Volume and Light Keys Not working
My volume cannot be adjusted using the keyboard and neither can the light display on the screen and keyboard..
MacBook Pro (15-inch Mid 2012), OS X Mavericks (10.9.5)
If you hold the 'fn' key in the lower left corner of your keyboard while you try to adjust the volume brightness keys, does have work?
System Preferences -> Keyboard -> Keyboard tab, make sure "Use all F1, F2, etc. keys as standard function keys" is unchecked.
If that is not the problem, then it might be some 3rd party addition. Try booting into Safe Mode
<http://support.apple.com/kb/ht1564>
This is just an experiment to see if a 3rd party addition is causing the problem.
You could experiment with creating a new account and see if the problem occurs in that account.