Predictors of language lateralization in temporal lobe epilepsy

Area of Science:

• Neuroscience
• Epileptology
• Cognitive Neurology

Background:

• Atypical language lateralization in epilepsy is linked to factors like left-handedness and seizure focus, but associations are inconsistent.
• Previous research has not comprehensively examined these factors together in temporal lobe epilepsy (TLE) patients.
• The interplay between these factors and their unique predictive power for language lateralization remains underexplored.

Purpose of the Study:

• To investigate the combined influence of handedness, seizure focus, age at onset, and familial sinistrality on language lateralization in TLE patients.
• To identify unique predictors of language lateralization within this patient group.
• To explore interaction effects between these factors on language lateralization.

Main Methods:

• Functional MRI (fMRI) language mapping was used to derive language lateralization indexes in 162 TLE patients.
• Handedness was assessed using the Edinburgh Handedness Inventory.
• Linear regressions and Fisher exact tests analyzed main and interaction effects, followed by multiple regressions to identify unique predictors.

Main Results:

• Individually, left-handedness and a left seizure focus predicted atypical (rightward) language lateralization.
• Interaction effects revealed that stronger left-hand preference correlated with atypical lateralization only with a left seizure focus, early/intermediate age at onset, or no familial sinistrality.
• Side of seizure focus and its interaction with handedness were unique predictors of language lateralization indexes.

Conclusions:

• Degree of left-handedness is a marker for atypical language lateralization in TLE, contingent on seizure characteristics or absence of genetic predisposition for left-handedness.
• Seizure focus and its interaction with handedness significantly and uniquely predict language lateralization in TLE.
• This study elucidates the complex interplay of factors influencing language lateralization in TLE, advancing understanding beyond individual associations.