No fault there- any given type of brain fault (damage might be a poor choice of words on my part, given my primary examples involved extra wiring in the brain rather than physical damage) will be wildly different in effect, duration and recovery. Strokes are, to my knowledge, some of the worst.
And given that the consequence taken is up to the receiving player, any sort of predicability goes out the window on behalf of the caster (appropriately given the complexity and variation in brains on that detailed a level).
Maybe in event of a maneuver, some detailed control would be possible... But then we're not talking about stress track anymore, and my question becomes moot, so...