45F presents with painless progressive left eye vision loss. MR shows homogenous enhancement encasing the left optic nerve with an associated lesion at the entrance of the optic canal (yellow arrow) #radres#futureradres#NeuroRad#MedTwitter@AlbanyMedRadRes
Differential Diagnosis:
Optic Neuritis
Optic nerve sheath meningioma
Optic nerve glioma
Orbital sarcoidosis
Orbital lymphoma
Orbital pseudotumor
Remember the optic nerve is an extension of the CNS and therefore, is surrounded by meninges and arachnoid cap cells from which meningiomas arise. Look for the “tram-track” sign of enhancement surrounding the optic nerve #Ophthalmology
Optic neuritis would be painFUL and display enhancement of the nerve itself and perineural fat
Optic nerve gliomas create enlargement of the nerve with variable enhancement typically in NF-1 patients
Other diagnoses are variable though typically present as intraorbital masses
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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