A method of performing a medical procedure in a cerebral vessel of a patient including advancing a first catheter system towards an embolus within a cerebral blood vessel and a second catheter system towards the embolus through the first catheter, applying aspiration pressure through the lumen of the second catheter; anchoring a distal end of the second catheter onto the embolus via the aspiration pressure; applying a proximally-directed force on the second catheter; and advancing the first catheter over the second catheter towards the embolus while the distal end of the second catheter remains anchored onto the embolus; and automatically applying aspiration pressure within the first catheter upon the second catheter portion entering into the first catheter.