60 yo w/ hx insulin dependent diabetes, HTN, HLD, presents to the ED complaining of double vision and drooping eyelid for 3 days. POC glucose 359. CTH w/o and CTA head negative. What's the diagnosis and likely cause for this patient?

CN3 (Oculomotor) palsy

• CN3 innervates superior, medial and inferior rectus muscles, inferior oblique & levator palpebrae > Palsy causes eye to deviate lateral and down
• Parasympathetic - pupillary sphincter and ciliary muscle
• Sparing of pupil - likely ischemic
• Abnormal pupil - likely compressive cause (aneurysm)
• Binocular diplopia - double vision stops when cover either eye
• DDx: aneurysm, ischemia, trauma, neoplasm, cavernous sinus thrombosis, giant cell arteritis, myasthenia gravis
• CTA head imaging modality of choice +/- MRI/A
• Ischemic causes tend to resolve in 4-8 weeks

Most likely cause for this patient:

This patient with pupil sparing CN3 palsy was felt to have an ischemic etiology w/ hx of uncontrolled diabetes after negative imaging

Want a refresher on other causes of diplopia?  Check out our prior post from Dr. Ginty

References:

Margolin E, and Freund P. "A Review of Third Nerve Palsies". International Ophthalmology Clinics, vol. 59, no. 3, July 2019, pp. 99–112. doi: 10.1097/IIO.0000000000000279.

Capo, H., M.D., Warren, F., M.D., Kupersmith, M. , M.D. Evolution of Oculomotor Nerve Palsies. J Clin Neuroophthalmol. 1992 Mar;12(1):21-5