Methanol Poisoning: An Unusual Case of White Matter Changes on MRI

Abstract

A 47-year old Bangladeshi gentleman presented with the complaints of sudden onset bilateral blurring of visionfor 3 days with aggressive behaviour. The visual loss was acute, and the patient had become rather drowsy, with incoherent speech and tremors. There was no preceding history of trauma, fever, neck rigidity, limb weakness, seizures or other comorbidities requiring toxic drugs. On query, his relatives gave a history of chronic alcohol intake for over 10 years, possibly including methanol due to adulteration of ethyl alcohol. The patient had taken an alcoholic binge the night before to onset of symptoms. He was hypertensive, well controlled on amlodipine-atenolol combination.On examination, GCS was 15/15 (i.e. conscious) but he was delirious and extremely aggressive. Pulse was 96 beats/ min. Blood pressure was 95/60mmHg. Pupils were slightly dilated bilaterallywith sluggish reaction to light. Visual acuity was no perception of light (NPL). Ophthalmoscopy revealed bilateral optic atrophy (Figure 1). There was no nystagmus but extraocular muscles could not be tested owing to NPL. Other cranial nerves were intact and there was no focal neurological deficit, although higher psychic function was severely impaired. He also had retrograde amnesia. There were no abnormalities on other systemic examinations. Random blood sugar was 6.1mmol/L so hypoglycaemia as a cause for visual loss and delirium were effectively excluded. Serum electrolytes: Na + 141mmol/L. MRI of brain revealed lesions of subcortical white matter of both frontal lobes showing increased signal intensity signifying restricted diffusion on diffusion-weighted imaging (DWI), while on FSET2 and T2 FLAIR the same lesions showed hyperintensity.These findings were consistent with toxic myelinosis (Figure 2 a & b). Corpus callosum, optic chiasma, basal ganglia including the putamen, cerebellum, thalami, pituitary and para-sellar areas appeared normal in signal characteristics and morphology. J MEDICINE 2015; 16 : 64-66 . Fig. 2(a): MRI showing toxic myelinosis involving frontal lobe on DWI