Toxic Trauma to the Nervous System

Equally, toxic agents both natural and man-made can act directly on the nerves themselves causing a failure in transmission, as in the case of many toxins which cause disruption of the ionic pump which controls the passage of the all-important sodium ions across the nerve membrane to ensure the passage of the nerve impulse. 

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Secondary demyelination is the loss of myelin secondary to loss of axons. Axonal trophic factors sustain myelin. When the axon is severed or not sustained by its neuron of origin, the axon and then its myelin degenerates. This can happen secondary to infarcts, trauma, toxic, metabolic, or degenerative nervous system diseases. In contrast to primary demyelination, straight and long NF-positive axons are not seen in secondary demyelination. Acutely, the axons crumble into short pieces, and in a few days they are eaten by macrophages and disappear. NF stains thus distinguish secondary from primary demyelination. 

Neuropathic pain is initiated or caused by a primary lesion in the peripheral or central nervous system. The causative agent may be trauma, nerve-invading cancer, herpes zoster, HIV, stroke, diabetes, alcohol or other toxic substances. Neuropathic pain is refractory to most analgesic drugs. Altered sodium channel activity is characteristics of neuropathic pain states. 

In addition to battlefield trauma, there is also the risk of exposure to chemical weapons such as the nerve agents, notably the organophosphorus gases (soman, sarin, VX, tabun) [6]. Organophosphorus toxicity arises largely from their ability to irreversibly inhibit acetyl-cholinesterases, leading to effects associated with peripheral acetyl-choline accumulation (muscarinic syndrome) such as meiosis, profuse sweating, bradychardia, bronchioconstriction, hypotension, and diarrhoea. Central nervous system effects include anxiety, restlessness, confusion, ataxia, tremors. 

The immune system is subject to modulation by a number of environmental cues including, but not limited to, microbial infections, toxic agents, stress, drugs and trauma. Endogenous immunoregulatory factors include those produced by the nervous and endocrine systems. This chapter discusses how these factors, as well as drugs targeting the immune, autonomic and central nervous systems, affect the immune system. 

The wide range of CW agents and toxic industrial chemicals produces patterns of toxic trauma which can be analysed according to actions on somatic systems. In the case of agents which act upon the central and peripheral nervous systems, there is a good understanding of the pathophysiological mechanisms which has led to a... 

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