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Overview of Stroke
Strokes are a heterogeneous group of disorders involving sudden, focal interruption of cerebral blood flow that causes neurologic deficit. Strokes can be ischemic (80%), typically resulting from thrombosis or embolism, or hemorrhagic (20%), resulting from vascular rupture (eg, subarachnoid or intracerebral hemorrhage). Transient stroke symptoms (typically lasting< 1 h) without evidence of acute cerebral infarction (based on diffusion-weighted MRI) are termed a transient ischemic attack (TIA). In the US, stroke is the 4th most common cause of death and the most common cause of neurologic disability in adults.
Strokes involve the arteries of the brain (see Figure: Arteries of the brain.), either the anterior circulation (branches of the internal carotid artery) or the posterior circulation (branches of the vertebral and basilar arteries).
Arteries of the brain.
The following are the modifiable factors that contribute the most to increased risk of stroke:
Lack of physical activity
High-risk diet (eg, high in saturated fats, trans fats, and calories)
Psychosocial stress (eg, depression)
Heart disorders (particularly disorders that predispose to emboli, such as acute MI, infective endocarditis, and atrial fibrillation)
Hypercoagulability (thrombotic stroke only)
Intracranial aneurysms (subarachnoid hemorrhage only)
Use of certain drugs (eg, cocaine, amphetamines)
Unmodifiable risk factors include the following:
Initial symptoms occur suddenly. Generally, they include numbness, weakness, or paralysis of the contralateral limbs and the face; aphasia; confusion; visual disturbances in one or both eyes (eg, transient monocular blindness); dizziness or loss of balance and coordination; and headache.
Neurologic deficits reflect the area of brain involved (see Table: Selected Stroke Syndromes). Anterior circulation stroke typically causes unilateral symptoms. Posterior circulation stroke can cause unilateral or bilateral deficits and is more likely to affect consciousness, especially when the basilar artery is involved.
Selected Stroke Syndromes
Systemic or autonomic disturbances (eg, hypertension, fever) occasionally occur.
Other manifestations, rather than neurologic deficits, often suggest the type of stroke. For example, sudden, severe headache suggests subarachnoid hemorrhage. Impaired consciousness or coma, often accompanied by headache, nausea, and vomiting, suggests increased intracranial pressure (see page Overview of Intracranial Tumors : Symptoms and Signs), which can occur 48 to 72 h after large ischemic strokes and earlier in many hemorrhagic strokes; fatal brain herniation may result (see page Pathophysiology).
Stroke complications can include sleep problems, confusion, depression, incontinence, atelectasis, pneumonia, and swallowing dysfunction, which can lead to aspiration, dehydration, or undernutrition. Immobility can lead to thromboembolic disease, deconditioning, sarcopenia, UTIs, pressure ulcers, and contractures.
Daily functioning (including the ability to walk, see, feel, remember, think, and speak) may be decreased.
Evaluation aims to establish the following:
Stroke is suspected in patients with any of the following:
Glucose is measured at bedside to rule out hypoglycemia. If stroke is still suspected, immediate neuroimaging is required to differentiate hemorrhagic from ischemic stroke and to detect signs of increased intracranial pressure. CT is sensitive for intracranial blood but may be normal or show only subtle changes during the first hours of symptoms after anterior circulation ischemic stroke. CT also misses some small posterior circulation strokes and up to 3% of subarachnoid hemorrhages. MRI is sensitive for intracranial blood and may detect signs of ischemic stroke missed by CT, but CT can usually be done more rapidly. If CT does not confirm clinically suspected stroke, diffusion-weighted MRI can usually detect ischemic stroke (see page Ischemic Stroke). If consciousness is impaired and lateralizing signs are absent or equivocal, further tests to check for other causes are done (see page Coma and Impaired Consciousness).
After the stroke is identified as ischemic or hemorrhagic, tests are done to determine the cause. Patients are also evaluated for coexisting acute general disorders (eg, infection, dehydration, hypoxia, hyperglycemia, hypertension). Patients are asked about depression, which commonly occurs after stroke. A dysphagia team evaluates swallowing; sometimes a barium swallow study is necessary.
Stabilization may need to precede complete evaluation. Comatose or obtunded patients (eg, Glasgow Coma Score ≤8) may require airway support (see page Overview of Mechanical Ventilation). If increased intracranial pressure is suspected, intracranial pressure monitoring (see page Monitoring and Testing the Critical Care Patient : Intracranial Pressure Monitoring) and measures to reduce cerebral edema (see page Traumatic Brain Injury : Increased intracranial pressure) may be necessary.
Specific acute treatments vary by type of stroke. They may include reperfusion (eg, recombinant tissue plasminogen activator, thrombolysis, mechanical thrombectomy) for some ischemic strokes (see page Acute).
Strategies to Prevent and Treat Stroke Complications
Providing supportive care, correcting coexisting abnormalities (eg, fever, hypoxia, dehydration, hyperglycemia, sometimes hypertension), and preventing and treating complications are vital during the acute phase and convalescence (see Table: Strategies to Prevent and Treat Stroke Complications); these measures clearly improve clinical outcomes. During convalescence, measures to prevent aspiration, deep venous thrombosis, UTIs, pressure ulcers, and undernutrition may be necessary. Passive exercises, particularly of paralyzed limbs, and breathing exercises are started early to prevent contractures, atelectasis, and pneumonia. Most patients require occupational and physical therapy (see page Stroke Rehabilitation) to maximize functional recovery. Some need additional therapies (eg, speech therapy, feeding restrictions). Depression after stroke may require antidepressants; many patients benefit from counseling. For rehabilitation, an interdisciplinary approach is best.
Modifying risk factors through lifestyle changes (eg, stopping cigarette smoking) and drug therapy (eg, for hypertension) can help delay or prevent subsequent strokes. Other stroke prevention strategies are chosen based on the patient's risk factors. For ischemic stroke prevention, strategies may include procedures (eg, carotid endarterectomy, stent placement), antiplatelet therapy, and anticoagulation.
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