Vasospasm can be detected by the signs observed on physical examination of the patient and by radiological methods such as cerebral angiography, and Trans-Cranial Doppler (TCD) ultrasound. The physical exam is sensitive for vasospasm in patients who are otherwise awake and able to participate in a neurological examination. Many patients with subarachnoid hemorrhage are not keenly aware nor participative to make this clinical exam meaningful. Therefore clinical examination alone lacks sensitivity.