Thread by @AaronLBerkowitz

🧠Neurology Tweetorial🧠I'm often asked about localization/diagnosis in the challenging clinical presentation MULTIPLE CRANIAL NEUROPATHIES. Here is my approach, what is yours #MedTwitter #neurotwitter @NMatch2023 @rabihmgeha @DxRxEdu @caseyalbin @AvrahamCooperMD @a_charidimou?

Multiple CNs can be caused by a STRUCTURAL lesion in
👉🏼Brainstem
👉🏼Subarachnoid space/meninges
👉🏼Skull base
👉🏼Face
👉🏼Neck

🚨 Non-Structural mimics🚨
⚡️PNS (Guillain Barre)
⚡️Motor neuron dz (bulbar ALS)
⚡️NMJ (botulism, myasthenia)
⚡️Myopathy (oculopharyngeal musc dystrophy)

How to localize? #1
👉🏼Know levels of CN nuclei in brainstem

🐭Midbrain: 3, 4
🧠Pons: 6 and 7 (medial); 5 and 8 (lateral)
🧠Medulla: 5 (pain/temp) 8 9 10 (lateral), 12 medial

See diagram:

How to localize? #2
Know skull foramen combinations

👁️Orbital apex: 2, 3, 4, V1, 6
💀Cavernous sinus: 3 4, V1-2, 6
👂🏼Internal auditory canal, CP angle: 7, 8
💀Jugular foramen: 9-12

See table!

How to localize? #3

- Neck (lower cranial nerves 9-12 can be affected in carotid dissection, often w/accompanying Horner)

- Nerves within the face: perineural spread of squamous cell cancer along the CNs-- commonly 5 and 7

How to localize? #4

Know when it DOESN'T fit with any of the above patterns--consider meninges, skull base, mimics

Localization Pearl #1

🌟Brainstem lesions causing cranial neuropathies often also cause LIMB motor (medial) or sensory (lateral) signs and/or ataxia (lateral)
❎ Limb motor/sensory CONTRALATERAL to CN deficit
➡️ Limb ataxia ipsilateral to CN deficit

Localization Pearl #2

🌟 If MULTIPLE CNs

AND CNs from >1 brainstem level OR bilateral

AND pt awake

AND no long tract signs:

Likely NOT in brainstem ➡️consider meninges, skull base, face/neck, or mimics

Localization Pearl #3

🌟if multiple CNs
AND UNILATERAL look for pattern associated with particular brainstem level OR Particular skull foramen...

If doesn't fit consider: meninges, skull base, face/neck, mimics

In this review of 979 (!) cases pubmed.ncbi.nlm.nih.gov/16286545/

*Avg #CNs affected per pt=2.7 (1 pt had all 12 affected unilaterally (nasopharyngeal CA)!)

*Of 50 pts w >/= 8 CNs involved ~1/2=GBS! (others=tumor, botulism)

* Most common localizations cavernous sinus & brainstem

In this review of 979 (!) cases pubmed.ncbi.nlm.nih.gov/16286545/
Most common CNs affected:
- 👁️6 (due to many cavernous sinus cases)
- 🫤 7(most commonly in GBS)
- 5 and 3 (also 2/2 cav sinus)

In this review of 979 (!) cases pubmed.ncbi.nlm.nih.gov/16286545/
The most common causes of multiple CNs (in decreasing order of frequency)
-Tumor (schwannoma, mets, meningiomas)
-Brainstem stroke
-Trauma
-Infection (meningitis (bacterial and fungal), botulism, mucor, syphilis)
-GBS

🌟Note how many times GBS shows up on this list: Aside from CN2, the CNs are PERIPHERAL nerves and commonly affected in Guillain-Barre syndrome!

I hope this is helpful! If so, please check out my other tweetorials and let me know what you would like me to cover next. #EndNeurophobia 🧠♥️ @MariaMjaleman @gabifpucci @CPSolvers @valeroldan23

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Focus above was on localization–what about etiology?
Brainstem–stroke, demyelination, neoplasm
Meninges–infxn, inflam (eg sarcoid), leptomening mets, SAH
Skull base–mets, osteopetrosis, Paget
Face–perineural spread of squamous CA
Neck–carotid dissection
Mimics–GBS, botulism, ALS