Neurotoxicity occurs when the exposure to natural or manmade toxic substances (neurotoxicants) results in observable physical damage of the nervous system. This can eventually disrupt or even kill neurons, key cells that transmit and process signals in the brain and other parts of the nervous system.

Neurotoxicity can result from exposure to substances used in chemotherapy, radiation treatment, drug therapies, and organ transplants, as well as exposure to heavy metals such as lead and mercury, certain foods and food additives, pesticides, industrial and/or cleaning solvents, cosmetics, and some naturally occurring substances.

The presence of neurocognitive deficits alone is not usually considered sufficient evidence of neurotoxicity, as many substances exist which may impair neurocognitive performance without resulting in the death of neurons. This may be due to the direct action of the substance, with the impairment and neurocognitive deficits being temporary, and resolving when the substance is metabolised from the body.

Symptoms may appear immediately after exposure or be delayed. They may include:

• Limb weakness or numbness
• Loss of memory
• Loss of vision
• Loss of intellect
• Headache
• Cognitive and behavioral problems
• Sexual dysfunction

Individuals with certain disorders may be especially vulnerable to neurotoxicants.

The prognosis depends upon the length and degree of exposure and the severity of neurological injury. In some instances, exposure to neurotoxicants can be fatal. In others, patients may survive but not fully recover. In other situations, many individuals recover completely after treatment.

Treatment involves eliminating or reducing exposure to the toxic substance, followed by symptomatic and supportive therapy.