Clinical considerations and surgical approaches for low-grade gliomas in deep hemispheric locations: thalamic lesions

Background: Tumors with epicenter in the thalamus occur in about 4�% of pediatric brain tumors. The histological diagnosis is mainly gliomas. Among them, low-grade glioma (LGG) constituted of a significant entity of the tumors (Cuccia et al., Childs Nerv Syst 13:514–521, 1997; Puget et al., J Neurosurg 106:354–362, 2007; Bernstein et al., J Neurosurg 61:649–656, 1984; Bilginer et al., Childs Nerv Syst 30:1493–1498, 2014). Since Kelly’s report in 1989, >90�% resection of thalamic tumors were achieved in reported series (Ozek and Ture, Childs Nerv Syst 18:450–6, 2002; Villarejo et al., Childs Nerv Syst 10:111–114, 1994; Moshel et al., Neurosurgery 61:66–75, 2007; Albright, J Neurosurg 100(5 Suppl Pediatrics): 468–472, 2004; Kelly, Neurosurgery 25:185–195, 1989; Drake et al., Neurosurgery 29: 27–33, 1991). Materials and methods: Sixty-nine cases of thalamic tumors in children were retrospectively reviewed. There were 25 cases of LGGs. We analyzed our experience and correlated it with reported series. Results: Summing up of 4 reported series and the present series, there were 267 cases of thalamic tumors in children. Among these tumors, 107 (40.1�%) were LGGs and 91 (34.1�%) were low-grade astrocytomas (LGAs). In the present series, all of the 25 LGGs were LGAs that consisted of 11 pilocytic astrocytomas (PAs) and 14 diffuse astrocytomas (DAs). Six cases received biopsy sampling only. The remaining 19 cases received different degrees of surgical resection via several approaches. Radical (>90�%) resection was achieved better in PAs comparing with DAs. There was no operative mortality. Two patients had increased neurological deficits. In a mean follow-up period of 11.9�years, three patients died of tumor progression and one patient died of anaplastic change. The 5- and 10-year overall survival (OS) was 87.1 and 87.1�%, respectively. Conclusion: Thalamic LGGs are mainly LGAs and are indolent. The rate of >90�% resection was relatively low in the present series. By applying contemporary diagnostic MRI studies, surgical facilities, and appropriate approaches in selective cases, we may try maximum neuroprotective radical (>90�%) resection.