The Lindegaard Index helps distinguish between true vasoconstriction (Vasospasm) and hyperemia. An isolated increase in MCA flow velocity may reflect either condition. Normalization to the flow velocity of the extracranial Internal carotid artery increases diagnostic specificity.
Definition
The Lindegaard Index is defined as[^1]:
Lindegaard Index = mean flow velocity of the MCA / mean flow velocity of the ipsilateral extracranial ICA
Interpretation
Lindegaard Index | Interpretation |
<3 | more likely hyperemia |
3-6 | Vasospasm |
>6 | Severe vasospasm |