Quantification of white matter injury following neonatal stroke with serial DTI

Abstract

Background: Diffusion tensor imaging (DTI) can be used to predict outcome following perinatal arterial ischemic stroke (PAIS), although little is known about white matter changes over time.

Methods: Infants with PAIS were serially scanned in the neonatal period (n = 15), at 3 mo (n = 16), and at 24 mo (n = 8). Fractional anisotropy (FA) values in five regions of interest (anterior and posterior limb of the internal capsule, corpus callosum, optic radiation, and posterior thalamic radiation) were obtained and compared with FA values of healthy controls and neurodevelopmental outcome.

Results: In the neonatal period, no differences in FA values were found. At 3 mo, the six infants who ultimately developed motor deficits showed lower FA values in all affected regions. Four infants developed a visual field defect and showed lower FA values in the affected optic radiation at 3 mo (0.22 vs. 0.29; P = 0.03). Finally, a correlation between FA values of the corpus callosum at 3 mo and the Griffiths developmental quotients was found (r = 0.66; P = 0.03). At 24 mo, a similar pattern was observed.

Conclusion: Neonatal FA measurements may underestimate the extent of injury following PAIS. FA measurements at 3 mo could be considered a more reliable predictor of neurodevelopmental outcome and correlate with DTI findings at 24 mo.

Figures

Figure 1

Example of the normalization of two DTI datasets acquired in the neonatal period (A-C) and at the age of three months (D-F) in an infant with a stroke of the main trunk of the MCA. After the affine registration (A,D) and subsequent LDDMM procedure (B,E) FA values were determined in the regions of interest (C,F).

Figure 2:

The FA values (vertical axis) in the different ROIs versus the age at scan (horizontal axis) of 16 infants who were scanned in the neonatal period and at three months (A) and of the 8 infants who were also scanned at 24 months (B), shown for infants with a normal motor development (left column) and with development of motor deficits (right column). The FA value of the affected side is depicted as a filled symbol, while the unaffected side is depicted by the corresponding open symbol. For the corpus callosum, the mean FA was determined and depicted. The different colours represent the different kinds of strokes observed: main branch MCA stroke (red), posterior branch MCA stroke (green), cortical MCA branch (purple), lenticulostriate branch MCA stroke (black) and PCA stroke (brown). The child with the antenatal MCA stroke is depicted as the upside down triangle. The dashed lines represent the 95% and 99% prediction intervals for each ROI, based on the controls.

Figure 3:

FA values as determined in the affected optic radiation of the ten infants who were subsequently tested for visual field defects. The circles represent the infants who developed a visual field defect, while the triangles represent the infants with a normal visual field on follow-up.

Figure 4:

Coronal views of serial DTI datasets after normalization to the template. The neonatal mDWI shows an ischemic area in the MCA territory, which resulted in a cyst as observed at 3 and 24 months. The neonatal Z-map shows a normal Z-value in all regions. At three months, low Z-values, representing abnormal FA values, can be observed in the affected corticospinal tract, which corresponded with the subsequent development of unilateral motor deficits. The Z-map at 24 months shows an almost identical image. Interestingly, FA values in the fornix showed continued decrease from neonatal to 24 months, suggesting delayed degeneration in this tract.