Adult brainstem gliomas

Abstract

Brainstem gliomas are uncommon in adults and account for only 1%-2% of intracranial gliomas. They represent a heterogeneous group of tumors that differ from those found in their pediatric counterparts. In adults, a low-grade phenotype predominates, which is a feature that likely explains their better prognosis compared to that in children. Because biopsies are rarely performed, classifications based on the radiological aspect of magnetic resonance imaging results have been proposed to establish treatment strategies and to determine outcomes: (a) diffuse intrinsic low-grade, (b) enhancing malignant glioma, (c) focal tectal gliomas, and (d) exophytic gliomas. Despite significant advances in neuroradiology techniques, a purely radiological classification remains imperfect in the absence of a histological diagnosis. Whereas a biopsy may often be reasonably avoided in the diffuse nonenhancing forms, obtaining histological proof seems necessary in many contrast-enhanced brainstem lesions because of the wide variety of differential diagnoses in adults. Conventional radiotherapy is the standard treatment for diffuse intrinsic low-grade brainstem gliomas in adults (the median survival is 5 years). In malignant brainstem gliomas, radiotherapy is the standard treatment. However, the possible benefit of combined radiotherapy and chemotherapy (temozolomide or other agents) has not been thoroughly evaluated in adults. The role of anti-angiogenic therapies in brainstem gliomas remains to be defined. A better understanding of the biology of these tumors is of primary importance for identifying homogeneous subgroups and for improving therapy options and outcomes.

Figure 1.

Low-grade oligoastrocytoma in a 19-year-old man presenting a progressive cerebellar syndrome and dysphagia. Upper panel: (A, B): Evocative radiologic pattern in magnetic resonance showing a diffuse intrinsic brainstem hypointense lesion without contrast enhancement as seen in T1 sequences and T2-Fluid Attenuation Inversion Recovery (FLAIR). (C): Magnetic resonance spectroscopy showing only a mild increase of the choline/N-acetyl aspartate ratio without lipids/lactates peaks modification (white arrow). Lower panel: (D, E): Histologic sample obtained after biopsy showing a low-grade glioma with an astrocytic component and oligodendroglial differentiation. (F): Immunohistochemistry showing a low MIB-1 proliferation index.

Figure 2.

Diffuse intrinsic “low-grade” brainstem glioma (without biopsy) in a 24-year-old man suffering from facial palsy, dysarthia, and gait imbalance. Left panel (A): Magnetic resonance imaging showing a diffuse nonenhancing lesion in T1 sequences (top and middle) and hyperintensity in T2-Fluid Attenuation Inversion Recovery (FLAIR) sequences. Note the ventral extension of the lesion surrounding the basilar artery (white arrow). Right panel (B): Follow-up MRI showing multiple nodular enhancing brainstem lesions in T1 (top, middle) and increased T2-FLAIR hyperintensity (bottom).

Figure 3.

Low-grade oligoastrocytoma. (A): Follow-up magnetic resonance image of the patient in Figure 1 showing an infiltrative lesion seen as T2 hyperintensity without contrast enhancement at baseline. (B): Five years later, the tumor remains stable as seen in Fluid Attenuation Inversion Recovery (FLAIR) and T1 sequences. (C): Tumor progression seen as an increase of hyperintensity signal in FLAIR sequence, significant mass effect, and contrast-enhanced lesion (white arrow).

Figure 4.

Oligodendroglioma grade II in a 42-year-old woman presenting an ataxic gait and vertigo. Left panel: (A): Diffuse intrinsic lesion involving the pons and medulla oblongata. T1-weighted sequence (top) shows a nonenhancing lesion, and T2- Fluid Attenuation Inversion Recovery (FLAIR) sequences (bottom) show a hyperintensity of the brainstem. Right panel: (B): Four years later follow-up magnetic resonance imaging shows a locoregional progression seen as multiple tumoral enhancing lesions in the cerebellum (top, white arrow) and extension of T2-FLAIR hyperintensity.

Figure 5.

Anaplastic oligodendroglioma in a 25-year-old woman suffering from headache, ataxic gait, diplopia, and facial paresthesia. Upper panel: (A): Magnetic resonance image showing a hyperintensity in T2 sequences involving the pons. (B): T1-weighted sequence showing a contrast-enhanced pontine tumor with “ringlike” pattern. (C): Magnetic resonance spectroscopy showing an increase in Cho peak and notable reduction in Naa (Cho/Naa = 3.5). Lower panel: (D, E): Histologic sample obtained after biopsy showing a microvascular proliferation (black arrow) and diffuse expression of glial fibrillary acidic protein. (F): Immunohistochemistry showing a high MIB-1 proliferation index. Abbreviations: Cho, choline; Naa, N-acetyl aspartate.