Połczyńska Monika M, Beck Lilian, Kuhn Taylor, Benjamin Christopher F, Ly Timothy K, Japardi Kevin, Cavanagh Lucia, Bookheimer Susan Y
1Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine at UCLA, University of California, Los Angeles, California; and.
Departments of2Neurology.
J Neurosurg. 2021 Apr 2;135(6):1674-1684. doi: 10.3171/2020.9.JNS202036. Print 2021 Dec 1.
Brain tumors located close to the language cortex may distort functional MRI (fMRI)-based estimates of language dominance. The nature of this distortion, and whether this is an artifact of numerous confounders, remains unknown. The authors hypothesized tumor bias based on laterality estimates independent of confounders and that the effects are the greatest for tumors proximal to Broca's area.
To answer this question, the authors reviewed more than 1113 patients who underwent preoperative fMRI to match samples on 11 known confounders (tumor location, size, type, and grade; seizure history; prior neurosurgery; aphasia presence and severity; and patient age, sex, and handedness). The samples included 30 patients with left hemisphere tumors (15 anterior and 15 posterior) and 30 with right hemisphere tumors (15 anterior and 15 posterior), thus totaling 60 patients (25 women; 18 left-handed and 4 ambidextrous; mean age 47 [SD 14.1] years). Importantly, the authors matched not only patients with left and right hemisphere tumors but also those with anterior and posterior tumors. Standard fMRI laterality indices (LIs) were calculated using whole-brain and region of interest (ROI) approaches (Broca's and Wernicke's areas).
Tumors close to Broca's area in the left hemisphere decreased LIs independently of known confounders. At the whole-brain level, this appeared to reflect a decrease in LI values in patients with left anterior tumors compared with patients with right anterior tumors. ROI analysis replicated these findings. Broca's area LIs were significantly lower (p = 0.02) in patients with left anterior tumors (mean LI 0.28) when compared with patients with right anterior tumors (mean LI 0.70). Changes in Wernicke's area-based LIs did not differ as a function of the tumor hemisphere. Therefore, in patients with left anterior tumors, it is essential to assess language laterality using left posterior ROIs. In all remaining tumor groups (left posterior tumors and right hemisphere tumors), language laterality derived from the anterior language ROI was the most robust measure of language dominance.
Patients with tumors close to Broca's area showed more bilateral fMRI language maps independent of known confounders. The authors caution against the assumption that this reduced language laterality suggests no or little risk to language function following tumor resection in the left inferior frontal gyrus. Their results address how to interpret fMRI data for neurosurgical purposes, along with theoretical questions of contralesional functional compensation and disinhibition.
位于语言皮质附近的脑肿瘤可能会扭曲基于功能磁共振成像（fMRI）的语言优势半球估计。这种扭曲的本质以及这是否是众多混杂因素造成的假象尚不清楚。作者基于独立于混杂因素的偏侧性估计提出肿瘤偏倚假说，且认为对于靠近布洛卡区的肿瘤，这种影响最大。
为回答这个问题，作者回顾了1113例以上接受术前fMRI检查的患者，以在11个已知混杂因素（肿瘤位置、大小、类型和分级；癫痫病史；既往神经外科手术史；失语症的存在和严重程度；以及患者年龄、性别和利手）上匹配样本。样本包括30例左半球肿瘤患者（15例前部和15例后部）和30例右半球肿瘤患者（15例前部和15例后部），共60例患者（25名女性；18名左利手和4名双手灵巧；平均年龄47[标准差14.1]岁）。重要的是，作者不仅匹配了左、右半球肿瘤患者以及前部和后部肿瘤患者。使用全脑和感兴趣区域（ROI）方法（布洛卡区和韦尼克区）计算标准fMRI偏侧性指数（LI）。
左半球靠近布洛卡区的肿瘤独立于已知混杂因素降低了LI。在全脑水平上，这似乎反映了左前部肿瘤患者的LI值低于右前部肿瘤患者。ROI分析重复了这些发现。与右前部肿瘤患者（平均LI 0.70）相比，左前部肿瘤患者（平均LI 0.28）的布洛卡区LI显著更低（p = 0.02）。基于韦尼克区的LI变化并未因肿瘤半球不同而有所差异。因此，对于左前部肿瘤患者，使用左后部ROI评估语言偏侧性至关重要。在所有其余肿瘤组（左后部肿瘤和右半球肿瘤）中，源自前部语言ROI的语言偏侧性是语言优势半球最可靠的测量指标。
靠近布洛卡区的肿瘤患者显示出更多与已知混杂因素无关的双侧fMRI语言图谱。作者提醒不要假设这种降低的语言偏侧性表明在左下额回进行肿瘤切除后对语言功能没有或几乎没有风险。他们的结果涉及如何为神经外科目的解释fMRI数据，以及对侧功能补偿和去抑制的理论问题。
