 Our first case is a young adult woman with a history of ovarian cancer and a brain mass. Let's have a look. We've got a sagittal contrast-enhanced T1. We'll scroll it just a little bit. We have an axial T2. We'll scroll that a little bit. And we have an axial flare, which is a fluid-suppressed sequence. We'll scroll that a little bit. Let's go back to our midline now and take our first question. The most likely diagnosis is giant cellastrocytoma A, B-central neurocytoma, C-megaloblastoma, D-subapendomoma, E-intrafintricular metastasis. You can pause for a moment if you don't want the answer and to reflect. Question number two. Which of the following is true regarding neurocytoma? A, bubbly mass of the frontal horn of the body of the lateral ventricle attached to the septum palusitum. B, bubbly mass in the third ventricle origin common, 65%. C, bubbly mass in the fourth ventricle. D, bubbly mass attached to the coroid. E, bubbly mass attached to the embryologic parafysis in the anterosuperior third ventricle. Question number three. Which of the following regarding neurocytoma is false? A, calcification common, 60%. B, circumscribed lobulated mass. C, between the ages of 20 and 40, it accounts for 50% of ventricular tumors. D, world health organization grade 3 slash 4. E, hydrocephalus due to foramen of monro obstruction. Okay, let's go back and attack our questions and their answers. The most likely diagnosis is B, central neurocytoma. Giant cell astrocytoma, also known as subapendymal giant cell astrocytoma or SEGA, is associated with Bourneville Pringle's disease, and you should see the intracranial signs of tuberous sclerosis, like subapendymal calcifications or subcortical tubers, not present here, no supportive history. Meduloblastoma, a hyper dense, hypo intense on T2, vascular enhancing mass near the fourth ventricle in the region of the posterior medullary vellum. We're not in the posterior fossa, we're in the supertentorial space, nowhere near where the locus of meduloblastoma would be, and in addition it occurs most commonly under age 10. So meduloblastoma, not a good choice. Subapendymoma likes the inferior fourth ventricle, but can occur in other intraventricular areas. It's non-enhancing most of the time, bland looking, smooth, intermediate and signal on T2. Our lesion is lobulated, somewhat irregular, and if you look at it on the sagittal T1, it looks like it has little hairs on it, a little bit like Bart Simpson's hairdo. Not at all the shape of a subapendymoma. Intraventricular metastases are also smooth margins because they've come from elsewhere. Even though they may generate edema, even though they may subsequently invade, they're usually not isolated, they usually don't have this very irregular, hair-like appearance and this internal bubbly appearance, although admittedly ovarian carcinoma may be cystic in appearance, but not this irregular and with more of a reaction around it would be metastatic disease. Also the vascularity of an intraventricular metastasis would be expected to be greater. Let's move on to question number two, which of the following is true regarding central neurocytoma? And the correct answer is bubbly mass in the frontal horn of the body of the lateral ventricle often attached to the septum palusinum. It can be attached, by the way, to the lateral wall of the ventricle, but it is not a common mass in the third ventricle. In fact, even though it involves the foramen of Monroe commonly and produces obstruction, it does not arise from the third ventricle, probably less than 3-5% of cases, as little as 1% of cases. Bubly mass in the fourth ventricle, not a good site at all, a very rare site. Bubly mass arising from or attached to the choroid plexus, that's true for choroid plexus papilloma and carcinoma, but it is not true for neurocytoma. Bubly mass attached to the embryologic parapheicis and the enterosuperyther ventricle, those are the features of colloid cyst, not of this lesion. Question number three, which of the following regarding central neurocytoma is false? The answer to this one is D. World Health Organization Grade 3 or 4? No, it's not. It's a World Health Organization Grade 2 lesion. Occasionally you'll find a more aggressive Grade 3, but not Grade 4. The other choices are all true. Calcification is common. The lesion is a circumscribed, lobulated mass. The age is 20 to 40 years of age, so it is a very uncommon to rare intraventricular tumor between the ages of 20 and 40. It does account for 50% of intraventricular tumors, not masses, tumors. It is true that hydrocephalus, due to foramen of monro obstruction, is a feature, a common feature of this lesion. The foramen of monro seems to be a little bit of a magnet. It draws some very unique lesions to it. So that often helps narrow the differential diagnosis. So your lesions are 1B, 2A, and 3D. Let's talk a little further about central neurocytoma. It is a very small percentage of intracranial tumors, less than 0.5% of all intracranial tumors. It is a World Health Organization Grade 2 lesion, but its etiology is unclear. It may be derived from bi-potential progenitor cells that are capable of both neuronal and glial differentiation. Another lesion that produces neuronal and glial elements would be a ganglioglioma. It likes the lateral and less commonly the third ventricle. But when it's in the third ventricle, it usually gets there secondarily, as we said, rather than primary. So the third ventricle is the second most common primary site. It is much less common than lateral ventricular involvement with third ventricular secondary involvement via the foramen of monro. They do like the septum palusitum, and less commonly the lateral ventricular wall as the site of origin. And the mean age, depending upon who you read, is somewhere around 29 to 26 years of age. You may get back a pathologic report that says oligo-dendroglioma. This is not at all a typical intraventricular lesion, and the odds are that the pathologist has made a histologic error. Sometimes these lesions, because of their bubbly appearance, may mimic the white portion of a fried egg, giving what's known as the fried egg phenomenon sign. As mentioned, these are well circumscribed lesions. They don't invade the adjacent parenchyma, but they do have a bubbly appearance, and you can tell we like that bubbly word a lot. They do calcify at least 50% of the time, and 60% of the time is a perfectly reasonable number. They may hemorrhage, but hemorrhage is rare. It's not a feature of the typical central neurocytoma. Extraventricular neurocytomas have been described, but they are also rare. Usually if they are adequately resected, it's curative. The CT findings are iso to hyperdensity. The enhancement is at best moderate, so not intense like some of the other intraventricular lesions you'll see, and it's very heterogeneous because of the bubbly character of the lesion. MR, the T1, is mostly intermediate signal matching that of gray matter. As mentioned, hemorrhage, menhemoglobin staining would be highly unusual. The T2 signal is heterogeneous, bubbly, and hyper-intense. The enhancement is moderate and heterogeneous. Craniospinal dissemination of this lesion, unlike, say, appendemoma and meduloblastoma, is extremely rare. Okay, that's central neurocytoma. Let's move on to the next case, shall we?