Colloid Cyst

Monroi Cysta

Fig. 11.28a The T1-weighted image beautifully displays this cyst in the area of the foramen of Monroe (arrows) even before contrast administration. It is high in signal because its content is protein rich. b This sagittal postcon-trast image demonstrates the origin of the cyst (arrow) at the roof of the third ventricle.

Fig. 11.28a The T1-weighted image beautifully displays this cyst in the area of the foramen of Monroe (arrows) even before contrast administration. It is high in signal because its content is protein rich. b This sagittal postcon-trast image demonstrates the origin of the cyst (arrow) at the roof of the third ventricle.

Arteriovenous malformation: A congenital vascular malformation may become symptomatic owing to repetitive intraparenchymal and subarachnoidal bleeds. Without therapy the prognosis is dismal. On CT, calcifications within the brain parenchyma point to the diagnosis. MRI shows to advantage the vascular character of the lesion as well as remnants of previous hemorrhages (Fig. 11.29). Preferred therapy is minimally invasive occlusion of the lesion by the neurointerventional radiologist (Fig. 11.30). This dangerous procedure should only be done by experienced specialists in the field.

• Diagnosis: Giufeng and Paul scratch the back of their heads. This is definitely an infratentorial tumor within or around the fourth ventricle. Medulloblastoma, ependymo-ma, or a pilocytic astrocytoma? The last is the most probable. A hemangioblastoma would fit morphologically but does not occur in this age group. Gregory comes around and cuts their academic discussion short. "It's gonna have to come out anyway," he says and blows his nose. "For crying out loud, call it a pilo!" Giufeng and Paul are taken aback a little by his cavalier tone—it is a brain tumor in a child, after all. Greg sinks back into his chair: "Listen, folks, for you it is the first pediatric brain tumor. I have been through this a couple of times. You somehow need a little distance from the situation. Otherwise you crack up." He pulls himself up again, adjusts his tie, and walks to the door slowly. "I'm gonna have a word with the parents," he mutters.

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