"Giddy-brained" is a term usually used to describe someone who is easily confused or disoriented. If you're looking for synonyms, you might consider the words dizzy, befuddled, scatterbrained, or addle-brained. Other options include discombobulated, muddle-headed, or perplexed. Each of these words describes someone who might have trouble focusing or making sense of their surroundings. If you're trying to describe someone who is simply overly excited or energetic, you might instead use words like enthusiastic, animated, or spirited. But if you're looking for synonyms specifically for "giddy-brained," the above options are some good places to start.