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Comparison of FMRI with the Wada test for lateralisation of language in pre-surgical epilepsy patients
Neurolmage
13, Number
o,
ZWI,
Part
L of L Parts
IOE~L’
NEUROLOGY
Comparison of FMRI with the Wada test for lateralisation of language in pre-surgical epilepsy patients JE Adcock*?, SM Smith*, PM Matthews*? *Oxford Centre for Functional Magnetic Resonance Imaging of the Brain, University of Oxford, UK TDepartment of Neurology, Radcliffe Injbnary,
Oxford, UK
Introduction: The accepted standard for pre-surgical evaluation of language dominance in patients with intractable temporal lobe epilepsy is the invasive intracarotid sodium amobarbital test (Wada test). Determination of language dominance is important as dominant hemisphere resections can cause post-operative language deficits. Language lateralisation is particularly important in epilepsy surgery patients, as this population has a higher degree of atypical language dominance compared to the normal population. Functional magnetic resonance imaging (FlvIRI) offers a safe, non-invasive potential alternative technique for the lateralisation and localisation of language before surgery. Here, we compare language lateralisation as determined by the Wada to that as determined by FMRI in a temporal lobe pre-surgical group. Method: 19 right-handed patients (7 with right TLE, 12 with left TLE) and 5 left-handed patients (2 with right TLE, 3 with left TLE) undergoing evaluation for epilepsy surgery and 18 normal controls (12 right-handed, 6 left-handed) were studied using FMRI. All epilepsy patients underwent Wada testing. Subjects performed a silent word generation task (phonetic fluency). The experiment was a 5-minute boxcar design with alternating 30-second on/off periods. EPI dam were acquired using a 3T Siemens-Vatian scanner (TR=3s; TF=3Oms) across 20 axial 5mm slices (64 x 64 matrix) and analysed using MEDx. A laterality index (LI) was calculated as (L-R)/(L+R), based on the number of voxels activated in tbe left (L) or right (R) hemisphere ROI that exceeded a threshold of Z=2.3. Laterality as determined by the Wada was based on the number of language errors.
Normals: All demonstrated clear left hemisphere dominance with FMRI (mean LI = 0.70, SE 0.04, range = 0.48-0.95), with activation of left frontotemporoparietal language areas (including left inferior and middle frontal gyri, left superior temporal gyms, left anterior cingulate and precentral gyri, left superior parietal lobule). There was no significant difference in either the pattern of activation or the lateralisation indices between males and females, or left- and right-handers. Patients: The hemispheric dominance of the Wada test correlated with that of FMRI in all patients. All right-handed patients with right TLE were left hemisphere dominant on Wada and FhIRI, and there was no significant difference in the FMRI activation pattern and lateralisation indices between tbis group and the normal controls (mean LI = 0.81, SE 0.07, range = 0.45-0.97). 6/12 of the right-handed left TLE group were left dominant on Wada and FMRI, similar to the normal group. However, the remaining 6/12 were “bilateral” on Wada testing. These patients also demonstrated bilateral activations with FMRI, corresponding to low or negative lateralisation indices (mean LI = 0.41, SE 0.17, range = -0.92-0.96). Similarly, 4/5 left-handed patients were bilateral for language (right hemisphere dominant in 2) demonstrated with both Wada and FMRI (mean LI = 0.08, SE 0.26, range = -0.92-0.61). Conclusion: FMRI appears to correlate well with Wada, and demonstrates atypical patterns of language dominance in many pre-surgical epilepsy patients. In particular, right-handed patients with left TLE, as well as left-handed patients show more bi-hemispheric language representation by both FMRI and Wada.
S766
13, Number
o,
ZWI,
Part
L of L Parts
IOE~L’
NEUROLOGY
Comparison of FMRI with the Wada test for lateralisation of language in pre-surgical epilepsy patients JE Adcock*?, SM Smith*, PM Matthews*? *Oxford Centre for Functional Magnetic Resonance Imaging of the Brain, University of Oxford, UK TDepartment of Neurology, Radcliffe Injbnary,
Oxford, UK
Introduction: The accepted standard for pre-surgical evaluation of language dominance in patients with intractable temporal lobe epilepsy is the invasive intracarotid sodium amobarbital test (Wada test). Determination of language dominance is important as dominant hemisphere resections can cause post-operative language deficits. Language lateralisation is particularly important in epilepsy surgery patients, as this population has a higher degree of atypical language dominance compared to the normal population. Functional magnetic resonance imaging (FlvIRI) offers a safe, non-invasive potential alternative technique for the lateralisation and localisation of language before surgery. Here, we compare language lateralisation as determined by the Wada to that as determined by FMRI in a temporal lobe pre-surgical group. Method: 19 right-handed patients (7 with right TLE, 12 with left TLE) and 5 left-handed patients (2 with right TLE, 3 with left TLE) undergoing evaluation for epilepsy surgery and 18 normal controls (12 right-handed, 6 left-handed) were studied using FMRI. All epilepsy patients underwent Wada testing. Subjects performed a silent word generation task (phonetic fluency). The experiment was a 5-minute boxcar design with alternating 30-second on/off periods. EPI dam were acquired using a 3T Siemens-Vatian scanner (TR=3s; TF=3Oms) across 20 axial 5mm slices (64 x 64 matrix) and analysed using MEDx. A laterality index (LI) was calculated as (L-R)/(L+R), based on the number of voxels activated in tbe left (L) or right (R) hemisphere ROI that exceeded a threshold of Z=2.3. Laterality as determined by the Wada was based on the number of language errors.
Normals: All demonstrated clear left hemisphere dominance with FMRI (mean LI = 0.70, SE 0.04, range = 0.48-0.95), with activation of left frontotemporoparietal language areas (including left inferior and middle frontal gyri, left superior temporal gyms, left anterior cingulate and precentral gyri, left superior parietal lobule). There was no significant difference in either the pattern of activation or the lateralisation indices between males and females, or left- and right-handers. Patients: The hemispheric dominance of the Wada test correlated with that of FMRI in all patients. All right-handed patients with right TLE were left hemisphere dominant on Wada and FhIRI, and there was no significant difference in the FMRI activation pattern and lateralisation indices between tbis group and the normal controls (mean LI = 0.81, SE 0.07, range = 0.45-0.97). 6/12 of the right-handed left TLE group were left dominant on Wada and FMRI, similar to the normal group. However, the remaining 6/12 were “bilateral” on Wada testing. These patients also demonstrated bilateral activations with FMRI, corresponding to low or negative lateralisation indices (mean LI = 0.41, SE 0.17, range = -0.92-0.96). Similarly, 4/5 left-handed patients were bilateral for language (right hemisphere dominant in 2) demonstrated with both Wada and FMRI (mean LI = 0.08, SE 0.26, range = -0.92-0.61). Conclusion: FMRI appears to correlate well with Wada, and demonstrates atypical patterns of language dominance in many pre-surgical epilepsy patients. In particular, right-handed patients with left TLE, as well as left-handed patients show more bi-hemispheric language representation by both FMRI and Wada.
S766