Stroke: Emergency Department Evaluation

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By Michael Jay Katz, MD, PhD

LEARNING OBJECTIVES

Upon completion of this course, you will be able to:

• Discuss the basic responsibilities of a stroke center
• List the steps for evaluating a potential acute stroke
• Review the neurological examinations and imaging techniques used to diagnose strokes

Each year, almost 800,000 Americans suffer a stroke. This means that, on average, one American suffers a stroke every 40 seconds. There are about 140,000 stroke deaths each year, and stroke is listed as a contributor to an additional 100,000 deaths. Thus, stroke is the third leading cause of death in this country, after heart disease and cancer (CDC, 2010a, b).

Strokes produce the sudden loss of brain abilities. Many things can be done to reverse or to temper the effects of a stroke, but successful therapy depends on quick medical attention. Therefore, stroke victims need to be taken immediately to an emergency department (ED) that has the personnel and equipment to provide comprehensive acute stroke treatment.

STROKE CENTERS

Acute strokes are best treated in an accredited stroke center, which by definition has well-rehearsed protocols for dealing efficiently with a range of stroke patients.

Stroke treatment protocols require medical care providers who have specialized knowledge, appropriate tools, and practical experience. The necessary facilities, equipment, and personnel are expensive and are not available at most community hospitals. It is not economical for every emergency department to be a high-tech stroke treatment center because stroke visits to EDs are relatively rare: 25% of ED visits are for injuries or poisonings and 4% are for chest pain, but only 0.6% of ED patients need stroke care (Merrill et al., 2008).

High-quality stroke management improves the health of a community, but the healthcare system cannot afford to outfit every hospital with full-service stroke care. Therefore, the public health goal has been to develop regional centers responsible for maintaining the complement of people and technologies needed to treat acute strokes. These hospitals are called primary stroke centers (Gerber, 2003; Goldstein, 2007a, b).

Primary Stroke Centers

To facilitate the development of a core of high-quality primary stroke centers throughout the United States, the Joint Commission (the U.S. national accrediting organization for hospitals and other health delivery organizations) has developed a program to certify particular EDs as designated Primary Stroke Centers. As of October 2009, there were more than 600 certified primary stroke centers in 49 states. The eventual goal is to have a specialized stroke center within 100 miles of all cities across the nation (Adams et al., 2007).

To be certified as a primary stroke center, an emergency department (or its hospital) must meet these criteria:

• Ability to deliver basic acute stroke care
• A CT scanner available for emergency use, with experienced neuroradiologists on-call
• A stroke team with neurologists or specially trained emergency physicians and neurology nurses
• Equipment and staffing to treat ischemic stroke patients quickly with intravenous thrombolytic drugs
• Medical units that can care for uncomplicated stroke patients
• A neurosurgical team, endovascular surgeons, and a neurosurgical ICU in the hospital or within secondary transport range (JCAHO, 2010)

A primary stroke center must have written protocols for the diagnosis and treatment of a full range of strokes, and the protocols must be compatible with the most current American Heart Association/American Stroke Association recommendations. In addition, a primary stroke center must keep standardized records of its patients, their treatments, and the outcomes; these records are used to monitor the performance of the center (JCAHO, 2008, 2010).

Healthcare directors and hospital administrators who would like to transform their hospitals into primary stroke centers can begin with the detailed practical guide Building the Case for a Primary Stroke Center: A Resource Guide, available from the National Stroke Association’s website.

Comprehensive Stroke Centers

A primary stroke center has the ability to efficiently diagnose and categorize strokes and to quickly administer certain acute therapies, most notably intravenous rtPA. Ischemic strokes with major complications and hemorrhagic strokes can require an even higher level of care, needing dedicated neurological ICUs and experienced neurosurgeons, endovascular surgeons, and neuroradiologists. Hospitals with these advanced stroke facilities are called comprehensive stroke centers (Smith, 2007; White et al., 2007).

More hospitals have the staff and facilities to become primary stroke centers than to become comprehensive stroke centers. It is estimated that there are currently at least 200 comprehensive stroke center hospitals in the United States, but there is still no national accreditation plan for these centers. Experts hope that, throughout the country, primary stroke centers in a region will eventually become satellites of a centrally located comprehensive stroke center. In such regions, EMS teams would transport acute stroke patients to the nearest primary stroke center, where eligible patients could be quickly treated with rtPA. Patients with complex strokes, hemorrhagic strokes, and complications from rtPA treatments would be rapidly transferred to the affiliated comprehensive stroke center.

Stroke Center Timetables

Stroke centers are dedicated to quick, efficient care. The recommended time targets for key steps in the management of acute stroke are as follows:

Time Taken for Key Stroke Management Steps

• From the door to a physician, 10 minutes
• From the door to a completed CT, 25 minutes
• From the door to the reading of the CT scan by a specialist, 45 minutes
• From the door to thrombolytic treatment, 60 minutes
• From the door to admission to a monitored bed, 3 hours
  (Adams et al., 2007; Jauch et al., 2007)

Specialists must also be easily accessible in a primary stroke center, with a neurologist available within 15 minutes and a neurosurgeon (possibly at another hospital) within 2 hours.

Nurses’ Leadership Roles in Stroke Centers

Just as in the general accreditation process for hospitals, nurses are central players in getting a stroke center certified. The head nurse in a hospital’s stroke team is the key organizational figure. The head nurse ensures that there is a written protocol for guiding stroke victims through the steps leading to a treatment decision. The head nurse is also responsible for organizing and training a team of nurses and technicians who understand strokes and who are sufficiently experienced to keep the stroke protocol moving while watching over the patient’s often-fragile health.

The American Stroke Association (ASA, 2010) offers plans and detailed materials that nurses can use to help organize a primary stroke center, build a competent stroke team, and regularly assess and improve the center’s stroke care. These materials include the outlines of a quality improvement program, which has always been one of nursing’s important contributions to hospitals and clinics. In addition, the stroke team nurses are usually the most available sources of medical and care information for patients. To help nurses in this role, the ASA (2009) provides downloadable material for patients about stroke prevention, stroke recovery, and stroke support groups (Summers et al., 2009).

TRIAGE

Emergency department care begins with triage. The EMS team will have identified any potential stroke victims that it is bringing, but approximately 1/2 of all stroke patients will not use an EMS service for transportation to the ED. For this reason, all EDs need to have protocols in place for:

• Quickly assessing patients for possible stroke
• Determining the type and severity of the stroke
• Treating it quickly, or
• Having the patient immediately transported to the nearest stroke treatment center

Identification of Potential Stroke Victims

Stroke victims are not common ED clients. The front desk nurse should have a written stroke-recognition checklist at the front desk. This will ensure that any triage nurse can quickly channel potential stroke victims into the ED’s stroke protocol.

Assign Potential Stroke Victims a High Priority

Time-to-treatment is critical. Therefore, patients with suspected acute stroke are assigned the same high priority as patients with acute myocardial infarction or serious trauma, regardless of the severity of the neurological deficits.

The Emergency Nurses Association and the American College of Emergency Physicians recommend a 5-level Emergency Severity Index as a preferred system for triage in a busy ED. This index puts all stroke patients in the level 2 or “needs immediate assessment” category, the same as for an unstable trauma patient or a critical-care cardiac patient (Summers et al., 2009).

For patients with acute onset of neurological signs, triage nurses fill out:

1. A stroke recognition checklist
2. A time sheet documenting:
   • Time of onset of symptoms or last time when the patient was symptom-free
   • Time of the patient’s arrival at the ED
   • Time goal for the initial doctor’s assessment (e.g., 10 minutes after the patient’s arrival at the ED)
   • Time goal for a completed CT scan (e.g., 25 minutes after the patient’s arrival)
   • Time windows for the rtPA treatment of eligible patients
   • ED goal (e.g., within 1 hour of the patient’s arrival)
   • 3-hour time window after onset of symptoms
   • 4.5-hour time window after onset of symptoms
   • 6-hour time window after onset of symptoms
   • Time goal for admission to a monitored bed (e.g., 3 hours after arrival)
     (Summers et al., 2009)

The time sheet then follows the patient to keep doctors, nurses, and technicians on schedule.

Mobilize the Stroke Team and Begin Stroke Protocol

When a potential stroke patient has been identified, a stroke page is initiated from the incoming EMS vehicle or from the ED triage nurse. The stroke code team then reports to the ED, joins the ED receiving team, and begins the acute stroke protocol once the patient is medically stable.

The first parts of the stroke protocol include drawing blood and taking a medical history; these can be done immediately by the nurses, who should have standing orders. Next, the patient needs a selected physical examination and a complete neurological examination with a formal stroke assessment—the NIH Stroke Scale and, for patients with a reduced level of consciousness, a Glasgow Coma Scale Score. (In this time-limited evaluation stage, a chest x-ray is warranted only when needed for immediate decisions about heart or lung problems.) Finally, stroke patients need head imaging.

For speed and efficiency, the ED nurses should have standing written orders for as many steps in the acute stroke protocol as possible. These orders can be enacted while the code stroke team is reporting to the ED (Lutsep & Clark, 2007).

MEDICAL STABILIZATION

As the stroke protocol proceeds, the basic nursing plan begins with stabilization and continuous monitoring of the patient:

Airway. Increased intracranial pressure can suppress the respiratory drive in a stroke victim, and intubation may be needed to ensure sufficient ventilation. Vomiting can be another consequence of increased intracranial pressure, and intubation can protect the lungs from aspiration.

Bed rest. Keep the neck straight and the airway patent. Head position is decided on an individual basis. In general, keeping the head flat will maximize blood flow to the brain. Elevating the head 25°–30° is suggested for:

• Suspected increased intracranial pressure
• Aspiration risk
• Airway obstruction risk
• Chronic respiratory problems
• Heart failure

Oxygen. For oxygen saturation <92%, give nasal cannula O₂ at 2–3 L/min

Vital Signs and Neurological Check. Every 30 minutes in the ED

Cardiac Monitoring. Continuous

Fluids.

• Record intake and output
• I.V. should be normal saline at 75–100 ml/h
• NPO until the dysphagia risk has been assessed

Call doctor if:

• BP: Systolic >220 mm Hg or <110 mm Hg, Diastolic >120 mm Hg or <60 mm Hg
• Pulse >110 beats/min or <50 beats/min
• Temperature >37.6° C (99.6° F)
• Respiration >24 breaths/minute
• Worsening stroke signs or symptoms or any deterioration in neurologic status

IV access. Patients eligible for thrombolytic (rtPA) therapy will need 2 to 3 IV sites: one for IV fluids, one for IV medications, and one for rtPA administration. (Oliveira-Filho & Koroshetz, 2009c; Summers et al., 2009.)

STROKE WORK-UP

Draw Rapid Blood Work

For all potential stroke patients a comprehensive metabolic panel, a CBC, coagulation studies, and urinalysis are appropriate. Oximeter readings of blood oxygen saturation can be taken immediately, and a finger stick for blood glucose level will rule out hypoglycemia.

For blood work of a potential stroke victim, the minimum stat tests are listed in the box below. For certain patients, hepatic function tests, a lipid profile, a toxicology screening, a blood alcohol level, or a pregnancy test will also be appropriate. In addition, in the case of an intracerebral hemorrhage, blood typing and cross matching should be done if fresh frozen plasma may be needed to reverse a coagulopathy. The ED’s stroke protocol should explain how to determine if any of these extra tests are necessary.

To get lab results quickly, blood should be drawn early in the evaluation, before sending the patient for imaging. For speed and efficiency, ED nurses should have standing written orders for the blood work for patients who fit the ED stroke profile (Lutsep & Clark, 2007).

The two most essential lab tests for acute stroke victims are blood sugar levels and coagulation studies because:

• Hypoglycemia can mimic a stroke by causing focal neurological deficits, while persistent hyperglycemia will worsen stroke damage. Either extreme needs treatment.
• Before using a thrombolytic agent (i.e., rtPA) to treat an ischemic stroke, the likelihood of inducing hemorrhaging must be assessed with, minimally, a platelet count and a prothrombin time or INR.

The importance of other tests depends on the situation. Young or middle-aged patients may need drug screening tests. Women of childbearing age must be given pregnancy tests. Not yet knowing the results of any other lab values should not delay treatment with rtPA (Adams et al., 2007; Crocco et al., 2009). Lumbar punctures are not usually needed (see below).

The Medical History

While blood is being drawn, the patient needs a focused history and physical exam. ED nurses can take the lead in getting a useful history from the patient, relatives, and any witnesses (Summers et al., 2009). The key information that is needed includes:

Symptoms

• List of neurological problems
• Other concurrent symptoms
• Time of appearance of each problem (See “Pattern of Symptom Onset” below.)
• Changes in symptoms over time (See “Pattern of Symptom Onset” below.)
• Descriptions by anyone else who witnessed the appearance of the problems

Recent medical events

• List of recent illnesses
• List of recent injuries

Health problems, asking specifically about a history of stroke or TIA, diabetes, seizures, hypertension, cardiac problems, drug abuse/overdoses, and mental disorders.

Current medications, asking specifically about insulin, oral hypoglycemics, and anticoagulants (e.g., Coumadin/warfarin).

Physical Exam

The physical exam can be selective, but certain features deserve special attention (Chung et al., 2007; Jauch et al., 2007).

Vital signs.

• Monitor oxygen saturation (with pulse oximetry) continuously. If supplemental oxygenation is being given, be sure it is sufficient.
• Blood pressure is often elevated in a stroke. Systolic pressure of >220 mm Hg may indicate intracerebral hemorrhage. Blood pressure fluctuations may indicate cardiac problems.
• Stroke can decrease the respiratory drive or cause airway obstruction. Check the respiratory rate, because hypoventilation can cause cerebral vasodilation and increase intracranial pressure.
• Fever is worrisome—it can be caused by bleeding into the ventricles.

Head.

• Look for trauma, which may have caused the neurological symptoms.
• Severe headache often accompanies hemorrhagic strokes.
• Contusions or tongue lacerations may indicate a seizure.
• Retro-orbital bruits may indicate atherosclerosis or intracranial vascular lesions.
• Papilledema (i.e., a swollen optic disc) indicates increased intracranial pressure.

Neck.

• Carotid bruits may signal atherosclerotic disease.
• Jugular venous distension (JVD) may indicate heart failure.
• If there is suspicion of head trauma, immobilize the neck until it is evaluated radiologically.

Heart.

• 12-lead ECG recordings should be recorded and evaluated.
• Atrial fibrillation can be a cause of stroke.
• Myocardial infarction can precipitate a stroke.
• Murmurs may indicate a cardiogenic cause for stroke.

GI. Vomiting is common in hemorrhagic strokes but rare in ischemic strokes.

Skin. Jaundice, ecchymoses, purpura, or petechiae may be signs of coagulation problems.

Limbs. Asymmetric or diminished peripheral pulses can be signs of atherosclerotic artery disease or aortic dissection.

Neurological Exam

A complete neurological exam is vital. The checklist below can be used as a template for identifying specific neural deficits.

NEUROLOGICAL ASSESSMENT TOOLS

In addition to a complete neurological exam, the American Heart Association/American Stroke Association guidelines (Adams et al., 2007) recommend all potential stroke victims be assessed using the NIH Stroke Scale. This is a measure of the severity of neurological deficits and can be used to objectively monitor the improvement or deterioration of the stroke.

NIH Stroke Scale (NIHSS)

Standardized stroke assessment tools do not replace a neurological exam. Instead, the stroke scale is an efficient way to objectively determine the extent of neurological damage. The initial stroke score is an aid when choosing between available treatments, while subsequent scores can be used to quantify the amount of neurologic change.

The NIHSS rates thirteen neurological characteristics of a patient (Scott &; Timmerman, 2004):

1. Level of consciousness
2. Orientation
3. Ability to respond to commands
4. Range of gaze
5. Fullness (completeness) of visual fields
6. Symmetry of facial movements
7. Motor function of each arm
8. Motor function of each leg
9. Presence of ataxia
10. Presence of sensory loss
11. Presence of aphasia
12. Presence of dysarthria
13. Extinction or inattention to sensation

A sample scoring form with an explanation can be downloaded from NINDS (2003).

Testing takes 5–8 minutes and requires no special equipment. Learning to administer the test takes about 45 minutes and can be done online (for one free CME credit) at NINDS (n.d.).

In the NIHSS, points are assigned for neurological deficits, and the final scores range from 0 to 42, with higher scores indicating more severe deficits. The chances of a good recovery fall off dramatically in patients with scores greater than 10. A score >22 is labeled a major stroke.

MEANINGS OF NIHSS SCORES

Score	Meaning
Neurological deficit
<5	Mild impairment
10–20	Moderate impairment
>20	Severe impairment
Predicted outcome after a year
<10	60%-70% chance the outcome will be considered good to excellent
>20	4%-16% chance the outcome will be considered good to excellent
Predicted need for long-term nursing care
<6	Most patients will be discharged home
6-13	Most patients will need short-term hospital care
>13	Most patients will need long-term nursing care
Predicted location of occlusion (for ischemic strokes) ( Fischer et al., 2005)
>10	>96% chance a cerebral vessel is occluded and the occlusion will be identifiable with arteriography
>12	>91% chance the occluded vessel is the internal carotid, the basilar, or the middle cerebral artery

Glasgow Coma Scale (GCS)

For hemorrhagic strokes, another neurological assessment tool, the Glasgow Coma Scale, is an important guide for predicting outcomes (Smith & Grady, 2005; Bleck, 2007). Like the NIHSS, the GCS is not a diagnostic tool, and it does not replace the neurological exam.

The Glasgow Coma Scale has been a part of neurologic practice for 35 years and has proved to be an objective and reproducible way to describe a patient’s level of consciousness and arousal. Administering the scale takes 3–5 minutes and requires no special equipment. External stimuli are given to a patient, and the tester rates 3 neurological aspects of the patient’s response: eye opening, limb movement, and vocalization. A sample scoring form can be downloaded from the Internet Stroke Center (ISC, 1974).

On the Glasgow Coma Scale, points are given for higher levels of response and consciousness. Final scores can range from 3 to 15, with lower scores indicating more severe neurological deficiency. (This is opposite to the NIHSS, in which higher scores indicate more severe deficits.)

MEANINGS OF GCS SCORES

Score	Meaning
Clinical interpretations
>12	Minor brain injury
9–12	Moderate brain injury
3–8	Severe brain injury (coma)
<3	Vegetative state
Predictions
>11	>85% chance of recovery with no worse than moderate disability
<5	>85% chance of dying in first 24 hours

A comprehensive resource for stroke assessment scales can be found on the Internet Stroke Center website (ISC, 2010).

DIAGNOSE AND CATEGORIZE THE STROKE

As information accumulates, the stroke team builds evidence for the diagnosis of stroke or nonstroke. For likely strokes, the team will also be weighing the evidence for and against intracranial bleeding.

Consider Metabolic Versus Structural Causes

The evaluation of a patient with acute neurological dysfunction moves rapidly down a branching pathway toward a treatment plan. The appropriate treatment depends on the type of neurological injury, and an early branch point requires distinguishing between structural causes (e.g., ischemic stroke, hemorrhagic stroke, and brain parenchymal injury from head trauma) and metabolic causes (e.g., organ failure, drug overdose, and systemic hypoxia). Either class of insult—structural or metabolic—can reduce a patient’s level of consciousness and cause neurologic dysfunction.

As the stroke team learns details of the medical history and physical state of a patient, they formulate a hypothesis as to the class of insult.

• Structural causes are suggested by a history or a physical exam that indicates trauma. Structural causes are also suggested by distinct focal signs, such as asymmetric functioning of the pupils, hemiparesis (one-sided weakness), or hemiplegia (one-sided paralysis). The hypothesis that the patient’s stroke symptoms are caused by structural injury should be immediately followed up with CT or MRI head images.
• Metabolic causes are suggested by abnormalities in stat blood work (serum electrolytes, glucose level, renal and hepatic function indicators, complete blood count, and coagulation function tests) or in vital signs (including blood oxygen saturation). If these values do not point to a particular metabolic cause and if there is little evidence for structural causes, the metabolic testing continues with serum and urine toxicology screens and, possibly, a lumbar puncture. EEG can also be useful, because it can show the generalized slowing caused by metabolic encephalopathy or the presence of clinically unapparent seizures (Hemphill & Smith, 2008).

Rule Out Stroke Mimics

Other disorders can look like stroke; these should be considered in the differential diagnosis. Besides ischemic stroke, other causes of focal neurological defects include:

• Alcoholic intoxication
• Cerebral infections
• Drug overdose
• Epidural hematoma
• Hypoglycemia
• Metabolic disorders (e.g., hyponatremia)
• Migraines
• Neuropathies (e.g., Bell’s palsy)
• Seizure and post-seizure
• Tumors

Besides hemorrhagic stroke, other intracranial causes of severe headache and vomiting include:

• Hypertensive encephalopathy
• Migraine
• Subdural and epidural hematomas

Besides hemorrhagic stroke, other causes of impaired consciousness include:

• Alcoholic intoxication
• Cranial trauma
• Drug overdose
• Hepatic, renal, or pulmonary encephalopathies
• Hypo- or hyperglycemia
• Seizure and post-seizure
• Severe infections, especially cerebral infections
• Systemic hypotension

It is also important to remember that acute systemic illnesses can unmask or reactivate focal neurological deficits from a previous stroke. In some patients with previous stroke damage, the onset of a new nonstroke illness can make it appear as if the patient has suffered another stroke (Crocco et al., 2007).

Important ways to pare down the differential diagnosis are blood work, medical history, pattern of symptom onset, and electroencephalography:

• Blood Work. Lab results can help to rule out hypoglycemia, coagulopathies, thrombocytosis, metabolic disorders, hepatic or renal dysfunction, and systemic infections.
• Medical History. The absence of a history of diabetes, drug or alcohol over-use, seizures, migraines, and head trauma makes stroke a more likely diagnosis. Current Coumadin/warfarin therapy or a history of stroke, atherosclerosis, heart disease, or coagulopathies also make stroke a more likely diagnosis.
• Pattern of Symptom Onset. Strokes have a characteristic pattern of onset. Ischemic strokes and intracerebral hemorrhages tend to cause the abrupt appearance of focal (i.e., specific) neurological deficits, and if the symptoms worsen, they worsen quickly, in minutes or hours. In contrast, focal deficits caused by tumors, abscesses, and demyelinating disorders tend to worsen gradually, over a period of days or weeks.
• Electroencephalography. EEGs can document seizures.
  (Kistler et al., 2009; Summers et al., 2009)

Image the Head

Clinical signs can be suggestive, but early in a stroke investigation, an intracranial radiographic evaluation is needed. Imaging studies can usually distinguish ischemia from hemorrhage. They can also detect certain stroke mimics (e.g., tumors). Often, they can also identify the specific vessel(s) injured in the stroke.

Brain imaging is part of the standard work-up of all patients with potential acute stroke. For speed, it is usually most efficient for members of the stroke code team to transport stroke patients to the scanner themselves (Lutsep & Clark, 2007).

Noncontrast or nonenhanced computed tomography (NECT) of the head is still the recommended initial diagnostic imaging tool for acute stroke. CT is rapid, effective for recognizing intracranial hemorrhage, and more widely available than magnetic resonance imaging (MRI) in U.S. emergency departments. Conventional MRI is an acceptable alternative to NECT (Crocco et al., 2007; Oliveira-Filho & Koroshetz, 2009b), although MRI cannot be used on some patients due to contraindications, such as electronic or metal implants, transdermal patches with metal in them, respiratory or hemodynamic instability, vomiting, agitation, impaired consciousness, or patient claustrophobia (Chernoff & Stark, 2009).

A transverse (axial) noncontrast CT scan of a patient with a hemorrhagic stroke. Blood is seen as light areas along the left cerebral ventricle. (The front of the head is at the top of the image.) (Source: ISC, 2004. © 2008, The Internet Stroke Center at Washington University.)

To keep to the stroke evaluation timetable, there should be a standing order for a cranial scan for all potential stroke patients, and there should be a plan for getting the scan read quickly. Specifically, cranial imaging should be completed within 25 minutes of the patient’s arrival at the ED, and the interpretation by an expert should be available within 20 minutes of the scan’s completion. This means that for an ED which treats strokes an experienced imaging technician and a radiologist must always be available.

With the availability of a range of imaging techniques, current techniques are being designed to answer questions that are more specific than "Is this a hemorrhagic or an ischemic stroke?" Imaging techniques are now being specialized to focus on one of three areas:

1. Showing details of brain parenchyma (brain tissue)
2. Showing details of brain vasculature (blood vessels)
3. Displaying the degree of perfusion (blood flow) in various brain regions

AVAILABLE IMAGING TECHNIQUES

At the end of 2009, the computed tomography (CT) techniques in use were:

• Nonenhanced CT (NECT)
• CT angiography (CTA)
• Source images from CTA (CTA-SI)
• Quantitative (dynamic) CT perfusion (CTP)
• Single-photon emission CT (SPECT)
• Xenon-enhanced CT (XeCT)

The magnetic resonance (MR) techniques in use were:

• Magnetic resonance imaging (MRI)
• MR diffusion-weighted imaging (MR-DWI)
• MR perfusion-weighted imaging (MRP or MR-PWI)
• MR angiography (MRA)
• Contrast-enhanced MRA (CE-MRA)
• MR gradient-recalled echo (GRE)
• MR fluid-attenuated inversion recovery (FLAIR)

Vascular studies are also done using:

• Carotid ultrasound
• Digital subtraction angiography (DSA) (i.e., catheter-based cerebral angiography)
• Transcranial Doppler (TCD)

Brain imaging is an actively advancing technology that provides significantly more detail than the identification of bleeds. For example:

• CT angiography (CTA) can be done rapidly for the entire neck and head. CT cerebral blood volume (CBV) maps can show the topography of an infarction. Quantitative perfusion CT (CTP) can distinguish infarct from hypoperfused brain.
• MRI diffusion-weighted imaging (DWI) can detect a new infarct within minutes of its occurrence. MR perfusion (MRP) will highlight hypoperfused brain tissue. MR angiography (MRA) shows vascular occlusions. Gradient echo (GRE) MR sequences can rule out intracerebral hemorrhage. Fluid-attenuated inversion recovery (FLAIR) MR sequences show fluid accumulations (Latchaw et al., 2009).

CHOOSING AMONG IMAGING TECHNIQUES

The American Heart Association recommends the use of these imaging techniques (Latchaw et al., 2009):

For imaging brain parenchyma (functional tissue):

• To exclude intracerebral hemorrhage, CTA-SI or MR-DWI is preferred, NECT or MRI is acceptable.
• To identify subarachnoid hemorrhage, NECT is preferred, MR FLAIR is acceptable.

For imaging brain vasculature (blood vessels):

• For large vessels (e.g., the Circle of Willis):
  • To image thromboses, CTA, MRA, or DSA are acceptable (if <3 hr after onset of symptoms, then vascular imaging is suggested; if >3 hr, then vascular imaging is recommended).
  • To image stenoses or aneurysms, CTA or DTA is preferred.
• For smaller cerebral vessels, DSA should be used for all vascular imaging.

For imaging brain perfusion (passage of blood through the vessels):

• The American Heart Association has not yet published recommendations.

Identify the Stroke Type

The two distinct classes of stroke are ischemic and hemorrhagic. Each requires rapid management, but each requires different treatment. If treated early enough, many ischemic stroke patients will benefit from thrombolytic therapy. On the other hand, hemorrhagic strokes will worsen if given a thrombolytic drug. Therefore, it is important to distinguish ischemic from hemorrhagic stroke patients early in the medical evaluation.

CT or MRI head imaging is the key to evaluating stroke type. In neurology, as is the case throughout medicine, diagnoses are made from indirect evidence, and a robust diagnosis depends on compiling consistent evidence from many different perspectives. Sometimes, the CT or MRI images can definitively identify the type of stroke in a particular patient. Often, the radiographs are suggestive of or at least consistent with a specific diagnosis. In all cases, however, the results of brain imaging need to be put into a clinical context to decide the type of a particular patient’s stroke (Oliveira-Filho & Koroshetz, 2009b).

ISCHEMIC STROKES

Most ischemic strokes are caused by thrombi or emboli that result from atherosclerosis. On its own, atherosclerosis develops slowly, and otherwise healthy people younger than 40 years do not often have an ischemic stroke unless they have a strong family history of stroke at a young age. On the other hand, atherosclerosis is accelerated by diabetes, hypertension, hyperlipidemia, and smoking, and people with any of these conditions need not be elderly to have an ischemic stroke (Caplan, 2009a; Oliveira-Filho & Koroshetz, 2009c).

The obstructive strokes are divided into those generated by clots originating within the cerebral vasculature (i.e., thrombotic strokes) and those generated by clots originating elsewhere (i.e., embolic strokes). Pure motor strokes tend to be thrombotic, and a stroke is more likely to be thrombotic if it has been preceded by transient ischemic attacks (TIAs) giving similar symptoms. Early on, thrombotic strokes often produce symptoms that fluctuate, going back and forth between worsening and improving, but most ischemic strokes do not worsen after the second day.

Embolic strokes usually occur in patients with atherosclerosis or heart problems; coronary artery disease, myocardial infarction, atrial fibrillation, atrial or ventricular enlargement, or endocarditis increase a patient’s risk of embolic stroke. An ischemic stroke is more likely to be embolic than thrombotic if two different arterial territories are obstructed or if the obstructed artery is large. Embolic strokes often produce symptoms that are maximal at the beginning followed by improvement, which can sometimes be rapid.

Not all ischemic strokes are caused by obstructions of individual arteries. Occasionally, ischemic strokes are caused by systemic hypoperfusion problems, such as cardiac arrest or hypovolemia.

HEMORRHAGIC STROKES

In contrast to most ischemic strokes, hemorrhagic strokes often begin with a severe headache and vomiting, and they tend to present with acutely elevated blood pressure. Compared to ischemic strokes, hemorrhagic stroke is more common in young people, it is more likely to be triggered by trauma or physical activity, and it is more common in people taking anticoagulants (Ropper & Samuels, 2009a).

Hemorrhagic strokes are divided into those caused by bleeding inside the brain tissue (intracerebral hemorrhages) and those caused by bleeding directly into the cerebrospinal fluid (subarachnoid hemorrhages).

Symptoms from an intracerebral hemorrhage typically begin with a severe headache and vomiting, and the neurologic problems worsen during the first hour or hours. Often, the patient remains alert and has little or no neck stiffness. Most intracerebral hemorrhages lead to focal neurologic deficits. After the bleeding stops, blood from an intracerebral hemorrhage is absorbed slowly; therefore, the neurological problems do not disappear quickly but diminish gradually, over months (Ropper & Samuels, 2009a).

Symptoms from a subarachnoid hemorrhage typically come on instantaneously with a severe headache and vomiting and with the maximum level of neurologic problems, especially when the cause is a ruptured aneurysm. The patient may remain awake but often has a decreased level of consciousness. A stiff neck is common. Focal neurologic defects, such as hemiparesis, are not typical of subarachnoid hemorrhages (Ropper & Samuels, 2009b).

Make a Treatment Decision

The rapid diagnosis of an acute stroke and the determination of its type allow a stroke team the widest range of direct treatment options. The time of 45 minutes is set as a milestone in the ED stroke protocol. Within the first 45 minutes of a patient’s evaluation, they should be channeled from the ED into one of two treatment pathways:

• Stroke patients with any sign of intracranial bleeding (i.e., a hemorrhagic stroke) are managed using a protocol that is based on close monitoring and individualized treatment of medical complications.
• Stroke patients with no bleeding and with evidence of an obstructed cerebral artery (i.e., an ischemic stroke) are managed using a protocol that can lead to rapid intervention, typically with the IV administration of the “clot-busting” drug rtPA.

The hemorrhagic protocol begins with a neurosurgical consult if the vascular injury could be a ruptured subarachnoid aneurysm, a condition that may benefit from surgically clipping the aneurysm remnant or from endovascularly inserting a coil. For other subarachnoid hemorrhages and for intracerebral hemorrhages, patients are admitted directly to an ICU and monitored carefully.

The ischemic protocol begins by checking the patient’s eligibility for rtPA. To be eligible, patients must not be pregnant, must have a sufficiently high platelet count, and can have no indication of intracranial hemorrhage, no recent major surgery, no evidence of internal bleeding, no known bleeding diatheses, and no current anticoagulant therapy. After receiving IV rtPA, patients must be carefully monitored for at least 24 hours in an ICU. Patients with ischemic strokes that are inelegible for rtPA treatement are admitted directly to an ICU and monitored carefully.

SUMMARY

Like the treatment for an acute myocardial infarction, treatment for an acute stroke is given high priority by emergency department personnel. For a stroke, there is a 4.5-hour interval after the onset of symptoms in which thrombolytic therapy (i.e., intravenous administration of rtPA) has a chance to reopen clogged cerebral arteries and save some of the underperfused brain tissue. Primary stroke centers, which are emergency departments experienced in thrombolytic therapy for strokes, have the goal of getting eligible acute stroke patients from the door to thrombolytic treatment in less than an hour.

While making a detailed diagnosis, the first step in treating a stroke is to establish an airway, possibly by intubation. Next, one must check for evidence of head trauma and consider immobilizing the spine. If the patient’s neurological condition is deteriorating (e.g., if there is a decreasing level of consciousness, pupillary dysfunction suggesting brainstem damage, or decorticate or decerebrate posturing), there may be cerebral edema or continued hemorrhaging, so neurosurgery must be consulted.

After a brief medical history (that includes defining the time course of the onset of symptoms) and a physical exam (with special attention to the neurological and cardiac exams), stat blood work (blood glucose, serum electrolytes, renal function tests, cardiac markers, CBC, prothrombin time/INR, aPTT, and a toxicology screen if drug use is suspected) is drawn.

As in pre-hospital (i.e., EMS) stroke management, emergency department stroke care is facilitated by using standardized tests; in the ED, the recommended assessment tool is the NIH Stroke Scale, which can be administered in 5 to 8 minutes using no special equipment. The NIH Stroke Scale quantifies the severity of a stroke, and it has been widely used to measure both deterioration and improvement of stroke patients.

The critical step in evaluating an acute stroke is making the distinction between ischemic and hemorrhagic strokes. For this, there is no clinical test: the determination must be made by CT (or MRI) imaging, as interpreted by an experienced radiologist. Emergency head imaging (usually, a noncontrast CT scan) is needed within 25 minutes of the patient’s delivery to the ED, and a completed radiologic evaluation is needed less than 20 minutes later. By 45 minutes, the stroke team will have decided on a treatment pathway.

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