Long-term survival of a patient with diffuse midline glioma in the pineal region: A case report and literature review

Background: Diffuse midline glioma (DMG) is an invasive astrocytic tumor arisen from midline structures, such as the pons and thalamus. Five cases of DMG in the pineal region have been reported, but the clinical course was poor; there was no case of survival for more than 2 years. Case Description: We report the case of a 12-year-old boy with DMG in the pineal region who is living a normal daily life for more than 6 years following multimodal treatment. He complained of a headache accompanied by vomiting that had gradually worsened 1 month previously, and initial magnetic resonance imaging revealed a pineal tumor. Germinoma was initially suspected; however, a combination of chemotherapy using carboplatin and etoposide was ineffective. The first surgery was performed through the left occipital transtentorial approach (OTA); the diagnosis was DMG. After 60 Gy radiotherapy concomitant with temozolomide (TMZ), the tumor enlarged. Second surgery was performed through bilateral OTAs, and 90% of the tumor was removed. In addition, stereotactic radiotherapy (30 Gy, six fractions) was administered, and the local equivalent dose in 2 Gy/fraction reached 97.5 Gy. Maintenance chemotherapy using TMZ and bevacizumab was continued for 2 years. After finishing chemotherapy, the enhancing lesion enlarged again, and bevacizumab monotherapy was effective. Now, at 6 years after diagnosis, the patient leads an ordinary life as a student. Conclusion: Maximum resection and high-dose radiotherapy followed by bevacizumab may have been effective in the present case.

Microsurgical approaches to the cerebellar interpeduncular region: qualitative and quantitative analysis

OBJECTIVE The cerebellar interpeduncular region (CIPR) is a gate for dorsolateral pontine and cerebellar lesions accessed through the supracerebellar infratentorial approach (SCITa), the occipital transtentorial approach (OTa), or the subtemporal transtentorial approach (STa). The authors sought to compare the exposures of the CIPR region that each of these approaches provided. METHODS Three approaches were performed bilaterally in eight silicone-injected cadaveric heads. The working area, area of exposure, depth of the surgical corridor, length of the interpeduncular sulcus (IPS) exposed, and bridging veins were statistically studied and compared based on each approach. RESULTS The OTa provided the largest working area (1421 mm2; p < 0.0001) and the longest surgical corridor (6.75 cm; p = 0.0006). Compared with the SCITa, the STa provided a larger exposure area (249.3 mm2; p = 0.0148) and exposed more of the length of the IPS (1.15 cm; p = 0.0484). The most bridging veins were encountered with the SCITa; however, no significant differences were found between this approach and the other approaches (p > 0.05). CONCLUSIONS To reach the CIPR, the STa provided a more extensive exposure area and more linear exposure than did the SCITa. The OTa offered a larger working area than the SCIT and the STa; however, the OTa had the most extensive surgical corridor. These data may help neurosurgeons select the most appropriate approach for lesions of the CIPR.

Right occipital transtentorial approach for a pineal malignant germ cell tumor

Germ cell tumors account for up to 53% of the malignant lesions found in the pineal region and are typically managed with a combination of radiation therapy and chemotherapy. Malignant somatic transformation of intracranial germ cell tumors is exceedingly rare and has only been reported on two other occasions. Here the authors present the case of a pineal yolk sac tumor that failed optimum first-line treatment and underwent malignant somatic transformation to an enteric mucinous adenocarcinoma requiring surgical intervention. This video demonstrates the technical nuances of the occipital transtentorial approach and the safe microsurgical dissection of lesions within the pineal region. The video can be found here: https://stream.cadmore.media/r10.3171/2021.4.FOCVID2151.

Posterior interhemispheric occipital transtentorial approach for resection of a falcotentorial meningioma

Falcotentorial meningiomas arise along the junction of the falx cerebri and the tentorium cerebelli. The authors present a woman in her 60s with an incidentally discovered falcotentorial meningioma, approximately 3 cm in diameter, resected with a torcular craniotomy and posterior interhemispheric approach. The galenic complex was dissected away from the tumor. In the final view, the bilateral internal cerebral veins and basal veins of Rosenthal were seen. A Simpson grade I resection was achieved. The patient experienced transient contralateral hemianopsia and was discharged home. At 1-year follow-up, her neurological examination findings were unremarkable, and there was no radiographic evidence of tumor. The video can be found here: https://stream.cadmore.media/r10.3171/2021.4.FOCVID2125.

Orofacial dyskinesia post resection of pineal gland tumor

We reported a case of a 33-year-old lady who was diagnosed with a Pineal tumor and underwent craniotomy and gross total surgical resection of the mass through a right occipital transtentorial approach. Immediately upon extubation, the patient started to have persistent chewing-like movements typical of orofacial dyskinesia that resulted later in buccal mucosal injury and swelling of the lips. The movements spontaneously resolved after 3 days. The patient was not taking any medications that were known to induce such movements. Literature review showed that one of the possible mechanisms could be that the suddenly reduced melatonin level in the acute postoperative period leads to dysregulation of dopamine secretion in the nigrostriatal and limbic system causing these abnormal movements. To the best of our knowledge, this is the first such reported complication of orofacial dyskinesia post craniotomy for resection of the pineal tumor in humans.

SURG-15. THE SURGERY OF THALAMIC LESIONS IN PEDIATRIC BRAIN TUMORS

BACKGROUND Pediatric brain tumors are occurred in the center of central nervous system. Since mid-line glioma has defined in the new classification, thalamus has attracted attention as a site that requires surgical intervention. However, the surgery for thalamus is a challenging procedure for neurosurgeons. In this study, we studied our surgical cases of patients suffering from pediatric brain tumors in thalamus and/or thalamic regions to evaluate the safety of surgeries and the consideration of appropriate surgical approaches. METHODS We reviewed neuroradiological images, medical record, and, surgical videos for the assessment of surgical fields in patients under the age of 15 who had surgical treatments at our institution. RESULTS We had six cases that could be analyzed. The lesions in the posterior parts of the thalamus had been operated by the occipital transtentorial approach. The lesions in the superior parts of thalamus were treated with transcortical transventricle approach. It was possible to achieve sufficient removal of tumors and have good surgical view. The monitoring of motor function and visual function was used in all cases. After removal, we could have a nice view of the important structures around thalamus. CONCLUSIONS The surgeries for thalamus and thalamic regions were safety with enough considerations for neurological examinations and radiological imaging. The intra operative monitoring for motor and visual function should be used.

RARE-54. MOLECULAR ANALYSIS OF ROSETTE-FORMING GLIONEURONAL TUMOR AT MIDBRAIN; REPORT OF TWO CASES

Rosette-forming glioneuronal tumor (RGNT) is a tumor that primarily arises at posterior fossa. We experienced two rare cases of RGNT located at midbrain and investigated their molecular features. Case 1 is a 23-year-old female, and Case 2 is an 18-year-old male. Both cases were surgically removed by the occipital transtentorial approach. Histological analysis demonstrated a biphasic pattern of neurocytic and glial components. The former consisted of neurocytic rosettes and perivascular pseudorosettes, and the latter was GFAP positive, corresponding to the diagnosis of RGNT. Both cases have an excellent clinical course without receiving chemotherapy or radiation therapy. Small residual tumors of both cases shrunk and maintained for 27 and 12 months, respectively. Case 1 underwent DNA methylation array and a subsequent DNA methylation-based classifier, indicating that the case matched RGNT with a 0.99 calibrated score. Also, we identified FGFR1 K656 mutation. Pyrosequence analysis of other genes such as IDH1 R132, IDH2 R172, BRAF T599, BRAF V600, H3F3A K27, H3F3A G34, HIST1H3B K27, TERT C228, FGFR1 N546 had no mutations. RT-PCR of KIAA1549-BRAF fusion was not detected. DNA methylation status of Case 2 is under investigation. Pyorosequence analysis identified TERT C228 mutation but did not identify other mutations such as FGFR1 N546 and K656. Midbrain RGNT corresponds to the histological and molecular features of RGNT. RGNT needs to be differentially diagnosed in the case of a midbrain tumor.

Venous corridors in gravity-assisted retractor-less occipito-transtentorial approach – Our experience of an avenue through the tentacles of pod

Background: Occipital transtentorial approach for selected posterior third ventricular or retrosplenium region tumors provides an ergonomic and safe access. Over centuries, the opponents of this approach highlight the problem of postoperative visual field defect, related to the retraction of occipital lobe. The aim was to describe the surgical nuances of gravity-assisted retractor-less occipital-transtentorial approach (GAROTA) as a modification of originally described GAROTA to minimize the complications with a similar ease of surgery. Methods: In this study, we have retrospectively analyzed our prospectively maintained surgical databases of patients operated by occipito-transtentorial from 2015 to 2019. Demographic variables, preoperative and postoperative neurological deficits (especially visual field defect) were analyzed. Radiological data included relation of veins with tumor, presence of hydrocephalus, size, and extent of lesion. Results: Fifteen patients underwent GAROTA (right-sided extension, n = 7; left-sided extension, n = 4; and midline lesions, n = 4). Headaches (73.3%) and diplopia (40%) were the most common symptoms. No patient had any postoperative visual deficits in both short-term and long-term follow-up. Conclusion: A thorough anatomical knowledge of posterior third interhemispheric region in the semi-prone position is required for GAROTA. Meticulous arachnoid dissection around the deep venous complex and release of cerebrospinal fluid through the cisterns is required. Postoperative cortical vision loss may be prevented by following the key surgical principles in GAROTA.