A neurotoxin is any substance which possesses the ability to damage or destroy tissues of the nervous system. The differentiation between chemical agents and biological agents/ diseases sometimes overlaps because disease agents produce chemical agents. The action of neurotoxins may be direct by injuring or destroying neurotransmitters or the cells themselves which produce them, or indirectly by initiating an adverse secondary body response (i.e. immunologic) thus accomplishing the same result. Neurotoxins may affect the body in a systemic manner (i.e. nerve gases) or locally (i.e. introduced into the subarachnoid space). Neurotoxic injury may occur on an intentional or inadvertent basis. Chemical warfare is certainly intentional as are the toxin delivery systems of poisonous snakes, fish and animals. By eating fish which have ingested algae containing neurotoxins, not deactivated by cooking, a debilitating neurologic incapacitation referred to as “Cigutara’s Disease” can take occur. In the field of health care potential neurotoxins abound. Generally speaking there is little understanding on the part of physicians or patients regarding the potential liabilities of these substances (some of which are in common use).
Fortunately, unusual adverse reactions to standard drugs are uncommon and are referred to as “idiosyncratic” (a unique individual ypersensitivity). For the most part, however, the potential neurotoxic liabilities of commonly employed substances are well documented, but not necessarily well known. A number of potentially dangerous substances are handled in the health care field every day. Their use and application not infrequently reflect ignorance. While an idiosyncratic patient drug reaction on the part of a patient can occur at any time and is usually unpredictable, all too often poor medical judgment exists in this sphere because of a lack of professional education.
Neurotoxins as biological weapons for the purpose of assassination have been used by many countries throughout the world including the United States. The greatest application appears to have been by the Russian security services who considered poison to be “an ordinary tool.” The recent dioxin poisoning of Ukrainian Presidential candidate Viktor Yushchenko smacks of this déjà vue.
One of the many classic examples of chemical warfare employing deadly neurotoxins was the assassination of journalist and playwright, Georgi Markov in London on September 7, 1978. At the time Markov was Bulgaria’s most revered dissident and an enemy of the Bulgarian communist party. His assassin fired a hollow pellet into his leg from the needle of a injector device hidden in the shaft of a simple umbrella as he crossed the Waterloo bridge. This political execution was staged by the Bulgarian State Security with the cooperation of the Russian KGB . In 2004 Oleg Kalugin, a former KGB general (now living outside of Washington, D.C.), admitted that in 1978 he personally passed along orders directing Soviet agents to provide the Bulgarian Secret Service with the spring-loaded umbrella.
The umbrella device fired a tiny hollow ball containing a derivative of ricin (one of the most highly toxic substances known derived from the castor bean). Ricin is a ribosome inactivating protein, it prevents cells from producing essential protein enzymes required for normal cell function. Georgi Markov died on September 11, 1978. Until sophisticated laboratory analysis was performed his death was thought to be a case of blood poisoning (Click Here For More Information On The Markov Matter).
Various chemical substances are routinely placed in the vascular, epidural, subarachnoid, and other body spaces for diagnostic or therapeutic purposes. Those substances having the greatest neurotoxic injury potential are those placed closest to the nervous system. The epidural space has the greatest resiliency to chemical insult, the subarachnoid space, the “salum sactorum” of the human body, is the most sensitive and fragile. Because of the phenomenon of molecular diffusion across semi-permeable membranes substances placed in the epidural space diffuse (to varying degrees based on many factors) into the subarachnoid space. This diffusion is the scientific basis for epidural anesthesia. Because iodinated organic molecules show up under x-ray they have been extensively used as contrast agents. The logic for their use is sometimes reasonable and sometimes irrational. When “routine” myelographic agents are used in the wrong concentration, wrong location or inadvertently confused with more toxic substances, the result for the patient can be severe disability and even death.
Medical investigators who have studied adverse reaction cases have been able to document, in some circumstances the fact that the wrong drug or diagnostic dye agent (or concentration) was utilized. The risk of hospital error is always present. The risk of any patient having a idiosyncratic reaction to the right agent is always also a possibility. Sorting this out can be a difficult task.
The point also needs to be made that when potentially neurotoxic substances are being used it is always possible to pre-medicate patients with allergy blockers and steroids to cut down on the risk of a possible adverse reaction.