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Stroke accounts for 1 out of every 19 deaths in the United States, and it is the fifth leading cause of death [1]. The concept of “time is brain” has become increasingly prevalent given the availability of stroke treatment options, as well as the emphasis on public education for the awareness of stroke symptoms and the need for timely evaluation. Rapid assessment and intervention allow for the possibility of a return to baseline neurologic function. EMS plays a critical role. Patient transfer to an appropriate receiving center, as well as early notification to it, serve to activate a health care system and facilitate time‐critical interventions. The value of EMS participation in public education regarding stroke awareness cannot be overstated, as early detection of symptoms is paramount to achieving the best possible outcomes.

In general terms, strokes are classified as either ischemic or hemorrhagic, but it is difficult to differentiate between these two subtypes in the prehospital setting. Radiographic imaging is required. Approximately 87% of strokes are ischemic, and 13% are hemorrhagic (10% are intracerebral hemorrhage [ICH] and 3% are subarachnoid hemorrhage). Approximately 610,000 strokes per year are believed to be first episodes, and approximately 185,000 are recurrent.

An ischemic stroke is caused by either in situ thrombus formation from atherosclerosis or an embolic event (usually from the heart or large vessels) that leads to the occlusion of a cerebral blood vessel and subsequent interruption of blood flow and oxygen supply to an area of the brain. For example, one of the contributing causes of embolic strokes is atrial fibrillation, which may lead to embolization of a clot from the heart. Hypertension is a significant risk factor for stroke, with studies showing evidence that blood pressure control to <150/90 mmHg reduces the incidence of stroke and moderate evidence that control to <140/85 mmHg is associated with a more significant decrease in incidence. Diabetes mellitus is a risk factor for stroke in all ages, but most prominently in those less than 65 years old. It is also an independent risk factor for recurrent stroke. Atrial fibrillation is a significant risk factor for stroke, increasing the risk approximately fivefold. Studies regarding the risk of high cholesterol have shown inconsistent associations at best. Smoking is proven to increase the risk of stroke up to fourfold. Genetic components have also been shown to increase risk, as stroke is known to be a hereditable disease [1].

When occlusion of a cerebral vessel occurs, there is a central area or “core” of ischemia in that region of the brain. However, there can also be a surrounding area that has decreased blood supply with the potential to recover without permanent damage. This zone surrounding the central area of ischemia is referred to as the “ischemic penumbra.” Salvage potential for the ischemic penumbra depends on the severity and duration of ischemia. Restoring blood flow to this penumbra will serve to improve neurologic recovery and patient outcomes. In addition to the effects of lack of blood supply, several chemical responses occur on a cellular level and affect brain function. These include the release of excitatory amino acids, alterations in calcium release, and free radical formation. Inflammatory responses and alterations in chemical function also affect the penumbra and its ability to recover [2].

Spontaneous ICH may result from several underlying diseases. Risk factors include hypertension, arteriovenous malformations, brain masses, and current anticoagulation or antiplatelet medication use. Patients with ICH may have more dramatic presentations, accompanied by nausea and vomiting, headache, or a sudden decrease in level of consciousness. These are the result of the nature of the insult, where the hemorrhage acts to abruptly increase intracerebral pressure. Specific neurologic deficits will be dependent on the location and extent of the bleeding. Patients with ICH may deteriorate rapidly and require airway support as the hemorrhage expands. The mass effect of an expanding hematoma may also cause contralateral motor deficits, ECG abnormalities, and dysrhythmias.

When neurologic deficits consistent with a stroke occur, but then resolve spontaneously, this is referred to as a transient ischemic attack (TIA). A TIA, according to the National Institute of Neurological Disorders and Stroke (NINDS), is a focal neurologic deficit lasting only a few minutes [3]. TIAs had been previously defined as a neurologic deficit that resolved within 24 hours. In fact, most TIAs resolve within 60 minutes, and many do so within half an hour. Patients who experience a TIA have a 10% to 20% risk of stroke in the subsequent 90 days, and half will occur within the next 24 to 48 hours [4]. TIAs should be considered very serious events that require prompt diagnostic evaluations.

An estimated 7.2 million Americans over the age of 20 self‐report a personal history of stroke. Studies differ slightly, but the generally accepted prevalence of stroke is 2.7% for both males and females over the age of 18. There are racial and geographical disparities, with African‐Americans and residents of southeastern United States having the highest prevalence. An estimated 4.1% of non‐Hispanic blacks, 1.5% of Asian/Pacific Islanders, 2.3% of Hispanics, 5.2% of American Indian/Alaska Natives, and 4.7% of other races/multiracial people have a history of stroke. Geographically, 1.9% of Minnesota residents and 4.3% of Alabama residents have a history of stroke. These data offer further evidence for the existence of a “stroke belt” in the southeastern United States, which has experienced higher rates of stroke since 1940 [1].

Each year, an estimated 795,000 individuals experience new or recurrent strokes, with a stroke occurring every 40 seconds within the United States. The death rate has decreased significantly due to early identification and intervention. Non‐Hispanic black females and males have higher death rates for stroke. Females account for approximately 58% of all U.S. stroke deaths. Geographical disparities also exist concerning mortality, with a death rate approximately 30% higher in the “stroke belt” than in the rest of the nation [1].