Table 1.

Proposed definitions of ND etiologies

Etiology of ND	Definition
Reversible
Infectious	When in the presence of a diagnosed infection (eg, of the urinary or respiratory tracts, cerebral ventricles or meninges, skin or soft tissue, blood vessels or heart valves)* with identified pathogen on microbiology or consolidation on chest imaging with clinical symptoms, in the case of pneumonia
Metabolic	When in the presence of a new clinically relevant derangement in laboratory value based on our laboratory standards (eg, uremia, hyper/hypocalcemia, hyper/hypoglycemia, hyper/hyponatremia, or hyperammonemia) during the 24-h window surrounding the documentation of ND
Hemodynamic	When in the presence of a significant rise or drop in blood pressure during the 24 h before documentation of ND as determined clinically, new-onset arrhythmia as determined via electrocardiography or telemetry, or cardiovascular event (including myocardial infarction) as determined via electrocardiographic, telemetric, and/or laboratory methods (for instance, elevated serum troponin I level†) that may have impaired cerebral perfusion but did not cause a new imaging-confirmed stroke
Edema	When focal cerebral or cerebellar mass effect was identified on follow-up computed tomographic or magnetic resonance imaging in the 24-h window surrounding the date of ND
Fluctuation	When the patient returned to prior (day before ND) NIHSS score on the day after the episode of ND in the absence of other identified causes of ND
Sedation	When the patient was given any medication with sedative effects, as determined by the attending physician’s clinical experience, in the 24 h before documentation of ND and when no other cause of ND was identified
Seizure	When in the presence of electroencephalogram-confirmed epileptiform activity or periodic rhythm or clinical observation of seizure-like activity during the 24-h window surrounding the documentation of ND
Nonreversible
New stroke	New ischemic findings on CT or MRI (detected within the 24-h window surrounding the documentation of ND) outside the distribution of the initial vessel occlusion after new deficits on physical examination
Progressive stroke	When extension of ischemic findings were detected on computed tomographic or magnetic resonance imaging by the attending physician or staff radiologist within the distribution of the initial vessel occlusion (during the 24-h window surrounding the documentation of ND)
Intracerebral hemorrhage	When new or progressive hemorrhage of PH1 or PH2 grade was identified on 24-h follow-up imaging study
Cardiopulmonary arrest	When documented by progress notes as having occurred within the 24-h window surrounding the documentation of ND
Unknown etiology	When no etiology of ND was determined by the attending physician, and none of the above findings were documented in the progress notes

Abbreviations: CT, computed tomography; MRI, magnetic resonance imaging; ND, neurologic deterioration; NIHSS, National Institutes of Health Stroke Scale.

^*Bacteremia was defined as the growth of a bacterium on a culture from a venous blood sample (excluding common contaminants). Urinary tract infection was defined as > 10,000 colony-forming units per millimeter of urine in a clean-catch specimen (excluding contaminants) or suggestive findings on urinalysis. Pneumonia was defined as an infiltrate on chest radiography with appropriate clinical correlates. Other infection types (eg, cellulitis, pseudomembranous colitis, meningitis, ventriculitis) were diagnosed clinically or via laboratory/imaging findings. Clinical symptoms producing ND may have occurred hours or days before the diagnosis of ND because of infection, depending on the manner in which the infection was diagnosed. For example, pneumonia diagnosed via chest radiography in the presence of clinical symptoms may only take 1 h for the imaging order to be processed, performed, and interpreted, whereas confirmation of bacterial specimen in blood culture may have taken up to 5 days according to our laboratory standards.

^†Elevated serum troponin I is defined as troponin I level > .015 mg/dL, according to our laboratory standards.