The purpose of this study is to assess the ability of the Fluids Monitor to detect hemispheric bioimpedance asymmetry associated with acute brain pathology in patients presenting with suspected Acute Ischemic Stroke (AIS).

A prospective non-significant-risk (NSR) multi-site observational study. This study will examine up to 318 subjects undergoing evaluation for acute brain pathology who directly arrive at, or are transferred to, the participating sites.

Inclusion Criteria:

1. Must be at least 18 years of age.
2. Being evaluated for acute ischemic stroke.
3. Able to safely wear the study device for up to 2 minutes per reading.
4. Have NIHSS performed before before study device monitoring.
5. Must be able to provide written Informed Consent (either self or via an LAR) at any point during the hospital stay, or if unable to provide such consent, must have permission granted by the governing IRB to enroll in the study (i.e., waiver of consent).

Exclusion Criteria:

1. Known or suspected traumatic brain injury, either closed or penetrating.
2. Contraindication to neuroimaging, such as a contrast allergy, or other condition that prohibits CT, MRI, and/or angiography.
3. Presence of any implanted electro-stimulating devices in the head and neck.
4. Presence of any large metallic craniofacial implants, such as bone fixation plates, mesh, et cetera. (Note that small metallic objects, such an aneurysm coils, are acceptable.)
5. Presence of an intracranial pressure monitor or any other similar sensor that may compromise the placement of the investigational device.
6. Under arrest or otherwise in custody.
7. Inability to wear the investigational device (skin lesions on scalp, previous intracranial surgeries, etc.).
8. Pregnant or nursing.
9. Any other condition, which in the judgment of the PI would prevent the patient from completing the study or tolerating monitoring sessions and brain imaging, such as mental illness, severe agitation, or hemodynamic instability.

Males and females, aged 18 years or older, who are undergoing evaluation for acute ischemic stroke