Effect of Grade I and II intraventricular hemorrhage on visuocortical function in very low birth weight infants

Abstract

The neurological outcome for infants with Grade I/II intraventricular hemorrhage (IVH) is debated. The aim of this study was to determine whether very low birth weight infants (VLBW, <1500 g) with Grade I/II (IVH) have altered visuocortical activity compared with infants with no IVH. We assessed the quantitative swept parameter visual evoked potential (sVEP) responses evoked by three different visual stimuli. Data from 52 VLBW infants were compared with data from 13 infants with Grade I or II IVH, enrolled at 5-7 months corrected age. Acuity thresholds and suprathreshold response amplitudes were compared. Grating acuity (GA), contrast sensitivity (CS) and vernier acuity (VA) were each worse in the Grade I/II IVH compared with the no IVH groups (8.24 cpd in IVH group vs. 13.07 cpd in no IVH group for GA; 1.44% vs. 1.18% for CS and 1.55 arcmin vs. 0.58 arcmin for VA). The slopes of the response amplitude for CS and VA were significantly lower in IVH infants. The spatial frequency tuning function was shifted downward on the spatial frequency axis, without a change in slope. These results indicate that Grade I/II IVH are associated with deleterious effects on cortical vision development and function.

Figure 1. Mean response functions for each of the three visual measures

Vector averaged sVEP response functions at O_z derivation in infants with IVH (black diamonds) and without IVH (gray squares) for (clockwise from bottom left) vernier offset, grating acuity, and contrast sensitivity. Error bars are +/− 1 standard error of the means. The solid lines are the regression lines used to estimate threshold and slope of the function (see Table 2 and 3). Amplitudes were lower for the all visual measures in the Grade I/II IVH group compared to no IVH group. Statistically significant differences are present across the entire sweep range for all 3 functions, except for vernier acuity, as shown.