BACKGROUND Our case report demonstrates acute onset of diplopia due to Isolated Sixth Nerve Palsy (ISNP) secondary to uncontrolled T2DM, presenting as an ophthalmoplegia. The most frequent one, is ISNP with an incidence of 11.3/100.000 1. Vasculopathic ISNP is associated with atherosclerosis in patients older than 50 years 1.
CASE PRESENTATION A 63 year-old male with history of T2DM, HTN, HL, came for evaluation of acute onset double vision 3 days prior. He noted diplopia while attempting to park his car; he saw that tracking to the left with his eyes would elicit double vision. Denied recent travel, trauma, headache or dizziness. He was awake and alert, BP 200/110mmHg, BMI 33. No pathologic murmur. He had PERRLA bilaterally but impaired lateral rectus muscle movement on the left side. Otherwise, EOMI on the right side. No facial asymmetry or ptosis. Overall, findings positive for ISNP. BMP only remarkable for a glucose of 297, HA1c was 10.0. Head CT was negative for any acute intracranial abnormality. Orbital MRI did not show acute infarction or masses. Patient was admitted for acute diplopia due to ISNP. Differential diagnoses were neoplasm, migraine, MS and diabetic neuropathy. Based on the aforementioned data, we suggested that T2DM was the probable cause. Counseling on improving glycemic control was given. Unfortunately, patient was lost to follow up. DISCUSSION ISNP remains an elusive entity; atherosclerotic risk factors such as DM, HTN, HL, hyperhomocysteinemia 2 or viral infections 3 have been reported in association. This type of palsy seems to be more frequent in children and can be recurrent in nature.
In adults, the most likely cause of ISNP seems to be ischemic mononeuropathy or more aggressive etiologies such as temporal arteritis 4. Inconclusive images prove even a higher diagnostic challenge 3. Of note, we found a case demonstrating evidence for Eicosapentaenoic Acid in the improvement of ISNP with recovery in as shortly as 8 weeks. The basis of this treatment lies in the recovery of endothelial function focusing on the anti-platelet and anti-inflammatory effects of the drug2,4. REFERENCES (1). Elder, Christopher, et al. “Isolated abducens nerve palsy: update on evaluation and diagnosis.” Current neurology and neuroscience reports 16.8 (2016): 69. (2). Takenouchi, Yasuhiro, et al. “Eicosapentaenoic acid ethyl ester improves endothelial dysfunction in type 2 diabetic mice.” Lipids in health and disease 17.1 (2018): 118. (3). Azarmina, Mohsen, and Hossein Azarmina. “The six syndromes of the sixth cranial nerve.” Journal of ophthalmic & vision research 8.2 (2013): 160. (4). Yanai, Hidekatsu, and Mariko Hakoshima. “Eicosapentaenoic Acid for Diabetic Abducens Nerve Palsy.” Journal of Endocrinology and Metabolism 7.4 (2017): 131–132.