Central and peripheral neurotoxic effects of chronic methyl bromide intoxication

To examine all methyl bromide poisonings reported to the Marseille Poison Centre and to describe more precisely the infrequent cases of chronic, nonacute exposure.

Retrospective observational cohort.

Data retrieval from the French Poison Centres National Data Bank (ARIT) which contains all the cases of poisonings collected by the Marseille Poison Centre (Hot Line observations, Toxicovigilance, Toxicological intensive care unit). All methyl bromide poisonings 1973-1994 were examined to evaluate to frequency of the different circumstances.

Of the 89 methyl bromide intoxications studied, there were two cases of chronic exposure: two workers presented with neurological signs of cerebello-vestibular and pyramidal deficits, visual troubles and peripheral neuropathy of the lower limbs at the end of a season of exposure during which no acute incident involved. In one patient, the symptoms improved within five months; in the other, paresthesia were still present two years later and were associated with visual after-effects.

The incidence of chronic methyl bromide intoxication is low. The risk for chronic exposure or persistent toxic effects may be masked by the severity of the acute toxic effects. The development of peripheral neuropathy immediately after the central neurological signs was noted in our two subjects. A dying back axonopathy may explain this unique chronological evolution.