Lindegaard ratio (MCA/ICA) — vasospasm
| Ratio | Interpretation |
|---|---|
| < 3 | Hyperemia / normal |
| 3–4,5 | Mild vasospasm |
| 4,5–6 | Moderate vasospasm |
| > 6 | Severe vasospasm |
Source: J Vasc Surg / StatPearls
Transcranial Doppler / ONSD — Reference values
Transcranial Doppler / ONSD — Reference values: MCA — mean velocity, Optic nerve sheath diameter (ONSD), Lindegaard ratio (MCA/ICA) — vasospasm.
Measurements and reference values
| Measurement | Usual value | Note |
|---|---|---|
| MCA — mean velocity | < 120 cm/s | > 120 suggests vasospasm; > 200 criticalSource: StatPearls |
| Optic nerve sheath diameter (ONSD) | ≤ 5 mm | > 5.8 mm suggests raised ICPSource: POCUS Atlas / touchNEUROLOGY |