Abbreviation or formula | Normal values | Elevated ICP | Brain death | Cerebral autoregulation | Cerebral vasospasm | |
---|---|---|---|---|---|---|
Pulsatility index | PI = (sFV − dFV)/mFV | < 1.4 | > 1.4 | – | – | – |
Mean FV | mFV | 60–80 cm/s [2] | – | – | – | Mild ≥ 120 cm/s Moderate = 120–200 cm/s Severe ≥ 200 cm/s (with LR < 3) |
Diastolic FV | dFV | > 20 cm/s | < 20 cm/s | Negative or absent | – | Increased |
Mean flow index | Mx | < 0.3 | > 0.3 | – | > 0.3 (impaired) | > 0.3 |
Lindegaard ratio | LR = mFV MCA/mFV extracranial ICA | < 3 | – | – | – | Mild ≥ 3 Moderate = 3–6 Severe ≥ 6 |
THR test | Less than 10% increase from baseline sFV (impaired) |