Localization of function-specific segments of the primary motor pathway in children with Sturge-Weber syndrome: a multimodal imaging analysis

To explore whether diffusion-weighted imaging (DWI) can localize specific segments of primary motor areas in children with Sturge-Weber syndrome (SWS), this study investigated the corticospinal tract (CST) between precentral gyrus (PCG) and posterior limb of internal capsule (PIC).

DWI was performed on 32 healthy children and seven children with unilateral SWS affecting the sensorimotor area variably. A hierarchical dendrogram was applied to find PCG-segments uniquely connected to PIC-segments. The resulting PCG-clusters were used to image primary motor pathways in DWI and find metabolic abnormalities of primary motor areas in positron emission tomography (PET) scans.

In healthy children, five PCG-clusters were found to have unique CST courses, corresponding to CST segments of mouth/lip, fingers, and leg/ankle primary motor areas determined by functional magnetic resonance imaging (fMRI). In children with SWS, reduced streamlines in these PCG clusters were highly correlated with glucose-hypometabolism on PET (R(2) = 0.2312, P = 0.0032). Impaired CST segment corresponding to finger movements correlated with severity of hand motor deficit.

The presented method can detect impaired CST segments corresponding to specific motor functions in young children who cannot cooperate for fMRI. This approach can be clinically useful for a noninvasive presurgical evaluation of cortical motor areas in such children.