Screening and Diagnosis of Cerebrovascular Disease

Stroke is the most prevalent cause of permanent disability in the Western world, and the third leading cause of death among Americans. Each year about 700,000 Americans have a cerebrovascular accident and every 3 minutes, stroke causes the death of one of them.[1]

There are two types of stroke: ischemic stroke, which occurs when a blood vessel supplying blood to the brain is obstructed, and hemorrhagic stroke, which occurs when a blood vessel ruptures.[2]

Risk factors for cerebrovascular disease

There are a variety of risk factors for stroke, including demographic factors, lifestyle factors, and clinical factors.[3] In terms of demographic correlates, advancing age, male gender, and African American race are all associated with increased stroke risk.[3] Lifestyle variables that increase the likelihood of stroke include tobacco use, excessive alcohol use, cocaine use, and physical inactivity and obesity.[3] Clinical correlates of increased stroke risk include diabetes, high blood pressure, carotid artery disease, atrial fibrillation, TIAs, personal or family history of stroke, high cholesterol, sickle cell disease, and certain blood disorders.[3]

Hyperglycemia and cerebrovascular disease

Hyperglycemia is highly correlated with ischemic stroke, with approximately two thirds of all ischemic stroke subtypes evidencing blood glucose levels greater than 108 mg/dL.[4,5] Given the approximate 10-year delay between the onset and diagnosis of diabetes, stroke or transient ischemia attacks (TIA) are often present the first time an elevated glucose is recognized. Thus, the presentation of stroke or TIA may finally trigger a long-standing diagnosis of diabetes. Although A1C is not yet used for the diagnosis of diabetes, an elevated A1C in the face of an acute stroke or TIA, accompanied by hyperglycemia, indicates that there have been glucose elevations for months prior to the hospital presentation. Further, hyperglycemia is associated with poorer outcomes.[4]

Signs and symptoms

If a stroke is suspected, accurate and rapid diagnosis is essential. Diagnosis should include a medical history, as well as a physical and neurological exam.[8] In terms of clinical presentation, the patient with acute stroke may demonstrate alterations in consciousness, including stupor, coma, confusion or agitation, memory loss, seizures or delirium.[1] Additionally, intense or severe headaches, aphasia, facial weakness or asymmetry, changes in sensory or motor function, visual loss, vertigo, nausea and photophobia or phonophobia may also accompany a stroke. The signs and symptoms associated with stroke appear in Table 1.[8]

Table 1. Signs and symptoms of stroke

Screening and diagnosis

One strategy for stroke screening involves screening for risk factors. The results of the EUROSTROKE study showed that 40% of all strokes can be predicted from easily obtained medical and demographic information, such as age, stroke history, medically treated hypertension, smoking status, diabetes history, and diastolic blood pressure. Further, the addition of more cumbersome tests such as blood lipids, fibrinogen levels, and ECG did not improve the prediction of stroke.[8] According to the American Heart Association, screening should begin at the age of 20, and should include a family history of stroke, smoking status, diet, alcohol intake, and physical activity patterns.[9] Additionally, blood pressure, body mass index (BMI), waist circumference, and screening for atrial fibrillation should be taken at least every two years. Finally, risk for hyperlipidemia and diabetes should be assessed at least every 5 years.[9]

Another screening strategy involves the use of more sophisticated screening for people who are at risk for stroke due to history of TIA.[1] In this group, CT is recommended at initial diagnosis of TIA to rule out brain tumor or subdural hematoma. Magnetic resonance angiography is also indicated at time of diagnosis, as it provides noninvasive imaging of the extracranial carotid, vertebrobasilar, and major intercranial vessels.[10] Finally, the more invasive radiographic angiography is the preferred method of identifying carotid lesions that may be amenable to surgical intervention.[10]

In terms of stroke diagnosis, a variety of tools are available for use. Brain imaging techniques such as CT or MRI are a useful way to confirm a diagnosis of stroke, determine the type of stroke, pinpoint the location of the stroke, and determine the size and age of the lesion.[10] Imaging of the extracranial and intracranial vessels is beneficial for determining the mechanism of the stroke, identifying and localizing the occlusion, quantifying the degree of occlusion, determining the pathology, and identifying any other vascular lesions.[10] At the time of initial diagnosis, a CT scan is the recommended brain imaging procedure. Follow-up CT scan should be conducted within 2 to 7 days. MRI is not generally necessary for the diagnosis of stroke, but may be particularly useful for small hemorrhages or when dating of the hemorrhage is required.[10] Although vessel imaging techniques such as ultrasound, MRA, CT angiography or conventional angiography are a useful way to determine the etiology of the stroke, they are not necessary for the initiation of treatment and should not delay the start of treatment.[10]

References

1. American Stroke Association. Impact of stroke. Available at: http://www.strokeassociation.org. Accessed January 2006.
2. American Stroke Association. What are the types of stroke? Available at: http://www.strokeassociation.org/presenter.jhtml?identifier=1014. Accessed January 2006.
3. American Heart Association. Stroke risk factors. Available at: http://www.americanheart.org/presenter.jhtml?identifier=4726. Accessed January 2006.
4. Lindsberg PJ, Roine RO. Hyperglycemia and acute stroke. Stroke. 2004; 35:363-364.
5. Capes SE, Hunt D, Mulmberg K, Pathak P, Gerstein HC. Stress, hyperglycemia, and prognosis of stroke in non-diabetic and diabetic patients: a systematic review. Stroke. 2001; 32:2426-2432.
6. Neurology Channel. Stroke. Available at: http://www.neurologychannel.com/stroke/diagnosis.shtml. Accessed May 2004.
7. International Stroke Center. Emergency stroke evaluation and diagnosis. Available at: http://www.strokecenter.org/education/ais_evaluation/clinical_presentations.htm. Accessed May 2004.
8. Moons KGM, Bots ML, Salonen JT, et al. Prediction of stroke in the general population in Europe (EUROSTROKE): is there a role for fibrogin and electrocardiography? J Epidemiol Community Health. 2002; 56:i30-i36.
9. Pearson TA, Blair SN, Daniels SR, et al. AHA guidelines for the primary prevention of cardiovascular disease and stroke: 2002 update. Consensus panel guide to comprehensive risk reduction for adult patients without coronary or other atherosclerotic vascular diseases. Circulation. 2002;106:388-391.
10. Culebras A, Kase CS, Masdeu JC, et al. Practice guidelines for the use of imaging in transient ischemic attacks and acute stroke. Stroke. 1997; 28:1480-1497.