If untreated, the area around the bite would become gangrenous and turn black. Sometimes the venom would also attack the kidneys. In the worst cases, a bite victim usually had an hour or two to get to a hospital before the situation turned dire. Neurotoxic venom, on the other hand, doesn't allow for such leisure, because it blocks nerve impulses to muscles, including those in the diaphragm that are used in breathing. Usually associated with members of the cobra family, a neurotoxic bite can cause immediate shortness of breath, weakness or paralysis of the lower limbs, double vision, inability to speak or swallow, drooping eyelids, and involuntary tremors of the facial muscles.
Death can occur in as little as ten minutes, usually due to abrupt cessation of respiration.
Over the past few years, however, neurotoxic symptoms have appeared in several people who apparently were bitten by other species of rattler. The species was believed to be a southern Pacific rattlesnake, a subspecies of the prairie, or western, rattler. Within minutes, the young man developed general weakness, had difficulty breathing, and showed the classic neurotoxic symptoms of double vision, facial twitches, and an inability to swallow or talk. He recovered only after being treated with thirty-five vials of antivenom. The doctors who treated him, Sean Bush and Eric Siedenburg, of the Loma Linda University Medical Center, published a report of the episode, calling it the first known case of neurotoxicity associated with a suspected southern Pacific rattlesnake envenomation.