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J Neurosurg. 2012 Feb;116(2):365-72. doi: 10.3171/2011.9.JNS111068. Epub 2011 Oct 14.

Natural history and surgical management of incidentally discovered low-grade gliomas.

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  • 1Department of Neurological Surgery, Brain Tumor Research Center, University of California, San Francisco, California, USA.



Low-grade gliomas (LGGs) are rarely diagnosed as an incidental, asymptomatic finding, and it is not known how the early surgical management of these tumors might affect outcome. The purpose of this study was to compare the outcomes of patients with incidental and symptomatic LGGs and determine any prognostic factors associated with those outcomes.


All patients treated by the lead author for an LGG incidentally discovered between 1999 and 2010 were retrospectively reviewed. "Incidental" was defined as a finding on imaging that was obtained for a reason not attributable to the glioma, such as trauma or headache. Primary outcomes included overall survival, progression-free survival (PFS), and malignant PFS. Patients with incidental LGGs were compared with a previously reported cohort of patients with symptomatic gliomas.


Thirty-five patients with incidental LGGs were identified. The most common reasons for head imaging were headache not associated with mass effect (31.4%) and trauma (20%). Patients with incidental lesions had significantly lower preoperative tumor volumes than those with symptomatic lesions (20.2 vs 53.9 cm(3), p < 0.001), were less likely to have tumors in eloquent locations (14.3% vs 61.9%, p < 0.001), and had a higher prevalence of females (57.1% vs 36%, p = 0.02). In addition, patients with incidental lesions were also more likely to undergo gross-total resection (60% vs 31.5%, p = 0.001) and had improved overall survival on Kaplan-Meier analysis (p = 0.039, Mantel-Cox test). Progression and malignant progression rates did not differ between the 2 groups. Univariate analysis identified pre- and postoperative volumes as well as the use of motor or language mapping as significant prognostic factors for PFS.


In this retrospective cohort of surgically managed LGGs, incidentally discovered lesions were associated with improved patient survival as compared with symptomatic LGGs, with acceptable surgical risks.

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