Acute visual loss following administration of metronidazole: A case report

Abstract

We describe a patient with acute headache, disc swelling, and progressive visual loss following short exposure to the 5-nitroimidazole, metronidazole. There were no clinical features to suggest acute meningeal disease. Investigations revealed a moderately raised CSF pressure with mild pleocytosis and elevated protein. Cerebral venous sinus thrombosis was excluded by MRI with venography. The raised intracranial pressure alone is unlikely to have produced the patient’s severe and rapid visual loss. Therefore, metronidazole probably also had a direct effect on the optic nerves. The common underlying mechanism may be the development of perivascular oedema affecting both the vasa nervorum of the optic nerves and the intracranial vessels thus impairing optic nerve function and elevating intracranial pressure. The patient’s visual loss was eventually accelerated by his marked hypermetropia with crowded discs leading to secondary anterior ischaemic optic neuropathy in the presence of grossly swollen discs. Visual loss has not previously been reported in this context and should be added to the list of neurological complications of metronidazole.