The role of the thalamus in neuro-cognitive dysfunction in early unilateral hemispheric injury: a multimodality imaging study of children with Sturge-Weber syndrome.

BACKGROUND: Sturge-Weber syndrome (SWS) with unilateral hemispheric involvement is a clinical model of early onset, chronic, often progressive hemispheric injury, resulting in variable neuro-cognitive impairment.

AIMS: To evaluate if abnormal diffusion and metabolism of the thalamus, a central relay station with extensive cortical connections, may serve as a simple imaging marker of neuro-cognitive dysfunction in SWS.

METHODS: We obtained both diffusion tensor imaging and FDG PET in 20 children (11 girls; age range: 3-12.4 years) with unilateral SWS. Diffusion parameters as well as FDG uptake were measured in thalami, compared to normal control values, and correlated with the extent of cortical hypometabolism, deep venous abnormalities and cognitive (IQ) as well as fine motor functions.

RESULTS: Children with SWS had significantly higher thalamic glucose metabolic asymmetry than controls (p=0.001). Thalamic metabolic asymmetries correlated positively with the asymmetry of thalamic diffusivity (p=0.001) and also with the extent of cortical hypometabolism (p<0.001). Severe thalamic asymmetries of glucose metabolism and diffusion were strong predictors of low IQ (metabolism: p=0.002; diffusivity: p=0.01), even after controlling for age and extent of cortical glucose hypometabolism in children with left hemispheric involvement. Ipsilateral thalamic glucose hypometabolism was also associated with impairment of fine motor functions (p=0.002).

CONCLUSIONS: Both diffusion and glucose metabolic abnormalities of the thalamus are closely related to cognitive functions, independent of age and cortical metabolic abnormalities, in children with unilateral SWS. Thalamic metabolic asymmetry is a robust but simple imaging marker of neuro-cognitive outcome in children with early unilateral hemispheric injury caused by Sturge-Weber syndrome.