Clinical analysis of severe visual loss caused by inhalational methanol poisoning in a chronic process with acute onset:a retrospective clinical analysis

BACKGROUND: To analyze the clinical features and prognosis of the visual loss resulted from inhalational methanol poisoning in 8 Chinese patients. METHODS: Eight consecutive patients seen at the Beijing Tongren Hospital of Capital Medical University, Beijing, China between January 2003 to August 2017, with complains of vision loss in both eyes, identified as inhalational methanol poisoning. Detailed medical history was extracted. All patients underwent optic nerve and brain magnetic resonance imaging (MRI) scan, laboratory tests, and visual function analysis. Treatment protocols were large dosage of methylprednisolone and B vitamins over 3 months. Patients were seen at 3-month intervals until a year. RESULTS: Eight patients with optic neuropathy caused by inhalation toxicity of methanol were under observation, whose methanol-contact time spans were form 4 days to 5 years for occupational exposure. All the patients had acute onset, transient systemic symptoms on early stage, both eyes involved with severe visual impairment (visual acuity 0.1 or even worse). Retrobulbar optic nerves (ONs) were the major sites involved. Optic nerve MRI scan showed increased signal of bilateral ONs in the orbit and the canal parts, with enhancement. After treatment, the visual function of these patients got improved in different degree in a year follow-up, but not satisfactorily. CONCLUSIONS: Inhalational methanol toxicity may lead to serious damage to ON in a process of chronic intoxication with acute attack, and with poor prognosis.