Discussion:
Metronidazole is an effective antimicrobial that was first used against trichomonas infections in the late 1950s and then was found to have effects on anaerobic bacteria and protozoal species. It is frequently used and usually has gastrointestinal side effects of gastric upset and metallic taste feeling. Its neurological adverse effects have been infrequent and only reported in case reports; these include dizziness, ataxia, encephalopathy, and seizure [2]. Ophthalmic side effects have been rarely reported and only seen in case reports and are not frequently recognized by healthcare providers. Here we described a case report of 30-year-old lady who was medically free until around 20 days before her admission when she had a bout of gastroenteritis and was given a dose of Metronidazole 500 mg IV the next day. She noticed progressively worsening vision in her right eye, which progressed to complete vision loss in one-day duration. She did not seek medical advice due to financial issues and stayed for around one week waiting for spontaneous recovery of her vision. Upon admission, she was vitally stable, and her physical examination was unremarkable apart from complete vision loss in her right eye and right pupillary afferent defect. Her Basic laboratory blood tests were normal, and her MRI findings were consistent with left optic neuritis. CSF analysis showed lymphocytic pleocytosis and elevated protein level but was negative for culture, viral panel, and oligoclonal bands. Her hospital course has been uneventful, and she was started on IV Methylprednisolone 1000 mg daily for five days. She showed a slight improvement in her right eye vision from complete vision loss to hand movement at 50 cm distance which then did improve to only counting fingers at 50 cm distance.
An extensive literature review was done, and we found 10 case reports and 1 case report with a literature review discussing the neuro-ophthalmic profile of Metronidazole. The age of patients ranged from 6 to 67 years, 8 were males, and 9 were females. All of the cases we could extract data for were administered Metronidazole orally. The dose ranged between 250 mg to 1500 mg per day, and the duration of drug administration to symptom development was from one dose of 250 mg up to chronic use of 2 years. 15 patients developed optic neuritis, three patients developed aseptic meningitis, one patient developed myelitis, and two patients had cerebellar involvement. All the patients were managed with the withdrawal of Metronidazole, except one patient with aseptic meningitis who was treated with a 3rd generation intravenous cephalosporin for one week, and another patient with optic neuritis who was initiated on coenzyme Q10 for 3 months in addition to cessation of metronidazole. Most patients fully recovered their vision, but one whose damage was irreversible, and seven other patients had 71% reversibility of their sight (Please see table 1 for the summary and comparison of literature review and our case).