The Related Factors to Atypical Language Dominance in Patients with Epileptic Foci in the Left Hemisphere

ABSTRACT

BACKGROUND: Several studies have revealed the increased incidence of atypical language dominance in patients with left hemisphere epileptic foci. We retrospectively investigated the incidence and related factors for language dominance shift determined by intracarotid amobarbital procedure (IAP) in patients with left hemispheric epilepsies. METHODS: We included 222 epileptic patients with epileptic foci in left hemisphere whose language dominance was determined by IAP at Asan Medical Center from 1994 to 2004. The items on the language test in IAP included spontaneous speech (6 items), understanding (2 items), and repetition (2 items). Language lateralization index (LI) was computed according to the formula L=(Score IAP right-Score IAP left)/(Score IAP right+Score IAP left). Clinical information was obtained from medical records including age, gender, age at onset of epilepsy, duration of epilepsy, frequency of seizures, risk factors, onset age of risk factors, and lateralization of MRI or EEG. RESULTS: Of the 222 patients (male 110 patients, 49.5%), complete left language dominance was 142 patients (64.0%), and complete right hemispheric language dominance was 29 patients (13.1%). Seizure onset age, onset age of risk factors, handedness and MRI lesions (hippocampal atrophy or left extensive lesion) had statistically significant association with atypical language dominance. On a linear regression analysis, the significant predictors of the atypical language dominancy were handedness and left extensive lesion (R2=.64). CONCLUSIONS: Atypical language dominancy in patients with left epileptic foci was highly correlated with non-right handedness and extensive lesion on the left hemisphere.