Transcranial Doppler ultrasonography is a safe technique, which allows non-invasive assessment of intracerebral blood flow. This article focuses on the recognition of physiological and pathological TCD waveforms. Transcranial Doppler can be used at the bedside aiding the diagnosis of stroke and complementing other imaging modalities. Due to the discovery of a new TCD finding called small vessel knock, TCD may detect small vessel arterial occlusion when conventional angiography is negative. This review provides evidence that TCD increases recanalization of occluded arteries with and without rtPA and preliminary but exciting evidence that TCD targeting of SVK using ultrasound alone can result in clinical recovery. Three cases are shown recovering on film using this new technique. Further trials are planned in acute stroke and other areas of medicine that may be associated with small vessel occlusion. This could establish TCD as one of the most important techniques used in medicine.
