MR susceptibility weighted imaging (SWI) complements conventional contrast enhanced T1 weighted MRI in characterizing brain abnormalities of Sturge-Weber Syndrome

Abstract

Purpose: To evaluate the efficacy of susceptibility weighted imaging (SWI) in comparison to standard T1 weighted postgadolinium contrast (T1-Gd) MRI in patients with Sturge-Weber Syndrome (SWS).

Materials and methods: Twelve children (mean age, 5.6 years) with the diagnosis of SWS and unilateral hemispheric involvement were recruited prospectively and examined with high resolution three dimensional SWI and conventional T1-Gd. Both SWI and T1-Gd images were evaluated using a four-grade scoring system according to six types of imaging findings (enlargement of transmedullary veins, periventricular veins, and choroid plexus, as well as leptomeningeal abnormality, cortical gyriform abnormality, and gray matter/white matter junctional abnormality). The scores of SWI versus T1-Gd images were then compared for each type of abnormality.

Results: SWI was superior to T1-Gd in identifying the enlarged transmedullary veins (P = 0.0020), abnormal periventricular veins (P = 0.0078), cortical gyriform abnormalities (P = 0.0020), and gray matter/white matter junction abnormalities (P = 0.0078). Conversely, T1-Gd was better than SWI in identifying enlarged choroid plexus (P = 0.0050) and leptomeningeal abnormalities (P = 0.0050).

Conclusion: SWI can provide useful and unique information complementary to conventional contrast enhanced T1 weighted MRI for characterizing SWS. Therefore, SWI should be integrated into routine clinical MRI protocols for suspected SWS.

Figure 1

Number of patients with each type of abnormality identified by SWI and T1-Gd. P values are from Wilcoxon Signed Rank Test results comparing the group difference between SWI and T1-Gd findings.

Figure 2

Patient # 1, a two year old girl. Image order: SWI mIP (over 4 adjacent slices with slab thickness of 8 mm ) (A), T1 post-gadolinium (T1-Gd) (B). On the T1-Gd MRI image (B), the enlarged transmedullary veins are observed as only mild enhancement (solid arrow) and periventricular veins observed as very tiny enlargement and barely seen (dashed arrow), in the right hemisphere. There is no connection information among these veins on T1-Gd. Comparatively, the transmedullary veins (solid arrow) and periventricular veins (dashed arrow) in the right hemisphere are much better visualized on SWI mIP image with a higher contrast and larger extent. Furthermore, SWI image clearly demonstrates the connection of these venous structures that cannot be seen on T1-Gd; the transmedullary veins wind through the white matter and are clearly connected to the periventricular veins.

Figure 3

Patient #11, a two-year old boy. Image order: SWI mIP (A) and T1 post-gadolinium (T1-Gd) (B). The transmedullary veins (white solid arrow) and the connecting periventricular veins (white dashed arrow) can be seen only as mild enhancements in the right hemisphere on the T1-Gd image. The T1-Gd image also shows the enlarged choroid plexus (white arrow head) and leptomeningeal abnormality (black solid arrow). In comparison, the SWI mIP image shows a clear network of transmedullary veins and periventricular veins with much larger extent and higher contrast than that on T1-Gd. However, the enlarged choroid plexus and leptomeningeal abnormality is not clearly visualized on SWI images.

Figure 4

Patient #7, an 8-year old girl. Image order: SWI mIP (A) and T1 post-gadolinium (T1-Gd) (B). Both SWI and T1-Gd reveal abnormally enlarged periventricular veins (solid black arrow) and atrophy. SWI reveals the abnormal hypointensities at the junction of white matter and gray matter (black dashed arrow) that cannot be seen on T1-Gd images. Furthermore, SWI demonstrates cortical gyriform abnormality (black arrow head) located along cerebral cortex and not shown on T1-Gd images. In contrast, T1-Gd demonstrates extensive and prominent leptomeningeal agioma (white arrow head) located at brain surface and subarachnoid space and not shown by SWI.

Figure 5

Patient #4, a 4.9 year old girl. Image sequence: SWI mIP(A) and T1-Gd (B). The abnormal gyri manifest as hypointensity on SWI image and extensive leptomeningeal enhancement on T1-Gd images (solid arrow). Abnormal gyriform hypointensities on SWI are located along cerebral cortex. Leptomeningeal enhancements are seen on the brain surface. Note that abnormalities on SWI are seen more within the cortex, while abnormalities on T1-Gd are seen more overlying the cortex, and slight hypointensities are seen along cortex. Both SWI and T1-Gd images reveal the winding transmedullary veins and abnormal periventricular vein (arrow head), and brain atrophy. However, the enlarged choroid plexus is visualized only by T1-Gd images (dashed arrow).