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The Rational Clinical Examination
David L. Simel, Drummond Rennie
Stroke
Larry B. Goldstein, David L. Simel
Experienced physicians consider their own views of the reliability of given findings (ie,...


Topics Discussed: cerebrovascular accident, diagnostic process, ischemic stroke, measures of outcome, nih stroke scale, prehospital stroke scale, summarizing the evidence, transient ischemic attack

Excerpt: "According to a prospective observational cohort study, when examination was performed by a physician, the presence of any of 3 physical examination findings (facial paresis, arm drift, and abnormal speech) was selected from the National Institutes of Health Stroke Scale (NIHSS) as the most useful. These 3 items, selected by statistical recursive partitioning techniques, identified patients with stroke with 100% sensitivity (lower 95% confidence limit, 95%) and 88% specificity (95% confidence interval [CI], 82%-91%) (positive LR [LR+], 7.9; 95% CI, 5.6-11; negative LR [LR–], 0; 95% CI, 0-0.12), although the sensitivity decreased to 66%, with a similar specificity when this instrument was validated in the hospital setting.17 Several schemes facilitate the rapid, accurate identification of stroke patients by emergency medical personnel.Transient ischemic attack is traditionally defined as a focal neurologic deficit of ischemic origin of less than 24 hours' duration.38 Because most TIAs last fewer than 4 hours, the diagnosis is usually based on medical history rather than findings on examination.39 However, many patients previously diagnosed with TIA actually had cerebral infarcts demonstrated on magnetic resonance imaging (MRI).40 Clinically silent infarcts (and potentially infarcts associated with a classically defined TIA) may contribute to vascular dementia.41 Traditionally defined TIA is an important marker of short- and long-term vascular risk. Of 1707 patients from a large health care plan in the United States, evaluated in the emergency department and diagnosed with TIA, 5.3% had a stroke within 2 days, whereas 10.5% had a stroke within 90 days.42 The diagnosis of a stroke or TIA indicates the need for urgent management.Historical and objective data help localize the affected portions of the nervous system, providing clues about the likely pathophysiology and etiology (essential for rational secondary prevention).61 Clinicians must recognize that computed tomographic (CT) scan results are frequently negative during the first hours after ischemic stroke and technical limitations often impair CT imaging of posterior fossa structures. These limitations in early neuroimaging of the evolving stroke serve to emphasize the importance of the clinical examination. MRI scans, with greater sensitivity than CT, are often not available for immediate, routine patient evaluations.63In this case, the example patient had an NIHSS score of 9 (item 2 = 1, item 3 = 2, item 4 = 2, item 5 = 1, item 8 = 1, item 9 = 1, item 10 = 1; Table 48-2).It is not enough to determine whether the patient with an acute focal neurologic deficit has had a stroke. Treatment with a thrombolytic or an antithrombotic drug is contraindicated in patients with hemorrhage. Three studies that provide information about the accuracy of medical history and physical examination in distinguishing hemorrhagic from ischemic strokes indicate that clinical judgment can be used to increase or decrease the likelihood of hemorrhage, but diagnostic errors occur (Table 48-5). In one study, a multivariate model showed that initial depressed level of consciousness, vomiting, severe headache, warfarin therapy, systolic blood pressure above 220 mm Hg, and glucose level above 170 mg/dL (9.4 mmol/L) in a patient without diabetes increased the likelihood of hemorrhagic stroke.23 The presence of any of these features more than doubles the odds of hemorrhage (LR+, 2.4; 95% CI, 1.8-3.2) and the absence of any of these features decreases the odds by one-third (LR–, 0.35; 95% CI, 0.18-0.68). The other 2 studies described the accuracy of the physician's overall assessment without the use of a predictive model and produced results that performed similarly to those of the multivariate model (the results were statistically homogenous for the diagnostic OR; P = .99). Thus, the clinical judgment that a stroke is hemorrhagic has an LR = 3.1 (95% CI, 2.1-4.6), whereas the assessment that the stroke is not hemorrhagic decreases the likelihood (LR, 0.61; 95% CI, 0.48-0.76). The use of a complex discriminant score (based on specific historical and objective physical factors) modestly improves accuracy relative to clinician judgment but is cumbersome and not clinically useful.72 A neuroimaging study is mandatory before the patient is given a thrombolytic agent or anticoagulant.60-62Ischemic stroke may be caused by a variety of pathophysiologic conditions and mechanisms. The distinction between ischemic stroke subtypes is important to guide specific secondary prevention measures such as treatment with anticoagulants that are useful in patients with cardiogenic embolism. In contrast, anticoagulants are not useful for patients with atherothrombotic stroke.74,75 Patients with carotid artery distribution symptoms who have an ipsilateral high-grade extracranial carotid artery stenosis benefit from carotid endarterectomy.76 Simple clinical features useful at the bedside can help. For example, the acute onset of a focal neurologic deficit in a patient with a cardiac or arterial embolic source increases the odds of embolic stroke up to nearly 11-fold (LR+, 11; 95% CI, 5.7-21), whereas the absence of these features decreases the odds of embolic stroke by approximately one-quarter to one-half (LR–, 0.36; 95% CI, 0.24-0.56).77The example patient was alert, was not hemiplegic, and did not have a conjugate gaze palsy. He has a low likelihood of in-hospital mortality related to the stroke. According to his NIHSS score of 9, he has an approximately 78% chance of having a good or excellent recovery by 3 months without treatment (Table 48-9). Twenty-four hours after he received tPA, a brain CT scan showed no evidence of hemorrhage, and he was administered warfarin for secondary stroke prophylaxis for an atrial fibrillation-related cardioembolic stroke. He was able to ambulate independently by the time of hospital discharge, and his speech disturbance improved (NIHSS score of 4). He received outpatient physical, occupational, and speech therapy and had an NIHSS score of 2 after 3 months...."
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