 Okay, we've got a nine-year-old with vision loss and right-sided optic atrophy. Let's have a look at our case. Let's scroll the images, and there is an abnormality in the visual pathway. It's obvious on the axial T2, on the axial T1, and on the axial contrast-enhanced T1. I'll scroll it a bit so you have a feel for the entity, and while I'm scrolling, you may wish to pause because I'm going to move on to the first question, and that will give away the answer. Let's go to the first question. The most likely diagnosis is A, optic pathway glioma, beam and angioma, C, hypothalamic comartoma, or D, craniopharyngeoma. Question number two. Regarding neurofibromatosis type 1, A, features autosomal dominant inheritance. B, maybe due to sporadic mutation. C, is later age of onset than NF2. D, is due to inactivation of a tumor suppressor gene or E, all of the above. Question three, optic glioma. A, occurs in a similar age group to optic nerve meningioma. B, usually high grade. C, has a better prognosis in non-NF patients. D, can be slow growing and not infrequently asymptomatic. Let's go back and look at our case. We have a large mass that involves the optic nerve. We can trace it back to the optic chiasm and even the supercellar region involving the hypothalamus. The non-contrast MRI shows a fluid-like character to the lesion, suggesting either necrosis or accumulation of cerebrospinal fluid around the optic nerve. The mass is again visible in the supercellar region and has a nugget of high signal intensity representing a focus of hemorrhage, making you think about the diagnosis of craniopharyngeoma. But as we'll see in a moment, craniopharyngeoma does not have a propensity to enter the optic canal or involve the optic nerve, and that is key. This lesion does enhance. It enhances in the back of the optic nerve, in the orbital apex, and in the region of the optic chiasm and supercellar region. Let's go back to our questions. Question number one, the most likely diagnosis is optic pathway glioma. While meningioma could have this growth pattern, it would be highly unusual for it to extend in a supercellar location like this and also involve the optic nerve. Also, when you have a meningioma, it wraps around the optic nerve, much like you would take a piece of bread and wrap it around some turkey or maybe a pig in a blanket. This lesion is intrinsically involving the neuro tissue, not growing around it. The hypothalamic hamartoma is a very uncommon lesion associated with various syndromes, like the palaster hall syndrome. It's isolated to the hypothalamus. It does not enhance. It does not bleed. It's associated with behavioral disturbances, like gelastic seizures or episodes of spontaneous laughter. Craniopharyngeoma, as mentioned, may have fat. It may bleed. It can have any signal it wants to, as a matter of fact. But it doesn't grow into the optic nerve. This lesion involves the optic pathway all the way back to the optic chiasm and in the supercellar region. Craniopharyngeoma is not a viable choice. Question number two, the correct answer is all of the above, which means that neurofibromatosis type one has features of autosomal dominant inheritance. It may be due to a sporadic mutation. It has a later age of onset than NF2. It is due to inactivation of a tumor suppressor gene. Question number three, regarding optic glioma, the correct answer is it can be, and frequently is, a slow growing and oft asymptomatic lesion. That's because the histology is very low grade. At least 50% of these lesions are of polycytic character. It is true that when they're associated with neurofibromatosis, they have a better prognosis. But in non-neurofibromatosis patients, it has a worse prognosis and is more likely to enhance and involve the optic chiasm and the supercellar region as in this case. This patient did not have the other features of NF1. This is an isolated optic nerve glioma with chiasmatic and hypothalamic involvement. These do not occur in a similar age group to meningiomas. Meningiomas occur in 40 to 50 year old individuals, women more common than men. An optic nerve meningiomas are not much different. They occur in 40 to 50 year old individuals, not in children. That makes the diagnosis of optic glioma with chiasmatic and hypothalamic involvement as an isolated lesion. The correct diagnosis in this case with all the accouterments. Thanks and have a great day.