Wellmer Jörg, Weber Bernd, Weis Susanne, Klaver Peter, Urbach Horst, Reul Jürgen, Fernandez Guillen, Elger Christian E
Department of Epileptology, University of Bonn, Sigmund-Freud-Str. 25, D-53105 Bonn, Germany.
Epilepsy Res. 2008 Jul;80(1):67-76. doi: 10.1016/j.eplepsyres.2008.03.005. Epub 2008 Apr 22.
Functional magnetic resonance imaging (fMRI) is being used increasingly for language dominance assessment in the presurgical work-up of patients with pharmacoresistant epilepsy. However, the interpretation of bilateral fMRI-activation patterns is difficult. Various studies propose fMRI-lateralization index (LI) thresholds between +/-0.1 and +/-0.5 for discrimination of atypical from typical dominant patients. This study examines if these thresholds allow identifying atypical dominant patients with sufficient safety for presurgical settings.
65 patients had a tight comparison, fully controlled semantic decision fMRI-task and a Wada-test for language lateralization. According to Wada-test, 22 were atypical language dominant. In the remaining, Wada-test results were compatible with unilateral left dominance. We determined fMRI-LI for two frontal and one temporo-parietal functionally defined, protocol-specific volume of interest (VOI), and for the least lateralized of these VOIs ("low-VOI") in each patient.
We find large intra-individual LI differences between functionally defined VOIs irrespective of underlying type of language dominance (mean LI difference 0.33+/-0.35, range 0-1.6; 15% of patients have inter-VOI-LI differences >1.0). Across atypical dominant patients fMRI-LI in the Broca's and temporo-parietal VOI range from -1 to +1, in the "remaining frontal" VOI from -0.93 to 1. The highest low-VOI-LI detected in atypical dominant patients is 0.84.
Large intra-individual inter-VOI-LI differences and strongly lateralized fMRI-activation in patients with Wada-test proven atypical dominance question the value of the proposed fMRI-thresholds for presurgical language lateralization. Future studies have to develop strategies allowing the reliable identification of atypical dominance with fMRI. The low-VOI approach may be useful.
功能磁共振成像（fMRI）在药物难治性癫痫患者的术前评估中越来越多地用于语言优势评估。然而，双侧fMRI激活模式的解读具有挑战性。各种研究提出了fMRI偏侧化指数（LI）阈值在±0.1至±0.5之间，用于区分非典型优势患者与典型优势患者。本研究探讨这些阈值是否能在术前环境中以足够的安全性识别非典型优势患者。
65例患者进行了严格对照、完全控制的语义决策fMRI任务以及用于语言偏侧化的Wada试验。根据Wada试验，22例为非典型语言优势。其余患者中，Wada试验结果与单侧左侧优势相符。我们为每个患者的两个额叶和一个颞顶叶功能定义、特定方案的感兴趣体积（VOI）以及这些VOI中偏侧化程度最低的（“低VOI”）确定了fMRI-LI。
我们发现，无论潜在的语言优势类型如何，功能定义的VOI之间存在较大的个体内LI差异（平均LI差异0.33±0.35，范围0-1.6；15%的患者VOI间LI差异>1.0）。在非典型优势患者中，布洛卡区和颞顶叶VOI的fMRI-LI范围为-1至+1，在“其余额叶”VOI中为-0.93至1。在非典型优势患者中检测到的最高低VOI-LI为0.84。
Wada试验证实为非典型优势的患者中，个体内VOI间LI差异较大且fMRI激活强烈偏侧化，这对术前语言偏侧化所提议的fMRI阈值的价值提出了质疑。未来的研究必须制定策略，以便通过fMRI可靠地识别非典型优势。低VOI方法可能有用。
