Whether severe stenosis of the left middle cerebral artery can be treated conservatively depends on whether there are clinical symptoms, collateral circulation and stenosis site. 1. Asymptomatic middle cerebral artery stenosis with good collateral circulation or stenosis site distal to the end, such as M3 segment, the main choice of conservative treatment; oral antiplatelet aggregation drugs and statins to stabilize plaque treatment. 2. For symptomatic middle cerebral artery stenosis or stenosis close to the end, such as severe stenosis in M1 and M2 segments without good collateral circulation, surgical treatment, such as middle cerebral artery balloon dilatation and stent implantation, is recommended for those who are eligible for surgery after evaluation by neurointerventionalists. For patients with severe stenosis of the left middle cerebral artery, it is recommended to consult a specialist and choose a treatment plan under the guidance of the physician.