It can be seen that aspects of different environments can have adverse effects on normal, healthy nervous systems. Aerospace and underwater neurology consultants are often required to evaluate aviators, divers, or astronauts who have neurologic problem to determine whether they should be granted a waiver. In general, these considerations include course of the disorder (static, progressive, or paroxysmal), potential for sudden incapacitation that may compromise safety, predictability of course of the disorder, ability to monitor disease, and potential adverse effects of medications. A background in the toxic effects of an abnormal environment on the nervous system can be used to make better clinical judgements when considering effects of exposing someone with an abnormal nervous system to such environmental stressors.