Atypical teratoid/rhabdoid tumor (ATRT) arising from the 3rd cranial nerve in infants: a clinical-radiological entity?

Atypical teratoid/rhabdoid tumor (ATRT) is a rare embryonal tumor of the central nervous system with preponderance in very young children, the majority of whom are younger than 3 years of age at diagnosis. Historically, outcomes of this aggressive disease, even with extensive multimodal therapy, have been dismal. Recent improvements have come from therapies directed exclusively towards ATRT, but misdiagnosis or delays in the correct diagnosis lead to significantly worse survival rates. ATRTs most commonly occur supratentorially but have been described in virtually all central nervous system locations, including the cerebellopontine angle cistern, meninges, and spinal canal, and extradural locations. ATRTs originating from cranial nerves are rare. Here, we describe three cases of solitary ATRT arising from the 3rd cranial nerve (CN III) or close to its origin in the midbrain, all of which presented in patients within 6 months of birth, with isolated unilateral oculomotor nerve palsy and strikingly similar magnetic resonance imaging (MRI) features. These MRI features include IV contrast enhancement, relative T2 hyposignal, and restricted water diffusion on apparent diffusion coefficient images, findings which are consistent with angiogenesis and high cellularity, and hence, suggestive of malignancy. We conclude that ATRT should be placed high on the differential diagnosis list when encountering a young infant presenting with isolated, unilateral 3rd nerve palsy and a small, solitary tumor arising from CN III that demonstrates malignant conventional and diffusion-weighted imaging features on MRI.

Incidental pineal cysts in children who undergo 3-T MRI.

BACKGROUND: Pineal cysts, both simple and complex, are commonly encountered in children. More cysts are being detected with MR technology; however, nearly all pineal cysts are benign and require no follow-up. OBJECTIVE: To discover the prevalence of pineal cysts in children at our institution who have undergone high-resolution 3-T MRI. MATERIALS AND METHODS: We retrospectively reviewed 100 consecutive 3-T brain MRIs in children ages 1 month to 17 years (mean 6.8 ± 5.1 years). We evaluated 3-D volumetric T1-W imaging, axial T2-W imaging, axial T2-W FLAIR (fluid attenuated inversion recovery) and coronal STIR (short tau inversion recovery) sequences. Pineal parenchymal and cyst volumes were measured in three planes. Cysts were analyzed for the presence and degree of complexity. RESULTS: Pineal cysts were present in 57% of children, with a mean maximum linear dimension of 4.2 mm (range 1.5-16 mm). Of these cysts, 24.6% showed thin septations or fluid levels reflecting complexity. None of the cysts demonstrated complete T2/FLAIR signal suppression. No cyst wall thickening or nodularity was present. There was no significant difference between the ages of children with and without cysts. Cysts were more commonly encountered in girls than boys (67% vs. 52%; P = 0.043). There was a slight trend toward increasing pineal gland volume with age. CONCLUSION: Pineal cysts are often present in children and can be incidentally detected by 3-T MRI. Characteristic-appearing pineal cysts in children are benign, incidental findings, for which follow-up is not required if there are no referable symptoms or excessive size.