There aren't many ways to cure a stroke
A stroke, at least usually, would not be cured simply by removing its conditions as strokes have lasting physical effects such as clotting and ruptured blood vessels, which would need to be healed, unless it's a transient ischemic stroke. Additionally a stroke may be caused by a disease but the stroke itself is not a disease so things such as lesser restoration may not work (it's up to the GM).
Additionally, as Ryan C. Thompson's answer points out, a stroke is not something modeled by the game rules of fifth edition, so whether things such as curing diseases and the like would work is going to be up to the GM.
Some out-of-the-box options:
The true resurrection and reincarnate spells:
Both of these spells revive a creature into a new body if the old one does not exist (some disassembly would thus be required), this would completely remove all the physical side-effects of the stroke, though it is more or less up to the GM whether the mental ones persist. Presumably they would also vanish as it's a new brain, only the soul remains the same.
However, as user Ryan C. Thompson pointed out in a comment, the true resurrection spell may have some oddities as it states:
You touch a creature that has been dead for no longer than 200 years and that died for any reason except old age. If the creature's soul is free and willing, the creature is restored to life with all its hit points. This spell closes all wounds, neutralizes any poison, cures all diseases, and lifts any curses affecting the creature when it died. The spell replaces damaged or missing organs and limbs [...]
If the stroke was caused by old age then that could certainly be interpreted as death due to old age, preventing this spell from working. Additionally, the cardiovascular system is often considered an organ, but whether blood vessels would be restored by this spell is, again, up to the GM.
The sequester spell helps a bit:
[...] If the target is a creature, it falls into a state of suspended animation. Time ceases to flow for it, and it doesn't grow older [...]
This would allow a temporary fix for some of the problems (similar to immediate cryogenic freezing) and allow you to wait until further medical/magical help can be found (perhaps there's some distant magical item that can heal this).