Transcranial Doppler is used to examine the general condition of intracranial blood vessels through the skull, as follows: 1. Transcranial Doppler can assess the degree of vascular sclerosis of intracranial arteries to see whether there is plaque and whether there is significant stenosis. 2. Transcranial Doppler can also be used to determine vascular malformations, whether there are arteriovenous malformations and arteriovenous fistulas in patients. 3. Transcranial Doppler can also be used to monitor for increased intracranial pressure and the presence of emboli in patients with headaches. If the patient has a history of recurrent headaches, transcranial Doppler can also be used to monitor the patient for vasospasm and cerebral hyperperfusion.