Peripheral polyneuropathy after acute methanol poisoning: Six-year prospective cohort study

Methanol is a widely used industrial short-chain aliphatic alcohol with known neurotoxic properties. Mass poisoning outbreaks due to the consumption of methanol-adulterated alcoholic drinks present a challenge to healthcare providers due to the high mortality and serious central nervous system (CNS) damage in survivors. However, the impact of methanol exposure on the peripheral nervous system is unknown.

To investigate the role of acute methanol exposure in the development of peripheral polyneuropathy (PNP) during the years following discharge from the hospital.

A total of 55 patients with confirmed methanol poisoning (mean age of 47.9 ± 3.6 years; 9 females) were examined 4 times within a 6-year prospective longitudinal cohort study. The program included neurological and electromyographic examinations, visual evoked potentials, ocular examinations with retinal nerve fibre layer thickness measurements, brain magnetic resonance imaging, and a series of biochemical and toxicological tests.

PNP was observed in 20/55 (36 %) patients, which, in most of the cases, was mild axonal sensorimotor neuropathy. In 8/55 (15 %) patients, worsening of electromyographic findings was registered during the follow-up period, including 5 cases with newly diagnosed PNP and 3 cases of PNP progression. In one subject, complete reversal of PNP was registered after cessation of alcohol intake. The patients with PNP were significantly older (57.3 ± 5.3 versus 42.5 ± 3.9 years; p < 0.001), with higher blood glucose (5.93 ± 0.97 versus 4.81 ± 0.32 mmol/L; p = 0.035) and lower vitamin B₁ (45.5 ± 7.4 versus 57.5 ± 5.2 ug/L; p = 0.015) concentrations. The number of chronic alcohol abusers was significantly higher in the PNP group (17/20 versus 20/35; p = 0.034). No associations between PNP prevalence/ dynamics and acute parameters of poisoning severity, arterial blood pH (7.26 ± 0.07 with PNP versus 7.18 ± 0.09 without PNP; p = 0.150), or serum methanol (1320.0 ± 700.0 with PNP versus 1430.0 ± 510.0 mg/L without PNP; p = 0.813) and ethanol (460.0 ± 560.0 with PNP versus 340.0 ± 230.0 mg/L without PNP; p = 0.675) concentrations at admission were found. No difference in the number of patients with visual (9/20 with PNP versus 12/35 patients without PNP; p = 0.431) and CNS sequelae (9/20 with PNP versus 15/35 patients without PNP; p = 0.877) of poisoning was present.

Despite the relatively high number of PNP cases, no association was found between the severity of acute methanol poisoning and the prevalence of PNP and its dynamics during six years of observation. We did not find an association between methanol-induced visual/ brain damage and the prevalence of PNP in survivors of poisoning. A high prevalence of PNP and its progression might be attributed to other causes, mainly a history of chronic alcohol abuse and insufficiently treated diabetes mellitus. Our results highlight the importance of complete cessation of alcohol consumption and better control of glycaemia in diabetic patients in the prevention and treatment of peripheral PNP.