Time is brain. Time of symptom onset is key to acute stroke treatment.
Hypoglycemia and hypoxia can mimic stroke. Assess and treat these conditions early in the evaluation of patients with stroke-like symptoms.
Resist the urge to aggressively lower blood pressure. Hypertension is the body's attempt to maintain perfusion to ischemic tissue. Hypotension can make things worse.
Transient ischemic attack (TIA) is a warning of a stroke to come (aborted stroke). Treat TIAs seriously and work up risk factors expediently.
Roughly 750,000 strokes occur annually in the United States, and this will increase as the population ages. Physical, emotional, and economic damages are multifactorial. The cost of initial care is only the beginning. Many stroke survivors are not only unable to return to work, they are unable to care for themselves, placing heavy demands on family and friends.
Stroke is defined as a neurologic deficit resulting from the interruption of blood supply to neuronal tissue. The brain is highly metabolically active, consuming roughly 25% of cardiac output, but has no mechanism for storing energy reserves. This makes it extremely sensitive to even transient interruption in its supply of oxygen and glucose. Vascular compromise may be caused by several different mechanisms, but the final common pathway is impaired neuronal perfusion and tissue starvation.
Strokes are often classified in 2 different ways: etiology and location. Etiologic causes can be classified as either hemorrhagic or ischemic. Hemorrhagic strokes account for 10–20% of all strokes. They sometimes result from the rupture of an aneurysm or arteriovenous malformation (AVM), usually causing bleeding on the surface of the brain. More commonly, the bleeding comes from disruption of an intracerebral arteriole, leading to bleeding inside the parenchyma of the brain. Uncontrolled hypertension is the most common precipitant of intracerebral bleeding, but other conditions such as amyloidosis and tumors can increase the chances of intracerebral bleeding. Vasospasm can occur from the irritant effects of blood on the surface of the brain, leading to an even greater decrease in blood flow.
Ischemic strokes are caused primarily by thrombosis of a blood vessel, very similar to mechanisms involved in myocardial infarction. Conditions such as atherosclerosis, hypercoagulable states, polycythemia, and vasculitis are common precipitants. About 20% of ischemic strokes result from embolic phenomenon. The carotid bifurcation is a common source of plaque embolism. Cardiac mural thrombus and valve disease are also likely sources of embolism.
Classification by location depends on the blood vessel or vascular distribution involved (Table 82-1). The blood supply to the brain comes from paired carotid and vertebral blood vessels. The carotid distribution (ie, anterior circulation) supplies primarily cerebral and cortical structures, whereas the vertebrobasilar vascular distribution (ie, posterior circulation) feeds the cerebellum and brainstem structures. The involved vessel can often be inferred from the clinical presentation. Carotid circulation strokes commonly present with motor and sensory deficits ...