Transcranial Doppler and Shunt Studies

Transcranial Doppler imaging is a specialized form of ultrasound imaging which utilizes low frequency ultrasonic waves to detect the change in frequency associated with moving blood (the Doppler effect), and thereby assessing the velocity of blood within intracranial vessels. It is a very accurate and real-time assessment of the brain’s physiology. At NIISwa, this test is commonly performed as a monitoring study for inpatients who have suffered a subarachnoid haemorrhage.

Transcranial Doppler Shunt Studies are also performed using similar equipment for the diagnosis of patients with abnormal communications between the right and left sides of the heart, as well as abnormal connections between the pulmonary (lung) and aortic (body) circulations. It is performed using agitated saline contrast as an outpatient service. A frame is mounted on the patient’s head, and an intravenous cannula is placed in the right elbow with sterile technique. The agitated saline contrast is injected, and the vessels of the brain are continuously monitored for any passing micro-bubbles.

The test is an alternative to micro-bubble echocardiography, however echocardiography looks at bubbles on the wrong side of the heart- whereas microbubble transcranial Doppler shunt studies look at the target tissue itself – the brain. This is important as the most common reason for requiring such a test is to exclude whether the abnormal connection between the two sides of the heart is the cause for a stroke, or a blockage in the artery of the brain.

The test does not require any sedation, which is an advantage over transesophageal echocardiography, as patients can be asked to strain or perform other maneuvers to maximize the likelihood of finding any abnormal connections. It has a similar small risk of a stroke as micro-bubble echocardiography. Patient are expected to remain in the hospital to be observed for a short amount of time prior to same-day discharge.