Stroke Syndromes

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Chapter 50 Stroke Syndromes

Providing rehabilitation care for patients with stroke is at once a compelling and complicated endeavor. Stroke is a common syndrome, and care of the stroke patient is often thought of as a prototype rehabilitation effort because of its high frequency and its reliance on virtually all members of the typical rehabilitation team. The fact that no two strokes are alike and no two patients react similarly to their situations, however, means that caring for patients with stroke is also a distinct experience requiring individual attention. Most patients who experience stroke can and do have improvement in functional ability, but the amount, rate, timing, pattern, type, and ultimate outcome of the improvements differ across patients and across situations. Therefore the approach that is required for appropriate assessment and treatment of stroke patients demands specialized knowledge, skills, and creativity.

The past 20 years has witnessed a transformation in the therapeutic approach to the rehabilitation of those with stroke, spurred by a growing literature on motor recovery after focal brain injury.181 It is now evident both clinically and scientifically that improvement in motor control after stroke is training dependent, responding best to repetitive practice mixed with continuous modification of the program to keep training tasks challenging to the patient.246 When this approach is focused on sensorimotor retraining in the hemiplegic limb it is called task-oriented therapy. Newer research is now leading beyond just therapeutic exercise, adding novel interventions such as pharmacology, new modalities, and robotics as potentially enhancing the results of motor retraining.

The emergence of training-dependent recovery and task-oriented therapy has pushed rehabilitation clinicians to carefully assess the balance between the restoration of neurologic control and a focus on functional independence with compensatory techniques. This is particularly challenging in the acute inpatient rehabilitation setting, where the desire to facilitate neurologic recovery is most desirable but the need to discharge the patient home safely is most imminent. Fortunately, our tradition of the interdisciplinary rehabilitation team is well suited to addressing these modern challenges.

Although formal therapeutic interventions such as exercise and sensorimotor retraining comprise the most prominent components of the rehabilitation process, other aspects of the program are important as well. Many rehabilitation activities extend beyond the specific therapy treatment sessions. For example, integrating functional activities learned in formal therapy into regular self-care under the supervision of inpatient nursing staff or later in the home environment can significantly reinforce newly gained skills. Recreational programs often serve as major therapeutic interventions. Dealing with psychologic and social issues can often be a more complicated clinical activity than the more routine motor control enhancement strategies. Interactions among patients can provide both emotional support and practical suggestions regarding skill performance. Most critically, the amount and nature of the interactions between patients and professionals can be highly motivating and instructive for patients and their families. A positive and encouraging rehabilitation milieu typically provides the opportunity for these “less formal” therapeutic interactions.

The major underlying theme of all rehabilitation interventions is to maximize quality of life for patients with stroke. It is quality of life, and not simply improved motor control, functional independence, or community placement, that is the real goal of the rehabilitation program. Indeed, for some stroke survivors, complete independence in daily living skills might be undesirable or impractical for physical, psychologic, or social reasons. The goal of enhancing quality of life is paramount and affects both the choices of specific interventions and the manner in which clinical activities are performed. The comprehensive rehabilitation management program is characterized by a holistic approach, in which patients as a whole and their overall situation are considered, rather than merely focusing on isolated aspects of existence. This goal usually, but not always, includes helping the patient to achieve as much functional independence as possible.

Understanding stroke and the rehabilitation of patients who sustain stroke is important, not only because stroke is a common diagnosis among patients in rehabilitation programs, but also because it provides an opportunity to learn about the functioning of the central nervous system, as well as the application of rehabilitation principles in general. This chapter reviews the mechanisms and clinical features of stroke; the preventive, diagnostic, and acute management techniques; and the principles and practices of stroke rehabilitation assessment and intervention that enable rehabilitation providers to assist the patient in achieving the ultimate goal of maximizing quality of life. Special emphasis is placed on new and recent developments in stroke rehabilitation. In light of the many challenges to both providing and investigating stroke rehabilitation, the recent developments in stroke care and research are striking. An important recurring theme during both acute management and rehabilitation care, which has been consistent over time, is the centrality of an attitude that replaces therapeutic nihilism with optimism and aggressiveness.26

Epidemiology of Stroke

Stroke is a neurologic syndrome caused by a heterogeneous group of vascular etiologies requiring different management.56 The causes can be grossly categorized as hemorrhagic or ischemic. Intracranial hemorrhage accounts for 15% of all strokes and can be further divided into intracerebral (10%) and subarachnoid (5%) hemorrhage. Subarachnoid hemorrhages (SAHs) typically result from aneurysmal rupture of a cerebral artery with blood loss into the space surrounding the brain. Rupture of weakened vessels within brain parenchyma as a result of hypertension, arteriovenous malformation (AVM), or tumor causes intracerebral hemorrhage (ICH).

The remaining 85% of strokes are caused by ischemic brain injury resulting from large vessel (40%) or small vessel (20%) thrombosis, cerebral embolism (20%), and other less common causes (5%) such as cerebral vasculitis or cerebral hypoperfusion. Vessel occlusion from thrombosis in both large and small arteries is most commonly caused by atherosclerotic cerebrovascular disease. Vascular changes or lipohyalinosis found in small, deep, perforating arteries as associated with chronic hypertension can lead to small vessel thrombosis. Cerebral emboli are usually of cardiac origin and are frequently a result of valvular disease or atrial fibrillation. In addition, they can arise from chronic ischemic cardiovascular disease with secondary ventricular wall hypokinesis, which can also increase the risk for intracardiac thrombus formation.

Stroke Incidence, Mortality, Prevalence, and Survival

Data from several population-based study cohorts estimate that the yearly incidence of stroke in the United States is 795,000, which comprise 600,000 new strokes and 185,000 recurrent strokes.9 Stroke continues to result in significant morbidity, mortality, and disability, particularly among people older than 65 years.

Stroke is primarily a disease of older individuals, but 28% of strokes occur in persons younger than 65 years. Children have an annual incidence of 2.7 strokes per 100,000. The primary cause of ischemic stroke in adults is atherosclerosis, whereas in children the causes include cerebrovascular anomalies, congenital heart disease, carotid dissection, sickle cell disease, inherited disorders of coagulation, and previous infection with varicella zoster.278 Hemorrhagic strokes in children can occur as a result of moyamoya disease and hemophilia.

The incidence of stroke is 50% higher among men compared with women of all races between ages 65 and 74, but the gender difference is much less thereafter. Among black men age 45 to 84, stroke incidence is twofold to threefold higher than among whites. The relative incidence of stroke among black women compared with white women is even higher. Many important risk factors for stroke are found in higher frequency among black people, including hypertension, diabetes mellitus, heart disease, smoking, excessive alcohol use, and sickle cell disease. The rate of stroke in Asian countries is higher than in the United States, with a greater proportion of strokes caused by intracranial hemorrhage.

Stroke was the primary cause of death in 143,579 persons in 2005, and it remains the third leading cause of death in the United States; it is exceeded only by cardiovascular disease and cancer.9 A well-documented reduction in annual stroke mortality, however, has taken place within the United States in the past century.203 A sharp decline was noted in the annual stroke deaths for both men and women that began in the 1970s, and this continued well into the 1980s before the slope flattened in the early 1990s.245,290 Approximately 200,000 fewer fatal strokes occurred in this period than would have been predicted from data of the previous decade.245 It can be argued that the improved detection and treatment of hypertension that began in the 1960s, and escalated in 1973 with introduction of the National High Blood Pressure Education and Control Program, are directly responsible for the steep decline in stroke mortality.245,290

Stroke survivors, many of whom require rehabilitation services, presently number nearly 6.5 million in the U.S. population. Although the mortality from stroke has declined in the United States, hospitalizations for stroke increased by 18.6% between 1988 and 1997.117 As our population ages, the incidence and prevalence of stroke will continue to increase. Stroke rehabilitation will have an important role in reducing the burden of long-term stroke care on society.

Modifiable Risk Factors

Hypertension

Prevalence of hypertension within the U.S. adult population is 35%. Defined as a systolic pressure greater than 165 mm Hg or a diastolic pressure greater than 95 mm Hg, hypertension increases the relative risk of stroke by a factor of 6. Among stroke survivors, 67% have chronic hypertension.171 Several metaanalyses of randomized trials of antihypertensive medications have demonstrated that a 10- to 12-mm Hg reduction of systolic and a 5- to 6-mm Hg reduction of diastolic pressure are associated with a 35% reduction in stroke risk in both hypertensive and normotensive subjects.76,280 It should be noted that no threshold diastolic value was found below which further pressure reduction lacked an additional effect on stroke risk. Consequently, reductions in diastolic blood pressure below traditionally normotensive values contributed to further risk reduction in these studies.

The Hypertension Detection and Follow-up Program was the first major study to demonstrate a reduction in stroke incidence with antihypertensive treatment. This was a population-based randomized clinical trial with a 5-year follow-up period involving 11,000 hypertensive persons who were either provided with a stepped care antihypertensive program or referred for traditional care. A 1.9% incidence of stroke among patients on stepped care treatment was observed compared with 2.9% on a referred care program, equaling a 35% reduction in stroke incidence and a 44% reduction in fatal strokes.212 Isolated systolic hypertension is more common among individuals older than 60 years and is an independent risk factor for stroke and cardiovascular disease.231 The Systolic Hypertension in the Elderly Program383 randomized more than 4700 subjects aged 60 years and older with systolic pressures greater than 160 mm Hg and diastolic pressure less than 90 mm Hg to antihypertensive treatment or placebo. During the 5-year study period, subjects treated with antihypertensive medication had an average reduction in systolic blood pressure of 17 mm Hg and a 36% reduction in the incidence of stroke compared with control subjects.

More recently, the role of angiotensin-converting enzyme inhibitors in the prevention of stroke has been appreciated. The Heart Outcomes Prevention Study demonstrated that ramipril provides a 32% relative reduction in stroke occurrence in patients with a history of myocardial infarction, stroke, peripheral vascular disease, or other risk factors.196 The Perindopril Protection Against Recurrent Stroke Study randomized patients with stroke or TIA with or without hypertension to perindopril versus placebo, finding a 28% relative risk reduction with antihypertensive treatment. The combination of a diuretic with the angiotensin-converting enzyme inhibitor improved blood pressure reduction and provided better risk reduction.339 A recent large clinical trial assessing the benefit of telmisartan (an angiotensin II receptor agonist) failed to reduce secondary stroke.471 Only a modest reduction in pressures was observed in this study, however, and the follow-up period was limited to 2.5 years. The benefit of antihypertensives in stroke reduction improves with greater pressure reduction and time.

Ample evidence supports public health efforts aimed at reducing the prevalence of poorly controlled blood pressure, thereby reducing the risk of stroke and heart disease. Improved public education, detection, and treatment of hypertension will have a positive impact on the further decline of stroke incidence and mortality.

Hypercholesterolemia.

The role of elevated serum cholesterol has not been epidemiologically linked to increased stroke incidence per se, but its strong influence on the development of coronary artery disease and atherosclerosis359 indicates that hypercholesterolemia is at least an indirect risk factor for stroke. Indeed, an association between carotid artery atherosclerosis and increased serum cholesterol levels has been noted.316,372 The use of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors or statins can reduce the risk of stroke,51,428 but their role in prevention can have as much to do with their ability to stabilize atherosclerotic plaques and reduce inflammation as their ability to reduce serum cholesterol285,400 In a metaanalysis that included 90,000 subjects there was a significant reduction in stroke risk (21%).8 This study showed that a 10% reduction in low-density lipoprotein (LDL) will reduce risk for stroke by 15.6% and carotid intima media thickness by 0.73%. There also remains a role for dietary reduction of cholesterol and saturated fatty acids in the prevention of stroke. Current targets for patients with coronary heart disease and stroke are an LDL less than 100 mg/dL and total cholesterol less than 200 mg/dL. High-density lipoprotein (HDL) levels more than 60 mg/dL are desirable.3

Diabetes Mellitus and Other Risk Factors.

Diabetes mellitus increases the relative risk of ischemic stroke to 3 to 6 times that of the general population. This risk can be partly attributed to the higher prevalence of hypertension and heart disease among persons with diabetes, but even after controlling for these factors, diabetes independently doubles stroke risk.1,21,232 The prevalence of diabetes among stroke survivors is 20%.1,171,296

Whether obesity is a risk factor for stroke has been challenged. Hypertension and diabetes mellitus are more common in the obese and are strong influences for stroke risk. Weight loss has a positive influence on blood pressure and diabetic control, and probably has a risk-reducing effect on stroke and cardiovascular disease. Although obesity can indirectly increase stroke risk, its independence as a risk factor remains questionable.

The metabolic syndrome is a cluster of interrelated metabolic risk factors for atherosclerotic disease. These include high waist circumference, increased blood pressure, low HDL level, elevated serum triglyceride, and elevated fasting glucose. A recent data analysis from the Atherosclerosis Risk in Communities Study showed a step-wise increase in stroke risk with an increased number of metabolic syndrome components, such that the presence of all five components resulted in a nearly fivefold increase in stroke risk.356

Heart disease, including electrocardiographic evidence of left ventricular hypertrophy, cardiac failure, and nonvalvular atrial fibrillation, increases stroke risk by 2 to 6 times normal. Control of hypertension, cessation of smoking, and reduction of serum cholesterol can reduce the development of heart disease and prevent stroke. In the presence of established conditions such as atrial fibrillation or left ventricular failure, however, the use of medical means to reduce stroke risk can become important. Prevention of heart disease through lifestyle changes has a positive influence on stroke prevention.

Elevated plasma levels of homocysteine have been associated with increased risk of stroke and carotid artery disease.381 Hyperhomocysteinemia can result from inherited enzyme deficiencies or acquired deficiencies of required enzyme cofactors such as folate, vitamin B12, or vitamin B6. The hyperviscosity that can occur with hyperhomocysteinemia can lead to hypercoagulability or enhanced atherogenesis by microvascular damage from traumatic shearing forces against vessel walls. Patients with acute stroke who have elevated plasma homocysteine are at risk for recurrent stroke, and supplementation with folate, vitamin B12, and vitamin B6 is advised.37

Stroke Pathophysiology

Ischemic Stroke

The unifying pathophysiology of thrombotic, embolic, and lacunar stroke is cerebral ischemia from compromise of cerebral blood flow (CBF). The location and temporal development of cerebral injury vary with the etiology.

Thrombosis

The entire pathophysiology of infarction from cerebral thrombosis remains controversial, but it is strongly associated with atherosclerotic cerebrovascular disease. Atherosclerotic plaque formation occurs frequently at major vascular branching sites, including the common carotid and vertebrobasilar arteries. Atherosclerosis is an inflammatory disease that often develops in the presence of chronic hypertension, beginning with increased permeability of vascular intima followed by leukocyte adhesion and infiltration. Monocyte and T-cell accumulation produce lipid-laden foam cells within the vessel wall, and fatty streaks appear on the endothelial surface. Eventually, smooth muscle cell migration, continued inflammatory activity, and the formation of a fibrous cap compromise blood flow, leading to turbulence. Rupture of the fibrous cap can rapidly promote initial thrombus formation by stimulating platelet aggregation and activation of the extrinsic pathway of the coagulation system. The loosely attached thrombus, or “white clot,” that forms is composed of platelet cells and fresh fibrin.358

It is unclear whether symptoms of transient ischemic attack (TIA) are caused by transient thrombotic occlusion of major cerebral arteries or by microemboli that break away from a thrombus, but both phenomena might be important. In either case, these events must resolve, usually in a few minutes, to be considered TIA. TIA is no longer defined based on time (i.e., events lasting <24 hours). The American Stroke Association recently redefined TIA as “a brief episode of neurologic dysfunction caused by focal brain or retinal ischemia, with clinical symptoms typically lasting less than an hour, and without evidence of acute infarction” as determined by cranial imaging.108 This means that any transient neurologic event that is associated with an acute infarction on imaging is considered a stroke rather than TIA, regardless how long the event lasts. Symptoms of transient monocular blindness, or amaurosis fugax, are probably due to microemboli from the internal carotid artery that cause a branch occlusion of the ipsilateral ophthalmic and retinal arteries.330 Other intracranial branch occlusions can similarly result from microemboli arising in the extracranial vessels, leading to injury or infarction in focal regions.95

In contrast, a large arterial thrombus can occlude a major extracranial artery, producing a low-flow state that causes ischemic injury to neural tissue supplied by the most distal arterial branches.30 The volume of damage that results from such hemodynamic compromise can be large, but it depends on the length of time the vessel is occluded, the rate of flow through the occluded site, and the effectiveness of the collateral circulation. Fibrinolytic enzymes are released that control acute thrombus formation, potentially dissolving the clot within minutes to hours. Recanalization might fail or be delayed, however, permitting the arterial thrombus to completely or partially occlude blood flow. Collateral circulation can support the compromised cortical zone, but it can be less effective in elderly persons or in those with diffuse atherosclerotic disease or diabetes.

Ischemic injury from a cerebrovascular thrombus probably results in simultaneous distal branch occlusions from microemboli and compromise of blood flow proximally. The neurologic outcome of cerebral thrombi varies widely and can include brief TIAs, minor strokes without functional compromise, or major strokes resulting in significant impairment and functional disability.

Embolism

Beyond the microemboli produced by cerebrovascular thrombi, the majority of embolic strokes have a cardiac origin. Thrombus formation within the cardiac chambers is generally caused by structural or mechanical changes within the heart. Atrial fibrillation is a significant risk factor for embolic stroke as a result of poor atrial motility and outflow, with stasis of blood and atrial thrombus formation. Atrial fibrillation is often caused by rheumatic valvular disease or coronary artery disease, but it can be idiopathic. Mural thrombus within the left ventricle after myocardial infarction, in the presence of cardiomyopathy or after cardiac surgery, is the other major cause of embolic stroke.55,63 Mechanical heart valves universally cause cerebral emboli if anticoagulation is insufficient. Infectious endocarditis can lead to septic emboli.

Cerebral emboli lodge within arterial branches of the major arteries, causing single or multiple branch occlusions resulting in sudden, focal neurologic impairment. These branch occlusions significantly compromise flow distally, inducing ischemic injury to neural tissue, glia, and vascular endothelium. Reperfusion of the occluded vessel can occur in response to endogenous fibrinolysis, but because ischemic damage to the vascular bed is often significant, the capillaries become incompetent and secondary cerebral hemorrhage ensues.

In contrast to thrombotic stroke, microemboli probably do not precede cardioembolic strokes, as TIAs are uncommon. Frequently no cardiac thrombus can be found after the event, and the only clue to an embolic cause is the sudden neurologic deficit without previous or progressive symptoms.

Lacunes

Lacunar infarcts are small, circumscribed lesions that measure less than 1.5 cm in diameter and are located in subcortical regions of the basal ganglia, internal capsule, pons, and cerebellum.295 The area of a lacune (meaning “little lake”) roughly corresponds to the vascular territory supplied by one of the deep perforating branches from the circle of Willis or major cerebral arteries. Lacunar strokes are strongly associated with hypertension and pathologically associated with microvascular changes that often develop in the presence of chronic hypertension. Histologic changes such as arteriolar thickening and evenly distributed deposition of eosinophilic material, called lipohyalinosis and fibrinoid necrosis, are commonly seen in the subcortical perforating arteries of hypertensive persons who have had lacunar strokes. Microatheromas within deep perforating arteries are also important causes of lacunar infarction. In addition to hypertension, diabetes mellitus is associated with lacunar stroke as a result of chronic microvascular changes.

Hemorrhagic Stroke

Intracerebral Hemorrhage

The deep perforating cerebral arteries are also the site of rupture preceding ICH. Unlike lacunar strokes, however, ICH does not obey the anatomic distribution of a vessel but dissects through tissue planes. Such damage can be significant, resulting in increased intracranial pressure, disruption of multiple neural tracts, ventricular compression, and cerebral herniation. Acute mortality is high, but those who survive ICH often experience rapid neurologic recovery during the first 2 or 3 months after the hemorrhage.

Nearly one half of all ICHs occur within the putamen and the cerebral white matter.144 Sudden hemorrhage into brain parenchyma is related to both acute elevations in blood pressure and chronic hypertension. Microvascular changes associated with hypertensive hemorrhages include lipohyalinosis and Charcot–Bouchard aneurysms.129 The latter are not true aneurysms of the vessel wall but are pockets of extravasated blood or “pseudoaneurysms,” a sign of previous microscopic ruptures within the vascular wall. The bleeding typically lasts no more than 1 to 2 hours, corresponding to the usual time course of acute symptom development. Late neurologic decline is related to posthemorrhagic edema or rebleeding.

Cerebral amyloid angiopathy is unusual but is gaining recognition as an important cause of ICH in the elderly population.121 Lobar hemorrhages located near the cortex that occur in patients older than 55 years who have some premorbid history of mild dementia are characteristic of this disease, but in the absence of tissue staining for Congo red amyloid deposits within the adventitia of cerebral vessels, diagnostic uncertainty remains. Other notable causes of ICH include the use of anticoagulants, intracranial tumor, and vasculitis.