Radiology MRI

Three years old child that suffered from a major infarct at the age of 7 months. MRI of the brain shows large porencephaly of the left hemisphere with compensatory larger right hemisphere corresponding with "age" of the infarct. Note thickness of the bone on second image. But why would a 7 months old child suffer from such extensive infarction? There are some clues when you look at the vessels of the Circle of Willis. Note tapering (progressively narrowing) of the distal Internal Carotid Arteries (ICA). Also you might notice extensive small collateral vessels centrally in the brain (mostly lenticulostriate). This is a case of MoyaMoya disease that is also known as  Idiopathic Progressive Arteriopathy of Childhood . Above images show source and reconstructions of the flow based Time of Flight (ToF) MR Angiography (MRA). You can see tapering of the distal ICA (arrows) as well as multiple small collateral arteries (arrow heads). Those collaterals would show as "puff of

Fall on mandible with blood from both external auditory canals. CT shows bilateral comminute fracture of the bony parts of external auditory canals (arrows). Fractures are not apparent at first glance, however clue here is emphysema - air in soft tissues medially to mandibular condyles (arrow heads). Mechanism of this trauma is impact of mandibular condyles against anterior parts of the bony external auditory canals. Lesson here is to look carefully at any abnormal air in soft tissues of trauma patients and ask yourself a question: Where does this air come from?

Patient presents with persistent hiccup since about a week. CT of the brain followed by CT Angiography (CTA) (not shown) revealed a large Arterio Venous Malformation (AVM) located dorsally to medulla oblongata and extending into the proximal spinal canal. Additional MRI investigation (above) has revealed a large thrombosed part of AVM that was not apparent on CT. Note two first images showing non-contrast T1 followed by two images after contrast. There is a large branch of the AVM stretching through the right foramen of Luschka (arrows) that shows high signal on non-contrast T1. The contrast enhanced T1 sequences show enhancement of the remaining parts of the AVM located posteriorly to medulla oblongata (arrowheads). High signal on non-enhanced T1 of the thrombus is due to free methemoglobin indicating about one week old thrombus. (Check my previous post about blood product signal on MRI ). This corresponds with onset of patients symptoms - since the AVM was "silent" and a

Incidental finding of Cavum Velum Interpositum (CVI) that is seen as triangular shaped CSF space between lateral ventricles, over thalami, below fornices. CVI is most posteriorly located - that is contrary to anterior and middle location of Cavum Septi Pellucidi (CSP) and Cavum Vergae (CV) as shown on this very good scheme from Wikipedia . You might also check my previous post showing Cavum Velum Interpositum on CT .

Not enhanced and contrast enhanced T1 sequences showing high signal well defined lesion dorsally to pituitary infundibulum and anterior to corpora mammillaria, caudally to hypothalamus. Lesion shows no contrast enhancement and its signal characteristics are of fat tissue. This is an incidental finding of Hypothalamic Lipoma . Note the lesion location on non enhanced T1, contrast enhanced T1, T2 and FLAIR (with fat saturation - see subcutaneous tissue). Also CT confirms fat tissue. The learning point is that in the hypothalamus region one can encounter various types of lesions. In this case the first next differential diagnosis would be Craniopharyngioma, or Germinoma. However lack of enhancement proves against the malign tumor. Always check for possible ectopic neurohypophysis, that in this case is in normal position (see first image). Tuber Cinereum Hamartoma - that can be found in this location has different signal characteristics. You can also check Tuber Cinereum Ham