Cognitive impairment in early onset epilepsy is associated with reduced left thalamic volume.

OBJECTIVE: The objective of this study was to investigate whether reduction of thalamic volumes in children with early onset epilepsy (CWEOE) is associated with cognitive impairment.

METHODS: This is a nested case-control study including a prospectively recruited cohort of 76 children with newly-diagnosed early onset epilepsy (onset <5years age) and 14 healthy controls presenting to hospitals within NHS Lothian and Fife. Quantitative volumetric analysis of subcortical structures was performed using volumetric T1-weighted magnetic resonance imaging (MRI) and correlated with the results of formal neurocognitive and clinical assessment. False discovery rate was used to correct for multiple comparisons as appropriate with q<0.05 used to define statistical significance.

RESULTS: Age, gender, and intracranial volume (ICV)-adjusted left thalamic volumes were significantly reduced in CWEOE with cognitive impairment compared to CWEOE without impairment (5295mm3 vs 6418mm3 , q=0.008) or healthy controls (5295mm3 vs 6410mm3 , q<0.001). The differences in left thalamic volume remained if gray matter or cortical/cerebellar volumes were used as covariates rather than ICV (q<0.05). The degree of volume reduction correlated with the severity of cognitive impairment (q=0.048).

SIGNIFICANCE: Reduced left thalamic volume may be a biomarker for cognitive impairment in CWEOE and could help inform the need for further formal cognitive evaluations and interventions.