Abstracts

Rationale: There is dispute regarding whether language is definitively lateralized to a single hemisphere from an early age, and whether this can be reliably determined with the intracarotid amobarbital procedure (IAP), fMRI or magnetic source imaging (MSI), especially in very young children. The possibility that bilateral language representation may be more common in early childhood has not been studied. This study sought to clarify the likelihood of bilateral language function in very young versus older children based on the IAP.  Methods: Patients included 14 young (3-7 years old) and 44 older children (8-12 years old) who underwent the IAP as part of their presurgical evaluation. Patients were included if both the left and right hemispheres were injected, the patient remained alert following both injections, and hemispheric language dominance or bilateral language representation could be successfully classified. Patients were classified as bilateral for language if they were unable to produce speech or displayed disrupted speech despite preserved alertness following both injections or produced meaningful speech following both injections. A hemisphere was judged to be dominant for language if speech was produced without paraphasic errors following contralateral injection and global aphasia was produced following ipsilateral injection. The proportion in each age group that demonstrated lateralized or bilateral language representation were compared with the chi-square and Fisher exact tests.  Results: Fifty-eight percent of young children and 30% of older children demonstrated bilateral language representation on the IAP (p= .06). Younger children were somewhat more likely to display bilateral language representation whether seizure onset was left (60% bilateral) or right (50% bilateral) than were older children with left (31% bilateral) or right hemisphere seizure onset (14% bilateral), although these comparisons also fell slightly short of statistical significance. Those demonstrating bilateral language did not differ in age of seizure onset from those who demonstrating lateralized language representation (4.7 and 4.2 years, respectively), nor did young children differ significantly in age of onset from older children (3.5 year and 4.7 years, respectively). Conclusions: These data suggest that language may become increasingly lateralized between early and middle childhood, consistent with some studies of healthy children indicating increasing hemispheric specialization for language with age. Over half of those age 7 or younger in this patient sample demonstrated bilateral language representation that could not be attributed to side or age of seizure onset. Implications for epilepsy surgery will be discussed. Funding: No funding