Age and Sex Variability and Normal Reference Values for the VMCA/VICA Index

BACKGROUND AND PURPOSE: The index of mean blood flow velocity (V) in the middle cerebral artery (MCA) divided by respective velocity in the ipsilateral internal carotid artery (ICA), or VMCA/VICA index, is commonly used as a marker of vasospasm, although reference values are not established. We sought to provide reference data for these velocities and index. METHODS: Transcranial color-coded duplex and carotid duplex sonography was performed in 335 healthy volunteers (211 women, 124 men; mean age SD, 42 18 years; range, 18–86 years). Age analyses were based on three groups: I, <40; II, 40–60; and III,>60 years. The VMCA/VICA index was calculated based on angle-corrected blood flow velocities determined in the MCA and extracranial ICA. RESULTS: Mean flow velocities in the MCA and ICA diminished with increasing age, most pronounced in those subjects>40 years. The VMCA/VICA index increased significantly (1.67 0.005 [age]; P <.05) with age in women, but not in men. In women, reference value