Brainstem gliomas (BSGs) account for approximately 10% to 20% of all pediatric central nervous system (CNS) tumors. Brainstem gliomas are a heterogeneous group of tumors which occur in the region of the brain stem. They may occur in children as well as adults but are not nearly as common in adults. They account for about 20% of all pediatric primary brain tumors, but constitute less than 2% of all adult gliomas.
According to the report from The Central Brain Tumor Registry of the United States, brainstem gliomas were reported to account for up to 20% or more of primary brain tumors. There does not appear to be a sex predilection for brain stem gliomas. No specific risk factors, either environmental or infectious, have been described to be related to the incidence of brainstem gliomas. They can occur in various parts of the brainstem and are classified based on the onset, location, growth pattern, imaging characteristics, and histological features. Brainstem gliomas arises from the midbrain, pons, and medulla. However, most brainstem gliomas arise in the pons of the brain stem. The most common type is the diffuse intrinsic pontine glioma (DIPG) which accounts for 75% of brain stem gliomas with approximately 400 new cases of DIPG occurring each year in the United States. Nondiffuse brainstem gliomas, includes focal, dorsal exophytic (outward growth of a tumor) and cervicomedullary gliomas, are encountered less often. BSGs present with varied clinical features.
The most common presenting symptoms (complaints of the patient) in brain stem gliomas are double vision, weakness, loss of coordination, trouble walking, difficulty in swallowing, slurred speech, headache, drowsiness, nausea, and vomiting. Although the exact presentation will vary according to location and size of the tumor; in general, patients will exhibit a combination of these signs (elicited by the clinician) namely ataxia, cranial nerve palsies, long tract signs and hydrocephalus. Brainstem glioma patients can have a combination of clinical presentations. Cranial neuropathies are common in most tumors of the brainstem. Simultaneous involvement of multiple cranial nerves is more frequently encountered with diffuse lesions. Focal lesions, in contrast, are often associated with more limited cranial nerve involvement.
The imaging modalities considered for radiological diagnosis of brainstem glioma are Computed Tomography (CT), Magnetic Resonance Imaging (MRI), MR Spectroscopy (MRS), MR Perfusion (MRP), Diffusion MRI /Diffusion Tensor Imaging (DTI) and Positron Emission Tomography (PET). MRI imaging forms the cornerstone for diagnosis as well as an aid in treatment planning. BSGs are difficult to diagnose, and are challenging to treat. The standard treatment modalities used in the management of brainstem glioma are Radiotherapy, Surgery and Chemotherapy, followed by Combined therapy, Symptomatic therapy, Palliative Care, Rehabilitation & Supportive therapy. The mainstay of management is radiotherapy and surgery. Disappointingly chemotherapy associated with combined therapies has not been very promising. Strategies such as gene therapy, microRNA (miRNA) therapy, stem cells, and immunotherapy may potentially lead to more effective treatment of brainstem gliomas in the future. Brainstem Gliomas are among the most difficult of pediatric CNS tumors to treat because of challenges in diagnosis, lack of effective treatment and a historical lack of consensus between specialists. Given the rapid advances in the fields of molecular classification, epigenetics, and cancer therapeutics, it is likely that significant gains will be made over the next decade, thereby enabling evidence-based management algorithms for both pediatric and adult brainstem gliomas. This, in turn, will improve early diagnosis, successful management of brainstem gliomas, and likely will enhance the quality of life and the survival rate of these patients.
Written by: Divyalakshmi Ramakrishna, M.D.S. (Rhenix LifeSciences) & Lawrence D. Jones, Ph.D. (CureScience)