**12. Thrombolysis and mechanical thrombectomy**

Before 1995, stroke therapy consisted exclusively of supportive management and efforts to prevent recurrence [81]. In 1995, the National Institute of Neurological Disorders and Stroke reported that early intravenous thrombolysis using tissue plasminogen activator was more effective than placebo [81]. The use of Alteplase for acute ischemic strokes was approved by The Food and Drug Administration (FDA) in 1996 [82]. Thrombolytic therapy was initially offered to eligible patients up to 4.5 hours from symptom onset. IV Alteplase was determined not to be as effective a therapy for patients with large vessel occlusions although it was proved to be an effective treatment. The concept of intraarterial pharmacologic thrombolysis was further expanded and solidified in 1999 with the completion of the Prolyse in Acute Cerebral Thromboembolism study [83]. Intravenous thrombolysis and intra-arterial thrombolysis received widespread acceptance and truly revolutionized the management of acute stroke.

Mechanical thrombectomy has transformed our field, leading to an explosion in intervention for large vessel occlusion. Endovascular thrombectomy became the standard of care of the large vessel occlusion as a result of 5 randomized control trials (RCTs) in 2015 [84]. These 5 trials, MR CLEAN, ESCAPE, SWIFT PRIME, EXTEND-IA, and REVASCAT, extended the field of endovascular neurosurgery. These RCTs proved that patients who had improved functional outcome scores at 90 days after thrombectomy with successful recanalization [84]. This was compared with patients who received IV thrombolytic therapy alone or were unable to receive IV thrombolytic therapy. Improved functional outcomes were also demonstrated by two additional landmark trials, DAWN and DEFUSE [85]. Endovascular thrombectomy for large vessel occlusion beyond the window of 3 to 4.5 hours has provided new treatment options and supportive data demonstrating improved functional outcome scores. Patients meeting eligibility criteria for mechanical thrombectomy had no additional risks in the extended window of 16 to 24 hours. The second generation of devices, including stent retrievers and aspiration catheters, has demonstrated a significantly improved safety, revascularization, and patient outcome. Therefore, the criteria for mechanical thrombectomy, including time limit and physiological preconditions should be re-examined. Not only were

time limits extended, but also discussions on the ability to preserve additional tissue at risk, even in the setting of an established stroke, have made stroke intervention a significant part of the foundation of endovascular practice. "Stroke center," "mechanical thrombectomy ready," and "comprehensive stroke center" designations have all been applied.
