Visual and neurologic sequelae of methanol poisoning in Saudi Arabia

Abstract

Objectives: To present the visual sequelae of methanol poisoning and to emphasize the characteristics of methanol exposure in the Kingdom of Saudi Arabia (KSA).

Methods: A retrospective case series was carried out on 50 sequential patients with methanol poisoning seen at the King Khaled Eye Specialist Hospital and King Saud University Hospitals in Riyadh, KSA between 2008 and 2014. All patients were examined by a neuro-ophthalmologist at least one month after methanol intoxication.

Results: All 50 patients were young or middle-aged males. All admitted to drinking unbranded alcohol within 2-3 days before profound or relatively profound, painless, bilateral visual loss. Mean visual acuity in this group was hand motions (logMAR 2.82; range 0.1 - 5.0) with some eye to eye variability within individuals. Worse visual acuity was correlated with advancing age (Pearson correlation: oculus dextrus [right eye] - 0.37, p=0.008; oculus sinister [left eye] - 0.36, p=0.011). All patients had optic atrophy bilaterally, and all tested patients had visual field defects. Tremors with or without rigidity were present in 12 patients, and 11 of 30 patients who had neuroimaging performed had evidence of putaminal necrosis.

Conclusion: Methanol intoxication causes visual loss within 12-48 hours due to relatively severe, painless, bilateral optic nerve damage that may be somewhat variable between eyes, and is generally worse with advancing age. The coincidence of bilateral optic nerve damage and bilateral putaminal necrosis in a young or middle-aged male is very suspicious for methanol-induced damage.

Figure 1

Acute and chronic fundoscopic changes. Fundus images of 4 patients with the right optic disk displayed on the left side and the left optic disk displayed on the right side. Images showing the optic disks of 2 patients taken within one week of methanol exposure showing modest pallid edema of the optic disks extending onto the peripapillary retina (Figures 1A & 1B). Images depicting the optic disks of 2 different patients taken approximately 6 weeks after methanol exposure, and showing flat, moderately pale optic disks bilaterally with no residual optic disk or retinal edema (Figures 1C & 1D).

Figure 2

Neuroimaging of methanol poisoning: A) axial fat suppressed T2W image showing attenuated caliber optic nerves bilaterally with abnormal signal intensity more obvious on the right side; B) Flair and C) T2W images of 2 different patients illustrating typical appearance of necrosis of the putamin and claustrum bilaterally (arrows); D) T2W image showing asymmetric injury to the basal ganglia, right worse than left in this patient (arrow). E) T2W image showing bilateral mild necrosis of the putamin (arrow); and F) flair image showing additional foci of demyelination in the subcortical and deep white matter sparing the thin rim of white matter adjacent to the cortex (present in 2 patients) (arrow).