Thanks Amanda for sharing your case of a middle aged male with a past history of diabetes and HTN presenting with diplopia found to have a sixth nerve palsy due to a pontine infarct.
- Your approach to diplopia should be the same as we approach any neurologic deficit – Localize the lesion along the anatomic pathway
- Peripheral cranial nerve
- Both a mononeuropathy or external compression of the cranial nerve
- Extraocular muscles
- neuromuscular junction
- Globe (retina, cornea, lens)
- Monocular diplopia vs. binocular diplopia
- Binocular diplopia: If the diplopia is present only when both eyes are open then the diplopia is due to ocular misalignment
- Monocular: Most often due to diseasse of the cornea or lens, less commonly the retina or cerebral lesion
- Extraoccular muscle weakness can be subtle. LT pearl: when testing EOM, move your finger fast as this will be more likely to demonstrate subtle weakness than slow movements.
- Cranial nerve palsies
- 3rd nerve: longest cranial nerve after exiting the brainstem, more commonly affected by compression from an aneurysm or tumor. When a third nerve palsy is due to microinfarction from diabetes it typically spares the pupil. Therefore pupillary defects should raise your suspicion for intracranial lesion
- 4th nerve: Most prone to injury from trauma and more rarely affected by microinfarction
- 6th nerve: Most commonly affected
Check out this excellent chart from EB Medicine reviewing CN III, IV, and VI palsies.
- Code stroke: time sensitive interventions may be changing in the future
- The latest trials are showing benefit to endovascular intervention in patients with large vessel occlusion within 6 hours of symptoms onset even after tPA administration.
- Newer trials are investigating endovascular intervention up to 24 hours after symptom onset
- Risk of future stroke after TIA: Use the ABCD2 score
- This helps estimate the risk of stroke within the next 2 days after TIA
- In patients with a risk < 1%, outpatient work-up may be appropriate
- Goal is to get work=up completed within 24 hours
Evernote link: https://www.evernote.com/l/AMphZJl3GedO_Zz0p6Mjya3DIEWYfNB-uB8