Need help diagnosing stripes on LCD Screen

I have an early 2009 Macbook Pro 17" and there are now stripes on the left hand side of the screen.

Connecting to external monitor is fine, taking a screenshot is fine.

Problem first appeared intermittently 6 months ago for a few weeks, then it disappeared. It appears by fading in and then disappears by fading out. It just appeared again a week ago and has not gone away since.

What are the proper troubleshooting steps? Is this is the cable, the LCD, the logic board, or does the whole display need to be replaced?