Pediatric and Adult Low-Grade Gliomas: Where Do the Differences Lie?

Abstract

Two thirds of pediatric gliomas are classified as low-grade (LGG), while in adults only around 20% of gliomas are low-grade. However, these tumors do not only differ in their incidence but also in their location, behavior and, subsequently, treatment. Pediatric LGG constitute 65% of pilocytic astrocytomas, while in adults the most commonly found histology is diffuse low-grade glioma (WHO II), which mostly occurs in eloquent regions of the brain, while its pediatric counterpart is frequently found in the infratentorial compartment. The different tumor locations require different skillsets from neurosurgeons. In adult LGG, a common practice is awake surgery, which is rarely performed on children. On the other hand, pediatric neurosurgeons are more commonly confronted with infratentorial tumors causing hydrocephalus, which more often require endoscopic or shunt procedures to restore the cerebrospinal fluid flow. In adult and pediatric LGG surgery, gross total excision is the primary treatment strategy. Only tumor recurrences or progression warrant adjuvant therapy with either chemo- or radiotherapy. In pediatric LGG, MEK inhibitors have shown promising initial results in treating recurrent LGG and several ongoing trials are investigating their role and safety. Moreover, predisposition syndromes, such as neurofibromatosis or tuberous sclerosis complex, can increase the risk of developing LGG in children, while in adults, usually no tumor growth in these syndromes is observed. In this review, we discuss and compare the differences between pediatric and adult LGG, emphasizing that pediatric LGG should not be approached and managed in the same way as adult LCG.

Keywords: malignant transformation; pediatric low-grade glioma.

Figure 1

A 21-year-old male, presenting with a generalized seizure. (A) Flair hyperintense fronto-temporal tumor of 8.6 × 4.5 × 5 cm with central hypointensity suggestive of aLGG. (B) T1 hypointense tumor surrounded by the vessels of the sylvian fissure. (C) Postoperative imaging after awake fronto-temporal craniotomy and partial tumor resection due to language impairment intraoperatively.

Figure 2

A 16-year-old girl previously diagnosed with TSC and presenting with acute headaches and vomiting. (A) Acute obstructive hydrocephalus and edema due to T2 hypointense lesion in the right frontal horn. (B) Contrast enhancing lesion in the right frontal horn suggestive of SEGA in the context of TSC. (C) Postoperative scan with reduction of ventricular size and showing complete resection of the SEGA.

Figure 3

An 11-year-old boy presenting with headaches and blurry vision. (A) Preoperative MRI scan showing a 6.1 × 4.0 × 3.4 cm T2 hyperintense and contrast enhancing (not shown) lesion suggestive of (non-NF) optic pathway glioma. (B) Postoperative MRI scan after partial resection with tumor rest in the optic pathway. Histology confirmed a BRAF600 mutated pilocytic astrocytoma. (C) Follow-up MRI scan after 4 weeks of MEK inhibitor treatment showing a nearly complete regression of the tumor.

Figure 4

An 8 year-old girl undergoing treatment for congenital scoliosis. (A) MRI head carried out in the setting of her scoliosis work-up showed an incidental finding of a T2 hyperintense cerebellar lesion (B) Interval scan after 6 months showed a spontaneous regression of the lesion. No resection or biopsy was attempted.