In this study, VEP demonstrated a strong correlation with GMFM at 6 months of corrected age, with the significance remaining high when compared with other clinical characteristics using hierarchical regression analysis. However, the association between the HINE results and Eps has not been confirmed.
In the hierarchical logistic regression analysis, VEP had significant associations that were distinct from those of AEP and SEP, particularly with GMFM scores, compared to other factors. The timing of synaptogenesis in different brain areas may account for their unique association with VEP. According to a study by Huttenlocher and Dabholkar on the maturation of the brain, the visual areas reach their peak of synaptogenesis earlier than the auditory and sensory areas [20]. Therefore, these results suggest that the observed associations, particularly in VEP, may be due to the different maturation processes that occur in different regions of the brain. The aforementioned findings are consistent with the results of a previous study that established that the auditory and visual areas of the brain develop more rapidly than the sensory areas during the first year after birth [21]. Although no significant findings were observed in the SEP analysis, statistically significant results were obtained in the VEP analysis. This study demonstrated that the Eps is a valuable diagnostic technique for the assessment of neurodevelopment in preterm and term infants, which is in line with previous research. This highlights the usefulness of Eps in assessment and reaffirms the association between Eps and neurodevelopmental outcomes [22]. This study identified the VEP as a highly promising predictor of developmental outcomes. Moreover, the high predictive value of VEP for outcomes such as death or CP has been demonstrated in other studies [7].
This study only included preterm infants with “normal VEP reports.” Previous studies that compared VEP with neurodevelopmental outcomes displayed that VEP was very useful in predicting neurodevelopmental outcomes in preterm infants, with a specificity of 94% but a relatively lower sensitivity of 78% [23]. This suggests that the possibility of neurological deficits could not be completely excluded, even in cases where the VEP reports were within the normal range. Therefore, in this study, significant associations between latency differences within the normal range of VEP reports and neurodevelopmental outcomes were confirmed using hierarchical logistic regression analysis. This highlights the need for continuous interpretation of VEP reports rather than binary normal/abnormal interpretations.
Although no significant differences in the EP latencies between the two study groups divided by HINE scores were identified, noting that the study's limited sample size and the early timing of HINE assessment may have contributed to these results is important. Therefore, to draw definitive conclusions regarding the prediction of developmental status at 3 months using Eps based on the results obtained in this study is difficult. The P-value for AEP wave three was 0.052, indicating a relatively closer statistical significance compared with the other SEP and VEP measures. A previous study by Wang et al. demonstrated a strong association between AEP and neurodevelopmental outcomes in preterm infants using the Bayley Scale [24].
In this study, the focus of the analysis was on the values of the left-hemisphere Eps. This decision was based on the observation that in the actual data from the participants, the measurements obtained from the left hemisphere generally demonstrated faster responses than those from the right hemisphere. Differences between the left and right hemispheres have been observed in neuroimaging techniques such as Neurite Orientation Dispersion and Density Imaging or Neurite Orientation Dispersion [25]. This indicates that asymmetry exists in brain development between the left and right hemispheres. Furthermore, other studies in healthy adults have confirmed a significant difference in amplitude between the left and right hemispheres in VEP testing [26, 27]. Therefore, the EP results exhibiting differences between the left and right hemispheres, as observed in this study, suggest that such asymmetry was not unique to this study particularly, but rather a common feature.
A limitation of this study is the small sample size, which may have led to a lack of controlling factors in the analysis. However, the value of this study is significant given the inherent difficulties in conducting research specifically on preterm births. The results of this study should be re-evaluated in future studies with large sample sizes. This is an important step in validating and extending the results of this study.
In conclusion, by combining VEP latency with other relevant factors, clinicians may increase the accuracy of their predictions. This integrated approach has the potential to improve the accuracy of medical interventions, and ultimately contribute to better patient outcomes.