Lindegaard ratio
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The Lindegaard ratio refers to the calculated productratio of the mean flow velocities in the middle cerebral artery and the ipsilateral extracranial internal carotid artery, as measured by transcranial Doppler 1. Its primary utility is, in the context of increased MCA velocities after subarachnoid hemorrhage, to confirm the presence of vasospasm.
Interpretation
A Lindegaard ratio above 3 supports the diagnosis of vasospasm in the presence of an increased MCA mean flow velocity, with a ratio above 6 classified as severe 2. A ratio of less than 3 may indicate the presence of an alternate etiology to the increased flow velocities measured, including 3:
- cerebral hyperemia
- hypertension
- hypervolemia
-<p>The <strong>Lindegaard ratio</strong> refers to the calculated product of the mean flow velocities in the middle cerebral artery and the ipsilateral extracranial internal carotid artery, as measured by <a title="Transcranial Doppler sonography (ultrasound)" href="/articles/transcranial-doppler-sonography-ultrasound-1">transcranial Doppler</a> <sup>1</sup>. Its primary utility is, in the context of increased MCA velocities after subarachnoid hemorrhage, to confirm the presence of <a title="Cerebral vasospasm following subarachnoid haemorrhage" href="/articles/cerebral-vasospasm-following-subarachnoid-haemorrhage">vasospasm</a>. </p><h4>Interpretation</h4><p>A Lindegaard ratio above 3 supports the diagnosis of vasospasm in the presence of an increased MCA mean flow velocity, with a ratio above 6 classified as severe <sup>2</sup>. A ratio of less than 3 may indicate the presence of an alternate etiology to the increased flow velocities measured, including <sup>3</sup>:</p><ul>- +<p>The <strong>Lindegaard ratio</strong> refers to the calculated ratio of the mean flow velocities in the middle cerebral artery and the ipsilateral extracranial internal carotid artery, as measured by <a href="/articles/transcranial-doppler-sonography-ultrasound-1">transcranial Doppler</a> <sup>1</sup>. Its primary utility is, in the context of increased MCA velocities after subarachnoid hemorrhage, to confirm the presence of <a href="/articles/cerebral-vasospasm-following-subarachnoid-haemorrhage">vasospasm</a>. </p><h4>Interpretation</h4><p>A Lindegaard ratio above 3 supports the diagnosis of vasospasm in the presence of an increased MCA mean flow velocity, with a ratio above 6 classified as severe <sup>2</sup>. A ratio of less than 3 may indicate the presence of an alternate etiology to the increased flow velocities measured, including <sup>3</sup>:</p><ul>