Thanks for contacting HSM I am sorry to hear about your father in law and his recent ER visit. Mini-strokes or TIAs are caused by a sudden but reversible arterial blockage to the brain. In my practice I take these episodes seriously and then embark on a series of test to determine the origin of the blockages. I would order a Doppler study of the arteries of the neck, an echocardiogram of the heart and a holter monitor of the heart to check for irregular heart beats. The next course of action is to start prevention with medication to prevent blood clots like aspirin or Plavix. Hope this answers your question. Please contact us again with your questions.