What should I do for stenosis of the M1 segment of the left middle cerebral artery? It depends on the condition and degree of stenosis. If the patient has a stenosis of the M1 segment of the left middle cerebral artery and the stenosis is pre-bifurcation, we first need to do a whole brain angiography to clarify the degree of stenosis of the M1 segment of the left middle cerebral artery. If the M1 segment of the left middle cerebral artery is a pre-bifurcation stenosis with a stenosis of more than 70%, the patient may undergo stenting of the left middle cerebral artery. If the stenosis of the M1 segment of the left middle cerebral artery is after the bifurcation, the treatment is mainly oral administration of statins. If the stenosis of the left middle cerebral artery is 50%, the treatment is also oral administration of statins. If the patient has hypertension or diabetes mellitus, a combination of antiplatelet drugs is required. Therefore, for stenosis of the M1 segment of the main middle cerebral artery, first of all, cerebral angiography should be done to clarify the degree of stenosis, and then the next treatment measures should be decided according to whether the stenosis is pre-bifurcation or post-bifurcation.