Stroke

What is a stroke?

A stroke, or cerebrovascular accident (CVA), occurs when blood supply to part of the brain is disrupted, causing brain cells to die. When blood flow to the brain is impaired, oxygen and glucose cannot be delivered to the brain. Blood flow can be compromised by a variety of mechanisms.

Blockage of an artery

• Narrowing of the small arteries within the brain can cause a so-called lacunar stroke, (lacune=empty space). Blockage of a single arteriole can affect a tiny area of brain causing that tissue to die (infarct).
  
  
• Hardening of the arteries (atherosclerosis) leading to the brain. There are four major blood vessels that supply the brain with blood. The anterior circulation of the brain that controls most motor, activity, sensation, thought, speech, and emotion is supplied by the carotid arteries. The posterior circulation, which supplies the brainstem and the cerebellum, controlling the automatic parts of brain function and coordination, is supplied by the vertebrobasilar arteries.

If these arteries become narrow as a result of atherosclerosis, plaque or cholesterol, debris can break off and float downstream, clogging the blood supply to a part of the brain. As opposed to lacunar strokes, larger parts of the brain can lose blood supply, and this may produce more symptoms than a lacunar stroke.

• Embolism to the brain from the heart. In situations in which blood clots form within the heart, the potential exists for small clots to break off and travel (embolize) to the arteries in the brain and cause a stroke.

Rupture of an artery (hemorrhage)

• Cerebral hemorrhage (bleeding within the brain substance). The most common reason to have bleeding within the brain is uncontrolled high blood pressure. Other situations include aneurysms that leak or rupture or arteriovenous malformations (AVM) in which there is an abnormal collection of blood vessels that are fragile and can bleed.

What causes a stroke?

Blockage of an artery

The blockage of an artery in the brain by a clot (thrombosis) is the most common cause of a stroke. The part of the brain that is supplied by the clotted blood vessel is then deprived of blood and oxygen. As a result of the deprived blood and oxygen, the cells of that part of the brain die. Typically, a clot forms in a small blood vessel within the brain that has been previously narrowed due to a variety of risk factors including:

• high blood pressure (hypertension),
  
  
• high cholesterol,
  
  
• diabetes, and
  
  
• smoking.

Embolic stroke

Another type of stroke may occur when a blood clot or a piece of atherosclerotic plaque (cholesterol and calcium deposits on the wall of the inside of the heart or artery) breaks loose, travels through open arteries, and lodges in an artery of the brain. When this happens, the flow of oxygen-rich blood to the brain is blocked and a stroke occurs. This type of stroke is referred to as an embolic stroke. For example, a blood clot might originally form in the heart chamber as a result of an irregular heart rhythm, such as occurs in atrial fibrillation. Usually, these clots remain attached to the inner lining of the heart, but occasionally they can break off, travel through the blood stream, form a plug (embolism) in a brain artery, and cause a stroke. An embolism can also originate in a large artery (for example, the carotid artery, a major artery in the neck that supplies blood to the brain) and then travel downstream to clog a small artery within the brain.

Cerebral hemorrhage

A cerebral hemorrhage occurs when a blood vessel in the brain ruptures and bleeds into the surrounding brain tissue. A cerebral hemorrhage (bleeding in the brain) can cause a stroke by depriving blood and oxygen to parts of the brain. Blood is also very irritating to the brain and can cause swelling of brain tissue (cerebral edema). Edema and the accumulation of blood from a cerebral hemorrhage increases pressure within the skull and causes further damage by squeezing the brain against the bony skull.

Subarachnoid hemorrhage

In a subarachnoid hemorrhage, blood accumulates in the space beneath the arachnoid membrane that lines the brain. The blood originates from an abnormal blood vessel that leaks or ruptures. Often this is from an aneurysm (an abnormal ballooning out of the wall of the vessel). Subarachnoid hemorrhages usually cause a sudden, severe headache and stiff neck. If not recognized and treated, major neurological consequences, such as coma, and brain death will occur.

Vasculitis

Another rare cause of stroke is vasculitis, a condition in which the blood vessels become inflamed.

Migraine headache

There appears to be a very slight increased occurrence of stroke in people with migraine headache. The mechanism for migraine or vascular headaches includes narrowing of the brain blood vessels. Some migraine headache episodes can even mimic stroke with loss of function of one side of the body or vision or speech problems. Usually, the symptoms resolve as the headache resolves.

Risk factors

Overall, the most common risk factors for stroke are:

• high blood pressure,
  
  
• high cholesterol,
  
  
• smoking,
  
  
• diabetes and
  
  
• increasing age.

Heart rhythm disturbances like atrial fibrillation, patent foramen ovale, and heart valve disease can also be the cause.

When strokes occur in younger individuals (less than 50 years old), less common risk factors are considered including illicit drugs, such as cocaine or amphetamines, ruptured aneurysms, and inherited (genetic) predispositions to blood clotting.

An example of a genetic predisposition to stroke occurs in a rare condition called homocystinuria, in which there are excessive levels of the chemical homocystine in the body. Scientists are trying to determine whether the non-hereditary occurrence of high levels of homocystine at any age can predispose to stroke.

What is a transient ischemic attack (TIA)?

A transient ischemic attack (TIA) is a short-lived episode (less than 24 hours) of temporary impairment to the brain that is caused by a loss of blood supply. A TIA causes a loss of function in the area of the body that is controlled by the portion of the brain affected. The loss of blood supply to the brain is most often caused by a clot that spontaneously forms in a blood vessel within the brain (thrombosis). However, it can also result from a clot that forms elsewhere in the body, dislodges from that location, and travels to lodge in an artery of the brain (emboli). A spasm and, rarely, a bleed are other causes of a TIA. Many people refer to a TIA as a "mini-stroke."

Some TIAs develop slowly, while others develop rapidly. By definition, all TIAs resolve within 24 hours. Strokes take longer to resolve than TIAs, and with strokes, complete function may never return andreflect a more permanent and serious problem. Although most TIAs often last only a few minutes, all TIAs should be evaluated with the same urgency as a stroke in an effort to prevent recurrences and/or strokes. TIAs can occur once, multiple times, or precede a permanent stroke. A transient ischemic attack should be considered an emergency because there is no guarantee that the situation will resolve and function will return.

A TIA from a clot to the eye can cause temporary visual loss (amaurosis fugax), which is often described as the sensation of a curtain coming down. A TIA that involves the carotid artery (the largest blood vessel supplying the brain) can produce problems with movement or sensation on one side of the body, which is the side opposite to the actual blockage. An affected patient may experience paralysis of the arm, leg, and face, all on one side. Double vision, dizziness (vertigo), and loss of speech, understanding, and balance can also be symptoms depending on what part of the brain is lacking blood supply.

History

• The American Stroke Association advises the public to be aware of the symptoms of stroke that are easily recognized and to call 911 immediately. These symptoms include the following:
  • Sudden numbness or weakness of face, arm, or leg, especially on one side of the body
  • Sudden confusion, difficulty in speaking or understanding
  • Sudden deterioration of vision of one or both eyes
  • Sudden difficulty in walking, dizziness, and loss of balance or coordination
  • Sudden, severe headache with no known cause
• A focused medical history aims to identify risk factors for atherosclerotic and cardiac disease, including hypertension, diabetes mellitus, tobacco use, high cholesterol, and a history of coronary artery disease, coronary artery bypass, or atrial fibrillation. Consider stroke in any patient presenting with acute neurological deficit or any alteration in level of consciousness. Common signs of stroke include the following:
  • Acute hemiparesis or hemiplegia
  • Complete or partial hemianopia, monocular or binocular visual loss, or diplopia
  • Dysarthria or aphasia
  • Ataxia, vertigo, or nystagmus
  • Sudden decrease in consciousness
• In younger patients, elicit a history of recent trauma, coagulopathies, illicit drug use (especially cocaine), migraines, or use of oral contraceptives.
• Family members, bystanders, and especially prehospital personnel can provide invaluable information regarding the time and events surrounding the onset of symptoms or when the patient was last seen normal.
• Establishing the time the patient was last normal is especially critical when thrombolytic therapy is an option. If the patient awakens with the symptoms, then the time of onset is defined as the time the patient was last seen without symptoms. Family members, coworkers, or bystanders may be required to help establish the exact time of onset, especially in right hemispheric strokes accompanied by neglect or left hemispheric strokes with aphasia.
• If the patient is a candidate for thrombolytic therapy, a thorough review of the inclusion and exclusion criteria must be performed. The exclusion criteria largely focus on identifying risk of hemorrhagic complication associated with thrombolytic use.

Physical

Physical examination is directed toward 5 major areas: (1) assessing the airway, breathing, and circulation (ABCs), (2) defining the severity of the patient's neurologic deficits, (3) identifying potential causes of the stroke (4) identifying potential stroke mimics, and (5) identifying comorbid conditions.

• The physical examination must encompass all the major organ systems, starting with the ABCs and the vital signs. Patients with stroke, especially hemorrhagic, can clinically deteriorate quickly; therefore, constant reassessment is critical. Ischemic strokes, unless large or involving the brainstem, do not tend to cause immediate problems with airway patency, breathing, or circulation compromise. On the other hand, patients with intracerebral or subarachnoid hemorrhage frequently require intervention for both airway protection and ventilation.
  • Vital signs, while nonspecific, can point to impending clinical deterioration and may assist in narrowing the differential diagnosis. Many patients with stroke are hypertensive at baseline, and their blood pressure may become more elevated after stroke. While hypertension at presentation is common, blood pressure decreases spontaneously over time in most patients. Acutely lowering blood pressure has not proven to be beneficial in these stroke patients in the absence of signs and symptoms of associated malignant hypertension, AMI, congestive heart failure (CHF), or aortic dissection.
  • Head, ears, eyes, nose, and throat examination: A careful examination of the head and neck is essential. Contusions, lacerations, and deformities may suggest trauma as the etiology for the patient's symptoms. Auscultation of the neck may elicit a bruit, suggesting carotid disease as the cause of the stroke.
  • Cardiac: Cardiac arrhythmias, such as atrial fibrillation, are found commonly in patients with stroke. Similarly, strokes may occur concurrently with other acute cardiac conditions, such as AMI and acute CHF; thus, auscultation for murmurs and gallops is recommended.
  • Extremities: Carotid or vertebrobasilar dissections, and less commonly, thoracic aortic dissections, may cause ischemic stroke. Unequal pulses or blood pressures in the extremities may reflect the presence of aortic dissections.
• The neurologic examination must be thorough, and yet this is perhaps the weakest area of training for primary care and emergency providers. A directed and focused examination can be performed in minutes and not only provides great insight into the potential cause of the patient's deficits, but also helps determine the intensity of treatment required.
• A useful tool in quantifying neurological impairment is the National Institutes of Health Stroke Scale (NIHSS). This scale easily used, is reliable and valid, provides insight to the location of vascular lesions, and is correlated with outcome in patients with ischemic stroke. It focuses on 6 major areas of the neurologic examination: (1) level of consciousness, (2) visual function, (3) motor function, (4) sensation and neglect, (5) cerebellar function, and (6) language. The NIHSS is used most by stroke teams. It enables the consultant to rapidly determine the severity and possible location of the stroke. A patient's score on the NIHSS is strongly associated with outcome, and it can help identify those patients who are likely to benefit from thrombolytic therapy and those who are at higher risk to develop hemorrhagic complications of thrombolytic use.

Table 1. NIH Stroke Scale (For a printable version, see Media file 1.)

Open table in new window

[ CLOSE WINDOW ]

Table

	Category	Description	Score
1a	Level of consciousness (LOC)	Alert Drowsy Stuporous Coma	0 1 2 3
1b	LOC questions (month, age)	Answers both correctly Answers 1 correctly Incorrect on both	0 1 2
1c	Answers both correctly Answers 1 correctly Incorrect on both	Obeys both correctly Obeys 1 correctly Incorrect on both	0 1 2
2	Best gaze (follow finger)	Normal Partial gaze palsy Forced deviation	0 1 2
3	Best visual (visual fields)	No visual loss Partial hemianopia Complete hemianopia Bilateral hemianopia	0 1 2 3
4	Facial palsy (show teeth, raise brows, squeeze eyes shut)	Normal Minor Partial Complete	0 1 2 3
5	Motor arm left* (raise 90°, hold 10 seconds)	No drift Drift Cannot resist gravity No effort against gravity No movement	0 1 2 3 4
6	Motor arm right* (raise 90°, hold 10 seconds)	No drift Drift Cannot resist gravity No effort against gravity No movement	0 1 2 3 4
7	Motor leg left* (raise 30°, hold 5 seconds)	No drift Drift Cannot resist gravity No effort against gravity No movement	0 1 2 3 4
8	Motor leg right* (raise 30°, hold 5 seconds)	No drift Drift Cannot resist gravity No effort against gravity No movement	0 1 2 3 4
9	Limb ataxia (finger-nose, heel-shin)	Absent Present in 1 limb Present in 2 limbs	0 1 2
10	Sensory (pinprick to face, arm, leg)	Normal Partial loss Severe loss	0 1 2
11	Extinction/neglect (double simultaneous testing)	No neglect Partial neglect Complete neglect	0 1 2
12	Dysarthria (speech clarity to "mama, baseball, huckleberry, tip-top, fifty-fifty")	Normal articulation Mild to moderate dysarthria Near to unintelligible or worse	0 1 2
13	Best language** (name items, describe pictures)	No aphasia Mild to moderate aphasia Severe aphasia Mute	0 1 2 3
	Total	-	0-42

	Category	Description	Score
1a	Level of consciousness (LOC)	Alert Drowsy Stuporous Coma	0 1 2 3
1b	LOC questions (month, age)	Answers both correctly Answers 1 correctly Incorrect on both	0 1 2
1c	Answers both correctly Answers 1 correctly Incorrect on both	Obeys both correctly Obeys 1 correctly Incorrect on both	0 1 2
2	Best gaze (follow finger)	Normal Partial gaze palsy Forced deviation	0 1 2
3	Best visual (visual fields)	No visual loss Partial hemianopia Complete hemianopia Bilateral hemianopia	0 1 2 3
4	Facial palsy (show teeth, raise brows, squeeze eyes shut)	Normal Minor Partial Complete	0 1 2 3
5	Motor arm left* (raise 90°, hold 10 seconds)	No drift Drift Cannot resist gravity No effort against gravity No movement	0 1 2 3 4
6	Motor arm right* (raise 90°, hold 10 seconds)	No drift Drift Cannot resist gravity No effort against gravity No movement	0 1 2 3 4
7	Motor leg left* (raise 30°, hold 5 seconds)	No drift Drift Cannot resist gravity No effort against gravity No movement	0 1 2 3 4
8	Motor leg right* (raise 30°, hold 5 seconds)	No drift Drift Cannot resist gravity No effort against gravity No movement	0 1 2 3 4
9	Limb ataxia (finger-nose, heel-shin)	Absent Present in 1 limb Present in 2 limbs	0 1 2
10	Sensory (pinprick to face, arm, leg)	Normal Partial loss Severe loss	0 1 2
11	Extinction/neglect (double simultaneous testing)	No neglect Partial neglect Complete neglect	0 1 2
12	Dysarthria (speech clarity to "mama, baseball, huckleberry, tip-top, fifty-fifty")	Normal articulation Mild to moderate dysarthria Near to unintelligible or worse	0 1 2
13	Best language** (name items, describe pictures)	No aphasia Mild to moderate aphasia Severe aphasia Mute	0 1 2 3
	Total	-	0-42

Treatment of ischemic stroke

Ischemic stroke is caused by a thrombus (blood clot) occluding blood flow to an artery supplying the brain. Definitive therapy is aimed at removing the blockage by breaking the clot down (thrombolysis), or by removing it mechanically (thrombectomy). The more rapidly blood flow is restored to the brain, the fewer brain cells die.

Other medical therapies are aimed at minimizing clot enlargement or preventing new clots from forming. To this end, treatment with medications such as aspirin, clopidogrel and dipyridamole may be given to prevent platelets from aggregating.

In addition to definitive therapies, management of acute stroke includes control of blood sugars, ensuring the patient has adequate oxygenation and adequate intravenous fluids. Patients may be positioned with their heads flat on the stretcher, rather than sitting up, to increase blood flow to the brain. It is common for the blood pressure to be elevated immediately following a stroke. Although high blood pressure may cause some strokes, hypertension during acute stroke is desirable to allow adequate blood flow to the brain.

Posted in: stroke