The wires connecting the LCD to the motherboard might be bad, the connection itself on the mobo might be bad. If the outside display works, that means the video chip/card in the laptop is working fine as it's still able to push out a display, just not to the monitor. I'd recommend replacement of the wires (if you're able) to test it. If you can't do that, I'm not sure there's much you can do.
In before "lol alienwares" or "lol dell"