NEW YORK (Reuters Health) - Damage from methanol poisoning appears to be "irreversible," according to a follow-up report on several people exposed to the poison in September 2001.

And people who continue to drink heavily after methanol poisoning seem most at risk of developing even more problems later on, the researchers say. "Individuals affected by a methanol outbreak may benefit from counseling and other efforts aimed at reducing their alcohol abuse," Dr. Raido Paasma of Foundation Parnu Hospital in Estonia and colleagues conclude in the online journal BMC Clinical Psychopharmacology.

Little information is available on the long-term effects of methanol poisoning, although known effects include vision problems and neurological damage.

To help fill this gap in knowledge, Paasma's team followed up with survivors of an outbreak of methanol poisoning that took place in Estonia's Parnu region.

There were 154 people known to have consumed illegal methanol-containing spirits. Forty-three of these individuals were found dead, while the rest made it to the hospital for treatment.

Among the 86 patients who survived after being treated in the hospital, 66 appeared to have no lasting effects of exposure, while 20 did. Six years later, 26 of the survivors had died, usually from alcohol poisoning, and 33 could not be found. In the current report, Paasma and his colleagues report on 27 people, including 22 who had initially suffered no lasting ill effects and five who had.

In both groups of patients, the researchers found, 36 percent had developed new vision or neurological problems. Thirty-five percent of those who had left the hospital with symptoms had died, compared to 29 percent of those with no apparent symptoms.

Among the patients who initially had visual disturbances, there was no improvement in these symptoms. For the 22 patients who were discharged with no symptoms, eight had neurological impairment six years later, and eight had vision problems. The individuals who had continued drinking heavily were the most likely to have developed neurological problems.

It's possible that patients who appeared to have no vision symptoms at their initial discharge had not been evaluated by an ophthalmologist at that time, the researchers note; it's also possible that they developed vision problems over time.

"Regardless, this raises the question whether this phenomenon is an underreported feature in other outbreaks," the researchers say.

SOURCE: BMC Clinical Psychopharmacology, online March 27, 2009.

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