I had recently updated my computer with the recent windows updates and I had received a problem that affected my brightness. I was unable to even get the option of changing my brightness. Although I solved the problem before I got rid of it.
The Problem was that my Graphics driver was the problem. So I uninstalled it and then restarted my computer. My graphics card is an AMD Radeon 8670M. Before I uninstalled I went through and updated all my drivers then uninstalled it.
For me at least the setting had come back and after the reboot along with the amd driver.

I am not a tech guru. This is just how I solved this problem. Hope this helps. By the way you keep all the updated drivers.