 This is an MRI of the brain in a one-year-old child with neurofibromatosis type 1. We're not seeing any significant areas of myelodactylization, we're not seeing any focal lesions. At first glance, we're not really seeing anything abnormal or concerning. That's not unusual. We performed these studies for surveillance. Several years later, the patient was three years old, and presented with a vocal cord paralysis. At that time, we're starting to see some areas of myelodactylization, but those won't cause a vocal cord paralysis. We're seeing some signal abnormality in the region of the uncus of the temporal lobe, in the brainstem, here in the midbrain. But then if we get down to the inferior aspect of the medulla oblongata, the left posterior aspect, we're seeing focal enlargement. There's no associated abnormal enhancement. While this could be a waxing and waning appearance of a lesion in NF1, and warrants observation, but given that there's a vocal cord paralysis, this definitely warrants very close follow-up. The problem in the brainstem is that this is not an easy place to be able to resect a lesion without resulting in more permanent neurologic deficits. If a lesion persists, it is possible to do a very focal biopsy. They use a biopsy not to just say, is it a tumor or not, but to get histologic and genetic characterization of the lesion, because there may be targeted chemotherapy for a specific genetic subtype. The lesions in neurofibromatosis type 1 histologically are almost always pylocytic astrocytoma, even the solid infiltrating ones. And understanding its molecular profile can help with chemotherapy. So they did not proceed to biopsy on this patient, because it did not progress and the neurologic symptoms resolved, but that is something to be aware of. Also in this patient, when they were younger, we see this focal T2 hyper intense abnormality in the posterior orbital segment of the right optic nerve. And it looks different than the anterior orbital segment of the right optic nerve. That's a very subtle abnormality, but it persists on this coronal image and see perhaps slightly larger, but also more hyper intense and T2 weighted imaging. Five years later, we see this asymmetric enlargement, fusiform enlargement of the orbital segment of the right optic nerve. So this patient developed a right optic pathway glioma with fusiform enlargement of the optic nerve. And there is the lesion in the left posterior aspect of the medulla oblongata, which did not progress. So while histologically, it may be neoplasm. It did not warrant surgery, did not warrant biopsy, would not warrant any other treatment, but did warrant close continued imaging surveillance.