Ophthalmoplegia and gaze-evoked nystagmus in Wernicke encephalopathy

A 63-year-old man was admitted to our internal medicine service with a 3-week history of gait imbalance.His medical hist ory included alcohol use disorder, immunoglobulin A vas culitis, and hypertension.He consumed approximately 10 standard drinks per day (108 g alcohol) and ate only a small lunch daily.On examination, he was awake and responsive, with no acute cognitive changes.His eyes were nearly fixed in the primary position, with slight preservation of vertical gaze but no horizontal gaze (precluding assessment of horizontal gaze-evoked nystagmus), and vertical gaze-evoked nystagmus was observed on upward and downward gaze (Figure 1 and Appendix 1, Video 1, available at www. cmaj.ca/lookup/doi/10.1503/cmaj.252084/tab-related-content).Truncal ataxia was present without limb weakness.Our laboratory testing showed a low serum vitamin B 1 level of 30 (reference range 60 to 165) nmol/L.We diagnosed ophthalmoplegia caused by Wernicke encephalopathy.The patient was treated with intravenous prosultiamine, a disulfide thiamine derivative, 500 mg 3 times daily for 2 days, followed by 250 mg once daily for 5 days, and then transitioned to oral thiamine 100 mg daily.On day 2, his horizontal gaze was restored, allowing detection of lateral gazeevoked nystagmus (Appendix 1, Video 2).The patient's gait grad ually improved, although mild upbeat and horizontal gaze-evoked nystagmus remained at discharge on day 12 (Appendix 1, Video 3).Wernicke encephalopathy is characterized by a clinical triad of ocular dysfunction, ataxia, and altered mental status, although the complete triad occurs in only about one-third of patients. 1One of the earliest signs that can aid in the detection of Wernicke encephalopathy is horizontal gaze-evoked nystagmus. 1Ophthalmoplegia and upbeat nystagmus are also important manifestations.Most neuro-ophthalmic abnormalities improve dramatically within weeks of treatment, and ophthalmoplegia typically resolves within days. 1,2Notably, upbeat nystagmus may persist even after other neuro-ophthalmic abnormalities improve, 3 as was observed in our patient.The diagnosis of Wernicke encephalopathy remains clinical, with laboratory and imaging studies serving only a supportive role.Given the risk of permanent neurologic injury, intravenous thiamine should be administered immediately without awaiting test results.In patients with risk factors for thiamine deficiencyincluding alcohol use, malnutrition, gastrointestinal disease, and malignant disease (e.g., gastric cancer) -and ophthalmoplegia, clinicians should consider Wernicke encephalopathy as a cause.