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Methanol is known for causing blindness. One explanation I have read is that the optic nerve is especially active and so methanol will be preferentially taken up by the cells there which then die.

But I assume methanol is also bad for neurons concerned with, for example, memory and cognition. But is this wrong? Could it be that methanol for some reason tends to cause temporary or permanent blindness but is no more toxic to other neurons than ethanol is?

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Methanol toxicity is relatively rare and comparatively little is known about its etiology. I found a correspondence published in the journal Nature in 2004, it seems to a good review of the literature, given that I could not find a recent review on the topic. Please take a look, especially at the sources that the following paragraph cites:

Methanol is particularly toxic to the optic nerve, leading to acute blindness. Based on a histopathological study, the retrolaminar optic nerve myelin sheath seems to be selectively vulnerable to methanol poisoning due to its anatomical structure. In the acute phase, the hyperaemia and swelling of the optic disc has a papilloedema-like appearance. The axoplasmic flow stasis at the nerve head and alteration of the myelin sheath in the retrolaminar nerve segment were demonstrated in experiments using rhesus monkeys. The pathogenesis is presumed to be histotoxic anoxia in a vascular watershed area, which is the result of direct inhibition of cytochrome oxidase by formic acid. Additionally, the increasing pressure following oedema in the visual pathway might further aggravate the deterioration due to ischaemic changes. Therefore, effective methods to treat the oedema might be important, such as the use of intravenous steroids and diuretics. The mechanism of subsequent optic atrophy in patients with methanol poisoning is still unknown, it was suggested to be due to progressive demyelination. The distinct glaucomatous-like cupping of the optic disc suggests extensive loss of retina ganglion cells, which has been thought to result from retrograde degeneration of optic nerve axons.

It seems that in our best understanding, the optic-specificity of the action of methanol seems to be due to the nature of the myelin sheath that insulates the optic nerve.

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  • $\begingroup$ Thanks, interesting. But methanol I would guess is still not good for the brain overall, perhaps the same or perhaps worse than grain alcohol for areas concerned with memory, etc. $\endgroup$
    – releseabe
    Apr 29 at 14:35
  • $\begingroup$ What makes you think it only affects the eyes? Paraphrasing Wikipedia, upon ingestion, symptoms include decreased levels of consciousness, impaired (or loss of) coordination, vomiting, abdominal pain, smelly breath, kidney failure, and (alas!) blindness or vision loss. That doesn't sound to me like it only affects the retina. $\endgroup$
    – S Pr
    Apr 29 at 14:37
  • $\begingroup$ @S Pr: I did not say only eyes but basically I am trying to understand two things: why it seems to be especially bad for the optic nerve and whether it is more toxic in general than ethanol. $\endgroup$
    – releseabe
    Apr 29 at 16:16

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