I've updated my page on personality changes in persons with MS. I have often wondered whether these stereotypical changes were due to intoxication with volatile bacterial products behind the blood-brain barrier.
Recent research finds volatile molecules on the breath of persons with MS. [Ionescu R et al. Detection of multiple sclerosis from exhaled breath using bilayers of polycyclic aromatic hydrocarbons and single-wall carbon nanotubes. ACS Chem Neurosci. 2011 Dec 21;2(12):687-93. Epub 2011 Sep 22.] Hexanal (hexanaldehyde), found in the breath by these workers, is a product of lipid peroxidation.