PMC3401655_01
Computed tomography shows a hypodense (2-20 Hounsfield Unit) cyst seen in front of the brain stem in the premedullary cistern lifting the basilar artery (arrow), with flattening of the anterior surface of medulla (arrow head)
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F1
Reevaluation of the old CT showed a hypodense (2-20 Hounsfield Unit) cyst seen in front of the brain stem, with minimal flattening of the anterior surface of medulla which was initially missed [Figure 1].
(a) A 30 x 23 x 39 mm well-defined T1 hypointense lesion (white arrow), with flattening of the anterior surface of medulla (arrow head). (b) Its T2 hyperintense occupying the premedullary and prepontine cistern displacing medulla oblongata and inferior part of pons posteriorly. (c) FLAIR images differentiate epidermoids from arachnoid cysts demonstrating lesion to be hyperintense to CSF. (d) Diffusion-weighted imaging show high signal intensity suggesting restricted diffusion with corresponding. (e) ADC showing hypointensity. (f) No enhancement on sagittal T1 postcontrast images
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F2
Magnetic resonance imaging (MRI) with spectroscopy confirmed the presence of an epidermoid cyst in the premedullary cistern [Figure 2] with a prominent lipid peak.