Trigeminal ganglionic neuronal death in a case positive for the botulinum neurotoxin B

Abstract

Botulinum neurotoxin B (BoNT-B) is a well known lethal agent in humans. In the last years botulinum neurotoxins have been used as therapeutic agents in pain management; their intimate effects on the peripheral nervous ganglia were however not thoroughly described. We present here a rare case of a BoNT-B serologically positive human adult in which trigeminal ganglia were found immunopositive for caspases 3 and 9. Thus the intrinsic apoptotic pathway was proposed as the cell death mechanism involving primary trigeminal neurons. Scavengers such as macrophages and resident satellite glial cells, with a CD68 immunopositivity were also identified, presumably being in the process of eliminating apoptotic remnants. Taking into account that the downregulation of metalloproteinases leads to inactivation of neuronal caspase 3, exogenous metalloproteinases, such as BoNT, may lead to apoptosis. If this causal relation, neurotoxin-to-apoptosis is valid, similar apoptotic processes can be presumed to occur in various ganglia, sensory and autonomic, involved in vital functions of the body. In conclusion, further morphological and experimental studies are needed to extensively evaluate the apoptotic effect of BoNT within the peripheral nervous ganglia in botulinum infections and BoNT treatments.