Last week or so Traci Giuliano asked:
> A student in intro today said that he learned in high school
> that alcohol use can damage myelin...can anybody verify that for me?
Well, I couldn't, and I seem to recall no response from anyone
else either. But today I was going through PubMed looking for
something else entirely, and stumbled across the answer, which is
sort-of, or possibly.
According to their PubMed abstract, Menger and Jorg (1999)
reported on 44 cases of "central pontine myelinolysis", which I
translate as loss of myelin in the pons region of the brain. Of
their 44 cases, 42 were chronic alcoholics. They followed up on
34: 2 died, 11 recovered completely, , 11 had deficits but could
function independently, and 10 were dependent. Their deficts
included memory and cognitive disorders, "tetraparesis"
[paralysis of all limbs?], ataxia, and peripheral nerve disease.
Now you might conclude from this that it's the alcohol intake
that's responsible. And you might be wrong. According
to a PubMed abstract (Brown, 2000), the demyelination may be
"precipitated" by "aggressive correction of a hyper- or
hypo-osmolar state". This seems to be saying that it's the
_treatment_ for dehydration or overhydration that causes the loss
of myelin.
Another curiosity is that I'd have thought that the primary
hydrational risk in alcohol intake would be dehydration, as
alcohol inhibits anti-diuretic hormone. Not so, apparently
(Hettema & Halma, 1999). It seems that excessive beer drinking
("beer potomania") can cause hyponatremia [literally low blood
sodium, a sign of over-hydration]. I guess for a serious beer
drinker, fluid goes in faster than it can flow out. But this is
also puzzling, because the condition should be self-correcting by
stopping alcohol intake, without the need for "aggressive
treatment". So perhaps alcohol intake does have a direct effect
as well. Severe hyponatremia causes the brain to swell against
the skull, which surely can't be good for myelin. But this is
speculation. I guess reading the papers rather than their
abstracts might be more enlightening.
But the short answer to Traci seems to be that demyelination is a
risk factor for alcoholics.
-Stephen
Brown, W. (2000). Osmotic demyelination disorders: central
pontine and extrapontine myelinolysis. Current Opinion
in Neurology, 13, 691-7
Hettema, h., & Halma, C. (1999). Beer drinker's
hyponatraemia: a case report. Netherland Journal of
Medicine, 54, 105-7.
Menger H, Jorg J. (1999. Outcome of central pontine and
extrapontine myelinolysis (n = 44). J Neurol 246(8):700-5
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Stephen Black, Ph.D. tel: (819) 822-9600 ext 2470
Department of Psychology fax: (819) 822-9661
Bishop's University e-mail: [EMAIL PROTECTED]
Lennoxville, QC
J1M 1Z7
Canada Department web page at http://www.ubishops.ca/ccc/div/soc/psy
Check out TIPS listserv for teachers of psychology at:
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