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 that occur in the region of the brain stem. They may occur in children as well as adults but are not nearly as common in the latter. 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 usually arise 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.
The clinical behavior and presentation of brainstem gliomas are highly variable, depending on the anatomic location, growth pattern of the tumor, age of the patient, and certain other factors. The evolution of symptoms reflects the aggressiveness of the tumor. Low-grade tumors typically present with an insidious course over several months of gradual symptom progression whereas high-grade tumors present a shorter and more abrupt onset of symptoms. Non-diffuse brainstem gliomas including focal, dorsal exophytic, 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:
Loss of coordination
Difficulty in swallowing
Although the exact presentation varies according to the location and size of the tumor. In general, patients exhibit a combination of these signs (elicited by the clinician) namely ataxia, cranial nerve palsies, long tract signs, and hydrocephalus.
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 aid in treatment planning. Diagnosis of brain stem gliomas is based on the clinical findings, neuroimaging studies using MRI followed by histological confirmation. BSGs are difficult to diagnose and are challenging to treat.
Once a definitive diagnosis is determined, a multidisciplinary team of expert clinicians including a pediatrician, neurologist, radiologist, pathologist, neuro-oncologist, radiation oncologist, neurosurgeon, rehabilitation specialist, psychologist, and child life specialist carries out the various phases of management on an individualistic approach. 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 the effective treatment of brainstem gliomas in the future.