For patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes, prospective multicenter single-arm studies suggest that oral l-arginine may extend the interictal phase of stroke-like spells and intravenous l-arginine may improve headache, nausea/vomiting, impaired consciousness, and visual disturbances. However, the intravenous treatment may result in fevers and lower hemo- l-Arginine may work by acting as a nitric oxide precursor.747 Although l-citrulline raises nitric oxide production more than l-argi- nine, it has not been systematically studied in Future RCTs are needed to clarify dosage, timing of initiation relative to onset of an attack, duration of therapy, and safety for nitric oxide precursors for treating patients with mito- chondrial myopathy, encephalopathy, lactic aci- dosis, and stroke-like episodes before treatment recommendations can be made. 5.15. Carotid Web Recommendations for Carotid Web Referenced studies that support recommendations are summarized in online Data Supplement 53. COR LOE Recommendations In patients with carotid web in the distribu- tion of ischemic stroke and TIA, without other attributable causes of stroke, antiplatelet therapy is recommended to prevent recurrent ischemic stroke or TIA.748,749 In patients with carotid web in the distribution of ischemic stroke refractory to medical man- agement, with no other attributable cause of stroke despite comprehensive workup, carotid stenting or CEA may be considered to prevent recurrent ischemic stroke.748 750 Synopsis Carotid web is a thin, circumferential shelf-like filling defect that arises from the posterior wall of the ICA bulb visualized on CTA or carotid angiography. Pathologi- cally, carotid web is a variant of fibromuscular dysplasia and can be classified as focal or multifocal. Platelet deposition can occur in the corrugations of carotid web, forming a nidus for potential blood flow stagna- tion and thromboembolism. 