Is mild stroke treatable?

Yes, time dependent. All strokes are treatable, but restoration of function depends on the location and extent of the stroke and the timing of, and type of, intervention. Some strokes can be treated with different types of blood thinners, body cooling to protect the brain, or even surgery. Ascertainment of risk factors and their control, plus psychosocial support and aggressive rehabilitation are required.
Prevention. As noted, "mild" strokes are treatable. However, the risk after having any type of stroke is high within months after the event. It is imperative that an evaluation for risk factors be done and appropriate therapy(ies) are prescribed to best avoid any events in the future.