Neuroepithelial Tumors of the Brain Stem

Abstract

Summary: We review 86 brain stem tumors that are classified into three groups according to strict pathological criteria [World Health Organization (WHO) classification] to give the elements of diagnosis and prognosis. Group I gathers 39 cases of benign tumors, usually WHO grade I pilocytic astrocytoma, involving the cervicomedullary junction, the medulla oblongata, the mesencephalon, or the 4th ventricle (with dorsal exophytosis). The duration of symptoms before diagnosis is usually >6 months. Magnetic resonance imaging (MRI) scan shows well-delimited lesions with hyposignal in Tl-weighted sequences, with signal enhancement after gadolinium injection and sometimes with intratumoral cysts. Total surgical resection is the treatment of choice. The outcome is favorable because the Group I patients have a 2-year survival rate of 70%. Group II is composed of 30 malignant tumors (WHO grades III and IV anaplastic astrocytoma and glioblastoma) that mainly involve the pons, with possible cranial and caudal extensions. The duration of symptoms before diagnosis is usually <3 months. MRI shows poorly delimited tumors with iso- and hyposignals in Tl-weighted sequences. Surgery is not considered helpful. The outcome is poor: The 2-year survival rate is ˜12%. Group III includes intermediate tumors, i.e., 17 patients with WHO grade II fibrillary astrocytoma. Depending on their location, duration of symptoms, and radiological features, these tumors behave differently. The prognosis is part of their behavior as tumors of Group I or Group II.