If a new parasite in the brain is located and can affect importants blood vessel, propably can cause lightheadednes, or for compressing structures around de cyst.
Sure, standing up too quickly can have a lightheaded effect but that's not what causes it. It could be that the person isn't eating properly, that they're dehydrated, or even more issues that could...
Most likely hydrocodone, but some people also get light-headed from Tylenol. Vicodin contains a mixture of hydrocodone and Tylenol (APAP or Acetaminophen/Paracetamol).