hand shaking with overuse after brain surgery

[shangrila]

My brother was diagnosed with a Pilocytic astrocytoma and had brain surgery 4 months ago. The surgery was a success and they were able to remove 90% of the tumor. He has noticed recently that if he uses his right hand alot, it starts to tremble. Could this be a seizure happening or could it just be weakness in the muscle after the surgery? Any ideas?