Is a small (3mm) hyperintensity in the basal ganglia significant or not. also what are the causes?

MRI brain: It is likely not significant however the results of your MRI study should be discussed with a neurologist to put into context what the 3 mm spot means relative to the entire MRI study and your medical problems. The causes of the bright spots on MRI studies (T2) of the brain are many and range from aging, migraines, mini-strokes, bleeding, atherosclerosis, multiple sclerosis, and metastatic tumors.