The patient is an 83-year-old, right-handed woman with a past history of type 2 diabetes, hypertension, hyperlipidemia, and asthma who presents 10 days after experiencing an episode of right eye visual loss and left-sided hemiplegia lasting approximately 5 minutes, with spontaneous resolution. Given the transient nature of her symptoms, the patient did not seek medical care, but saw her primary care physician several days later, who subsequently ordered a magnetic resonance image/magnetic resonance angiogram (MRI/MRA) for further evaluation. She was sent to the emergency department (ED) when the scan was notable for subacute infarct in the right frontal cortex (Figure 23-1) and an absence of flow-related signal in the right common carotid bifurcation, highly suggestive of carotid stenosis (Figure 23-1). In the ED, the patient was in no acute distress, her vitals were stable, and her physical examination was notable for mild left facial asymmetry but an otherwise benign neurologic examination.
Magnetic resonance imaging/magnetic resonance angiography of patient demonstrating cortical infarct in frontal lobe (left) and loss of signal at the level of right carotid bifurcation (right).
What is the next step in the management and workup of this patient?
The patient's imaging and physical examination findings are highly suggestive of an ischemic stroke in the right frontal cortex secondary to thromboembolism from a right carotid stenotic atherosclerotic lesion (while this patient's MRA is highly suspicious for carotid stenosis as the cause of the ischemic stroke, an electrocardiogram [ECG] and transesophageal echocardiogram should be ordered to rule out cardiac causes as well). Since this patient is well outside the time window for intravenous thrombolysis, she should be started on acetylsalicylic acid (ASA) 325 mg tid for secondary prevention of stroke and should receive further diagnostics for her suspected carotid artery disease.
Extracranial, large-vessel stenosis should be evaluated by at least two of the following three noninvasive modalities to determine the extent and degree of stenosis: MRA, computed tomographic angiography (CTA), and carotid Doppler ultrasound. Carotid Doppler ultrasound is a quick, inexpensive, and portable modality that is easily performed at the bedside and assesses stenosis via focal measurements of flow velocity; however, the quality of the study is highly dependent on the physician/technician. MRA, which can be performed with or without contrast, does not expose patients to radiation and has demonstrated greater discriminatory power than ultrasound in assessing high-grade stenosis.1 CTA, while an excellent modality for identifying carotid occlusion, has less discriminatory power in identifying high-grade stenosis.2 If stenting is considered as a possible treatment modality, the patient can be evaluated with angiography, the gold standard for evaluating carotid disease, for possible intervention. However, it is a costly and an invasive procedure and is associated with risk of contrast nephropathy, especially in patients with underlying ...