Atypical teratoid rhabdoid tumors of the central nervous system in infancy

Purpose: To investigate whether reliable neuroradiologic signs may be defined and successfully employed to identify atypical teratoid rhabdoid tumors (ATRT) in infancy. Methods: The clinical, pathologic, and neuroradiologic findings were reviewed in five infants (2 boys and 3 girls, ages 1 to 24 months) who underwent both computed tomography (CT) and magnetic resonance imaging (MRI) at presentation. The imaging studies were analyzed for common features. The CT density and MRI signal intensity were compared with unaffected gray matter. The children were then followed for a period of 3 to 16 months (mean 5.8 months). Results: Three children had single intracranial tumors, One child harbored two large, separate brain lesions, and a second had both an intracranial and a neck tumor. Thus, a total of six intracranial and one neck ATRT were found in the five patients, Three intracranial tumors were supratentorial and three infratentorial. Five of these six tumors were judged to have originated in the extra-axial compartment and secondarily infiltrated the overlying brain. One intracranial mass was totally extra-axial. All six cases showed markedly heterogeneous patterns of CT density and MRT signal intensity, necrotic portions within the tumor, and markedly hypointense zones on T-2-weighted MRI consistent with chronic hemorrhage, Marginal cystic components were seen in four masses at presentation, and became apparent during later follow-up examination in the remaining two tumors, CT detected foci of calcification in four of the six masses, Careful analysis of the ''solid'' (non-necrotic, non-cystic, non-calcified, nonhemorrhagic) portions of the tumors showed that five of the six brain tumors were totally or partially hyperdense on unenhanced CT, and all six of these masses showed an iso-hypointense texture on T-2-weighted MRI, The behavior on T-1 MRI and the patterns of contrast enhancement on CT and MRI were variable, Contrast-enhanced studies did not reliably demonstrate tumor margins. Conclusion: ATRT are most common in children younger than 2 years of age. All of the tumors in this series were primarily extra-axial in location, contained areas of necrosis, and exhibited foci of chronic hemorrhage, All of the tumors bad a heterogeneous texture, with most showing solid portions that were isointense in T-2-weighted images and hyperdense on unenhanced CT. In this series, marginal cystic components were a finding suggestive of ATRT. Contrast-enhanced studies were nonspecific both on CT and MRI, and did not reliably delimit the extent of the tumor. Because no one imaging pattern proved to be specific for ATRT, histologic examination is still required to rule out other types of brain tumor. However, ATRT deserves to be included in the differential diagnosis of tumors of the central nervous system in the first 2 years of life.