Purpose
Visual field (VF) defects are a common sequela of perinatal arterial ischemic stroke (PAIS) and can be detected using specialized VF assessments, such as the ‘behavioral visual field screening’ test (BEFIE). Conventional MRI does not always predict VF deficits. The aim of this study was to investigate whether diffusion tensor imaging (DTI) based tractography of the optic radiation (OR) at 3 months of age improves the prediction of VF defects.
Methods
Seventeen patients with unilateral PAIS, who underwent conventional MRI (T1/T2) and DTI at the age of 3 months and a BEFIE VF examination later in life (median age 3yrs) were included. DTI-based tractography of the bilateral OR was performed, and the average fractional anisotropy (FA), axial (λ1), radial (λ23) and mean diffusion (MD) were extracted. Asymmetry of these parameters was used as a predictor of VF defects in the 15 patients with a conclusive result of the BEFIE test, using receiver operating characteristic (ROC) analysis. Conventional MRI was used to assess myelination of both ORs and scored as symmetrical, mildly asymmetrical or severely asymmetrical and compared with the VF results.
Results
Nine children had a normal VF, 6 children had a VF defect (5 hemianopia and 1 quadrantanopia) and 2 children had an inconclusive result of the BEFIE tests. ROC curve analysis revealed that VF outcome could be correctly predicted based on conventional MRI assessment in the majority of children, with an area under the curve (AUC) of 0.94 (95%CI 0.70-1.00). Prediction based on DTI parameter asymmetry indices showed an AUC of 0.98 (95%CI 0.75-1.00), 0.85 (95%CI 0.58-0.98), 0.96 (95%CI 0.72-1.00) and 0.94 (95%CI 0.70-1.00) for FA, λ1, λ23 and MD, respectively (see Figure 1 & Table 1).<br /> Both children who were excluded from the analysis since they had inconclusive BEFIE test results also had an inconclusive prediction of the VF according to the cut-off values of de DTI parameters based on the other 15 children.
Conclusions
Asymmetry in myelination of the OR at 3 months and especially DTI-based tractography of the OR can be used to predict VF defects after PAIS.