[Causative factors and neurological diseases]

Considering the pathogenesis of neurological diseases, it is important to determine causative factors directly affecting the nervous system. We discussed here some neurological diseases induced by exogenous agents (thallium, organic phosphorus, organic solvents, acrylamide) and by "endogenous" agents (Krabbe disease, Alzheimer disease, familial amyloidotic polyneuropathy). In diseases by exogenous toxic agents, it is not very difficult to find the toxic factors. However, because a single agent can induce a variety of clinical symptoms, we should consider the dose of the agents, the toxic mechanisms and the susceptibility of tissues or organs. In endogenous diseases, causative agents are either toxic factors or the substances inducing mechanical injury. Endogenous toxic agents are usually produced by affected cells themselves. In the case of the substances inducing mechanical injury, the pathogenesis is more complex. The structure of the abnormal agents and tissue susceptibility should be considered.