Q: Initially my friend’s doctor thought he might have Parkinson’s, but now they say he has CBGD. What is this?A: Cortical basal ganglionic degeneration is a rare degenerative brain condition first identified as a specific disease entity in 1967. It affects less than 1 per 100,000 people; it is thought to be sporadic, meaning it may occur in anyone, but it is possible there is a familial component in some cases.