Lindegaard Index

V MCA : VICA ratio

Lindegaard Index: differentiates vasospasm vs hyperemia

  1. MCA
    1. ratio between intracranial velocity and external carotid artery flow velocity
    2. >3 = vasospasm, ❤ hyperemia
  2. Vertebrobasilar artery
    1. ratio between basilar artery and extracranial vertebral artery
    2. >2 with elevated velocity in basilar = vasospasm

Indications of severe narrowing in TCDs:

  1.  BFV >200 cm/s
  2. rapid rise in flow velicities (>50cm/sec/day)
  3. Lindegaard ratio (VMCA:VICA) >6 (severe)

Best Doppler parameter = peak systolic velocity – threshold of 182 cm/s corresponds to maximal diagnostic accuracy

Lindegaard: differentiate high intracranial flow velocities associated with hyperemia from those with BFV increase from VSP

overall accuracy better than velocity measurements alone

3.6 appears to be threshold to diagnose mild spasm (<25% narrowing) in M1 segment whereas 4.4 indicates moderate to severe spasm (>25% narrowing)



Sn 42% Sp 76% for ACA when 120 cm/sec used as threshold for ACA spasm

TCCS threshold of 75cm/s mean BFV associated with Sn 71% and Sp 85%

V ACA : V ICA ratio can be helpful to differentiate spasm from the normal artery; the ratio VACA : V ICA varies between 0.54 and 2.55


Other Vessels:

few published data on TCD diagnosis of ICA, PCA, VA, BA spasm

sensitivity = 25%, 48%, 44%, and 77%

specificity = 91%, 69%, 88%, and 79%

Sn / Sp greater for BA spasm when ratio  of mean BFV in BA vs extracranial VA is used, with threshold at >2; Sn 100% Sp 95%

Normal reference ranges V PCA : V VA (0.76-2.90)

TCD is not useful to detect VSP in more distal branches. Data lacking.



Le Roux, Peter D, Joshua M Levine, and W. Andrew Kofke. Monitoring In Neurocritical Care. 1st ed. Philadelphia, PA: Elsevier/Saunders, 2013. Print.

Miller, Ronald D. Miller’s Anesthesia. 8th ed. 2015. Print.

Grading of EVD Placement

  1. Grade I
    • optimal placement in the ipsilateral frontal horn or third ventricle
  2. Grade 2
    • functional placement in the contralateral ventricle or noneloquent (parenchyma)
  3. Grade 3
    • suboptimal placement in the eloquent cortex [(parenchyma) or nontarget CSF space, with or without functional drainage


Kakarla, Udaya K. et al. “Safety and accuracy of bedside external ventricular drain placment”. Operative Neurosurgery 63 (2008): ONS162-ONS167.