In some cases stroke and transient ischemic attacks have occurred after sclerotherapy.[14] Varicose veins and reticular veins are often treated before treating telangiectasia, although treatment of these larger veins in advance of sclerotherapy for telangiectasia may not guarantee better results.[15][16][17] Varicose veins can be treated with foam sclerotherapy, endovenous laser treatment, radiofrequency ablation, or open surgery. The biggest risk, however, seems to occur with sclerotherapy, especially in terms of systemic risk of DVT, pulmonary embolism, and stroke.[citation needed]