Clinical history is key here as there is an association with ipilimumab. Helpful clues on imaging include a thickened non tapered pituitary stalk with bulbous enlargement of the gland though usually no significant widening of the sella
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Answer (probable): Wallerian degeneration of the pontocerebellar fibers
🔷I only have 1 time point w/o follow up nor images of the pontine infarct. This patient also had cirrhosis. It is possible that the tracts have degenerated due to hepatic encephalopathy or other process
🔷Regardless of the cause in this case, it is important to be aware of these fiber tracts and their appearance when degenerated. Additionally, many other diagnoses can look similar and involve the bilateral middle cerebellar peduncles w/ differential in 🧵
What is the most likely diagnosis in this 75 y/o M w/ history of Alzheimer’s disease on lecanemab (last infusion ~1 week prior) presenting w/ headache and confusion? 🧠
1️⃣Big issues and certain cranial nerves see on routine MR
2️⃣Thin slice high res axial and coronal T2 sequences (FIESTA, CISS, SPACE, etc.) useful for cisternal segments
3️⃣T1C- and T1C+ w/ fat sat best for extracranial segments
4️⃣CT often complementary
🔷OLFACTORY NERVE (CN 1)
📺 Imaging:
▶️Not well seen on routine brain MRI
▶️Seen well on coronal T2 MR
▶️Include medial temporal lobes in assessment
▶️Nasal vault and cribriform plate seen well on coronal CT of sinuses or orbits
▶️Headache that is worst when upright and improves with lying flat as it gets the sagging brain off the jagged skull base (at least that’s how I remember it)
💡May also present with chronic headaches or without headaches
▶️Rarely can have abducens palsy-> the nerve is anchored in Dorello’s canal so brainstem sagging can stretch the nerve 🧠
▶️Anything that reduces the volume of CSF can lead to intracranial HYPOtension