Establishing normal Lindegaard Ratio in healthy children 10-16 years of age

Transcranial doppler based diagnostic criteria for cerebral vasospasm are not well established in the pediatric population because there is no published normative data to support the diagnosis. Studies have relied on expert consensus, but the definitions have not been validated in children diagnosed with angiographic evidence of vasospasm. Obtaining normative data is a prerequisite to defining pediatric cerebral vasospasm and the Lindegaard Ratio (LR). In this study, we obtained normative data and calculation of the normal LR from healthy children aged 10-16 years.

TCD and carotid ultrasonography was used to measure steady state velocities of both the middle cerebral artery (V_MCA) and the extracranial internal cerebral artery (V_EICA) in healthy children aged 10-16 years. Demographic information, hemodynamic characteristics and the calculated LR (V_MCA/V_EICA) was determined for each subject using descriptive statistics.

Of the 26 healthy children, 13 were male and 13 were female. V_MCA ranged between 53 and 93 cm/sec. LR ranged between 1 and 2.2 for the cohort. V_MCA for both males and females were within 2 standard deviations (SD) of the normal mean flow velocity. As the V_MCA velocities approached 2 SD above the mean, LR did not exceed 2.2.

Our results help define a threshold for LR which can be used to establish radiographic criteria for cerebral vasospasm in children. Our data suggests that using V_MCA criteria alone would overestimate cerebral vasospasm and raises question of whether an LR threshold other than 3 is more appropriate for the cut off between hyperemia versus vasospasm in children.