Abstract
Aims: To evaluate the role of functional magnetic resonance imaging (fMRI) in epilepsy
management and to ascertain whether laterality index (LI) derived from fMRI data,
using routinely utilized paradigms, can serve as an adjunct to/or replace preoperative
neuropsychological testing for evaluation of language lateralization and impairment.
Materials and Methods: This was a prospective study which included 20 consecutive patients with a clinical
diagnosis of temporal lobe epilepsy over a period of 1 year. Neuropsychological assessment
included oral word association test and animal names test. The scores of both tests
were compared with normographic data provided in the NIMHANS neuropsychology battery.
Three fMRI paradigms were used, namely, picture naming, word generation, and sentence
completion. Processing and statistical analysis were performed subsequently. Results and Conclusion: Right temporal lobe epilepsy (RTLE) was seen in 12 patients and left temporal lobe
epilepsy (LTLE) in 8 patients. All patients were right handed. The activation pattern
was predominantly left lateralized. Language lateralization varied with the type of
paradigm. The overall percentage of patients showing left lateralization ranged from
44.00% for the picture naming task to 75% for the sentence completion. Reduced left
lateralization was noted in both LTLE and RTLE patients. A negative correlation was
observed in LTLE patients between performance in the verbal fluency and the lateralization
index in the temporal and parietal regions of interest (ROI) in the word generation
paradigm, suggesting that increased left lateralization was associated with a poorer
score on neuropsychological tests. In RTLE patients, however, there was no significant
correlation between performance in neuropsychological tests and LI. In conclusion,
language lateralization using LI can serve as an adjunct during preoperative evaluation.
However, it cannot replace neuropsychological testing.
Keywords
Epilepsy - functional magnetic resonance imaging - language - lateralization
