Gliomas in childhood
ALEXIOU G., GOUVIAS Th., VOULGARIS S.

Pediatric central nervous system tumors are the most common solid tumors of childhood. Astrocytomas, medulloblastomas, ependymomas, craniopharyngiomas and choroid plexus neoplasms are the most frequent tumors. Common presenting symptoms include headache, vomiting, nausea, seizures, and altered mental status. Diagnosis is usually made by neuroradiologic studies, including computed tomography (CT), MRI, diffusion-weighted imaging and Magnetic Resonance Spectroscopy (MRS). In the present study we focused on gliomas in children and we performed a critical review of the pertinent literature. We describe their histological characteristics and give a brief review of the possible causation, which is certainly multi-factorial. The most common histologic subtype of glioma in children is the juvenile pilocytic astrocytoma.

Regarding the presumed causes of brain tumors in children, the main fields of interest are the study of environmental factors and the genetic and molecular aspect of gliomas. Exposure to radiation significantly increases the risk of having a child suffering from a brain tumor. Furthermore, several viral infections have been implicated to have a possible tumorigenic potential. In the present study we also present the current knowledge regarding the molecular genetics of gliomas in children. A gain of chromosome arm 7q and losses on chromosome 10 and 22 may be associated with higher susceptibility to glioma development. In general, gliomas in children contrary to adults, most of whom present with high-grade gliomas, have more benign histologies. Furthermore, although most adult gliomas are supratentorial in location, in children predominate tumors in the posterior fossa and the brain stem. Consequently, gliomas in children have different management and prognosis. Optic pathway gliomas represent 3-5% of childhood intracranial tumors. They usually occur in the first decade of life and are common in neurofibromatosis Type 1. About 15% to 20% of individuals with neurofibromatosis type 1 suffer from an optic pathway glioma, which is usually benign. Chemotherapy is the mainstay treatment, whereas radiotherapy and surgical resection are usually reserved for large tumors. Especially in neurofibromatosis type 1 associated optic nerve gliomas, they should not be treated unless there is clear evidence of either ophthalmologic or radiographic progression. Regarding thalamic gliomas, the optimal management remains unclear. Surgical treatment may be used to relieve mass effects. Nevertheless, chemotherapy and radiotherapy are the main treatment for these tumors. Long-term survival is possible in patients with these tumors. Brainstem gliomas comprise 10-20% of all central nervous system tumors in the pediatric population. Diffuse gliomas are the most common. They usually have poor prognosis. Focal lesions are associated with better prognosis. Clinical presentations depend on tumor locations. MRI is the main diagnostic modality. Surgery for diffuse brainstem gliomas is generally not indicated, whereas focal brainstem tumors are amenable to surgical resection. Radiotherapy and chemotherapy remains an important adjunct for these patients but virtually all children with this disease die within 1-2 years of diagnosis. Supratentorial gliomas in children comprise 1% of all central nervous system tumors. Pilocytic astrocytomas and oligodendrogliomas have usually good prognosis after total resection. High grade tumors have poor prognosis despite total resection like in adult population. Some success is associated with the provision of chemotherapy, whereas radiotherapy remains an important adjunct in children older than 3 years. Cerebellar pilocytic astrocytomas constitute about 35% of the posterior fossa tumors. They are usually curable after total resection. High grade gliomas in the cerebellum are extremely rare. Only approximately 35 children with glioblastoma multiforme in the cerebellum have been described in the literature.

In conclusion, the management of pediatric gliomas has certainly benefited from advances in neurosurgical procedures and the new neuro-oncological treatments. In the near future, the constant multi-center collaboration between neurosurgeons, neuropathologists and neurooncologists promises better results in the treatment of brain tumors.

Key words: Glioma, childhood, surgery, chemotherapy, radiotherapy.