Bilateral thalamic tumors in children.

INTRODUCTION: The actual incidence of thalamic tumors is not known, but the frequency of the bilateral tumoral involvement of both thalami is even less defined. CASE REPORT: In the present paper we report 4 new pediatric cases of primary bilateral thalamic tumors (PBTTs) observed in the Pediatric Neurosurgery Section at the Catholic University Medical School, Rome. Neuroimaging studies could not detect the presence of abnormal neoplastic tissue at the level of the midline basal subependymal region of the third ventricle, in the midbrain, and in the pineal gland in any of these 4 patients, thus apparently excluding the diffusion of a firstly unilateral thalamic tumor to the contralateral thalamus. In all of the patients, the lesions appeared as large symmetrical masses on both sides of the third ventricle, a feature that seems to further exclude the contralateral growth of a previously unilateral tumor. PBTTs appear to remain confined to the thalamic nuclei for a long time, and, unlike the unilateral form, the border between gray and white matter may not be violated for a relatively long time. Unlike in adults, PBTTs do not present with dementia in children. Signs and symptoms of increased intracranial pressure (3 cases) and movement disorders (tremor, 2 cases) were the presenting clinical manifestations in our 4 patients.
CONCLUSIONS: The diffuse and bilateral involvement of both thalami makes surgical therapy barely feasible, even at the present time. Today, the main role of surgery is still to obtain a histological diagnosis. Generally, PBTTs are low-grade astrocytomas (grade II in the WHO classification), but limited anaplastic areas may be found in some patients, so that grade III and IV astrocytomas may be expected in a significant proportion of cases.