fMRI-Determined Language Lateralization in Patients with Unilateral or Bilateral Language Dominance According to the Wada Test.
Abstract number :
1.245
Submission category :
Year :
2001
Submission ID :
150
Source :
www.aesnet.org
Presentation date :
12/1/2001 12:00:00 AM
Published date :
Dec 1, 2001, 06:00 AM
Authors :
G-J.M. Rutten, MD, Neurosurgery, University Medical Center, Utrecht, Netherlands; N.F. Ramsey, PhD, Psychiatry, University Medical Center, Utrecht, Netherlands; P.C. van Rijen, MD,PhD, Neurosurgery, University Medical Center, Utrecht, Netherlands; W.C.J.
RATIONALE: Recent studies have shown good, but incomplete agreement between the results from functional MRI (fMRI) and the Wada test for the assessment of hemispheric language dominance. A critical issue is the wide range of lateralization indices (LI[ssquote]s) that has been reported across different studies. This variability lowers the power to differentiate between patients with either unilateral or bilateral language representation. In previous studies we have demonstrated that stringent statistical thresholding of activation maps as well as a combined analysis of different language tasks (CTA) allowed for reproducible and high LI[ssquote]s in groups of right-handed volunteers (see Ramsey NF et al., Neuroimage 2001; 13, 719-733). In the present study these strategies were expected to yield a clear differentiation between patients with either unilateral (either right or left) or bilateral language representation according to the Wada test.
METHODS: 21 epilepsy surgery patients underwent Wada testing as well as fMRI with four different language tasks (verb generation, picture naming, verbal fluency and sentence comprehension). LI[ssquote]s were defined for several frontal, temporal and parietal volumes of interest. In addition to the individual analyses, a CTA was performed. Statistical maps were stringently thresholded (T values [gt]= 4.5) and LI[ssquote]s were categorized and compared to Wada test results.
RESULTS: Overall, the CTA was the most robust analysis for detection of brain activity. In patients with unilateral language representation, both the CTA and verb generation task yielded concordance in 13 of 14 patients; there was a significant correlation between frontal and temporoparietal LI[ssquote]s for these tasks. In patients with bilateral language representation significantly less brain activation was detected as compared to the patients with unilateral language representation. After lowering of the statistical threshold to increase detection power in these patients, the CTA yielded best results (concordance in 3 of 4 patients).
CONCLUSIONS: The combined task analysis correlated with Wada test results better than any of the single fMRI tasks. In particular in patients that had bilateral language representation according to the Wada test, it was a more robust and reliable method to predict hemispheric language dominance. Discrepancies are discussed in the context of Wada test reliability and future clinical use of fMRI.