Bacterial toxins and Multiple Sclerosis

The primary pathogenetic mechanism responsible for the distinctive demyelinating lesions in the Central Nervous System (CNS) in Multiple Sclerosis (MS), first described in remarkable detail by Charcot more than 170 years ago, remains one of the most baffling conundrums in medicine. A possible role for bacterial cell molecules and transportable proteins in the pathogenesis of MS is reviewed. The ability of bacterial toxins to distort immunity and to cause distinctive toxic damage in the nervous system is discussed in the light of largely forgotten data linking bacterial nasopharyngeal infections with optic neuritis, optochiasmatic arachnoiditis and MS. While the blood­brain barrier substantially protects the CNS from hematogenous toxins, there is a route by which the barrier may be by-passed. Data is reviewed which shows that the CSF and extra-cellular fluid circulation is bi-directionally linked to the lymphatic drainage channels of the nasopharyngeal mucosa. While this provides a facility by which the CNS may mount immunological responses to antigenic challenges from within, it is also a route by which products of nasopharyngeal infection may drain into the CNS and be processed by the immune cells of the meninges and Virchow­Robin perivascular spaces. If potentially toxic bacterial products are identified in early MS tissues at these sites, this would provide an entirely new insight into the pathogenetic mechanisms of this frustratingly enigmatic disease.