Quantification of the Asymmetry between Right and Left Cerebral Lateral Ventricles by Indexing Methods

To retrospectively analyze hydrocephalus and lateral ventricular asymmetry by measuring the midline shift, Evans index, right and left semi-Evans index, Right and left semi-callosal angles, superior ophthalmic vein (SOV) diameters, and to compare these findings with the control group.

The study included 93 cases with hydrocephalus, 80 cases with asymmetrical lateral ventricles (ALV) and 83 control cases with normal findings who had cranial magnetic resonance imaging (MRI) in our institute between the years 2011 and 2016. A senior and junior radiologist analyzed the images and performed the measurements, and the results were compared.

The cut-off points for the Evans index and right and left semi-Evans indexes for differentiating hydrocephalus and ALV were calculated as 28.68%, 30.77%, and 30.88%, respectively. The septum shift degree was significantly higher in the ALV group compared to the control group (P = 0.010; P < 0.05). ALV or hydrocephalus were not found to be associated with SOV enlargement. The SOVs were not found to be enlarged ipsilateral to asymmetrically enlarged lateral ventricle.

Lower Evans and right and left semi-Evans indices are seen in ALV. Despite some limitations, the Evans index could still be used to differentiate hydrocephalus and ALV. Mild ALV is mostly associated with an off-midline septum. SOV diameter and enlargement are not indicators of hydrocephalus or ALV.