胚芽異形成性上皮腫瘍に伴う難治性てんかん症例における発作起始域の臨床的・病理学的検討

Clinical and Histological Characteristics of Ictal Onset Zone in Cases of Intractable Epilepsy Associated with Dysembryoplastic Neuroepithelial Tumor

胚芽異形成性上皮腫瘍（DNT）のてんかん原性はいまだに議論の多いところであるが，DNTのてんかん原性は病理学的に合併する皮質形成異常に存在するという考え方が主流である。九州大学脳神経外科で行ったてんかん原性域としてDNTがみられた難治性てんかんの手術3例のうち，2例は慢性硬膜下電極記録を経由して手術を行い，1例は術中皮質電位記録を用いて手術を行った。慢性硬膜下電極記録を用いた2例とも，DNTの周囲皮質に発作起始域を同定し，これらを含めて切除し，良好な発作転帰を得た。しかし，同部位の病理学的検索では，軽度のグリオーシスがみられるのみで，皮質形成異常は合併していなかった。術中皮質電位記録を用いた側頭葉外側部DNTの1例では，側頭葉内側部に脳波異常域を同定したが，腫瘍を含めた側頭葉外側部を切除し，良好な発作転帰は得られなかった。DNT症例のてんかん外科における摘出範囲は，腫瘍の摘出だけでよいという考え方と，周囲皮質を含めて追加切除したほうがよいという考え方があるが，本報告のようにDNTのてんかん原性は症例によりさまざまであると考えられるので，慢性硬膜下電極記録を中心とした詳細な術前検査により正確なてんかん原性域の同定が重要である。

Abstract

Although the epileptogenic location of dysembryoplastic neuroepithelial tumors (DNTs) is controversial, it has recently been thought to be located within cortical dysplasia (CD) due to its frequent association with CD. Among the 84 resection surgeries for intractable epilepsy performed in our institution between January 2003 and April 2010, three patients had epileptogenic DNTs. In two cases, chronic subdural electrocorticography (ECoG) was performed, and the ictal onset zone was revealed to be in the cortex around the DNT. The ictal onset zone was resected along with the DNT, and good seizure outcome was achieved. Although histological examination of the ictal onset zone revealed mild gliosis, coexistence of CD was not noted. In the third case, the DNT was located in the left lateral temporal lobe and the intraoperative ECoG revealed frequent paroxysmal activity in the medial temporal lobe. Resection of the lateral temporal lobe involving the tumor did not result in good seizure control. The optimal surgical treatment of DNT is controversial. Some authors consider lesionectomy to be sufficient for good seizure control, whereas others advocate that additional resection of the epileptogenic zone beside the tumor improves outcome. Because the epileptogenic location of DNT varies among cases, it is important to identify its location by preoperative multimodal examinations, including chronic subdural ECoG recordings.

(Received February 16, 2012; Accepted September 30, 2014; Published April 1 2015)