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

Clinical article

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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 cm3, 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.

Abbreviations used in this paper: KPS = Karnofsky Performance Scale; LGG = low-grade glioma; MPFS = malignant progression-free survival; OS = overall survival; PFS = progression-free survival; SMA = supplementary motor area; 18F-FET = fluorine-18–labeled fluoroethyl-l-tyrosine.

Article Information

Address correspondence to: Matthew B. Potts, M.D., 505 Parnassus Avenue, M779, San Francisco, California 94143-0112. email:

Please include this information when citing this paper: published online October 14, 2011; DOI: 10.3171/2011.9.JNS111068.

© AANS, except where prohibited by US copyright law.



  • View in gallery

    Graphs showing tumor volumes of 8 patients with LGGs followed up with serial imaging prior to resection. Volumes are based on volumetric analysis. The common linear slope was calculated as 0.187 cm3/month according to a linear mixed-effects regression analysis (p < 0.005). Left: Volumetric growth for individual patients, with Time 0 defined as the first available MR imaging study. Right: Volumetric growth curves adjusted for times based on random intercepts and a common slope. Gray line represents the common linear slope.

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    Kaplan-Meier survival curves for OS, PFS, and MPFS. Each curve compares patients harboring incidental LGGs with those harboring symptomatic LGGs. A: Overall survival (p = 0.039, log-rank test). B: Progression-free survival (p = 0.633, log-rank test). C: Malignant PFS (p = 0.55, log-rank test).


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