藤原 英治

Karnofsky Performance Status (KPS) is a widely used scale to assess performance status. KPS ≥ 50% implies that patients can live at home. Therefore, maintaining KPS ≥ 50% is important to improve the quality of life of patients with glioblastoma, whose median survival is less than 2 years. This study aimed to identify the factors associated with survival time with maintenance of KPS ≥ 50% (survival with KPS ≥ 50%) in patients with glioblastoma, IDH-wildtype. Ninety-eight patients with glioblastomas, IDH-wildtype, who were treated with concomitant radiotherapy (RT) and temozolomide (TMZ) followed by maintenance TMZ therapy, and whose KPS at the start of RT was ≥ 50%, were included. The median survival with KPS ≥ 50% was 13.3 months. In univariate analysis, preoperative KPS (≥ 80%), KPS at the start of RT (≥ 80%), residual tumor size (< 2 cm3), methylated MGMT promotor, and implantation of BCNU wafer were associated with survival with KPS ≥ 50%. In multivariate analysis, KPS at the start of RT (≥ 80%), methylated MGMT promotor, and residual tumor size (< 2 cm3) were significantly associated with increased survival with KPS ≥ 50%. A strategy of maximum possible tumor resection without compromising KPS is desirable to prolong the survival time with KPS ≥ 50%.

BACKGROUND AND IMPORTANCE: The usefulness of intraoperative real-time fluorescence navigation using indocyanine green (ICG) for metastatic brain tumors, schwannomas, and meningiomas is well established. However, its application in cases of radiation-induced brain necrosis remains unexplored. Surgical intervention is performed in symptomatic and medically refractory cases; however, radiation-necrotic lesions often exhibit a diffuse pattern with unclear surgical boundaries, making it challenging for surgeons to identify the lesion during the surgery. METHODS: Four patients with intracranial necrotic tissues received 1.5 mg/kg ICG 1 hour before observation during the surgery. We used near-infrared fluorescence to identify the necrotic location. CLINICAL PRESENTATION: Case 1: A 61-year-old man with lung cancer and metastatic brain tumor history exhibited left-sided weakness a year after craniotomy and radiotherapy. A new lesion required surgery, where ICG fluorescence imaging highlighted a significant contrast in the resection cavity, aiding in successful lesion removal without complications. Case 2: A 51-year-old man with resected glioblastoma developed paralysis. ICG fluorescence during surgery confirmed necrosis and enabled the lesion's removal despite potential inaccuracies due to brain shift, without ICG-related complications. Near-infrared fluorescence could visualize necrotic tissues in all 4 cases. The mean signal-to-background ratio of the necrotic tissues in delayed window ICG was 3.5 ± 0.7. The ratio of the gadolinium-enhanced T1 tumor signal to the brain (T1-weighted background ratio) was 2.3 ± 0.4. CONCLUSION: This report is the first to demonstrate the efficacy of ICG intraoperative fluorescence imaging in identifying radiation-induced necrotic brain tissues.

Schwannomas of the trochlear nerve are relatively rare, and most patients present with preoperative diplopia because of trochlear nerve palsy. We describe the case of a 61-year-old male patient with a trochlear nerve schwannoma and no pre- and postoperative diplopia, despite his trochlear nerve being cut during the operation. We aimed to investigate the frequency of postoperative diplopia associated with intraoperative trochlear nerve disturbance by reviewing previous case reports, wherein postoperative diplopia did not occur after the trochlear nerve was cut intraoperatively. We recorded the frequency of diplopia because of intraoperative trochlear nerve disturbance, such as the trochlear nerve being cut, in cases without pre- and postoperative diplopia. We searched the PubMed, Medline, and Google Scholar databases for works published from 1976 to 2020 and followed the preferred reporting items for systematic reviews and meta-analyses guidelines. We reviewed 36 publications and found 92 cases of trochlear nerve schwannoma. Surgical resection was performed for 43 patients, of whom 40 were kept under observation and 9 were treated with radiation therapy. Of the 43 cases, 9 without preoperative diplopia underwent gross total resection. We analyzed ten cases (including ours) without preoperative diplopia to check for postoperative diplopia. In total, four cases, including ours, did not display postoperative diplopia despite the trochlear nerve being cut. This may be attributed to the preoperatively acquired motor and sensory fusion in the patient's vision because of tumor progression. Our findings may benefit neurosurgeons who treat patients with schwannomas and help them predict patients' outcomes.