Simulated transcranial Doppler spectra for each basal cerebral artery, with vasospasm, hyperemia, raised ICP and cerebral circulatory arrest patterns. Freeze, measure, and grade like you would at the bedside.
Freeze the screen to measure.
| Vessel | Window | Depth | Direction | MFV |
|---|---|---|---|---|
| MCA (M1) | Temporal | 45 to 65 mm | Toward | 55 ± 12 cm/s |
| ACA (A1) | Temporal | 60 to 75 mm | Away | 50 ± 11 cm/s |
| PCA (P1) | Temporal | 60 to 70 mm | Toward | 40 ± 10 cm/s |
| Basilar | Suboccipital | 80 to 110 mm | Away | 41 ± 10 cm/s |
| Vertebral | Suboccipital | 60 to 80 mm | Away | 38 ± 10 cm/s |
| ICA (extracranial) | Submandibular | 40 to 60 mm | Away | About 30 cm/s |
| MCA MFV | Lindegaard ratio | Interpretation |
|---|---|---|
| < 120 cm/s | < 3 | Normal |
| 120 to 200 cm/s | 3 to 6 | Mild to moderate vasospasm |
| > 200 cm/s | > 6 | Severe vasospasm |
| High | < 3 | Hyperemia (high flow, not narrowing) |
Temporal window above the zygomatic arch for the MCA, ACA and PCA. Suboccipital window through the foramen magnum for the vertebral and basilar arteries. Submandibular window for the extracranial ICA, used as the denominator of the Lindegaard ratio. Orbital insonation needs reduced power. About 10 to 20 percent of adults, more often older women, have an inadequate temporal window.
Trace the outer envelope. MFV = (PSV + 2 × EDV) / 3 approximates the time-averaged peak. PI = (PSV − EDV) / MFV (Gosling), normal about 0.6 to 1.1. RI = (PSV − EDV) / PSV. Lindegaard ratio = MCA MFV / extracranial ICA MFV.
A rising PI with falling diastolic velocity suggests rising intracranial pressure or falling cerebral perfusion pressure, but PI also changes with heart rate, CO2, cardiac output and aortic regurgitation. Oscillating (to-and-fro) flow and small systolic spikes indicate cerebral circulatory arrest; use them only within your institution's brain death protocol, as an ancillary test, with repeated examinations of both MCAs and the basilar artery.