492: BLINDED BY THIAMINE DEFICIENCY: WERNICKE ENCEPHALOPATHY IN PREGNANCY DUE TO HYPEREMESIS GRAVIDARUM

Introduction: Wernicke’s encephalopathy (WE) is a serious neurological disorder caused by vitamin B1 (thiamine) deficiency. WE can cause permanent brain damage and death with prevalence of 2%. General risk factors include chronic alcoholism, parenteral nutrition, impaired absorption following bariatric surgery and excessive vomiting as seen in hyperemesis gravidarum (HG). Ophthalmoplegia, abnormal mental state, and gait ataxia triad is seen in only a minority of patients. We present a rare presentation of vision loss in WE from HG. Description: 21 yo F, G1P0 at 16 weeks presented with lethargy, hypotension and lactic acidosis. She was diagnosed with HG at 10 weeks’ gestation. She had severe vomiting for 10 days prior to admission and was not taking prenatal vitamins. She had blurry vision for 2 weeks and dark patches in her field of vision for 5 days rendering her unable to see from her right eye. She had no pain, diplopia, flashes or floaters. There was no history of trauma, fever, alcohol or substance use. Hypotension resolved with volume resuscitation. Ophthalmic evaluation demonstrated beating nystagmus, ophthalmoplegia with right eye abduction defect, inferior oblique muscle overaction without retinal or macular defects. There were no other focal deficits except ataxia. CT scans with angiography/venography of brain ruled out venous sinus thrombosis. MRI brain showed T2-FLAIR hyperintensity in bilateral medial thalami, periaqueductal gray matter and mamillary body. Thiamine level was sent and high-dose IV thiamine 500 mg q 8 hours was started. Classic MRI findings and thiamine level 21 nmol/l (70-180) confirmed WE. She had near resolution of symptoms by discharge on day 9. 2-week follow up on thiamine 100 mg/day, showed resolution of ophthalmoplegia. Discussion: Thiamine is essential for myelin sheath synthesis and ATP in Krebs cycle via thiamine diphosphate. Lactic acidosis occurs with ATP loss. It is stored as thiamine pyrophosphate in brain areas with high metabolic activity. WE is reported in 0.5-1 % pregnancies. A review of 82 cases of WE due to HG had mean gestational age16 weeks with vomiting for 6 weeks. Failure to diagnose maternal WE lead to fetal demise in 50%, and maternal death in 5%. Acute vision loss with lactic acidosis is an extremely rare presentation of WE in HG or otherwise.