Cortical calcification in Sturge-Weber Syndrome on MRI-SWI: relation to brain perfusion status and seizure severity

Abstract

Purpose: To determine the relationship between calcified cortex and perfusion status of white matter and seizure severity in patients with Sturge-Weber Syndrome (SWS), a sporadic neurocutaneous disorder characterized by a leptomeningeal angioma, progressive brain ischemia, and a high incidence of seizures using susceptibility weighted imaging (SWI) and dynamic susceptibility contrast-enhanced perfusion weighted imaging (DSC-PWI).

Materials and methods: Fifteen children (ages: 0.9-10 years) with unilateral SWS prospectively underwent magnetic resonance imaging (MRI). The degree of cortical calcification was assessed using SWI while perfusion status was quantified using DSC-PWI images (asymmetries of various perfusion parameters). Comparisons between calcification, perfusion status, and seizure variables were performed.

Results: Patients with severely calcified cortex demonstrated significantly lower perfusion in the ipsilateral white matter (mean asymmetry: -0.52 ± 0.22) as compared to patients with only mildly calcified cortex or no calcification (mean asymmetry: 0.08 ± 0.25). Patients with severely calcified cortex also suffered from a higher seizure burden (a composite measure of seizure frequency and epilepsy duration; P = 0.01) and a trend for earlier seizure onset and longer epilepsy duration.

Conclusion: Severe calcification in the affected hemisphere is related to severely decreased perfusion in underlying white matter and is associated with more severe epilepsy in SWS patients.

Figure 1

Examples of how the calcium score was determined based on the phase component images of the SWI data set. (a) A score of 0 was assigned to affected areas without high signal on the phase images. (b) A score of 1 was assigned to areas of punctate foci of high intensity. (c) A score of 2 was assigned to areas of linear hyperintensity.

Figure 2

Examples of ROI placement on the PWI images. ROIs approximately 20–40 voxels in size were placed in white matter beneath affected cortex and in homotopic contralateral cortex. The high resolution PWI images made it relatively easy to identify and avoid placement of ROIs over cortex, ventricle and enlarged transmedullary veins. Measurements were made by two neuroradiologists with a high degree of interobserver concordance. (a) Example of ROI placement on a rCBF image. (b) Example of ROI placement on a rCBV image.

Figure 3

A 4 year old girl with SWS. (a) Phase image from the SWI acquisition demonstrates dilated transmedullary veins in the white matter beneath the left frontal cortex without areas of increased signal intensity, indicating the lack any calcific deposits. Calcium score = 0 (b) Corresponding rCBF map for the same patient demonstrates increased blood flow in the affected lobe.

Figure 4

A 10 year old girl with SWS. (a) Phase image from the SWI acquisition demonstrates linear areas of increased signal signal intensity in the left occipital lobe. Calcification score = 2. (b) Corresponding rCBF map for the same patient demonstrates decreased flow in the corresponding cortex and white matter.