Management of posterior fossa gliomas in children

Abstract

Brain tumours form the most common type of solid tumour in children and more that 50% of these are infratentorial. Cerebellar astrocytomas and brain stem gliomas are the commonest posterior fossa glial tumours in children. Cerebellar astrocytomas represent up to 10% of all primary brain tumours and up to 25% of posterior fossa tumors in children, with Low grade gliomas forming the commonest of the cerebellar gliomas. They commonly present with symptoms and signs of raised intracranial pressure due to obstructive hydrocephalus. Radiologically they may be solid or cystic with or without a mural nodule. Surgical excision is the mainstay of treatment and forms the most consistent factor influencing progression free and long term survival. While majority of the tumours are pilocytic astrocytomas, they may also be fibrillary astrocytomas or even high grade tumours. Tumour histology does not appear to be an independent factor in the prognosis of these children, and therefore no palliative treatment after surgery is advocated. Brain stem gliomas account for approximately 10% of all pediatric brain tumours. Cranial nerve signs, ataxia and cerebellar signs with or without symptoms and signs of raised intracranial pressure are classically described symptoms and signs. Radiographic findings and clinical correlates can be used to categorize brain stem tumours into four types: diffuse, focal, exophytic and cervicomedullary. Histologically most brain stem gliomas are fibrillary astrocytomas. Diffuse brain stem gliomas are the most commonly seen tumour in the brain stem. These lesions are malignant high grade fibrillary astrocytomas. Focal tumours of the brain stem are demarcated lesions generally less than 2 cms in size, without associated edema. Most commonly seen in the midbrain or medulla, they form a heterogeneous pathological group, showing indolent growth except when the lesion is a PNET. Dorsally exophytic tumours lie in the fourth ventricle, while cervicomedullary lesions are similar to spinal intramedullary tumours. Expanding lesions are the only lesions amenable for excision while infiltrative and ventral lesions are not.

Neurologic impairments from pediatric low‐grade glioma by tumor location and timing of diagnosis

“…Our findings are in agreement with reports that children with LGG commonly exhibit signs of increased intracranial pressure before diagnosis and that localized symptoms, such as focal neurologic deficits, seizures, and endocrinopathies, are dictated by tumor location . The frequencies of neurologic impairments at first and last visits (that is, three and four, respectively) were similar to those reported in another study, with at least one long‐term impairment occurring in 85% of patients and a minimum of three occurring in 28% .…”

Atypical teratoid/rhabdoid tumor (ATRT) arising from the 3rd cranial nerve in infants: a clinical-radiological entity?

“…Low-grade astrocytomas/gliomas can be avidly enhancing and have an exophytic appearance in the brainstem, but these are often located dorsally in the medulla oblongata and are also hyperintense on T2-weighted images with increased water diffusion [28,29]. …”

Evaluating the safety of perioperative dexamethasone treatment: A retrospective analysis of a single center pediatric low‐grade glioma cohort

“…Focal symptoms, including seizures or endocrine disorders highly depend on tumor location. 10,11 In addition to surgical management, including removal of tumor mass to preserve functional integrity of surrounding brain tissue and external ventricular drainage to reconstitute CSF drainage, corticosteroids have proven to be beneficial in the management of acute symptoms related to CNS tumors, and have been widely used for many decades. 12,13 Due to its lack of mineralocorticoid activity and prolonged symptom control (biological t 1/2 : 36-54 hours), dexamethasone (DM) is the most commonly used agent.…”