Thanks to Joe fore presenting the case of a middle aged woman with a history of migraines who presented with acute onset of painless binocular diplopia, found to have an isolated CN3 palsy concerning for ophthalmoplegic migraine after an extensive work up.
- Types of diplopia:
- Binocular diplopia refers to diplopia that is only present when both eyes are open (goes away when one eye is closed) and results from ocular misalignment.
- Monocular diplopia refers to diplopia that is present even when one eye is closed and is more consistent with a local eye disease (globe related processes involving the cornea or the lens).
- Approach to diplopia is similar to any neurologic deficit in which you would localize the lesion!
- Upper motor neuron (brain)
- Peripheral nerve (cranial nerves)
- Neuromuscular junction
- Muscle (extra-ocular muscles)
- Globe (local eye disease or refractive error)
- CN3 palsy usually presents with the eye in the “down and out” position and can also impact the levator palpebrae muscle resulting in ptosis. These result from ischemia at the center of the nerve (secondary to diabetes/HTN).
- In a patient with CN3 and a dilated pupil, you must rule out a PCA aneurysm! Impingement of the CN3 by an enlarging aneurysm cuts off the parasympathetic fibers running on the outside of the nerve, resulting in a dilated pupil. This is the only aneurysm that gives a warning sign before rupture!
Commonly tested gaze palsies:
- Rare condition, often manifests in children and young adults
- Diagnosis of exclusion
- Most commonly affects CN3 (but can go to CN4 and CN6 as well)
- Can sometimes precede the headache
- Permanent nerve damage has been reported and some believe that it is a demyelinating neuropathy (for more info, refer to this review article)