Monitoring for Vasospasm with a Complete Exam

Vasospasm is a complication associated with  subarachnoid hemorrhage (SAH). SAH is usually secondary to a ruptured cerebral aneurysm but can also occur secondary to trauma, arteriovenous malformations or tumors. Vasospasm develops over a multi-stage process. A vasoconstriction occurs in response to vasoactive substances being released as the subarachnoid blood is broken down. This leads to degeneration and inflammatory reactions of the vessel wall causing an organic vasculopathy with structural wall changes and luminal narrowing.

After the initial hemorrhage, a transcranial Doppler (TCD) exam is performed daily to monitor for vasospasm. Daily monitoring allows for intervention before a patient shows any symptoms.

Performing a Complete Exam to Assess for Vasospasm with TCD

The Circle of Willis

Ensuring a Diagnostic Exam

It is important to ensure the envelope is accurately traced along the contour of the TCD waveform. When the envelope is traced accurately the TCD system will automatically provide accurate measures of the mean velocity and pulsatility index of the waveform. If the envelope does not trace correctly, it will result in inaccurate measurements.

Understanding Exam Results

Identifying vasospasm is done by looking for increased or elevated mean flow velocities, turbulent flow, and downstream effects. The level of increase in mean flow velocity correlates with the degree of vasospasm.

Lindegaard Ratio

The Lindegaard ratio is the calculated ratio of the highest mean velocities in the MCA and the ipsilateral extracranial ICA. This ratio compares inflow to outflow and determines the presence of vasospasm versus hyperemia. The MCA is obtained through the temporal window and the ipsilateral ICA is obtained through the submandibular window.

Categorizing the Degree of Vasospasm in the MCA and TICA

Categorizing the Degree of Vasospasm in the ACA and Posterior Circulation

Case Examples

Case Example 1

56 year old Caucasian male, status post aneurysm coiling. Left MCA mean velocity of 132 cm/sec and a left Lindegaard ratio of 3.38 is suggestive of mild vasospasm. The right MCA of 103 cm/sec is within normal limits.

Case Example 2

75 year old Caucasian female, status post aneurysm coiling. Patient is on continuous monitoring EEG, intubated, with multiple IVs in place. Highest mean velocities found are in the left MCA at 164 cm/sec. This is suggestive of moderate left MCA vasospasm. The Lindegaard ratio of 5 confirms left MCA moderate vasospasm.

Case Example 3

44 year old Caucasian female, status post aneurysm coiling. The MCAs have mean velocities greater than 200 cm/sec bilaterally with Lindegaard ratio’s greater than 6. This is suggestive of severe MCA vasospasm bilaterally.


Ali, M.F. Transcranial Doppler ultrasonography (uses, limitations, and potentials): a review article. Egypt J Neurosurg 36, 20 (2021).

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