Brainstem gliomas are a heterogeneous group of tumors whose prognosis and treatment depend not only on the histologic features but also on the location within the brainstem. Magnetic resonance imaging allows the recognition of a distinct type of brainstem glioma of the tectal region of the midbrain, leading to aqueductal compression and hydrocephalus. The radiologic appearance of these tumors is usually rather uniform, with a characteristic nonenhancing thickening of the tectal plate. Because of its protracted course, no further treatment is necessary beyond cerebrospinal fluid diversion and close clinicoradiologic follow-up. The authors report two children with tectal plate gliomas of unusual but strikingly similar appearance. They present a clinical picture suggestive of intracranial hypertension without localizing signs. Magnetic resonance images reveal hydrocephalus related to the presence of perfectly circular lesions, hypointense on T1 and hyperintense on T2, which could be mistaken for parasitic cysts or represent dilated rostral portions of the sylvian aqueduct. After the cerebrospinal fluid diversion procedures, no further treatment was given, with one of the patients being monitored for 10 years and the other for 8 months, without tumor progression. These patients demonstrate that tectal gliomas, despite sharing a good prognosis, may have various patterns of growth, leading to unusual radiologic appearances that may pose diagnostic difficulties.
