment group given the scientific objectives related to characterizing the natural history of noninvasive CA parameter evolution through the DCI window.