That's tough to say. I haven't heard of cables going bad like screens, although I suppose it has to happen now and then...
Another thought, although by the looks it doesn't quite seem like that, there's the possibility the onboard graphics are bad too. It'd be worth your while to hook up a monitor if the laptop allows for this, particularly if the system has separate RAM for the graphics.
It's probably not going to get any better. The cable is likely to be much cheaper than a new LCD, so if the graphics aren't shot, that'd be the next thing to try.