The venom of funnel-web spiders also has neurotoxins that stimulate neurotransmitter release, resulting in sensory disturbances and muscle paralysis. It may present with a stroke due to a severe coagulopathy. Loxoscelism is caused by envenoming by spiders of the family Sicariidae. Most cases present with headache, lethargy, irritability, myalgia, tremor, fasciculation, or ataxia. Latrodectism is related to neurotoxins present in the venom of widow spiders. Three main syndromes result from spider bite envenoming: latrodectism, loxoscelism, and funnel-web spider envenoming. Intracranial hemorrhages occur in the setting of acute increases in arterial blood pressure related to sympathetic overstimulation, and cerebral infarctions are related to either cerebral hypoperfusion, consumption coagulopathy, vasculitis, or cardiogenic brain embolism. Cerebrovascular complications have been reported after the sting of the Indian red scorpion. These manifestations occur as the result of release of catecholamines into the bloodstream or due to direct cardiac toxicity of the venom. The clinical picture of scorpion sting envenoming is dominated by muscle weakness associated with arterial hypertension, cardiac arrythmias, myocarditis, or pulmonary edema. The venom of elapids is rich in neurotoxins affecting the neuromuscular transmission at either presynaptic or postsynaptic levels. ![]() Metalloproteinases and other substances (common in vipers and colubrids) have anticoagulant or procoagulant activity, and may induce ischemic or hemorrhagic strokes. Snake bite envenoming may result in stroke or muscle paralysis. Neurological complications vary according to the offending animal, and are often directly related to toxic effects of the venom, affecting the central nervous system, the neuromuscular transmission, the cardiovascular system, or the coagulation cascade. Snake and spider bites, as well as scorpion sting envenoming, are neglected diseases affecting millions of people all over the world.
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