Acute visual loss following administration of metronidazole - A case report

We describe a patient with acute headache, disc swelling, and progressive v isual loss following short exposure to the 5-nitroimidazole, metronidazole. There were no clinical features to suggest acute meningeal disease. Invest igations revealed a moderately raised CSF pressure with mild pleocytosis an d elevated protein. Cerebral venous sinus thrombosis was excluded by MRI wi th venography. The raised intracranial pressure alone is unlikely to have p roduced the patient's severe and rapid visual loss. Therefore, metronidazol e probably also had a direct effect on the optic nerves. The common underly ing mechanism may be the development of perivascular oedema affecting both the vasa nervorum of the optic nerves and the intracranial vessels thus imp airing optic nerve function and elevating intracranial pressure. The patien t'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 co mplications of metronidazole.