IRCCS Istituto delle Scienze Neurologiche di Bologna, Epilepsy Center (full member of the European Reference Network EpiCARE), Via Altura 3, Bologna 40139, Italy; Department of Biomedical and NeuroMotor Sciences, University of Bologna, Via Massarenti, 9 - Pad. 11 - 40138 Bologna, Italy.
Department of Biomedical and NeuroMotor Sciences, University of Bologna, Via Massarenti, 9 - Pad. 11 - 40138 Bologna, Italy; Neurology Unit, Rimini "Infermi" Hospital-AUSL Romagna, Rimini, Italy.
Epilepsy Behav. 2024 Apr;153:109716. doi: 10.1016/j.yebeh.2024.109716. Epub 2024 Mar 19.
This study investigates the prevalence of pathogenic variants in the mechanistic target of rapamycin (mTOR) pathway in surgical specimens of malformations of cortical development (MCDs) and cases with negative histology. The study also aims to evaluate the predictive value of genotype-histotype findings on the surgical outcome.
The study included patients with drug-resistant focal epilepsy who underwent epilepsy surgery. Cases were selected based on histopathological diagnosis, focusing on MCDs and negative findings. We included brain tissues both as formalin-fixed, paraffin-embedded (FFPE) or fresh frozen (FF) samples. Single-molecule molecular inversion probes (smMIPs) analysis was conducted, targeting the MTOR gene in FFPE samples and 10 genes within the mTOR pathway in FF samples. Correlations between genotype-histotype and surgical outcome were examined.
We included 78 patients for whom we obtained 28 FFPE samples and 50 FF tissues. Seventeen pathogenic variants (22 %) were identified and validated, with 13 being somatic within the MTOR gene and 4 germlines (2 DEPDC5, 1 TSC1, 1 TSC2). Pathogenic variants in mTOR pathway genes were exclusively found in FCDII and TSC cases, with a significant association between FCD type IIb and MTOR genotype (P = 0.003). Patients carrying mutations had a slightly better surgical outcome than the overall cohort, however it results not significant. The FCDII diagnosed cases more frequently had normal neuropsychological test, a higher incidence of auras, fewer multiple seizure types, lower occurrence of seizures with awareness impairment, less ictal automatisms, fewer Stereo-EEG investigations, and a longer period long-life of seizure freedom before surgery.
This study confirms that somatic MTOR variants represent the primary genetic alteration detected in brain specimens from FCDII/TSC cases, while germline DEPDC5, TSC1/TSC2 variants are relatively rare. Systematic screening for these mutations in surgically treated patients' brain specimens can aid histopathological diagnoses and serve as a biomarker for positive surgical outcomes. Certain clinical features associated with pathogenic variants in mTOR pathway genes may suggest a genetic etiology in FCDII patients.
本研究旨在调查机械性靶标雷帕霉素（mTOR）通路中的致病变体在皮质发育畸形（MCD）手术标本和组织学阴性病例中的发生率。本研究还旨在评估基因型-组织型发现对手术结果的预测价值。
本研究纳入了接受癫痫手术的耐药性局灶性癫痫患者。病例选择基于组织病理学诊断，重点关注 MCD 和阴性发现。我们纳入了福尔马林固定、石蜡包埋（FFPE）或新鲜冷冻（FF）样本的脑组织。在 FFPE 样本中对 MTOR 基因和 FF 样本中 10 个 mTOR 通路基因进行单分子分子反转探针（smMIPs）分析。检查基因型-组织型与手术结果之间的相关性。
我们纳入了 78 名患者，获得了 28 个 FFPE 样本和 50 个 FF 组织。鉴定并验证了 17 种致病性变体（22%），其中 13 种为 MTOR 基因内的体细胞变体，4 种为种系变体（2 种 DEPDC5、1 种 TSC1、1 种 TSC2）。mTOR 通路基因中的致病性变体仅在 FCDII 和 TSC 病例中发现，FCD IIb 型与 MTOR 基因型之间存在显著相关性（P=0.003）。携带突变的患者的手术结果略优于总体队列，但无统计学意义。FCDII 诊断病例更频繁地具有正常的神经心理学测试，先兆发作的发生率更高，多种发作类型更少，意识障碍发作时的癫痫发作发生率更低，发作自动症更少，立体脑电图检查更少，手术前癫痫无发作的时间更长。
本研究证实，体细胞 MTOR 变体代表 FCDII/TSC 病例脑组织中检测到的主要遗传改变，而种系 DEPDC5、TSC1/TSC2 变体则相对罕见。在接受手术治疗的患者的脑组织标本中系统筛查这些突变，可以辅助组织病理学诊断，并作为手术结果阳性的生物标志物。mTOR 通路基因中的致病性变体相关的某些临床特征可能提示 FCDII 患者存在遗传病因。
