The anteroposterior diameter of the lateral ventricle index (ALVI) is a quantitative metric to evaluate the size of the lateral ventricles, particularly in normal pressure hydrocephalus.
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Usage
The anteroposterior diameter of the lateral ventricle index has only recently been described and is not very widely used although it is purported to be superior to the very widely used Evans index 1.
Importantly the measurement of ALVI does not involve measuring the maximum diameter from multiple adjacent axial slices as is the case for the Evans index. As a result, the ALVI measurement technique is thought to be more reproducible and faster 1,2.
Measurement
The ALVI is calculated on axial images obtained or reconstructed in the AC-PC plane. The most inferior axial image is chosen where the entire body of the lateral ventricle is visible without being obscured by the thalamus 1.
The anteroposterior diameter of the lateral ventricle and the anteroposterior diameter of the skull at the same level are measured 1. These values are then divided to give a number less than 1.
Interpretation
A normal ALVI is considered to be less than 0.5. Ventriculomegaly is defined as being present above a value of 0.5 1.
History and etymology
This novel index was first described by Wenjie He and colleagues in 2020 1.
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