Stroke

the patient until the problem can be treated. Positive pressure ventilation will help improve oxygenation.

STROKE

There are three major types of stroke. The ischemic stroke can be thrombotic or embolic in origin. A thrombotic stroke involves an in-situ clot in an artery that either supplies a part of the brain, such as the vertebral or carotid artery, or that is within the brain itself. An embolic stroke is similar but involves a clot that originated elsewhere in the body that traveled to the brain, occluding an artery within the brain itself. On the other hand, a hemorrhagic stroke involves a disruption of an artery of the brain itself, which bleeding into the brain.

Ischemic strokes have both modifiable and nonmodifiable risk factors. The modifiable risk factors include hypertension, which is perhaps the most significant risk factor, cigarette smoking, diabetes, dyslipidemia, abdominal obesity, insulin resistance, sedentary lifestyle, alcoholism, poor dietary habits, psychological stress, such as depression, certain heart conditions, such as atrial fibrillation, myocardial infarction, and infective endocarditis, the use of cocaine or amphetamines, vasculitis, and hypercoagulability states. Nonmodifiable risk factors include advanced age, family history of stroke, and previous stroke.

If an embolic stroke is anticipated, you will need to look for a possible source. The most common source is atrial fibrillation. In this case, the embolism comes from a fibrillating left atrium. Much less likely, an embolic stroke can come from a prosthetic heart valve, post-MI situation, rheumatic heart disease, bacterial endocarditis with vegetations, or a mechanical circulatory assist device, such as an LVAD. Long bone fractures can lead to fat emboli and compression sickness can lead to an air embolism.

Lacunar infarcts are also ischemic strokes. These are small strokes that do not involve thrombosis but that involve degeneration of the small arteries that get replaced by collagen and lipids. The deep cortical structures are what are mostly involved in these types of strokes, with things like uncontrolled hypertension, diabetes, and old age being the most common underlying factors.

You also need to consider factors that impair systemic perfusion tha affect watershed areas where circulation is already compromised. These systemic conditions include hypotension, polycythemia, hypoxia, and severe anemia—each of which compromises the oxygenation of the body as a whole.

Ischemia can less commonly be due to vasospasm of the cerebral arteries. It can happen after using cocaine or amphetamines, after a subarachnoid hemorrhage, or if there is venous sinus thrombosis for any reason, such as an intracranial infection or hypercoagulability disorder.

There are many possible symptoms associated with an ischemic stroke, all of which involve some type of neurological dysfunction. Things to look out for include aphasia or dysarthria, facial droop, numbness on one side of the body, hemiparesis or hemiplegia, gait abnormalities, and visual disturbances. While embolic strokes happen in the daytime, thrombotic strokes more often happen during the night. Lacunar infarcts may have no or few symptoms but many of these can lead to multi-infarct dementia. The symptoms tend to have an acute or subacute onset, although there can be deterioration if there is cerebral edema, usually happening about 48 to 72 hours.

Your diagnosis of ischemic stroke is primarily based on your clinical evaluation of the patient. Neuroimaging as soon as possible will differentiate between hemorrhagic and ischemic stroke. Bedside glucose testing is essential. Once the diagnosis is established, you will need to identify the underlying cause, particularly if an embolism is suggested. The MRI examination of the head will identify early ischemia better than a CT of the head.

Evaluation of the cause of the stroke should include an ECG, possibly Holter monitoring to look for intermittent atrial fibrillation, troponin level, and an echocardiogram. A magnetic resonance or CT angiography can identify the vessels involved. Thrombotic disorders from things like hypercoagulability include obtaining coagulation studies, CBC, platelets, lipid profile, and fasting blood sugar. Rare causes that might need to be examined include those related to hypercoagulability, such as antiphospholipid antibodies or factor V Leiden disease. A urine drug screen for amphetamines or cocaine should be done.

In treating an ischemic stroke, you should know that some patients can be treated with some type of reperfusion therapy if less than 4.5 hours have passed since the stroke onset. All patients need antiplatelet therapy and those not candidates for thrombolysis can have anticoagulation therapy. Antihypertensive therapy is cautiously given because some degree of hypertension is necessary to maintain cerebral perfusion. Patients at certain stroke centers can be treated with angiographically directed thrombolysis with fewer systemic complications. Others can have a mechanical thrombectomy.

Intracerebral hemorrhage is another form of stroke that comes from focal bleeding in the parenchyma of the brain. Almost all cases are associated with hypertension. Expect focal neurological deficits similar to ischemic strokes, with an increased chance of having seizures, headache, impairment of consciousness, and nausea.

Hemorrhagic strokes, especially large ones, can be catastrophic. The most modifiable risk factor is hypertension, with others being cigarette smoking, poor dietary habits, obesity, and the use of stimulant drugs, such as cocaine or amphetamines. Things like arteriovenous malformations, congenital aneurysms, or other arterial malformations are less likely to be causative. Brain tumors, bleeding disorders, vasculitis, and excessive anticoagulation must also be considered.

A sudden headache is a common presenting complaint as is loss of consciousness or seizures. The neurological deficits have a sudden onset and can be fatal within hours to days. Small hemorrhages have fewer symptoms besides minor headache and nausea. The only way to detect these strokes definitively is through neuroimaging, usually a noncontrast CT of the head. Figure 3 shows what an intracerebral hemorrhage looks like under CT scanning:

Figure 3.

Patients with a hemorrhagic stroke need to be treated supportively with moderate blood pressure reduction and possible surgical evacuation. Cerebellar hemorrhages are most prone to herniation so evacuation can be a life-saving measure.