Transcranial doppler

This was vaguely touched upon in several questions, but never directly assessed:

Question 13 from the first paper of 2006 (regarding brain death)

Question 2 from the first paper of 2008 (regarding the use of ultrasound in general)

Question 8 from the first paper of 2008 (regarding the diagnosis of vasospasm)

Question 5 from the first paper of 2013 (regarding the diagnosis of brain death)

Question 2 from the second paper of 2013 (again about the vasospasm)

2MHz low frequency probe on temporal bone to measure flow in MCA.

• normal flow: mean = 55cm/sec
• mild stenosis: > 120cm/sec
• moderate stenosis: > 160cm/sec
• severe stenosis: > 200cm/sec

Useful for the following:

• emboli
• stenosis
• vasospasm post SAH
• assessment of cerebral blood flow

Non-invasive and easily repeatable.

Limitations

• Vasospasm or hyperaemia can both cause increased flow velocity
• sensitivity 80% compared to angiography
• Operator dependent
• Other than ICA and MCA, unable image the other vessels
• Dependent on a good view
• Multiple confounding factors; haematocrit, blood pressure, etc.
• Not validated for use in diagnosis of brain death by ANZICS